The document describes two improved direct torque control (DTC) methods for a three-level inverter-fed induction motor drive. Method I selects voltage vectors based on torque and flux demands while inserting intermediate vectors to ensure neutral point balance and smooth switching. Method II uses discrete space vector modulation to synthesize vectors, decoupling vector selection from circuit limitations and solving neutral point and switching issues. Both methods were validated through MATLAB simulation and experiments to enhance DTC performance for three-level inverters while considering their unique challenges.
Modified SVPWM Algorithm for 3-Level Inverter Fed DTC Induction Motor DriveIJPEDS-IAES
In this paper, a modified space vector pulse width modulation (MSVPWM)
algorithm is developed for 3-level inverter fed direct torque controlled
induction motor drive (DTC-IMD). MSVPWM algorithm simplifies
conventional space vector pulse width modulation (CSVPWM) algorithm for
multilevel inverter (MLI), whose complexity lies in sector/subsector/subsubsector
identification; which will commensurate with number of levels. In
the proposed algorithm sectors are identified as in two level inverter
and subsectors/sub-subsectors are identified by shifting the original reference
vector to sector 1 (S1). This is valid due to the fact that a three level space
vector plane is a composition of six two level space planes, and are
symmetrical with reference to six pivot states. Switching state/sequence
selection is also very important while dealing with SVPWM strategy for
MLI. In the proposed algorithm out of 27 available switching states apt
switching state is selected based on sector and subsector number, such that
voltage ripple is considerably less. To validate the proposed algorithm, it is
tested on a three level neutral point clamped (NPC) inverter fed DTC-IMD.
The performance of the MSVPWM algorithm is analyzed by comparing no
load stator current ripple of the three level DTC-IMD with two level
DTC-IMD. Significant reduction in steady state torque and flux ripple is
observed. Hence, reduced acoustic noise is a distinctive facet of the proposed
method.
International Journal of Computational Engineering Research (IJCER) ijceronline
International Journal of Computational Engineering Research(IJCER) is an intentional online Journal in English monthly publishing journal. This Journal publish original research work that contributes significantly to further the scientific knowledge in engineering and Technology
Renewable energy sources are increasingly being used today and solar energy is the most readily and abundantly available energy source. Boost converters are an integral part of any solar energy system. In order to obtain maximum possible energy from the solar system multi-phase interleaved boost converters are used. This paper presents the small-signal ac modelling and closed loop control of three-phase interleaved boost converter. State–space modelling methodology has been adopted to have linearized equivalent model of the boost converter. The interleaved three-phase boost converter is averaged over its one switching period and perturbed with small ac variations and finally linearized around its quiescent point to have a small signal ac model. Type III compensator is employed to improve the frequency response and closed loop control of three-phase boost converter. The controller design procedure is discussed in detail. The effect of right-half plane zero in non-minimum phase system and the appropriate pole-zero placements to overcome the maximum phase lag in such system is discussed. The compensated closed loop system is tested for load variations to observe the transient response.
Dynamic model of zeta converter with full state feedback controller implement...eSAT Journals
Abstract Zeta converter is a fourth order dc-dc converter that can increases (step-up) or decreases (step-down) the input voltage. By considering dynamic model of the converter, the accuracy of the converter’s modeling and simulation are increased thus make it easier to produce the hardware version of the converter. State-space approach is a time-domain method for modeling, analyzing, and designing a wide range of systems which can be described by differential equations or difference equations. This gives great advantages because it particularly suited for digital computer implementation for their time-domain approach and vector-matrix description. The converter needs feedback control to regulate its output voltage. This paper presents the dynamic model of zeta converter. The converter is modeled using state-space averaging (SSA) technique. Full-state feedback controller is implemented on the converter to regulate the output voltage. The simulation results are presented to verify the accuracy of the modeling and the steady-state performance subjected to input and load disturbances. Index Terms: Modeling, Zeta converter, SSA technique, Full-state feedback controller
The traction inverter is a crucial power device in the electric vehicle’s powertrain, and its failure is intolerable as it would considerably compromise the system’s safety. For more reliable driving, installing a traction inverter that is sufficiently resistant to electrical failure is inherent. Due to its compact size and the small number of switches incorporated in three-phase four-switch inverter, this modular topology was used to compensate for the open switch’s failure. However, it is known to have manifold weaknesses mainly distinguished in the low-frequency region. This paper introduces a new fault-tolerant indirect control that handles the IGBT’s failure constituting the traction inverter. The fault compensator is designed first based on the Proportional Integral regulator combined with the notch filter to mitigate the current imbalance and restore the DC voltage equilibrium.Furthermore, to conceive a comprehensive fault-tolerant control, there must therefore contain an accurate fault detector. In this regard, an uncomplicated fault diagnosis method based on the current spectral analysis has been performed. The effectiveness of the submitted controller was validated by simulation using Matlab.
International Journal of Engineering Research and Applications (IJERA) is an open access online peer reviewed international journal that publishes research and review articles in the fields of Computer Science, Neural Networks, Electrical Engineering, Software Engineering, Information Technology, Mechanical Engineering, Chemical Engineering, Plastic Engineering, Food Technology, Textile Engineering, Nano Technology & science, Power Electronics, Electronics & Communication Engineering, Computational mathematics, Image processing, Civil Engineering, Structural Engineering, Environmental Engineering, VLSI Testing & Low Power VLSI Design etc.
Modelling and Simulation of Three Level VSI-Neutral Point Balancing -Fed AC D...IJERA Editor
Multilevel inverter topology has developed recently as a very important alternative in the area of high power
medium voltage energy control. In multilevel inverter, thethree basic types of topologies used are diode clamped
inverter (neutral point clamped), capacitorclamped (flying capacitor) and cascaded multi cell with separate dc
sources. Multilevel inverters are used in medium voltage and high power applications with less harmonic
contents. This paper proposes a software implementation of neutral point clamped (NPC) three level voltage
source inverter using space vector pulse width modulation (SVPWM) techniques. The inverter feeds an
electrical system which is controlled by field oriented control (FOC).The improvement of the control technique
is achieved using intelligence techniques. The operation of the electrical system is verified in steady state and
transient state responses. This software implementation is performed by using matlab/Simulink software. This
paper gives comparison between SVPWM three phase three level with neutral point clamped and without
neutral point clamped. Finally, the comparative study of different techniques was implemented.
Modified SVPWM Algorithm for 3-Level Inverter Fed DTC Induction Motor DriveIJPEDS-IAES
In this paper, a modified space vector pulse width modulation (MSVPWM)
algorithm is developed for 3-level inverter fed direct torque controlled
induction motor drive (DTC-IMD). MSVPWM algorithm simplifies
conventional space vector pulse width modulation (CSVPWM) algorithm for
multilevel inverter (MLI), whose complexity lies in sector/subsector/subsubsector
identification; which will commensurate with number of levels. In
the proposed algorithm sectors are identified as in two level inverter
and subsectors/sub-subsectors are identified by shifting the original reference
vector to sector 1 (S1). This is valid due to the fact that a three level space
vector plane is a composition of six two level space planes, and are
symmetrical with reference to six pivot states. Switching state/sequence
selection is also very important while dealing with SVPWM strategy for
MLI. In the proposed algorithm out of 27 available switching states apt
switching state is selected based on sector and subsector number, such that
voltage ripple is considerably less. To validate the proposed algorithm, it is
tested on a three level neutral point clamped (NPC) inverter fed DTC-IMD.
The performance of the MSVPWM algorithm is analyzed by comparing no
load stator current ripple of the three level DTC-IMD with two level
DTC-IMD. Significant reduction in steady state torque and flux ripple is
observed. Hence, reduced acoustic noise is a distinctive facet of the proposed
method.
International Journal of Computational Engineering Research (IJCER) ijceronline
International Journal of Computational Engineering Research(IJCER) is an intentional online Journal in English monthly publishing journal. This Journal publish original research work that contributes significantly to further the scientific knowledge in engineering and Technology
Renewable energy sources are increasingly being used today and solar energy is the most readily and abundantly available energy source. Boost converters are an integral part of any solar energy system. In order to obtain maximum possible energy from the solar system multi-phase interleaved boost converters are used. This paper presents the small-signal ac modelling and closed loop control of three-phase interleaved boost converter. State–space modelling methodology has been adopted to have linearized equivalent model of the boost converter. The interleaved three-phase boost converter is averaged over its one switching period and perturbed with small ac variations and finally linearized around its quiescent point to have a small signal ac model. Type III compensator is employed to improve the frequency response and closed loop control of three-phase boost converter. The controller design procedure is discussed in detail. The effect of right-half plane zero in non-minimum phase system and the appropriate pole-zero placements to overcome the maximum phase lag in such system is discussed. The compensated closed loop system is tested for load variations to observe the transient response.
Dynamic model of zeta converter with full state feedback controller implement...eSAT Journals
Abstract Zeta converter is a fourth order dc-dc converter that can increases (step-up) or decreases (step-down) the input voltage. By considering dynamic model of the converter, the accuracy of the converter’s modeling and simulation are increased thus make it easier to produce the hardware version of the converter. State-space approach is a time-domain method for modeling, analyzing, and designing a wide range of systems which can be described by differential equations or difference equations. This gives great advantages because it particularly suited for digital computer implementation for their time-domain approach and vector-matrix description. The converter needs feedback control to regulate its output voltage. This paper presents the dynamic model of zeta converter. The converter is modeled using state-space averaging (SSA) technique. Full-state feedback controller is implemented on the converter to regulate the output voltage. The simulation results are presented to verify the accuracy of the modeling and the steady-state performance subjected to input and load disturbances. Index Terms: Modeling, Zeta converter, SSA technique, Full-state feedback controller
The traction inverter is a crucial power device in the electric vehicle’s powertrain, and its failure is intolerable as it would considerably compromise the system’s safety. For more reliable driving, installing a traction inverter that is sufficiently resistant to electrical failure is inherent. Due to its compact size and the small number of switches incorporated in three-phase four-switch inverter, this modular topology was used to compensate for the open switch’s failure. However, it is known to have manifold weaknesses mainly distinguished in the low-frequency region. This paper introduces a new fault-tolerant indirect control that handles the IGBT’s failure constituting the traction inverter. The fault compensator is designed first based on the Proportional Integral regulator combined with the notch filter to mitigate the current imbalance and restore the DC voltage equilibrium.Furthermore, to conceive a comprehensive fault-tolerant control, there must therefore contain an accurate fault detector. In this regard, an uncomplicated fault diagnosis method based on the current spectral analysis has been performed. The effectiveness of the submitted controller was validated by simulation using Matlab.
International Journal of Engineering Research and Applications (IJERA) is an open access online peer reviewed international journal that publishes research and review articles in the fields of Computer Science, Neural Networks, Electrical Engineering, Software Engineering, Information Technology, Mechanical Engineering, Chemical Engineering, Plastic Engineering, Food Technology, Textile Engineering, Nano Technology & science, Power Electronics, Electronics & Communication Engineering, Computational mathematics, Image processing, Civil Engineering, Structural Engineering, Environmental Engineering, VLSI Testing & Low Power VLSI Design etc.
Modelling and Simulation of Three Level VSI-Neutral Point Balancing -Fed AC D...IJERA Editor
Multilevel inverter topology has developed recently as a very important alternative in the area of high power
medium voltage energy control. In multilevel inverter, thethree basic types of topologies used are diode clamped
inverter (neutral point clamped), capacitorclamped (flying capacitor) and cascaded multi cell with separate dc
sources. Multilevel inverters are used in medium voltage and high power applications with less harmonic
contents. This paper proposes a software implementation of neutral point clamped (NPC) three level voltage
source inverter using space vector pulse width modulation (SVPWM) techniques. The inverter feeds an
electrical system which is controlled by field oriented control (FOC).The improvement of the control technique
is achieved using intelligence techniques. The operation of the electrical system is verified in steady state and
transient state responses. This software implementation is performed by using matlab/Simulink software. This
paper gives comparison between SVPWM three phase three level with neutral point clamped and without
neutral point clamped. Finally, the comparative study of different techniques was implemented.
Improvement the voltage stability margin of Iraqi power system using the opti...IJECEIAES
The detection of potential voltage collapse in power systems is essential to maintain the voltage stability in heavy load demand. This paper proposes a method to detect weak buses in power systems using two stability indices: the voltage stability margin factor (dS/dY) and the voltage collapse prediction index (VCPI). Hence, the paper aims to improve the voltage stability of Iraqi transmission grid by allocating FACTS devices in the optimal locations and optimal sizes. Two types of FACTS are used in this paper which are Thyristor controlled series compensator (TCSC) and static var compensator (SVC). The objective function of the problem is fitted using particle swarm optimization (PSO). The proposed method is verified using simulation test on Diyala-132 kV network which is a part of the Iraqi power system. The results observed that improvement the voltage stability margin, the voltage profile of Diyala-132 kV is increased and the power losses is decreased.
Convergence analysis of the triangular-based power flow method for AC distribu...IJECEIAES
This paper addresses the convergence analysis of the triangular-based power flow (PF) method in alternating current radial distribution networks. The PF formulation is made via upper-triangular matrices, which enables finding a general iterative PF formula that does not require admittance matrix calculations. The convergence analysis of this iterative formula is carried out by applying the Banach fixed-point theorem (BFPT), which allows demonstrating that under an adequate voltage profile the triangular-based PF always converges. Numerical validations are made, on the well-known 33 and 69 distribution networks test systems. Gauss-seidel, newton-raphson, and backward/forward PF methods are considered for the sake of comparison. All the simulations are carried out in MATLAB software.
Review of the DTC Controller and Estimation of Stator Resistance in IM DrivesIAES-IJPEDS
In recent years an advanced control method called direct torque control
(DTC) has gained importance due to its capability to produce fast torque
control of induction motor. Although in these systems such variables as
torque, flux modulus and flux sector are required, resulting DTC structure is
particularly simplistic. Conventional DTC does not require any mechanical
sensor or current regulator and coordinate transformation is not present, thus
reducing the complexity. Fast and good dynamic performances and
robustness has made DTC popular and is now used widely in all industrial
applications. Despite these advantages it has some disadvantages such as
high torque ripple and slow transient response to step changes during start
up. Torque ripple in DTC is because of hysteresis controller for stator flux
linkage and torque. The ripples can be reduced if the errors of the torque and
the flux linkage and the angular region of the flux linkage are subdivided into
several smaller subsections. Since the errors are divided into smaller sections
different voltage vector is selected for small difference in error, thus a more
accurate voltage vector is selected and hence the torque and flux linkage
errors are reduced. The stator resistance changes due to change in
temperature during the operation of machine. At high speeds, the stator
resistance drop is small and can be neglected. At low speeds, this drop
becomes dominant. Any change in stator resistance gives wrong estimation
of stator flux and consequently of the torque and flux. Therefore, it is
necessary to estimate the stator resistance correctly. This paper aims to
review some of the control techniques of DTC drives and stator resistance
estimation methods.
Simulation of 3 Phase to 3 Phase Power Conversion Using Matrix Converter with...IJERA Editor
This paper proposes a new approach of design and implementation of 3 phase to 3 phase conversion using
matrix converter. It includes the design, modeling and implementation. The entire matrix converter circuits are
developed by mathematical model so as to reduce computational time and performances of the converter are
evaluated using MATLAB/SIMULINK for RL Load. The mathematical expressions relating the input and
output of the three phase matrix converter are implemented by using simulink block set. The duty cycles of the
matrix converter bidirectional switches are calculated using modified venturini algorithm for maximum (0.866)
and minimum (0.5) voltage transfer ratio.
International Journal of Engineering Research and DevelopmentIJERD Editor
Electrical, Electronics and Computer Engineering,
Information Engineering and Technology,
Mechanical, Industrial and Manufacturing Engineering,
Automation and Mechatronics Engineering,
Material and Chemical Engineering,
Civil and Architecture Engineering,
Biotechnology and Bio Engineering,
Environmental Engineering,
Petroleum and Mining Engineering,
Marine and Agriculture engineering,
Aerospace Engineering.
A Comparison Between Two Average Modelling Techniques of AC-AC Power ConvertersIAES-IJPEDS
In this paper, a comparative evaluation of two modelling tools for switching AC-AC power converters is presented. Both of them are based on average modelling techniques. The first approach is based on the circuit averaging technique and consists in the topological manipulations, applied to a converter states. The second approach makes use of a state-space averaged model of the converter and is based on analytical manipulations using the different state representations of a converter. The two modelling techniques are applied to a same AC-AC called matrix-reactance frequency converter based on buck-boost topology. These techniques are compared on the basis of their rapidity, quantity of calculations and transformations and its limitations.
Cascade forward neural network based on resilient backpropagation for simulta...Mellah Hacene
Cascade-Forward Neural Network Based on Resilient Backpropagation for Simultaneous Parameters and State Space Estimations of Brushed DC Machines
Advances in Modelling and Analysis B
Passivity Based Control for PV Applications by Using a Buck Power Converter
The use of power converters for everyday applications is becoming more and more important. Current technological applications simultaneously demand a high level of precision and performance, so DC-DC converters have a very important role in systems requiring energy level conversion and adaptation. As part of the work of this paper, we are interested in an analysis of modeling and control law synthesis approaches to ensure stability and a certain level of performance in the entire operating domain. The objective of our research work is therefore to propose a control law whose synthesis is based on a formalized (modeling & control) approach with a view to obtaining a control law adapted to the operating point. The principles used are based on the control and observation by the theory of passivity for the synthesis of control law of buck power converter for PV Applications.
IJRET : International Journal of Research in Engineering and Technology is an international peer reviewed, online journal published by eSAT Publishing House for the enhancement of research in various disciplines of Engineering and Technology. The aim and scope of the journal is to provide an academic medium and an important reference for the advancement and dissemination of research results that support high-level learning, teaching and research in the fields of Engineering and Technology. We bring together Scientists, Academician, Field Engineers, Scholars and Students of related fields of Engineering and Technology.
Master slave vector controlled double induction motor using unity power facto...eSAT Journals
Abstract
In the recent days most of the industries uses Induction motors as the primary loads. In order to meet the total load requirement
multiple motors are used. In this paper two Vector Controlled (VC) Induction Motors and a double closed loop PWM rectifier are
used to explain the operation of Master Slave Configuration. The work mainly concentrates on the operation of a Unity Power factor
Controlled (UPFC) PWM Rectifier as the input source for both the Vector Controlled Induction Motors. This UPFC PWM Rectifier
uses two closed loop pi control algorithms the inner loop controls the current and the outer loop controls the DC voltage. The
proposed model is simulated in Matlab/ Simulink and the results shows good synchronization for two induction motors operated in
master slave configuration.
Keywords: Vector Control, Induction Motor, PWM Rectifier, and Unity Power Factor Control
Power transformer faults diagnosis using undestructive methods and ann for dg...Mellah Hacene
Power transformer faults diagnosis using undestructive methods (Roger and IEC) and artificial neural network for dissolved gas analysis applied on the functional transformer in the Algerian north-eastern: a comparative study
Bouchaoui Lahcene, Kamel Eddine Hemsas, Hacene Mellah, saad eddine benlahneche
Nowadays, power transformer aging and failures are viewed with great attention in power transmission industry. Dissolved gas analysis (DGA) is classified among the biggest widely used methods used within the context of asset management policy to detect the incipient faults in their earlier stage in power transformers. Up to now, several procedures have been employed for the lecture of DGA results. Among these useful means, we find Key Gases, Rogers Ratios, IEC Ratios, the historical technique less used today Doernenburg Ratios, the two types of Duval Pentagons methods, several versions of the Duval Triangles method and Logarithmic Nomograph. Problem. DGA data extracted from different units in service served to verify the ability and reliability of these methods in assessing the state of health of the power transformer. Aim. An improving the quality of diagnostics of electrical power transformer by artificial neural network tools based on two conventional methods in the case of a functional power transformer at Sétif province in East North of Algeria. Methodology. Design an inelegant tool for power transformer diagnosis using neural networks based on traditional methods IEC and Rogers, which allows to early detection faults, to increase the reliability, of the entire electrical energy system from transport to consumers and improve a continuity and quality of service. Results. The solution of the problem was carried out by using feed-forward back-propagation neural networks implemented in MATLAB-Simulink environment. Four real power transformers working under different environment and climate conditions such as: desert, humid, cold were taken into account. The practical results of the diagnosis of these power transformers by the DGA are presented. Practical value.....
International Journal of Engineering Research and Applications (IJERA) is an open access online peer reviewed international journal that publishes research and review articles in the fields of Computer Science, Neural Networks, Electrical Engineering, Software Engineering, Information Technology, Mechanical Engineering, Chemical Engineering, Plastic Engineering, Food Technology, Textile Engineering, Nano Technology & science, Power Electronics, Electronics & Communication Engineering, Computational mathematics, Image processing, Civil Engineering, Structural Engineering, Environmental Engineering, VLSI Testing & Low Power VLSI Design etc.
Dynamic model of A DC-DC quasi-Z-source converter (q-ZSC)IJECEIAES
Two quasi-Z-source DC-DC converters (q-ZSCs) with buck-boost converter gain were recently proposed. The converters have advantages of continuous gain curve, higher gain magnitude and buck-boost operation at efficient duty ratio range when compared with existing q-ZSCs. Accurate dynamic models of these converters are needed for global and detailed overview by understanding their operation limits and effects of components sizes. A dynamic model of one of these converters is proposed here by first deriving the gain equation, state equations and state space model. A generalized small signal model was also derived before localizing it to this topology. The transfer functions (TF) were all derived, the poles and zeros analyzed with the boundaries for stable operations presented and discussed. Some of the findings include existence of right-hand plane (RHP) zero in the duty ratio to output capacitor voltage TF. This is common to the Z-source and quasi-Z-source topologies and implies control limitations. Parasitic resistances of the capacitors and inductors affect the nature and positions of the poles and zeros. It was also found and verified that rather than symmetric components, use of carefully selected smaller asymmetric components L1 and C1 produces less parasitic voltage drop, higher output voltage and current under the same conditions, thus better efficiency and performance at reduced cost, size and weight.
International Journal of Engineering Research and Applications (IJERA) is an open access online peer reviewed international journal that publishes research and review articles in the fields of Computer Science, Neural Networks, Electrical Engineering, Software Engineering, Information Technology, Mechanical Engineering, Chemical Engineering, Plastic Engineering, Food Technology, Textile Engineering, Nano Technology & science, Power Electronics, Electronics & Communication Engineering, Computational mathematics, Image processing, Civil Engineering, Structural Engineering, Environmental Engineering, VLSI Testing & Low Power VLSI Design etc.
International Journal of Engineering Research and Applications (IJERA) is an open access online peer reviewed international journal that publishes research and review articles in the fields of Computer Science, Neural Networks, Electrical Engineering, Software Engineering, Information Technology, Mechanical Engineering, Chemical Engineering, Plastic Engineering, Food Technology, Textile Engineering, Nano Technology & science, Power Electronics, Electronics & Communication Engineering, Computational mathematics, Image processing, Civil Engineering, Structural Engineering, Environmental Engineering, VLSI Testing & Low Power VLSI Design etc.
International Journal of Engineering Research and Applications (IJERA) is an open access online peer reviewed international journal that publishes research and review articles in the fields of Computer Science, Neural Networks, Electrical Engineering, Software Engineering, Information Technology, Mechanical Engineering, Chemical Engineering, Plastic Engineering, Food Technology, Textile Engineering, Nano Technology & science, Power Electronics, Electronics & Communication Engineering, Computational mathematics, Image processing, Civil Engineering, Structural Engineering, Environmental Engineering, VLSI Testing & Low Power VLSI Design etc.
International Journal of Engineering Research and Applications (IJERA) is an open access online peer reviewed international journal that publishes research and review articles in the fields of Computer Science, Neural Networks, Electrical Engineering, Software Engineering, Information Technology, Mechanical Engineering, Chemical Engineering, Plastic Engineering, Food Technology, Textile Engineering, Nano Technology & science, Power Electronics, Electronics & Communication Engineering, Computational mathematics, Image processing, Civil Engineering, Structural Engineering, Environmental Engineering, VLSI Testing & Low Power VLSI Design etc.
Improvement the voltage stability margin of Iraqi power system using the opti...IJECEIAES
The detection of potential voltage collapse in power systems is essential to maintain the voltage stability in heavy load demand. This paper proposes a method to detect weak buses in power systems using two stability indices: the voltage stability margin factor (dS/dY) and the voltage collapse prediction index (VCPI). Hence, the paper aims to improve the voltage stability of Iraqi transmission grid by allocating FACTS devices in the optimal locations and optimal sizes. Two types of FACTS are used in this paper which are Thyristor controlled series compensator (TCSC) and static var compensator (SVC). The objective function of the problem is fitted using particle swarm optimization (PSO). The proposed method is verified using simulation test on Diyala-132 kV network which is a part of the Iraqi power system. The results observed that improvement the voltage stability margin, the voltage profile of Diyala-132 kV is increased and the power losses is decreased.
Convergence analysis of the triangular-based power flow method for AC distribu...IJECEIAES
This paper addresses the convergence analysis of the triangular-based power flow (PF) method in alternating current radial distribution networks. The PF formulation is made via upper-triangular matrices, which enables finding a general iterative PF formula that does not require admittance matrix calculations. The convergence analysis of this iterative formula is carried out by applying the Banach fixed-point theorem (BFPT), which allows demonstrating that under an adequate voltage profile the triangular-based PF always converges. Numerical validations are made, on the well-known 33 and 69 distribution networks test systems. Gauss-seidel, newton-raphson, and backward/forward PF methods are considered for the sake of comparison. All the simulations are carried out in MATLAB software.
Review of the DTC Controller and Estimation of Stator Resistance in IM DrivesIAES-IJPEDS
In recent years an advanced control method called direct torque control
(DTC) has gained importance due to its capability to produce fast torque
control of induction motor. Although in these systems such variables as
torque, flux modulus and flux sector are required, resulting DTC structure is
particularly simplistic. Conventional DTC does not require any mechanical
sensor or current regulator and coordinate transformation is not present, thus
reducing the complexity. Fast and good dynamic performances and
robustness has made DTC popular and is now used widely in all industrial
applications. Despite these advantages it has some disadvantages such as
high torque ripple and slow transient response to step changes during start
up. Torque ripple in DTC is because of hysteresis controller for stator flux
linkage and torque. The ripples can be reduced if the errors of the torque and
the flux linkage and the angular region of the flux linkage are subdivided into
several smaller subsections. Since the errors are divided into smaller sections
different voltage vector is selected for small difference in error, thus a more
accurate voltage vector is selected and hence the torque and flux linkage
errors are reduced. The stator resistance changes due to change in
temperature during the operation of machine. At high speeds, the stator
resistance drop is small and can be neglected. At low speeds, this drop
becomes dominant. Any change in stator resistance gives wrong estimation
of stator flux and consequently of the torque and flux. Therefore, it is
necessary to estimate the stator resistance correctly. This paper aims to
review some of the control techniques of DTC drives and stator resistance
estimation methods.
Simulation of 3 Phase to 3 Phase Power Conversion Using Matrix Converter with...IJERA Editor
This paper proposes a new approach of design and implementation of 3 phase to 3 phase conversion using
matrix converter. It includes the design, modeling and implementation. The entire matrix converter circuits are
developed by mathematical model so as to reduce computational time and performances of the converter are
evaluated using MATLAB/SIMULINK for RL Load. The mathematical expressions relating the input and
output of the three phase matrix converter are implemented by using simulink block set. The duty cycles of the
matrix converter bidirectional switches are calculated using modified venturini algorithm for maximum (0.866)
and minimum (0.5) voltage transfer ratio.
International Journal of Engineering Research and DevelopmentIJERD Editor
Electrical, Electronics and Computer Engineering,
Information Engineering and Technology,
Mechanical, Industrial and Manufacturing Engineering,
Automation and Mechatronics Engineering,
Material and Chemical Engineering,
Civil and Architecture Engineering,
Biotechnology and Bio Engineering,
Environmental Engineering,
Petroleum and Mining Engineering,
Marine and Agriculture engineering,
Aerospace Engineering.
A Comparison Between Two Average Modelling Techniques of AC-AC Power ConvertersIAES-IJPEDS
In this paper, a comparative evaluation of two modelling tools for switching AC-AC power converters is presented. Both of them are based on average modelling techniques. The first approach is based on the circuit averaging technique and consists in the topological manipulations, applied to a converter states. The second approach makes use of a state-space averaged model of the converter and is based on analytical manipulations using the different state representations of a converter. The two modelling techniques are applied to a same AC-AC called matrix-reactance frequency converter based on buck-boost topology. These techniques are compared on the basis of their rapidity, quantity of calculations and transformations and its limitations.
Cascade forward neural network based on resilient backpropagation for simulta...Mellah Hacene
Cascade-Forward Neural Network Based on Resilient Backpropagation for Simultaneous Parameters and State Space Estimations of Brushed DC Machines
Advances in Modelling and Analysis B
Passivity Based Control for PV Applications by Using a Buck Power Converter
The use of power converters for everyday applications is becoming more and more important. Current technological applications simultaneously demand a high level of precision and performance, so DC-DC converters have a very important role in systems requiring energy level conversion and adaptation. As part of the work of this paper, we are interested in an analysis of modeling and control law synthesis approaches to ensure stability and a certain level of performance in the entire operating domain. The objective of our research work is therefore to propose a control law whose synthesis is based on a formalized (modeling & control) approach with a view to obtaining a control law adapted to the operating point. The principles used are based on the control and observation by the theory of passivity for the synthesis of control law of buck power converter for PV Applications.
IJRET : International Journal of Research in Engineering and Technology is an international peer reviewed, online journal published by eSAT Publishing House for the enhancement of research in various disciplines of Engineering and Technology. The aim and scope of the journal is to provide an academic medium and an important reference for the advancement and dissemination of research results that support high-level learning, teaching and research in the fields of Engineering and Technology. We bring together Scientists, Academician, Field Engineers, Scholars and Students of related fields of Engineering and Technology.
Master slave vector controlled double induction motor using unity power facto...eSAT Journals
Abstract
In the recent days most of the industries uses Induction motors as the primary loads. In order to meet the total load requirement
multiple motors are used. In this paper two Vector Controlled (VC) Induction Motors and a double closed loop PWM rectifier are
used to explain the operation of Master Slave Configuration. The work mainly concentrates on the operation of a Unity Power factor
Controlled (UPFC) PWM Rectifier as the input source for both the Vector Controlled Induction Motors. This UPFC PWM Rectifier
uses two closed loop pi control algorithms the inner loop controls the current and the outer loop controls the DC voltage. The
proposed model is simulated in Matlab/ Simulink and the results shows good synchronization for two induction motors operated in
master slave configuration.
Keywords: Vector Control, Induction Motor, PWM Rectifier, and Unity Power Factor Control
Power transformer faults diagnosis using undestructive methods and ann for dg...Mellah Hacene
Power transformer faults diagnosis using undestructive methods (Roger and IEC) and artificial neural network for dissolved gas analysis applied on the functional transformer in the Algerian north-eastern: a comparative study
Bouchaoui Lahcene, Kamel Eddine Hemsas, Hacene Mellah, saad eddine benlahneche
Nowadays, power transformer aging and failures are viewed with great attention in power transmission industry. Dissolved gas analysis (DGA) is classified among the biggest widely used methods used within the context of asset management policy to detect the incipient faults in their earlier stage in power transformers. Up to now, several procedures have been employed for the lecture of DGA results. Among these useful means, we find Key Gases, Rogers Ratios, IEC Ratios, the historical technique less used today Doernenburg Ratios, the two types of Duval Pentagons methods, several versions of the Duval Triangles method and Logarithmic Nomograph. Problem. DGA data extracted from different units in service served to verify the ability and reliability of these methods in assessing the state of health of the power transformer. Aim. An improving the quality of diagnostics of electrical power transformer by artificial neural network tools based on two conventional methods in the case of a functional power transformer at Sétif province in East North of Algeria. Methodology. Design an inelegant tool for power transformer diagnosis using neural networks based on traditional methods IEC and Rogers, which allows to early detection faults, to increase the reliability, of the entire electrical energy system from transport to consumers and improve a continuity and quality of service. Results. The solution of the problem was carried out by using feed-forward back-propagation neural networks implemented in MATLAB-Simulink environment. Four real power transformers working under different environment and climate conditions such as: desert, humid, cold were taken into account. The practical results of the diagnosis of these power transformers by the DGA are presented. Practical value.....
International Journal of Engineering Research and Applications (IJERA) is an open access online peer reviewed international journal that publishes research and review articles in the fields of Computer Science, Neural Networks, Electrical Engineering, Software Engineering, Information Technology, Mechanical Engineering, Chemical Engineering, Plastic Engineering, Food Technology, Textile Engineering, Nano Technology & science, Power Electronics, Electronics & Communication Engineering, Computational mathematics, Image processing, Civil Engineering, Structural Engineering, Environmental Engineering, VLSI Testing & Low Power VLSI Design etc.
Dynamic model of A DC-DC quasi-Z-source converter (q-ZSC)IJECEIAES
Two quasi-Z-source DC-DC converters (q-ZSCs) with buck-boost converter gain were recently proposed. The converters have advantages of continuous gain curve, higher gain magnitude and buck-boost operation at efficient duty ratio range when compared with existing q-ZSCs. Accurate dynamic models of these converters are needed for global and detailed overview by understanding their operation limits and effects of components sizes. A dynamic model of one of these converters is proposed here by first deriving the gain equation, state equations and state space model. A generalized small signal model was also derived before localizing it to this topology. The transfer functions (TF) were all derived, the poles and zeros analyzed with the boundaries for stable operations presented and discussed. Some of the findings include existence of right-hand plane (RHP) zero in the duty ratio to output capacitor voltage TF. This is common to the Z-source and quasi-Z-source topologies and implies control limitations. Parasitic resistances of the capacitors and inductors affect the nature and positions of the poles and zeros. It was also found and verified that rather than symmetric components, use of carefully selected smaller asymmetric components L1 and C1 produces less parasitic voltage drop, higher output voltage and current under the same conditions, thus better efficiency and performance at reduced cost, size and weight.
International Journal of Engineering Research and Applications (IJERA) is an open access online peer reviewed international journal that publishes research and review articles in the fields of Computer Science, Neural Networks, Electrical Engineering, Software Engineering, Information Technology, Mechanical Engineering, Chemical Engineering, Plastic Engineering, Food Technology, Textile Engineering, Nano Technology & science, Power Electronics, Electronics & Communication Engineering, Computational mathematics, Image processing, Civil Engineering, Structural Engineering, Environmental Engineering, VLSI Testing & Low Power VLSI Design etc.
International Journal of Engineering Research and Applications (IJERA) is an open access online peer reviewed international journal that publishes research and review articles in the fields of Computer Science, Neural Networks, Electrical Engineering, Software Engineering, Information Technology, Mechanical Engineering, Chemical Engineering, Plastic Engineering, Food Technology, Textile Engineering, Nano Technology & science, Power Electronics, Electronics & Communication Engineering, Computational mathematics, Image processing, Civil Engineering, Structural Engineering, Environmental Engineering, VLSI Testing & Low Power VLSI Design etc.
International Journal of Engineering Research and Applications (IJERA) is an open access online peer reviewed international journal that publishes research and review articles in the fields of Computer Science, Neural Networks, Electrical Engineering, Software Engineering, Information Technology, Mechanical Engineering, Chemical Engineering, Plastic Engineering, Food Technology, Textile Engineering, Nano Technology & science, Power Electronics, Electronics & Communication Engineering, Computational mathematics, Image processing, Civil Engineering, Structural Engineering, Environmental Engineering, VLSI Testing & Low Power VLSI Design etc.
International Journal of Engineering Research and Applications (IJERA) is an open access online peer reviewed international journal that publishes research and review articles in the fields of Computer Science, Neural Networks, Electrical Engineering, Software Engineering, Information Technology, Mechanical Engineering, Chemical Engineering, Plastic Engineering, Food Technology, Textile Engineering, Nano Technology & science, Power Electronics, Electronics & Communication Engineering, Computational mathematics, Image processing, Civil Engineering, Structural Engineering, Environmental Engineering, VLSI Testing & Low Power VLSI Design etc.
International Journal of Engineering Research and Applications (IJERA) is an open access online peer reviewed international journal that publishes research and review articles in the fields of Computer Science, Neural Networks, Electrical Engineering, Software Engineering, Information Technology, Mechanical Engineering, Chemical Engineering, Plastic Engineering, Food Technology, Textile Engineering, Nano Technology & science, Power Electronics, Electronics & Communication Engineering, Computational mathematics, Image processing, Civil Engineering, Structural Engineering, Environmental Engineering, VLSI Testing & Low Power VLSI Design etc.
International Journal of Engineering Research and Applications (IJERA) is an open access online peer reviewed international journal that publishes research and review articles in the fields of Computer Science, Neural Networks, Electrical Engineering, Software Engineering, Information Technology, Mechanical Engineering, Chemical Engineering, Plastic Engineering, Food Technology, Textile Engineering, Nano Technology & science, Power Electronics, Electronics & Communication Engineering, Computational mathematics, Image processing, Civil Engineering, Structural Engineering, Environmental Engineering, VLSI Testing & Low Power VLSI Design etc.
International Journal of Engineering Research and Applications (IJERA) is an open access online peer reviewed international journal that publishes research and review articles in the fields of Computer Science, Neural Networks, Electrical Engineering, Software Engineering, Information Technology, Mechanical Engineering, Chemical Engineering, Plastic Engineering, Food Technology, Textile Engineering, Nano Technology & science, Power Electronics, Electronics & Communication Engineering, Computational mathematics, Image processing, Civil Engineering, Structural Engineering, Environmental Engineering, VLSI Testing & Low Power VLSI Design etc.
International Journal of Engineering Research and Applications (IJERA) is an open access online peer reviewed international journal that publishes research and review articles in the fields of Computer Science, Neural Networks, Electrical Engineering, Software Engineering, Information Technology, Mechanical Engineering, Chemical Engineering, Plastic Engineering, Food Technology, Textile Engineering, Nano Technology & science, Power Electronics, Electronics & Communication Engineering, Computational mathematics, Image processing, Civil Engineering, Structural Engineering, Environmental Engineering, VLSI Testing & Low Power VLSI Design etc.
International Journal of Engineering Research and Applications (IJERA) is an open access online peer reviewed international journal that publishes research and review articles in the fields of Computer Science, Neural Networks, Electrical Engineering, Software Engineering, Information Technology, Mechanical Engineering, Chemical Engineering, Plastic Engineering, Food Technology, Textile Engineering, Nano Technology & science, Power Electronics, Electronics & Communication Engineering, Computational mathematics, Image processing, Civil Engineering, Structural Engineering, Environmental Engineering, VLSI Testing & Low Power VLSI Design etc.
International Journal of Engineering Research and Applications (IJERA) is an open access online peer reviewed international journal that publishes research and review articles in the fields of Computer Science, Neural Networks, Electrical Engineering, Software Engineering, Information Technology, Mechanical Engineering, Chemical Engineering, Plastic Engineering, Food Technology, Textile Engineering, Nano Technology & science, Power Electronics, Electronics & Communication Engineering, Computational mathematics, Image processing, Civil Engineering, Structural Engineering, Environmental Engineering, VLSI Testing & Low Power VLSI Design etc.
International Journal of Engineering Research and Applications (IJERA) is an open access online peer reviewed international journal that publishes research and review articles in the fields of Computer Science, Neural Networks, Electrical Engineering, Software Engineering, Information Technology, Mechanical Engineering, Chemical Engineering, Plastic Engineering, Food Technology, Textile Engineering, Nano Technology & science, Power Electronics, Electronics & Communication Engineering, Computational mathematics, Image processing, Civil Engineering, Structural Engineering, Environmental Engineering, VLSI Testing & Low Power VLSI Design etc.
International Journal of Engineering Research and Applications (IJERA) is an open access online peer reviewed international journal that publishes research and review articles in the fields of Computer Science, Neural Networks, Electrical Engineering, Software Engineering, Information Technology, Mechanical Engineering, Chemical Engineering, Plastic Engineering, Food Technology, Textile Engineering, Nano Technology & science, Power Electronics, Electronics & Communication Engineering, Computational mathematics, Image processing, Civil Engineering, Structural Engineering, Environmental Engineering, VLSI Testing & Low Power VLSI Design etc.
International Journal of Engineering Research and Applications (IJERA) is an open access online peer reviewed international journal that publishes research and review articles in the fields of Computer Science, Neural Networks, Electrical Engineering, Software Engineering, Information Technology, Mechanical Engineering, Chemical Engineering, Plastic Engineering, Food Technology, Textile Engineering, Nano Technology & science, Power Electronics, Electronics & Communication Engineering, Computational mathematics, Image processing, Civil Engineering, Structural Engineering, Environmental Engineering, VLSI Testing & Low Power VLSI Design etc.
International Journal of Engineering Research and Applications (IJERA) is an open access online peer reviewed international journal that publishes research and review articles in the fields of Computer Science, Neural Networks, Electrical Engineering, Software Engineering, Information Technology, Mechanical Engineering, Chemical Engineering, Plastic Engineering, Food Technology, Textile Engineering, Nano Technology & science, Power Electronics, Electronics & Communication Engineering, Computational mathematics, Image processing, Civil Engineering, Structural Engineering, Environmental Engineering, VLSI Testing & Low Power VLSI Design etc.
International Journal of Engineering Research and Applications (IJERA) is an open access online peer reviewed international journal that publishes research and review articles in the fields of Computer Science, Neural Networks, Electrical Engineering, Software Engineering, Information Technology, Mechanical Engineering, Chemical Engineering, Plastic Engineering, Food Technology, Textile Engineering, Nano Technology & science, Power Electronics, Electronics & Communication Engineering, Computational mathematics, Image processing, Civil Engineering, Structural Engineering, Environmental Engineering, VLSI Testing & Low Power VLSI Design etc.
International Journal of Engineering Research and Applications (IJERA) is an open access online peer reviewed international journal that publishes research and review articles in the fields of Computer Science, Neural Networks, Electrical Engineering, Software Engineering, Information Technology, Mechanical Engineering, Chemical Engineering, Plastic Engineering, Food Technology, Textile Engineering, Nano Technology & science, Power Electronics, Electronics & Communication Engineering, Computational mathematics, Image processing, Civil Engineering, Structural Engineering, Environmental Engineering, VLSI Testing & Low Power VLSI Design etc.
A Novel Optimal PI Parameter Tuning Strategy to Improve Constant Switching Pe...IJPEDS-IAES
This paper presents a novel method of optimal Propotional-Intergral (PI)
controller’s parameter tuning strategy in-order to improve the constant
switching performance of 3-phase direct torque control (DTC) shceme. The
DTC sheme is acknowledged to provide fast decoupled control over the
torque output and stator flux via a simple control structure. However, DTC
sheme has two major downsides, which are the inconsistent inverter
switching frequency and high torque output ripple. The main reason that
contributes to these tribulations is the usage of hysteresis comparators in
order to control the output torque. The realization of PI based controller
method as replacement of hyterisis controller in DTC system able to provide
significant solutions to over come the fall back while retaining the simple
control structure of conventional DTC. The combination usage of higher
sampling controller DS1004 and also 3-level cascaded H-bridge multilevel
inverters (CHMI) in this system can further minimize the output torque ripple
by providing higher resolution with lower digital error and greater number of
vectors. This paper presents detail explanation and calculation of optimal PI
parameter tuning strategy consecutively to enhance the performance of 3-
level DTC system. In order to verify the feasibility of the proposed method
experimentation, the proposed method is compared with convention DTC
system via simulation and experiment results.
MODELLING AND IMPLEMENTATION OF AN IMPROVED DSVM SCHEME FOR PMSM DTCpaperpublications3
Abstract: A very widely used drive strategy for PMSM is the field oriented control (FOC), which was proposed in 1971 for induction motors (IMs). However, the FOC scheme is quite complex due to the reference frame transformation and its high dependence upon the motor parameters and speed. To mitigate these problems, a new control strategy for the torque control of induction motor was developed by Takahashi known as the direct torque control (DTC) and by Depenbrock as the direct self control (DSC). The basic direct torque control (DTC) scheme may cause undesired torque, flux and current ripples because of the small number of applicable voltage vectors. The control system should be able to generate any voltage vector, implying the use of space vector modulation (SVM) which complicates the control scheme. The discrete space vector modulation (DSVM) method was proposed for DTC to overcome this problem which replaces the simple switching table by several switching tables, to apply a combination of three voltage vectors in the same sampling period. In this paper, after a brief review of the primary concept of DSVM DTC technique, a new scheme of DSVM DTC for PMSM is proposed with a new set of switching tables taking into account the motor speed and the absolute values of torque and flux feedback errors. In one fixed sampling time interval, three vectors are applied to the motor including the two null vectors. Comparisons of the basic DTC and the improved DSVM DTC schemes are made based on the system performance and switching loss. For this purpose the DSVM technique uses prefixed time intervals within a sampling cycle to synthesize a higher number of voltage vectors than the basic DTC scheme. A set of switching table is carried out to minimize the torque error. An optimal vector selector is developed to reduce the switching loss and make the system more stable. The sampling period does not need to be doubled in order to achieve a mean switching frequency practically equal to that of the basic DTC scheme. For a comparable performance, the switching loss of the proposed scheme is less than that of the basic DTC method. The vector application sequence is investigated and an optimal algorithm is developed to reduce the switching loss and torque ripple. Simulation and experiments on the improved DSVM DTC are carried out and compared with those on the basic DTC scheme.
Three-Level DTC Based on Fuzzy Logic and Neural Network of Sensorless DSSM Us...IJPEDS-IAES
This paper presents a direct torque control is applied for salient-pole double star synchronous machine without mechanical speed and stator flux linkage sensors. The estimation is performed using the extended Kalman filter known by it is ability to process noisy discrete measurements. Two control approaches using fuzzy logic DTC, and neural network DTC are proposed and compared. The validity of the proposed controls scheme is verified by simulation tests of a double star synchronous machine. The stator flux, torque, and speed are determined and compared in the above techniques. Simulation results presented in this paper highlight the improvements produced by the proposed control method based on the extended Kalman filter under various operation conditions.
In the proposed approach,instead of a conventional 3- Phase inverter a component minimized single pha se inverter is utilized which reduces the cost of the inverter,th e switching losses,and the complexity of interface circuits to generate logic signals. A performance comparison of the prop osed inverter fed drive with a conventional 3Phase inverter fed drive is also mode in terms of speed response and t otal harmonic distortion (THD) of the stator curren t. The proposed inverter fed IM drive is found acceptable consideri ng its cost reduction and other advantageous featur es. A general pulse width modulation (PWM) method for c ontrol of 1-phase inverters is presented. The vecto r PWM offers a simple method to select three or four vectors tha t effectively synthesize the desired output voltage,even in presence of voltage oscillations across the two dc-link capacit ors. The influence of different switching patterns on output voltage symmetry,current waveform,switching frequency and common mode voltage can be examined. The paper als o discusses how the use of the wye and delta connecti ons of the motor windings affects the implementatio n of the pulse width modulator.
Direct Torque Control (DTC) is widely applied for ac motor drives as it offers high performance torque control with a simple control strategy. However, conventional DTC poses some disadvantages especially in term of variable switching frequency and large torque ripple due to the utilization of torque hysteresis controller. Other than that, performance of conventional DTC fed by two-level inverter is also restricted by the limited numbers of voltage vectors which lead to inappropriate selection of voltage vectors for different speed operations. This research aims to propose a Constant Switching Frequency (CSF) torque controller for DTC of induction motor (IM) fed by three-level Neutral-Point Clamped (NPC) inverter. The proposed torque controller utilizes PI controller which apply different gain for different speed operation. Besides, the utilization of NPC inverter provides greater number of voltage vectors which allow appropriate selection of voltage vectors for different operating condition. Using the proposed method, the improvement of DTC drives in term of producing a constant switching operation and minimizing torque ripple are achieved and validated via experimental results.
Enhanced Torque Control and Reduced Switching Frequency in Direct Torque Cont...IJPEDS-IAES
Direct Torque Control (DTC) of induction machine has received wide
acceptance in many adjustable speed drive applications due to its simplicity
and high performance torque control. However, the DTC using a common
two-level inverter poses two major problems such as higher switching
frequency (or power loss) and larger torque ripple. These problems are due to
inappropriate voltage vectors which are selected among a limited number of
voltage vectors available in two-level inverter. The proposed research aims to
formulate an optimal switching strategy using Dual-Inverter Supplied Drive
for high performances of DTC. By using dual-inverter supplied, it provides
greater number of voltage vectors which can offer more options to select the
most appropriate voltage vectors. The most appropriate voltage vectors
should able to produce minimum torque slope but sufficient to satisfy torque
demands. The identification is accomplished by using an equation of rate of
change of torque which is derived from the induction machine equations. The
proposed strategy also introduces a block of modification of torque error
status which is responsible to modify the status such that it can determine the
most optimal voltage vectors from a look-up table, according to motor
operating conditions. The improvements obtained are as follows; 1)
minimization of switching frequency (reduce power loss), and 2) reduction of
torque ripple. Some improvements obtained in the proposed strategy were
verified via experimentations.
International Journal of Engineering Research and Applications (IJERA) is an open access online peer reviewed international journal that publishes research and review articles in the fields of Computer Science, Neural Networks, Electrical Engineering, Software Engineering, Information Technology, Mechanical Engineering, Chemical Engineering, Plastic Engineering, Food Technology, Textile Engineering, Nano Technology & science, Power Electronics, Electronics & Communication Engineering, Computational mathematics, Image processing, Civil Engineering, Structural Engineering, Environmental Engineering, VLSI Testing & Low Power VLSI Design etc.
Improvise 3-Level DTC of Induction Machine using Constant Switching Frequency...IJPEDS-IAES
This paper presents the advantage of using optimal PI parameter tuning strategy of constant switching method in the three phase Direct torque control (DTC) scheme. The DTC system is known to offer fast decoupled control of torque and flux via a simple control structure. Nevertheless, DTC system has two major drawbacks, which are the variable inverter switching frequency and high torque output ripple. The major factorthat contributes to these problems the usage of hysteresis based comparators to control the output torque. The implementation of PI based constant switching method in DTC able to solve these problems while retaining the simple control structure of conventional DTC. The combination usage of 3-level CHMI in this system can further minimize the output torque ripple by providing greater number of vectors. This paper presents detail explanation and calculationof optimal PI parameter tuning strategyconsecutively to enhance the performance of 3-level DTC system. In order to validate the feasibility, the proposed method compared with convention DTC system via simulation and experiment results.
Closed Loop Speed Control of a BLDC Motor Drive Using Adaptive Fuzzy Tuned PI...IJERA Editor
Brushless DC Motors are widely used for many industrial applications because of their high efficiency, high
torque and low volume. This paper proposed an improved Adaptive Fuzzy PI controller to control the speed of
BLDC motor. This paper provides an overview of different tuning methods of PID Controller applied to control
the speed of the transfer function model of the BLDC motor drive and then to the mathematical model of the
BLDC motor drive. It is difficult to tune the parameters and get satisfied control characteristics by using normal
conventional PI controller. The experimental results verify that Adaptive Fuzzy PI controller has better control
performance than the conventional PI controller. The modeling, control and simulation of the BLDC motor have
been done using the MATLAB/SIMULINK software. Also, the dynamic characteristics of the BLDC motor (i.e.
speed and torque) as well as currents and voltages of the inverter components are observed by using the
developed model.
OPTIMAL TORQUE RIPPLE CONTROL OF ASYNCHRONOUS DRIVE USING INTELLIGENT CONTROL...elelijjournal
The dynamic performance of an asynchronous machine when operated with cascaded Voltage Source Inverter using Space Vector Modulation (SVM) technique is presented in this paper. A classical model of Induction Motor Drive based on Direct Torque Control (DTC) method is considered which displays
appreciable run-time operation with very simple hysteresis control scheme. Direct control of the torque and flux variables is achieved by choosing suitable inverter voltage space vector from a lookup table. Under varying torque conditions the performance of the drive system is verified using MATLAB/Simulink software tool. The ripple content in the torque parameter is significant when traditional PI controller and Fuzzy approach are configured in the proposed system. Finally, by replacing the PI-Fuzzy controller with Hybrid Controller the torque ripple minimization can be achieved during no-load and loaded conditions.
The induction motors are indispensable motor types for industrial applications due to its wellknown advantages. Therefore, many kind of control scheme are proposed for induction motors over the past years and direct torque control has gained great importance inside of them due to fast dynamic torque response behavior and simple control structure. This paper suggests a new approach on the direct torque controlled induction motors, Fuzzy logic based space vector
modulation, to overcome disadvantages of conventional direct torque control like high torque ripple. In the proposed approach, optimum switching states are calculated by fuzzy logic
controller and applied by space vector pulse width modulator to voltage source inverter. In order to test and compare the proposed DTC scheme with conventional DTC scheme
simulations, in Matlab/Simulink, have been carried out in different speed and load conditions. The simulation results showed that a significant improvement in the dynamic torque and speed responses when compared to the conventional DTC scheme.
A NEW FUZZY LOGIC BASED SPACE VECTOR MODULATION APPROACH ON DIRECT TORQUE CON...csandit
The induction motors are indispensable motor types for industrial applications due to its wellknown
advantages. Therefore, many kind of control scheme are proposed for induction motors
over the past years and direct torque control has gained great importance inside of them due to
fast dynamic torque response behavior and simple control structure. This paper suggests a new
approach on the direct torque controlled induction motors, Fuzzy logic based space vector
modulation, to overcome disadvantages of conventional direct torque control like high torque
ripple. In the proposed approach, optimum switching states are calculated by fuzzy logic
controller and applied by space vector pulse width modulator to voltage source inverter. In
order to test and compare the proposed DTC scheme with conventional DTC scheme
simulations, in Matlab/Simulink, have been carried out in different speed and load conditions.
The simulation results showed that a significant improvement in the dynamic torque and speed
responses when compared to the conventional DTC scheme.
Dsp based implementation of field oriented control of three phase induction m...eSAT Journals
Abstract
The objective of this paper is to presents a practical implementation of field oriented control of three-phase induction motor based on Space Vector Pulse Width Modulation technique using Digital Signal Processing (DSP) board TMS320F2812. The control algorithm for the drive application is built with Code Composer Studio version 3.1. The motor control is divided into two control loops; inner current loop and outer speed control loop using PI controller. The rotor flux quantities are estimated using computational rotor time constant, rotor angular velocity and stator current. As a feedback of field oriented control, an incremental encoder is attached at the motor shaft and a Hall effect current sensor is used to detect the sent current to the motor. The performance of the drives system is tested under different speed command and load disturbances
Index Terms: digital signal processor, field oriented control, induction motor, Space Vector Pulse Width Modulation
Fuzzy logic based direct torque control of induction motor with space vector ...ijscai
The induction motors have wide range of applications for due to its well-known advantages like brushless
structures, low costs and robust performances. Over the past years, many kind of control methods are
proposed for the induction motors and direct torque control has gained huge importance inside of them due
to fast dynamic torque responses and simple control structures. However, the direct torque control method
has still some handicaps against the other control methods and most of the important of these handicaps is
high torque ripple. This paper suggests a new approach, Fuzzy logic based space vector modulation, on
the direct torque controlled induction motors and aim of the approach is to overcome high torque ripple
disadvantages of conventional direct torque control. In order to test and compare the proposed direct
torque control method with conventional direct torque control method simulations, in Matlab/Simulink,
have been carried out in different working conditions. The simulation results showed that a significant
improvement in the dynamic torque and speed responses when compared to the conventional direct torque
control method.
Total Harmonic Distortion of Dodecagonal Space Vector ModulationIJPEDS-IAES
Space vector modulation technique is one of the best PWM techniques which have been implemented to the Multilevel inverter circuit to get the purely sinusoidal cuurent. This is a important algorithm which is implemented in open wind induction motor. This type of I.M has great impact on Electric Drive system. SVM is nothing but the technique of switching algorithm. The Hexagonal space vector modulation has been implemented before, but elimination of higher order harmonics is not possible. Torque pulsation arises. Speed control of Induction motor was not smooth. So Dodecagonal (12) structure developed. A 12 side polygonal space vector structure is meant for eliminating (6n±1) harmonics in the phase current waveform throughout the modulating range. A high resolution of PWM technique is proposed involving multiple 12 sided polygonal (Dodecagonal) structure that can generate highly sinusoidal voltage at a reduced switching frequency. In this paper different values of frequencies have been taken for harmonic analysis. SVM method features a higher level of dc-bus voltage utilization compared to the conventional PWM.
Improved Torque Control Performance in Direct Torque Control using Optimal Sw...IJPEDS-IAES
This paper presents the significant improvement of Direct Torque Control (DTC) of 3-phases induction machine using a Cascaded H- Bidge Multilevel Inverter (CHMI). The largest torque ripple and variable switching frequency are known as the major problem founded in DTC of induction motor. As a result, it can diminish the performance induction motor control. Therefore, the conventional 2- level inverter has been replaced with CHMI the in order to increase the performance of the motor either in dynamic or steady-state condition. By using the multilevel inverter, it can produce a more selection of the voltage vectors. Besides that, it can minimize the torque ripple output as well as increase the efficiency by reducing the switching frequency of the inverter. The simulation model of the proposed method has been developed and tested by using Matlab software. Its improvements were also verified via experimental results.
International Journal of Engineering Research and Applications (IJERA) is an open access online peer reviewed international journal that publishes research and review articles in the fields of Computer Science, Neural Networks, Electrical Engineering, Software Engineering, Information Technology, Mechanical Engineering, Chemical Engineering, Plastic Engineering, Food Technology, Textile Engineering, Nano Technology & science, Power Electronics, Electronics & Communication Engineering, Computational mathematics, Image processing, Civil Engineering, Structural Engineering, Environmental Engineering, VLSI Testing & Low Power VLSI Design etc.
GDG Cloud Southlake #33: Boule & Rebala: Effective AppSec in SDLC using Deplo...James Anderson
Effective Application Security in Software Delivery lifecycle using Deployment Firewall and DBOM
The modern software delivery process (or the CI/CD process) includes many tools, distributed teams, open-source code, and cloud platforms. Constant focus on speed to release software to market, along with the traditional slow and manual security checks has caused gaps in continuous security as an important piece in the software supply chain. Today organizations feel more susceptible to external and internal cyber threats due to the vast attack surface in their applications supply chain and the lack of end-to-end governance and risk management.
The software team must secure its software delivery process to avoid vulnerability and security breaches. This needs to be achieved with existing tool chains and without extensive rework of the delivery processes. This talk will present strategies and techniques for providing visibility into the true risk of the existing vulnerabilities, preventing the introduction of security issues in the software, resolving vulnerabilities in production environments quickly, and capturing the deployment bill of materials (DBOM).
Speakers:
Bob Boule
Robert Boule is a technology enthusiast with PASSION for technology and making things work along with a knack for helping others understand how things work. He comes with around 20 years of solution engineering experience in application security, software continuous delivery, and SaaS platforms. He is known for his dynamic presentations in CI/CD and application security integrated in software delivery lifecycle.
Gopinath Rebala
Gopinath Rebala is the CTO of OpsMx, where he has overall responsibility for the machine learning and data processing architectures for Secure Software Delivery. Gopi also has a strong connection with our customers, leading design and architecture for strategic implementations. Gopi is a frequent speaker and well-known leader in continuous delivery and integrating security into software delivery.
JMeter webinar - integration with InfluxDB and GrafanaRTTS
Watch this recorded webinar about real-time monitoring of application performance. See how to integrate Apache JMeter, the open-source leader in performance testing, with InfluxDB, the open-source time-series database, and Grafana, the open-source analytics and visualization application.
In this webinar, we will review the benefits of leveraging InfluxDB and Grafana when executing load tests and demonstrate how these tools are used to visualize performance metrics.
Length: 30 minutes
Session Overview
-------------------------------------------
During this webinar, we will cover the following topics while demonstrating the integrations of JMeter, InfluxDB and Grafana:
- What out-of-the-box solutions are available for real-time monitoring JMeter tests?
- What are the benefits of integrating InfluxDB and Grafana into the load testing stack?
- Which features are provided by Grafana?
- Demonstration of InfluxDB and Grafana using a practice web application
To view the webinar recording, go to:
https://www.rttsweb.com/jmeter-integration-webinar
Neuro-symbolic is not enough, we need neuro-*semantic*Frank van Harmelen
Neuro-symbolic (NeSy) AI is on the rise. However, simply machine learning on just any symbolic structure is not sufficient to really harvest the gains of NeSy. These will only be gained when the symbolic structures have an actual semantics. I give an operational definition of semantics as “predictable inference”.
All of this illustrated with link prediction over knowledge graphs, but the argument is general.
Accelerate your Kubernetes clusters with Varnish CachingThijs Feryn
A presentation about the usage and availability of Varnish on Kubernetes. This talk explores the capabilities of Varnish caching and shows how to use the Varnish Helm chart to deploy it to Kubernetes.
This presentation was delivered at K8SUG Singapore. See https://feryn.eu/presentations/accelerate-your-kubernetes-clusters-with-varnish-caching-k8sug-singapore-28-2024 for more details.
Encryption in Microsoft 365 - ExpertsLive Netherlands 2024Albert Hoitingh
In this session I delve into the encryption technology used in Microsoft 365 and Microsoft Purview. Including the concepts of Customer Key and Double Key Encryption.
UiPath Test Automation using UiPath Test Suite series, part 3DianaGray10
Welcome to UiPath Test Automation using UiPath Test Suite series part 3. In this session, we will cover desktop automation along with UI automation.
Topics covered:
UI automation Introduction,
UI automation Sample
Desktop automation flow
Pradeep Chinnala, Senior Consultant Automation Developer @WonderBotz and UiPath MVP
Deepak Rai, Automation Practice Lead, Boundaryless Group and UiPath MVP
LF Energy Webinar: Electrical Grid Modelling and Simulation Through PowSyBl -...DanBrown980551
Do you want to learn how to model and simulate an electrical network from scratch in under an hour?
Then welcome to this PowSyBl workshop, hosted by Rte, the French Transmission System Operator (TSO)!
During the webinar, you will discover the PowSyBl ecosystem as well as handle and study an electrical network through an interactive Python notebook.
PowSyBl is an open source project hosted by LF Energy, which offers a comprehensive set of features for electrical grid modelling and simulation. Among other advanced features, PowSyBl provides:
- A fully editable and extendable library for grid component modelling;
- Visualization tools to display your network;
- Grid simulation tools, such as power flows, security analyses (with or without remedial actions) and sensitivity analyses;
The framework is mostly written in Java, with a Python binding so that Python developers can access PowSyBl functionalities as well.
What you will learn during the webinar:
- For beginners: discover PowSyBl's functionalities through a quick general presentation and the notebook, without needing any expert coding skills;
- For advanced developers: master the skills to efficiently apply PowSyBl functionalities to your real-world scenarios.
DevOps and Testing slides at DASA ConnectKari Kakkonen
My and Rik Marselis slides at 30.5.2024 DASA Connect conference. We discuss about what is testing, then what is agile testing and finally what is Testing in DevOps. Finally we had lovely workshop with the participants trying to find out different ways to think about quality and testing in different parts of the DevOps infinity loop.
Dev Dives: Train smarter, not harder – active learning and UiPath LLMs for do...UiPathCommunity
💥 Speed, accuracy, and scaling – discover the superpowers of GenAI in action with UiPath Document Understanding and Communications Mining™:
See how to accelerate model training and optimize model performance with active learning
Learn about the latest enhancements to out-of-the-box document processing – with little to no training required
Get an exclusive demo of the new family of UiPath LLMs – GenAI models specialized for processing different types of documents and messages
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Gr3612061213
1. Papi Naidu Tentu et al Int. Journal of Engineering Research and Applications
ISSN : 2248-9622, Vol. 3, Issue 6, Nov-Dec 2013, pp.1206-1213
RESEARCH ARTICLE
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OPEN ACCESS
An Improved Direct Torque Control for Three-Level InverterFed Induction Motor Drive
Papi Naidu Tentu1, Prof K.Vijay Kumar 2
1
2
Pg Student, Dadi Institute Of Engg.& Tech, Anakapalle, Visakhapatnam,Andhra Pradesh, India.
professor, Dept.Of Eee, Dadi Institute Of Engg.& Tech, Visakhapatnam,.India.
ABSTRACT
A three-level neutral-point-clamped inverter-fed induction motor drive is proposed in this paper. The
conventional direct torque control (DTC) switching table fails to consider the circuit limitations, such as neutralpoint-balance and smooth vector switching, caused by the topology of a three-level inverter. Two kinds of
modified schemes for three-level DTC are proposed to solve these problems. They provide performance
enhancement while maintaining robustness and simplicity.
In the present project the DTC is performed by using space vector pulse width modulation (SVPWM) technique
in order to achieve smooth operation of drive.
Fuzzy logic control and the speed-adaptive flux observer are introduced to enhance the performance of the
system. The issue of large starting current can be investigated and solved by introducing the technique of preexcitation. The effectiveness of the proposed schemes is confirmed by simulation using MATLAB/SIMULINK
implementation and experimental validation.
Index Terms — AC motor drives, adaptive observer, fuzzy logic, induction motor (IM) drives, three-level
inverter, torque control.
I.
INTRODUCTION
Direct torque control (DTC) has emerged as
an alternative to field-oriented control (FOC) for highperformance ac drives, since it was first proposed in
the mid-1980s .The merits of DTC can be summarized
as fast torque response, simple structure (no need of
complicated coordinate transformation, current
regulation, or modulation block), and robustness
against motor parameter variation. On the other hand,
multilevel inverters have attracted considerable
attention, especially in high-power application areas.
The three-level neutral-point-clamped (NPC) inverter
is one of the most commonly used multilevel inverter
topologies in high-power ac drives.
Compared to the standard two-level inverter, the
three-level inverter presents its superiority in terms of
lower voltage distortion, lower stress across the
semiconductors, less harmonic content, and lower
switching frequency. Because of these merits
mentioned, the three-level inverter-fed DTC motor
drive has become an important research topic in
industry and the academic community over the past
decades.
Compared to two-level DTC, three-level
DTC motor drives have two particular aspects. The
first is concerned with electromagnetic performance
enhancement, including torque ripple reduction and
low-speed performance improvement in a similar
manner to that of two-level DTC.
The second is inherited from the topology of
three-level inverter, i.e., the neutral point potential
balance and smooth vector switching. Neutral point
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unbalance will cause higher voltage in the power
semiconductors. This increases the demand of
capacity so that the cost increases. The balance of
neutral point potential can be achieved by exploiting
the opposite effect of redundant vectors on the neutral
point potential.
Smooth vector switching requires that there
is no excessive voltage “jumps” in both phase voltage
and line voltage. Phase voltage “jumps” fail to utilize
the advantages of three-level inverter and may
endanger the safe operation of inverter by causing full
dc voltage across one switch during transient
commutation, especially when the inverter uses only
one snubber circuit for three phases. Line voltage
“jumps” produce more harmonic content in output
voltage waveform, which is unfriendly to the motor
and increase the burden on the filter.
Most of the literature on three-level inverter
DTC motor drives concentrates on performance
improvement. These employ complicated algorithms
based
on
analytical
methods,
coordinate
transformation, and continuous space vector
modulation, among others.
Although good performance, such as torque
ripple reduction or fixed switching frequency, was
achieved, they failed to consider the limitations caused
by the circuit topology, i.e., neutral point potential
balance and smooth vector switching was almost not
mentioned at all.
However, there still exists the possibility of
undesired excessive line voltage jumps, e.g., from
++− to + - - . The aim of this paper is to achieve high1206 | P a g e
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performance DTC for a three-level inverter-fed
induction motor (IM) drive, as well as considering the
neutral point potential balance and smooth vector
switching.
Fig 1.1 BASIC THREE LEVEL INVERETR
Two kinds of DTC schemes are proposed to
obtain high-performance control of torque and stator
flux and the switching principle is illustrated to meet
the limitations required by the topology of three-level
inverter. As DTC is often referred for its drawbacks of
large starting-up current and flux droop at low speed,
the technology of pre-excitation is introduced to limit
the starting current.
To enhance the low-speed performance, a
fuzzy logic controller (FLC) is incorporated in the
outer speed loop to improve the speed response and a
speed-adaptive flux observer with novel gain and load
torque observation is employed to estimate stator flux,
torque, and rotor speed over a wide speed range.
Simulations, as well as experimental results,
are presented to validate the effectiveness of the
schemes proposed in this paper.
II.
PRINCIPLE OF DTC AND THREELEVEL INVERTER
2.1. Three-Level Inverter
The main circuit of a three-level inverter is
illustrated in Fig. 1.1 and there are three states for onephase output: +Udc/2, 0, and−Udc/2, with the neutral
point as reference. To be more universal, the negative
dc bus voltage will be selected as reference ground,
and the three states are indicated by “2,” “1,” and “0,”
for “+Udc/2,” “0,” and “−Udc/2,” respectively. More
output levels provide more freedom in vector selection
and it is possible to synthesize waveforms that are
more sinusoidal in shape. However, the complexity of
vector selection rises with the number of vectors. In
addition, there are further problems, including neutral
point balance and smooth vector switching, which
need to be carefully solved.
2.2. Basic Principle of DTC
A mathematical model of an IM described by
space vectors in a stationary frame can be expressed as
follows
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us = Rs is + p ψs
0 = Rr ir + p ψr – jωr ψr
ψs = Ls is + Lm ir
ψr = Lmis + Lr ir
2.1
2.2
2.3
2.4
where us , is , ir , ψs , and ψr are the stator
voltage vector, stator current vector, rotor current
vector, stator flux linkage vector, and rotor flux
linkage vector, respectively; Rs , Rr , Ls , Lr , and
Lm are the stator resistance, rotor resistance, stator
inductance, rotor inductance, and mutual inductance,
respectively; and ωr is the rotor speed and p = d/dt is
the differential operator.
From the stator voltage equation (2.1), it can
be seen that, by omitting the stator resistance voltage
drop, the stator flux can be controlled directly from
the stator voltage. The electromagnetic torque can be
obtained from
Te =
= Te =
2.5
where δsr is the spatial angle between the
stator and rotor fluxes, Np is the motor pole-pair
number, and Te is the electromagnetic torque. In DTC,
the amplitude of the stator flux is kept constant and a
fast torque response is obtained by changing angle δsr
quickly. From (2.1)–(2.4), the relationship between
the stator and rotor fluxes can be obtained as
P
+(
)
=
2.6
where σ = 1− L2 m/(LsLr ) and Tr = Lr/Rr . Equation
(2.6) indicates that the dynamic response of the rotor
flux is a first-order lag with respect to the stator flux,
so the torque can be changed quickly by changing the
angle of stator flux.
III.
TORQUE AND FLUX RIPPLE
REDUCTION IN DTC
The conventional switching table for twolevel DTC cannot be directly extended to three-level
DTC. This is because it is not only the performance
that is of concern, the limitation caused by the
topology of three-level inverter also should be
considered. Two kinds of scheme for three-level DTC
are proposed in this paper to solve these problems.
3.1. DTC Method - I
The first DTC scheme utilizes the vectors of
the three-level inverter directly and inserts appropriate
intermediate vectors to meet the demand of neutral
point balance and smoothed vector switching.The
switching principle is described in detail in the
following. First, the vector is selected according to the
demand of the flux and torque; vector switching and
neutral point balance will be considered later. Fig.3.1
shows the space vector diagram for a three-level DTC
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control strategy and its sector division. The 27 vectors
are marked by V1,V2 . . .V27. There are 12 sectors
and the shadowed area is the first sector, which is
different from that of the conventional two-level DTC.
The basic principles of the vector selection are shown
in Table 3.1 and these meet the demands of the flux
and torque; k represents the stator flux located in kth
sector. In addition, “↑” means increase, “↓”means
decrease, and “=”means no change is needed.
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There are three aspects with respect to
voltage jumps: 1) phase voltage jump, 2) line voltage
jump, and 3) three-phase jump at the same time.
High-voltage jump increases harmonic
content and the stress across power semiconductors,
which negates the advantages of the three-level
inverter. To overcome this problem, an appropriate
intermediate vector should be inserted to meet the
requirement of the voltage jump.
Another issue is the problem of neutral point
balance, which is inherited from the topology of threelevel inverter. Neutral point balance is mainly
controlled by selecting appropriate small vectors; this
is because of the opposite effects of redundant vectors.
In this paper, we also adopt the redundant
states of small vectors to keep the neutral point
balance.
The final vector selection rules are obtained
by considering the aspects introduced earlier, and the
principles are summarized as follows.
Step I: Select vector according to the demands for
flux and torque, which are listed in Table 3.1.
Step II:
If the selected vector cannot meet the
requirement of the voltage jump and neutral point
balance, an appropriate intermediate vector
will be inserted.
Fig. 3.1. SPACE VECTOR DIAGRAM FOR THE
THREE-LEVEL DTC.
TABLE 3.1
VECTOR SELECTION TABLE FOR THREELEVEL DTC
It should be noted that there may exist more
than two vectors to meet the demands of the flux, and
the one which meets the torque response better is
preferred. However, in many cases, the selected vector
usually cannot meet the requirements of the vector
switching and neutral point balance, which means that
the selected vector cannot be applied to the three-level
inverter directly.
For example, suppose the stator flux is
located in the first sector, and the working voltage
vector at the moment is V1(200). To increase the stator
flux and torque, according to Table 3.1, V3(220)
would be selected. But there is a high-voltage jump in
phase B from 0 to 2, which should be avoided. In this
case, V2(210) will be inserted as an intermediate
vector to smooth the high-voltage jump.
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The principles for selecting the intermediate vectors
are as follows.
1) Large vectors or middle vectors should be selected
preferably to increase the utilization ratio of
the dc bus.
2) Middle vectors can switch to adjacent small
vectors and large vectors freely.
3) Large vectors can switch to the small vectors in
the same spatial orientation.
4) Small vectors can switch to zero vectors freely.
5) When small vectors are available, select the one,
which can meet the requirement of neutral
Point balance. Using the steps earlier, an
appropriate vector can be selected to meet the
demand of the flux and torque, as well as the
requirement of voltage jump and neutral point
balance, which ensures the safe operation of the
three-level inverter.
3.2. DTC Method - II
In DTC method -I, by inserting the
appropriate intermediate vector, the problems of
neutral point balance and smooth vector switching
were solved. However, it may degrade the
performance of torque and increase the complexity of
vector selection, so another scheme is proposed here.
Method - II makes use of synthesizing
vectors, which is termed discrete space vector
modulation (SVPWM). This was first proposed in
two-level DTC. The two-level SVPWM-DTC
incorporates a more complicated and accurate
switching table by dividing one sampling period into
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two or three intervals, and thus, more vectors are
obtained.
Speed is also taken into account and more
levels of hysteresis are adopted to make the switching
table more accurate. The benefits of SVPWM-DTC
are reduced torque and flux ripple at a little extra
expense of computational time.
This paper extends SVPWM to three-level
DTC by using synthesizing vectors and the main aim
of introducing SVPWM is to solve the problems of
neutral point balance and smooth vector switching. To
reduce the complexity of the algorithm, the same
structure as Table 3.1 is adopted and the speed was not
taken into account in the switching table. First, we
should synthesize some vectors, which are expected to
solve the problems of neutral point balance and
smooth switching between any two vectors
simultaneously.
This means that the vector selection,
according to the need of the torque and flux, is
decoupled from the circuit limitation introduced by the
three-level topology. A series of novel synthesizing
vectors are produced, which are illustrated in Fig. 3.2
and marked by V s1, V s2, . . . , V s12.
Take Vs1 , for example, it is synthesized by
the nearest three vectors, namely, V1(200), V2 (210),
and V13/V14 (100/211). The duration time of each
vector can be calculated easily by utilizing the
principle of volt-second balance. To smooth the vector
switching, zero vector V26(111) is incorporated at the
beginning and ending of each synthesize sequence,
taking up 10% or less duty of the whole period.
The 12 synthesizing vectors are distributed
uniformly in the fixed-angle space (15◦ for V s1 ) with
constant or variable amplitude.
In this paper, constant amplitude for the
synthesis vector is selected for simplicity, so the
duration of each vector in Vs1 ,V s2 , . . . ,V s12 can be
obtained offline and stored in a look-up table for real
time implementation. The final synthesizing vectors
are listed in Table 3.2 and the sector division for threelevel DTC is presented in Fig. 3.2, which has a 15◦
shift compared to that in Fig. 3.1. From Table 3.1, it is
seen that the switching between any arbitrary two
vectors or adjacent vectors in a synthesis sequence are
smooth. The neutral point balance can be solved by
adjusting the “lasting time” of the small vectors in one
sampling period. Taking Vs1 as an example, 211 and
100 are a pair of small vectors and their total “lasting
time” is fixed during one sampling period, but their
individual working time can be arranged according to
the requirement of neutral point balance.
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Fig. 3.2 SYNTHESIS VECTOR DIAGRAM.
TABLE 3.2
NOVEL VECTOR SYNTHESIS
DTC method-II employs the same switching
table, as shown in Table 3.1, except that the selected
vector is replaced by the novel synthesis vector listed
in Table3.2. For example, if the selected vector
number is k according to Table 3.1, the synthesized
vector Vsk will be selected as the output vector, and
number 26 means the zero vector 111.
For DTC method - I, a further step- II should
be taken before the final vector is selected; however,
this process is not needed in method-II, which
simplifies the selection of vector. An example of
switching pattern for the two kinds of DTC method is
illustrated in Fig. 3.3. It is seen that for DTC methodI, there is only one vector in one sampling period,
while there is a sequence of vectors for DTC method II, with 111 as the beginning and ending.
Fig. 3.3 Example of switching pattern. (a) DTC
method I. (b) DTC method II.
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Fig. 3.4. Diagram of the FLC.
IV.
PERFORMANCE ENHANCEMENT
OF DTC
To enhance the dynamic performance and
steady-state accuracy, as well as robustness to external
disturbance and motor parameters variations, FLC is
used in the outer speed loop. Furthermore, a full-order
speed-adaptive flux observer with novel gains is
employed in this paper, and a load torque observation
is introduced to improve the dynamic response of the
speed estimation. Also, the well-known problem of
large start-up current in DTC is addressed by
introducing the technique of pre excitation. These
three aspects are described in this section in detail.
4.1 Fuzzy Logic Speed Control
FLC can handle complicated nonlinear
systems, which have a degree of uncertainty. It does
not require exact system modeling and parameters;
this makes FLC very suitable for motor drive control.
A classical FLC is composed of three parts:
fuzzification of input variables, fuzzy reasoning, and
defuzzification. A diagram for the FLC used in this
paper is illustrated in Fig. 4.1. The inputs are the error
between commanding value and real value, and its
derivative. The output is the control increment du,
whose integral is the real output.
Fig. 4.1 Input membership function.
The input and output variables are scaled to the range
of (−1.4, 1.4). For the input variables, there are seven
variables defined in the fuzzy sets: PB,PM, PS, Z, NS,
NM, and NB in descending order. To improve the
dynamic performance and obtain more refined output,
two other variables are added in the fuzzy sets for the
output variables, i.e., PVB and NVB. Figs. 6 and 7
show the membership functions of the inputs and the
output, respectively. To obtain a fast response for
dynamic performance, and high accuracy for steady
state, the asymmetric triangle is selected as the
membership function, which is different from the
conventional design. Table III shows the inference
rule used in this paper, which is the key part of the
FLC. By careful design of the inference rule, excellent
performance can be achieved. The mapping
relationship between the input and the output variable
is illustrated in Fig. 4.3.
4.2 Speed-Adaptive Flux Observer
Motor drives can work in a hostile
environment, which increases their reliability and
decreases their complexity and the cost of the system.
Hence, operation is very attractive proposition in
many industrial applications. Among various
approaches, observer-based techniques are very
popular and versatile. Compared with open-loop speed
estimation techniques, the observer-based methods are
more robust to motor parameter variations because
they introduce an error feedback of the stator current
estimation. In a classical observer, the gain is such
designed that the poles of observer are proportional to
those of the IM (usually a factor k > 1). This strategy
of gain selection results in poles with large imaginary
parts, which may cause instability in high-speed
operation. In addition, the observer gain usually
contains speed-dependent terms, which may be
affected by the accuracy of the observed speed. This
paper adopts a speed-adaptive flux observer with
novel gains to improve the stability of the system.
Load torque observation is also incorporated to
enhance the dynamic response of the speed estimation.
The mathematical model of the observer can be
expressed as follows
P s = -[(
s+
(
-
+
Fig.4.2. Output membership function.
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s)
-
4.1
P
+us+
s)
P
=
(λLr
- 4.2
(T
e
–T L) + Kw [∆is *
s)]
4.3
PT
L=
- KT [∆is *( λLr
s)]
-
4.4
TABLE 4.1
RULE MATRIX OF FLC
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4.3 Decreasing Starting Current
To decrease the starting current and maintain
sufficient starting torque, pre excitation of the stator
flux is proposed in this paper. For an open-loop V / f
motor drive, the starting current is restricted by
switching between nonzero and zero vectors according
to the error between the reference and measured
currents. It cannot control the stator flux accurately
because no observer or estimator is employed to
obtain the stator flux as a feedback.
In the system proposed here, as an adaptive
flux observer is incorporated in the system, the stator
flux can be controlled accurately and achieve the pre
excitation in the true sense. It should be noted that
current limitation is needed and it works only during
the pre excitation process, because the magnetization
process without current limitation still produces
undesired large current. However, the current limit in
the pre excitation does not have to be large to produce
the needed stator flux.
The amplitude of current limitation only
affects the lasting time of pre excitation. In this paper,
the current limit it set to be 80% of rated current.
During the pre excitation process, when the current
exceeds the imitation setting, a zero vector will be
selected to reduce the current; otherwise a fixed vector
will be selected to produce stator flux, which acts in a
bang-bang fashion. When stator flux tilts the lower
limit of flux hysteresis, the process of pre excitation is
terminated and the motor can start with sufficient
torque by DTC, because there is sufficient flux to
produce torque. In all, the three-level DTC drive can
restrict the start-up current effectively and establish
accurate stator flux at the same time, which benefits
from the flux observation employed in the system.
V.
SIMULATION AND
EXPERIMENTAL RESULTS
Fig. 4.3 . Control surface of FLC.
g1r = 2b
g1i = 0
g2r = σ Lsb
g2i = 0
Where b is a negative constant gain
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4.5
4.6
4.7
4.8
To validate the effectiveness of the two DTC
methods, a three-level DTC motor drive is developed
and experimental results are presented here. The threelevel DTC drive is illustrated in Fig.5.1. FLC is
employed in the outer speed loop for speed control,
and a speed-adaptive flux observer with load torque
observation is used to estimate the rotor speed, stator
flux, and torque. The estimated states are fed back to
the outer loop of speed, flux, and torque. The motor
inertia is 0.05 kg / m2, and the sampling frequency of
system for DTC method I and II are 30 and 10 kHz,
respectively
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Fig. 5.1 Three-level DTC drive.
SIMULATION AND EXPERIMENT
PARAMETERS
Fig 5.1 Starting response of DTC method I with pre excitation.
established
in
several
milliseconds,
Figs. 5.1 show the starting response for DTC
unfortunately, at the expense of large current.
method I from 0 to 1200 r/min, and with and without
pre excitation, respectively. In Fig. 5.1 , the stator flux
is first established by using the pre excitation
VI.
CONCLUSION
technique, which can be seen from the upper half in
Two kinds of modified DTC schemes have
Fig. 5.1. The motor then accelerates up to 1200 r/min
been proposed in this paper and both achieve highwith the permitted maximum torque. The maximum
performance control of a three-level inverter-fed
starting current is restricted to 7.5 A; this value
motor drive. They both work over a wide speed range
reaches almost 27 A without pre excitation. The stator
and overcome the limitations caused by the topology
flux is established with current limitation before
of the three-level inverter. By using appropriate
starting the motor, so sufficient torque can be
intermediate vectors, the problems of neutral point
produced, which may result better dynamic
balance and smooth vector switching are solved.
performance. However, the dynamic response
Furthermore, a novel vector synthesis sequence was
difference between the one with and without pre
proposed and this decoupled the performance control
excitation is not significant, if the pre excitation time
from the circuit limitation. A FLC and a speedis excluded; this is because the stator flux can be
adaptive flux observer were incorporated in the drive
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to enhance the performance of system. In addition, the
issue of large starting current are investigated and
solved by introducing the technique of pre excitation.
Very low speed operation of 6 r/min was
demonstrated. Simulations as well as experimental
results were presented to verify the effectiveness of
the proposed schemes.
[11]
[12]
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