[9_CV] FCS-Model Predictive Control of Induction Motors feed by MultilLevel C...Nam Thanh
Ha Thanh Vo, Nam Thanh Hoang, Phuong Hoang Vu, Minh Trong Tran, Dich Quang Nguyen, “FCS-Model Predictive Control of Induction Motors feed by MultilLevel Casaded H-Bridge Inverter”, RCEEE-2018.
An Improved Repetitive Control for Circulating Current Restraining in MMC-MTDCTELKOMNIKA JOURNAL
The modular multilevel converter (MMC) is widely used in many important application fields such
as high voltage DC transmission system. And the multi-terminal architecture of it attracts many attentions.
However, the circulating current of MMC is an inherent problem which is mainly caused by the voltage
mismatch between arms and DC bus. In this paper, an advanced repetitive control method is proposed.
This method is based on the even-harmonic characteristic of the circulating current and the potential
feature of repetitive control that it has an internal integration part. The pole diagram of the closed loop
transform function of the proposed control system proves the stability of the proposed method. And
according to the simulation results of a three-terminal MMC-MTDC model in PSCAD/EMTDC, the
improved repetitive control presents better circulation repression ability and superior anti-interference
capability by comparing with traditional PI control method. Additionally, the simulation results also indicate
that the proposed repetitive controller can restrain the fluctuation of SM voltage more effectively than PI
control.
Investigation of the Common Mode Voltage for a Neutral-Point-Clamped Multilev...IJPEDS-IAES
The purpose of this paper is to provide a comprehensive Investigations and its control on the common mode Voltage (CMV) of the three-phase three-level neutral-point diode-clamped (NPC) multilevel inverter (MLI). A widespread space-vector pulse width modulation (SVPWM) technique to mitigate the perpetual problem of the NPC-MLI, the CMV, proposed. The proposed scheme is an effectual blend of nearest three vector (NTV) and selected three vector (STV) techniques. This scheme is capable to reduce the CMV without compromise the inverter output voltage and Total harmonics distraction (THD). CMV reduction achieved less than +Vdc/6 using the proposed vector selection procedure. The theoretical Investigations, the MATLAB software based computer simulation and Field Programmable Gate Array (FPGA) supported hardware corroboration have shown the superiority of the proposed technique over the conventional SVPWM schemes.
Investigation of THD for Cascaded Multi-Level Inverter Using Multicarrier Mod...IJERA Editor
A novelty kind of Multilevel converters are used in high voltage and high power application of industry field, can able to produce near sinusoidal voltage/currents with only operating at fundamental frequency switching. This paper presents a initial level of 5-level up to its giant level 13-level cascaded multilevel converter. In now a days multilevel inverters has become very popular for motor drive applications of industry. Multicarrier pulse width modulation techniques is an effective solution for increases the number of levels of the output wave form and thereby dramatically reduced the harmonics and total harmonic distortion(THD). The output waveform has 5,7,9,11 and 13 levels. In this paper three multicarrier pulse width modulation techniques such as phase shifted, level shifted and the wave level shifted Multi-carrier modulation PWM techniques are discussed. These methods are modeled for all level CMC by using the MATLAB/SIMULINK and the THD of the these methods are compared.
Average Phase-Leg Technique on Coupling Impedance Impact Modular Inverter Par...IJMTST Journal
The modular multilevel converter (MMC) is an emerging and highly attractive multilevel converter topology
for high-voltage and high-power applications. This paper proposes the control method of parallel-connected
modular multilevel converters (parallel-MMCs), which assumes that the multiple MMCs are directly connected
at both ac and dc sides to effectively enhance the power rating as expected. Two key problems were first
solved for the parallel-MMCs under the normal operation conditions: voltage balancing of sub modules and
mitigation of circulating currents, where the novel transformed third-order harmonic resonant controller in the
synchronous reference frame was employed to mitigate the dominant second-order and fourth-order
circulating currents and a sixth-order harmonic resonant controller is used to attenuate the zero-sequence
sixth-order circulating current existed in all phase currents per MMC. Considering the high risk of switches
fault in the parallel-MMCs, the fault-tolerant operation schemes were then proposed in this paper to address
the major concerns of open-circuit and short-circuit switch fault in a sub module, respectively. Carefully
controlling the healthy sub modules and the corresponding phase arms, the parallel-MMCs can successfully
maintain their balanced capacitor voltages and mitigate the circulating currents with the qualified output
waveform obtained. In addition, the parallel configuration of MMCs provides the unique solution for the
short-circuit switch fault operation which was seldom discussed in the published literature works with
respect to the MMC fault-tolerant operation schemes. MATLAB simulations and the constructed experimental
prototype have verified the performance of the proposed control strategy.
Performance improvement of parallel active power filters using droop control ...Ghazal Falahi
In this paper, a new method based on droop control scheme is proposed for controlling parallel operation of active filters. The harmonic components of the load current are extracted by an enhanced phase-locked loop (EPLL). In the parallel group, each filter operates as a conductance and the harmonic workload is shared among them. A droop relationship between the conductance and non-fundamental apparent power controls the operation of each unit. The non-fundamental apparent power has been calculated based on IEEE Std 1459. Principles of operation are explained in this paper and simulation results which are presented approve the effectiveness of this method. The results indicate a significant reduction in Total Harmonic Distortion (THD) in a rectifier application.
[9_CV] FCS-Model Predictive Control of Induction Motors feed by MultilLevel C...Nam Thanh
Ha Thanh Vo, Nam Thanh Hoang, Phuong Hoang Vu, Minh Trong Tran, Dich Quang Nguyen, “FCS-Model Predictive Control of Induction Motors feed by MultilLevel Casaded H-Bridge Inverter”, RCEEE-2018.
An Improved Repetitive Control for Circulating Current Restraining in MMC-MTDCTELKOMNIKA JOURNAL
The modular multilevel converter (MMC) is widely used in many important application fields such
as high voltage DC transmission system. And the multi-terminal architecture of it attracts many attentions.
However, the circulating current of MMC is an inherent problem which is mainly caused by the voltage
mismatch between arms and DC bus. In this paper, an advanced repetitive control method is proposed.
This method is based on the even-harmonic characteristic of the circulating current and the potential
feature of repetitive control that it has an internal integration part. The pole diagram of the closed loop
transform function of the proposed control system proves the stability of the proposed method. And
according to the simulation results of a three-terminal MMC-MTDC model in PSCAD/EMTDC, the
improved repetitive control presents better circulation repression ability and superior anti-interference
capability by comparing with traditional PI control method. Additionally, the simulation results also indicate
that the proposed repetitive controller can restrain the fluctuation of SM voltage more effectively than PI
control.
Investigation of the Common Mode Voltage for a Neutral-Point-Clamped Multilev...IJPEDS-IAES
The purpose of this paper is to provide a comprehensive Investigations and its control on the common mode Voltage (CMV) of the three-phase three-level neutral-point diode-clamped (NPC) multilevel inverter (MLI). A widespread space-vector pulse width modulation (SVPWM) technique to mitigate the perpetual problem of the NPC-MLI, the CMV, proposed. The proposed scheme is an effectual blend of nearest three vector (NTV) and selected three vector (STV) techniques. This scheme is capable to reduce the CMV without compromise the inverter output voltage and Total harmonics distraction (THD). CMV reduction achieved less than +Vdc/6 using the proposed vector selection procedure. The theoretical Investigations, the MATLAB software based computer simulation and Field Programmable Gate Array (FPGA) supported hardware corroboration have shown the superiority of the proposed technique over the conventional SVPWM schemes.
Investigation of THD for Cascaded Multi-Level Inverter Using Multicarrier Mod...IJERA Editor
A novelty kind of Multilevel converters are used in high voltage and high power application of industry field, can able to produce near sinusoidal voltage/currents with only operating at fundamental frequency switching. This paper presents a initial level of 5-level up to its giant level 13-level cascaded multilevel converter. In now a days multilevel inverters has become very popular for motor drive applications of industry. Multicarrier pulse width modulation techniques is an effective solution for increases the number of levels of the output wave form and thereby dramatically reduced the harmonics and total harmonic distortion(THD). The output waveform has 5,7,9,11 and 13 levels. In this paper three multicarrier pulse width modulation techniques such as phase shifted, level shifted and the wave level shifted Multi-carrier modulation PWM techniques are discussed. These methods are modeled for all level CMC by using the MATLAB/SIMULINK and the THD of the these methods are compared.
Average Phase-Leg Technique on Coupling Impedance Impact Modular Inverter Par...IJMTST Journal
The modular multilevel converter (MMC) is an emerging and highly attractive multilevel converter topology
for high-voltage and high-power applications. This paper proposes the control method of parallel-connected
modular multilevel converters (parallel-MMCs), which assumes that the multiple MMCs are directly connected
at both ac and dc sides to effectively enhance the power rating as expected. Two key problems were first
solved for the parallel-MMCs under the normal operation conditions: voltage balancing of sub modules and
mitigation of circulating currents, where the novel transformed third-order harmonic resonant controller in the
synchronous reference frame was employed to mitigate the dominant second-order and fourth-order
circulating currents and a sixth-order harmonic resonant controller is used to attenuate the zero-sequence
sixth-order circulating current existed in all phase currents per MMC. Considering the high risk of switches
fault in the parallel-MMCs, the fault-tolerant operation schemes were then proposed in this paper to address
the major concerns of open-circuit and short-circuit switch fault in a sub module, respectively. Carefully
controlling the healthy sub modules and the corresponding phase arms, the parallel-MMCs can successfully
maintain their balanced capacitor voltages and mitigate the circulating currents with the qualified output
waveform obtained. In addition, the parallel configuration of MMCs provides the unique solution for the
short-circuit switch fault operation which was seldom discussed in the published literature works with
respect to the MMC fault-tolerant operation schemes. MATLAB simulations and the constructed experimental
prototype have verified the performance of the proposed control strategy.
Performance improvement of parallel active power filters using droop control ...Ghazal Falahi
In this paper, a new method based on droop control scheme is proposed for controlling parallel operation of active filters. The harmonic components of the load current are extracted by an enhanced phase-locked loop (EPLL). In the parallel group, each filter operates as a conductance and the harmonic workload is shared among them. A droop relationship between the conductance and non-fundamental apparent power controls the operation of each unit. The non-fundamental apparent power has been calculated based on IEEE Std 1459. Principles of operation are explained in this paper and simulation results which are presented approve the effectiveness of this method. The results indicate a significant reduction in Total Harmonic Distortion (THD) in a rectifier application.
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.
Low voltage ride through control of modular multilevel converter based hvdc s...Ghazal Falahi
Low Voltage Ride Through (LVRT) is an important grid requirement for Voltage Source Converter (VSC) based HVDC links. This paper studies the performance of the modular multilevel converter (MMC) VSC based HVDC systems during faults or voltage dips and proposes a new control strategy to improve the LVRT performance. The proposed algorithm controls the system to generate the required active and reactive powers that are calculated mathematically based on the ratings of the MMC-HVDC system and LVRT requirements. The injected active and reactive power values obey the LVRT guidelines and are adaptable to different grid codes. The mathematical calculations are presented and EMTDC/PSCAD simulation evaluates the performance of the proposed method.
Design consideration of an mmc hvdc system based on 4500 v:4000a emitter turn...Ghazal Falahi
Excessive power loss is a major concern in high voltage and high power applications and is considered one of the main drawbacks of VSC-HVDC system when compared with traditional HVDC system based on thyristor technology. This is primarily caused by high switching loss associated with switching devices used in the VSC-HVDC. This issue can be largely addressed by using the emerging MMC-HVDC topology, which requires much lower switching frequency than traditional VSC-HVDC. Emitter turn-off thyristor (ETO) is one of the best high power switching devices packed with many advanced features. ETO thyristor based MMC-HVDC system is therefore an extremely attractive choice for ultra-high voltage and high power HVDCs. This paper discusses the operation principle of ETO based MMC-HVDC as well as its design and loss comparison with other solutions.
Comparative Analysis of PWM Techniques for Three Level Diode Clamped Voltage ...IAES-IJPEDS
Multilevel inverters are increasingly being used in high-power medium voltage industrial drive applications due to their superior performance compared to conventional two-level inverters. Thre are a number of Pulse width modulation (PWM) techniques applied in recent years. The most widely applied PWM techniques are Sine Pulse Width Modulation (SPWM) and Space Vector Pulse Width Modulation (SVPWM). SPWM is the most simple modulation technique that can realize easily in analog circuit. However, it has some drawbacks such as higher total harmonic distortion (THD), lower effective DC utilization and lower switching frequency. Space vector pulse width modulation (SVPWM) is widely used because of their easier digital realization and better DC bus utilization and lower THD. The complexity is due to the difficulty in determining the reference vector location, on times calculation, and switching states selection. This paper presents a simple SVPWM algorithm for diode clamped three level inverters based on standard two-level SVPWM which can easily determine the location of reference vector, calculate the on-times, the selection of switching states. Three level diode clamped inverter (3LDCI) using space vector modulation technique has been modeled and simulated using MATLAB/SIMULINK and Origin 6.1 with a passive R-L load that can be extended to any level. Simulation results are presented to verify the proposed SVPWM control in terms of THD. The results arecompared with conventional sinusoidal pulse width modulation (SPWM) where SVPWM shows better performance than SPWM in terms of THD.
ENHANCEMENT OF FUNDAMENTAL RMS OUTPUT VOLTAGE OF 5-LEVEL CASCADED H-BRIDGE MU...IAEME Publication
Cascaded H-bridge Multilevel Inverter (CHBMLI) is the most suitable topology for the PV power converters. In this paper an effort has been made to increase the performance of CHBMLI by improving the fundamental Root Mean Square (RMS) value of the output voltage. This work proposes a Modified Multi Carrier PWM (MMCPWM) technique where, reference sine wave has been replaced by ellipse wave, resulting in enhanced performances on the fundamental rms output voltage and lower Total Harmonic Distortion (THD). Analysis of single phase 5-level CHBMLI with and without load are carried for the different Multi Carrier PWM (MCPWM) techniques.
Thd minimization of modular multilevel converter with unequal dc valuesGhazal Falahi
Different modulation techniques used to control multilevel converters can be classified based on the selected converter topology and optimization goals. Among all proposed modulation methods low switching frequency modulation techniques are very popular for multilevel converters yet non-real time low switching frequency methods cannot be applied to multilevel converters with unequal or varying DC values because these modulation techniques rely on look up tables and the size of look up tables will be huge in this case. This paper proposes a new modular multilevel converter (MMC) structure with unequal DC values. Some well-known low switching frequency modulation techniques and the commonly used PWM based methods are compared and using the new low switching frequency modulation technique called minimal total harmonic distortion (THD) modulation for MMC with unequal DC values is proposed. The PSCAD simulation results show that the new converter topology with unequal DC values has much lower THD compared to the typical MMC. Modulation algorithm is implemented in digital signal processor (DSP) and controller hardware in the loop (CHIL) implementation in RTDS verifies the real-time performance of the algorithm.
Equal Switching Distribution Method for Multi-Level Cascaded Inverterijsrd.com
the paper proposes a new method of equal switching distribution that can be applied to cascaded multilevel inverters. This method is based on the fact that in the cascaded multilevel inverters, the output phase voltage is the sum of voltage waveforms produced by all cascaded cells. By periodically exchanging cells' voltage waveforms, the proposed method ensures equal average switching's distribution between all cascaded cells. This method is applied to the 13-level inverter, which consists of three cascaded 5-level H-bridge cells per phase. However, the proposed method can be extended to any desired number of voltage levels and applied to any type of cascaded multilevel inverter. Extensive simulation results of the tested 13- level inverter with the equal switching distribution are presented. Moreover, the proposed method is compared to the standard control approaches and its advantages are shown.
IJERA (International journal of Engineering Research and Applications) is International online, ... peer reviewed journal. For more detail or submit your article, please visit www.ijera.com
Control of modular multilevel converter based hvdc systems during asymmetrica...Ghazal Falahi
Modular multilevel converter (MMC) is a relatively new and promising topology for HVDC systems. HVDC systems should remain connected during grid faults and isolate the fault. This paper studies the dynamic performance of transformer-less MMC integrated HVDC systems during unbalanced conditions and asymmetrical grid faults. It proposes a new control technique to improve unbalanced system’s performance. The objective of the proposed controller is eliminating negative and zero sequence currents and to improve the overall performance. The controller calculates zero and negative sequence reference voltages and eliminates zero and negative sequence currents without using any current regulator. Therefore the controller is very fast and robust. The effectiveness of the proposed control technique has been validated by EMTDC /PSCAD simulations.
A Review on Performance Analysis of Matrix Converter Fed AC Motor DriveIAES-IJPEDS
This paper presents a review on the analysis of characteristics that determines
the performance of the Matrix Converter (MC) fed AC motor drive. Review
is made based on the analysis of the different characteristics achieved in the
literature. Different characteristic parameters considered in this paper are
total harmonic distortion, common mode voltage, voltage transfer ratio and
efficiency. Comparison and analysis of these characteristic parameters is
done based on various semi conductor switches, topology, and control and modulation techniques.
State-space averaged modeling and transfer function derivation of DC-DC boost...TELKOMNIKA JOURNAL
This paper presents dynamic analysis of a boost type DC-DC converter for high-brightness LED (HBLED) driving applications. The steady state operation in presence of all system parasitics has been discussed for continuous conduction mode (CCM). The state-space averaging, energy conservation principle and standard linearization are used to derive ac small signal control to inductor current open-loop transfer function of the converter. The derived transfer function can be further used in designing a robust feed-back control network for the system. In the end frequency and transient responses of the derived transfer function are obtained for a given set of component values, hence to provide a useful guide for control design engineers.
The International Journal of Engineering & Science is aimed at providing a platform for researchers, engineers, scientists, or educators to publish their original research results, to exchange new ideas, to disseminate information in innovative designs, engineering experiences and technological skills. It is also the Journal's objective to promote engineering and technology education. All papers submitted to the Journal will be blind peer-reviewed. Only original articles will be published.
The papers for publication in The International Journal of Engineering& Science are selected through rigorous peer reviews to ensure originality, timeliness, relevance, and readability.
IOSR Journal of Electrical and Electronics Engineering(IOSR-JEEE) is an open access international journal that provides rapid publication (within a month) of articles in all areas of electrical and electronics engineering and its applications. The journal welcomes publications of high quality papers on theoretical developments and practical applications in electrical and electronics engineering. Original research papers, state-of-the-art reviews, and high quality technical notes are invited for publications.
Modelling and Simulation of a Sensorless Control of a True Asymmetric Cascade...IJPEDS-IAES
This paper introduces a new method to track the saliency of an AC motor fed
by a multilevel converter through measuring the dynamic current response of
the motor line currents due the IGBT switching actions. The method uses
only the fundamental PWM waveform (i.e there is no modification to the
operation of the multilevel converter) similar to the fundamental PWM
method proposed for a 2-level converter. Simulation results are provided to
demonstrate the performance of the complete sensorless speed control of a
PM motor driven by such a converter over a wide speed range. Finally the
paper introduces a comparison between the 2-level converter and the
multilevel converter in terms of the reduction of the total harmonic distortion
(THD) using the fundamental PWM method in both cases.
IJERA (International journal of Engineering Research and Applications) is International online, ... peer reviewed journal. For more detail or submit your article, please visit www.ijera.com
Fuzzy Logic Controller Based on Voltage Source Converter-HVDC with MMC TopologyIJMTST Journal
This paper presents Modular Multi Level Converters (MMC) are used for high voltage high power DC to AC conversion. The MMCs with increased number of levels offer close to sine wave operation with reduced THD on the AC side. This is a new type of voltage source converter (VSC) topology. The use of this converter in a high-voltage direct current (HVDC) system is called by a MMC-HVDC system. The MMC-HVDC has the advantage in terms of scalability, performance, and efficiency over two-and three-level VSC-HVDC. The proposed HVDC system offers the operational flexibility of VSC based systems in terms of active and reactive power control, in addition to improved ac fault ride-through capability and the unique feature of current-limiting capability during dc side faults. The proposed VSC-HVDC system, in this project assesses its dynamic performance during steady-state and network alternations, including its response to AC and DC side faults. In this project using a fuzzy controller and the proposed topology is implemented in MATLAB/SIMULINK environment and the simulation results are observed.
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.
Low voltage ride through control of modular multilevel converter based hvdc s...Ghazal Falahi
Low Voltage Ride Through (LVRT) is an important grid requirement for Voltage Source Converter (VSC) based HVDC links. This paper studies the performance of the modular multilevel converter (MMC) VSC based HVDC systems during faults or voltage dips and proposes a new control strategy to improve the LVRT performance. The proposed algorithm controls the system to generate the required active and reactive powers that are calculated mathematically based on the ratings of the MMC-HVDC system and LVRT requirements. The injected active and reactive power values obey the LVRT guidelines and are adaptable to different grid codes. The mathematical calculations are presented and EMTDC/PSCAD simulation evaluates the performance of the proposed method.
Design consideration of an mmc hvdc system based on 4500 v:4000a emitter turn...Ghazal Falahi
Excessive power loss is a major concern in high voltage and high power applications and is considered one of the main drawbacks of VSC-HVDC system when compared with traditional HVDC system based on thyristor technology. This is primarily caused by high switching loss associated with switching devices used in the VSC-HVDC. This issue can be largely addressed by using the emerging MMC-HVDC topology, which requires much lower switching frequency than traditional VSC-HVDC. Emitter turn-off thyristor (ETO) is one of the best high power switching devices packed with many advanced features. ETO thyristor based MMC-HVDC system is therefore an extremely attractive choice for ultra-high voltage and high power HVDCs. This paper discusses the operation principle of ETO based MMC-HVDC as well as its design and loss comparison with other solutions.
Comparative Analysis of PWM Techniques for Three Level Diode Clamped Voltage ...IAES-IJPEDS
Multilevel inverters are increasingly being used in high-power medium voltage industrial drive applications due to their superior performance compared to conventional two-level inverters. Thre are a number of Pulse width modulation (PWM) techniques applied in recent years. The most widely applied PWM techniques are Sine Pulse Width Modulation (SPWM) and Space Vector Pulse Width Modulation (SVPWM). SPWM is the most simple modulation technique that can realize easily in analog circuit. However, it has some drawbacks such as higher total harmonic distortion (THD), lower effective DC utilization and lower switching frequency. Space vector pulse width modulation (SVPWM) is widely used because of their easier digital realization and better DC bus utilization and lower THD. The complexity is due to the difficulty in determining the reference vector location, on times calculation, and switching states selection. This paper presents a simple SVPWM algorithm for diode clamped three level inverters based on standard two-level SVPWM which can easily determine the location of reference vector, calculate the on-times, the selection of switching states. Three level diode clamped inverter (3LDCI) using space vector modulation technique has been modeled and simulated using MATLAB/SIMULINK and Origin 6.1 with a passive R-L load that can be extended to any level. Simulation results are presented to verify the proposed SVPWM control in terms of THD. The results arecompared with conventional sinusoidal pulse width modulation (SPWM) where SVPWM shows better performance than SPWM in terms of THD.
ENHANCEMENT OF FUNDAMENTAL RMS OUTPUT VOLTAGE OF 5-LEVEL CASCADED H-BRIDGE MU...IAEME Publication
Cascaded H-bridge Multilevel Inverter (CHBMLI) is the most suitable topology for the PV power converters. In this paper an effort has been made to increase the performance of CHBMLI by improving the fundamental Root Mean Square (RMS) value of the output voltage. This work proposes a Modified Multi Carrier PWM (MMCPWM) technique where, reference sine wave has been replaced by ellipse wave, resulting in enhanced performances on the fundamental rms output voltage and lower Total Harmonic Distortion (THD). Analysis of single phase 5-level CHBMLI with and without load are carried for the different Multi Carrier PWM (MCPWM) techniques.
Thd minimization of modular multilevel converter with unequal dc valuesGhazal Falahi
Different modulation techniques used to control multilevel converters can be classified based on the selected converter topology and optimization goals. Among all proposed modulation methods low switching frequency modulation techniques are very popular for multilevel converters yet non-real time low switching frequency methods cannot be applied to multilevel converters with unequal or varying DC values because these modulation techniques rely on look up tables and the size of look up tables will be huge in this case. This paper proposes a new modular multilevel converter (MMC) structure with unequal DC values. Some well-known low switching frequency modulation techniques and the commonly used PWM based methods are compared and using the new low switching frequency modulation technique called minimal total harmonic distortion (THD) modulation for MMC with unequal DC values is proposed. The PSCAD simulation results show that the new converter topology with unequal DC values has much lower THD compared to the typical MMC. Modulation algorithm is implemented in digital signal processor (DSP) and controller hardware in the loop (CHIL) implementation in RTDS verifies the real-time performance of the algorithm.
Equal Switching Distribution Method for Multi-Level Cascaded Inverterijsrd.com
the paper proposes a new method of equal switching distribution that can be applied to cascaded multilevel inverters. This method is based on the fact that in the cascaded multilevel inverters, the output phase voltage is the sum of voltage waveforms produced by all cascaded cells. By periodically exchanging cells' voltage waveforms, the proposed method ensures equal average switching's distribution between all cascaded cells. This method is applied to the 13-level inverter, which consists of three cascaded 5-level H-bridge cells per phase. However, the proposed method can be extended to any desired number of voltage levels and applied to any type of cascaded multilevel inverter. Extensive simulation results of the tested 13- level inverter with the equal switching distribution are presented. Moreover, the proposed method is compared to the standard control approaches and its advantages are shown.
IJERA (International journal of Engineering Research and Applications) is International online, ... peer reviewed journal. For more detail or submit your article, please visit www.ijera.com
Control of modular multilevel converter based hvdc systems during asymmetrica...Ghazal Falahi
Modular multilevel converter (MMC) is a relatively new and promising topology for HVDC systems. HVDC systems should remain connected during grid faults and isolate the fault. This paper studies the dynamic performance of transformer-less MMC integrated HVDC systems during unbalanced conditions and asymmetrical grid faults. It proposes a new control technique to improve unbalanced system’s performance. The objective of the proposed controller is eliminating negative and zero sequence currents and to improve the overall performance. The controller calculates zero and negative sequence reference voltages and eliminates zero and negative sequence currents without using any current regulator. Therefore the controller is very fast and robust. The effectiveness of the proposed control technique has been validated by EMTDC /PSCAD simulations.
A Review on Performance Analysis of Matrix Converter Fed AC Motor DriveIAES-IJPEDS
This paper presents a review on the analysis of characteristics that determines
the performance of the Matrix Converter (MC) fed AC motor drive. Review
is made based on the analysis of the different characteristics achieved in the
literature. Different characteristic parameters considered in this paper are
total harmonic distortion, common mode voltage, voltage transfer ratio and
efficiency. Comparison and analysis of these characteristic parameters is
done based on various semi conductor switches, topology, and control and modulation techniques.
State-space averaged modeling and transfer function derivation of DC-DC boost...TELKOMNIKA JOURNAL
This paper presents dynamic analysis of a boost type DC-DC converter for high-brightness LED (HBLED) driving applications. The steady state operation in presence of all system parasitics has been discussed for continuous conduction mode (CCM). The state-space averaging, energy conservation principle and standard linearization are used to derive ac small signal control to inductor current open-loop transfer function of the converter. The derived transfer function can be further used in designing a robust feed-back control network for the system. In the end frequency and transient responses of the derived transfer function are obtained for a given set of component values, hence to provide a useful guide for control design engineers.
The International Journal of Engineering & Science is aimed at providing a platform for researchers, engineers, scientists, or educators to publish their original research results, to exchange new ideas, to disseminate information in innovative designs, engineering experiences and technological skills. It is also the Journal's objective to promote engineering and technology education. All papers submitted to the Journal will be blind peer-reviewed. Only original articles will be published.
The papers for publication in The International Journal of Engineering& Science are selected through rigorous peer reviews to ensure originality, timeliness, relevance, and readability.
IOSR Journal of Electrical and Electronics Engineering(IOSR-JEEE) is an open access international journal that provides rapid publication (within a month) of articles in all areas of electrical and electronics engineering and its applications. The journal welcomes publications of high quality papers on theoretical developments and practical applications in electrical and electronics engineering. Original research papers, state-of-the-art reviews, and high quality technical notes are invited for publications.
Modelling and Simulation of a Sensorless Control of a True Asymmetric Cascade...IJPEDS-IAES
This paper introduces a new method to track the saliency of an AC motor fed
by a multilevel converter through measuring the dynamic current response of
the motor line currents due the IGBT switching actions. The method uses
only the fundamental PWM waveform (i.e there is no modification to the
operation of the multilevel converter) similar to the fundamental PWM
method proposed for a 2-level converter. Simulation results are provided to
demonstrate the performance of the complete sensorless speed control of a
PM motor driven by such a converter over a wide speed range. Finally the
paper introduces a comparison between the 2-level converter and the
multilevel converter in terms of the reduction of the total harmonic distortion
(THD) using the fundamental PWM method in both cases.
IJERA (International journal of Engineering Research and Applications) is International online, ... peer reviewed journal. For more detail or submit your article, please visit www.ijera.com
Fuzzy Logic Controller Based on Voltage Source Converter-HVDC with MMC TopologyIJMTST Journal
This paper presents Modular Multi Level Converters (MMC) are used for high voltage high power DC to AC conversion. The MMCs with increased number of levels offer close to sine wave operation with reduced THD on the AC side. This is a new type of voltage source converter (VSC) topology. The use of this converter in a high-voltage direct current (HVDC) system is called by a MMC-HVDC system. The MMC-HVDC has the advantage in terms of scalability, performance, and efficiency over two-and three-level VSC-HVDC. The proposed HVDC system offers the operational flexibility of VSC based systems in terms of active and reactive power control, in addition to improved ac fault ride-through capability and the unique feature of current-limiting capability during dc side faults. The proposed VSC-HVDC system, in this project assesses its dynamic performance during steady-state and network alternations, including its response to AC and DC side faults. In this project using a fuzzy controller and the proposed topology is implemented in MATLAB/SIMULINK environment and the simulation results are observed.
The power electronics device which converts DC power to AC power at required output voltage and frequency level is known as inverter. Multilevel inverter is to synthesize a near sinusoidal voltage from several levels of dc voltages. In order to maintain the different voltage levels at appropriate intervals, the conduction time intervals of MOSFETS have been maintained by controlling the pulse width of gating pulses. In this paper single phase to three phase power conversion using PWM technique. The simulation is carried out in MATLAB/Simulink environment which demonstrate the feasibility of proposed scheme.
Performance comparison of different control strategies for the regulation of ...IJECEIAES
In last years, DC-DC converters solve the most issues in the industrial application in the area of power electronics, especially renewable energy, military applications and affiliated engineering developments. They are used to convert the DC input that unregulated to regulated output perhaps larger or smaller than input according to the type of converters. This paper presents three primary control method used for negative output Super lift Luo DC-DC converter. These methods include a voltage mode control (VMC), current mode control (CMC), and Sliding mode control (SMC). The goal of this article is to study and selected an appropriate and superior control scheme for negative DC-DC converters. The simulation results show the effectiveness of Sliding mode control for enhancing the performance of the negative DC-DC converter. Also, this method can keep the output voltage constant under load conditions. Simulation results obtained by the MATLAB/Simulink environment.
In present days of electrical industries, adjustable speed controlled induction
motor drives are very common due to its versatile features. For the speed control of induction
motor, variable frequency sources are the heart of such drives. To attain variable frequency
and variable voltage supply a power electronics device; single phase matrix converter is
proposed.
In this paper, the single phase matrix converter is modeled in MATLAB Simulink
environment; controlled with sinusoidal pulse width modulation technique, control scheme is
implemented in a Xilinx system generator environment and interfaced with power circuit in
MATLAB Simulink. Analyses this SPMC with different type of loads in both frequency step
up and step down modes. Based on simulation results, this converter is suitable for variable
frequency power supplies, varying load conditions and variable speed electrical drives.
FPGA control is best suitable for controlling a circuit like SPMC, consists of more
controlled elements to attain fast operation.
Adaptive terminal sliding mode control strategy for dc–dc buck convertersISA Interchange
This paper presents an adaptive terminal sliding mode control (ATSMC) strategy for DC–DC buck converters. The idea behind this strategy is to use the terminal sliding mode control (TSMC) approach to assure finite time convergence of the output voltage error to the equilibrium point and integrate an adaptive law to the TSMC strategy so as to achieve a dynamic sliding line during the load variations. In addition, the influence of the controller parameters on the performance of closed-loop system is investigated. It is observed that the start up response of the output voltage becomes faster with increasing value of the fractional power used in the sliding function. On the other hand, the transient response of the output voltage, caused by the step change in the load, becomes faster with decreasing the value of the fractional power. Therefore, the value of fractional power is to be chosen to make a compromise between start up and transient responses of the converter. Performance of the proposed ATSMC strategy has been tested through computer simulations and experiments. The simulation results of the proposed ATSMC strategy are compared with the conventional SMC and TSMC strategies. It is shown that the ATSMC exhibits a considerable improvement in terms of a faster output voltage response during load changes.
Digital Current Mode Controller for Buck ConverterIJMREMJournal
Power electronics applications are widely used in different fields of engineering like computer,
Telecommunication, electrical power and Mechanical), one of the most useful power electronics converters is
DC-DC buck converter. Owing to its numerous applications, its performance needs to be improved through a
suitable controller. In this Paper, A digital current mode controller is proposed and implemented for Buck
converter. Proposed current mode control technique is simulated in MATLAB/SIMULINK and results are
validated through hardware implementation. Both simulation and experimental analysis show effectiveness of
the proposed controller.
The strategy is based on an autonomous distributed control
scheme in which the DC bus voltage level is used as an indicator of the power balance in the
microgrid. The autonomous control strategy does not rely on communication links or a
central controller, resulting in reduced costs and enhanced reliability. As part of the control
strategy, an adaptive droop control technique is proposed for PV sources in order to
maximize the utilization of power available from these sources while ensuring acceptable
levels of system voltage regulation
Comparative performance of modular with cascaded H-bridge three level invertersIJECEIAES
The conventional two-level inverter becomes no longer has the ability to cope with the high-power requirement, so this paper discusses two very common topologies of multilevel inverter like modular multilevel converter (MMC) and cascaded H-bridge (CHB) multilevel inverter for induction motor drive applications. This work attempts to investigate the comparison between MMC and CHB. The comparison is done in aspects of the configuration, concept of operation, advantages and disadvantages, the comparison is also considering output voltage (line to line) waveform, total harmonic distortion (THD) of the output line voltage waveform and the current drawn by both inverters. The performance of the inverters under carrier-based pulse width modulation (PWM) technique and mainly in-phase disposition (IPD), level shifted pulse width modulation is viewed. The paper discusses the comparison between the two multilevel inverters (MLIs) with motor drive applications especially induction motor. The operation of the motor is studied under certain value of load torque. The simulation results for the induction motor with the two inverters (modular multilevel and Cascaded H-bride) for three numbers of levels using MATLAB/Simulink are provided). The obtained results are encouraging and promising especially in the improvement of the THD% results.
Small-signal modeling of current-mode controlled modular DC-DC converters us...IJECEIAES
Small-signal models are useful tools to preliminary understand the dynamics of interconnected systems like modular dc-dc converters which find a wide range of industrial applications. This work proposes a state-space-based averaged small-signal model in symbolic form for a peak current-mode controlled parallel-input/parallel-output buck converter operating in the continuous-conduction mode. In modeling the converter power-stage each module is independently represented. For modeling the current-mode control the state-space algebraic approach is used to incorporate the currentmode control-law into the power-stage equations. For each module two parasitic elements in addition to the current-loop sampling action are included in the derivation. Furthermore, the control-to-output voltage transfer functions are presented in symbolic form for two cases of interest: the first when the converter has two non-identical modules to study the effect of inductor mismatch, and the second when the converter is composed of n-connected identical modules to assess the effect of varying the number of modules. All responses from PSIM cycle-by-cycle simulations are in good agreement with the mathematical model predictions up to half the switching frequency.
DG FED MULTILEVEL INVERTER BASED D-STATCOM FOR VARIOUS LOADING CONDITIONSIJCI JOURNAL
During the past few decades, power industries have proved that the adverse impacts on the PQ can be
mitigated or avoided by conventional means, and that technique using fast controlled force commutated
power electronics (PE) are even more effective. PQ compensators can be categorized into two main types.
One is shunt connected compensation device that effectively eliminates harmonics. The other is the series
connected device, which has an edge over the shunt type for correcting the distorted system side voltages
and voltage sags caused by power transmission system faults. The STATCOM used in distribution systems
is called DSTACOM (Distribution-STACOM) and its configuration is the same, but with small
modifications. Recent advances in the power-handling capabilities of static switch devices such as 3.3kV,
4.5kV, and 6.5kV Insulated Gate Bipolar Transistors (IGBTs) with voltage rating commercially available,
have made the use of the voltage source inverters (VSI) feasible for high-power applications. High power
and high-voltage conversion systems have become very important issues for the power electronic industry
handling the large ac drive and electrical power applications at both the transmission and distribution
levels. For these reasons, new families of multilevel inverters have emerged as the solution for working
with higher voltage levels. Multilevel inverters (MLI) include an array of power semiconductors and
capacitor voltage sources, the output of which generate voltages with stepped waveforms. These converter
topologies can generate high-quality voltage waveforms with power semiconductor switches operating at a
frequency near the fundamental. It significantly reduces the harmonics problem with reduced voltage stress
across the switch. This research work is mainly focusing on application of multilevel DSTATCOM for
power quality improvement in distribution system with integration of RES. Matlab/Simulink based model is
developed and simulation results are presented.
Water scarcity is the lack of fresh water resources to meet the standard water demand. There are two type of water scarcity. One is physical. The other is economic water scarcity.
Immunizing Image Classifiers Against Localized Adversary Attacksgerogepatton
This paper addresses the vulnerability of deep learning models, particularly convolutional neural networks
(CNN)s, to adversarial attacks and presents a proactive training technique designed to counter them. We
introduce a novel volumization algorithm, which transforms 2D images into 3D volumetric representations.
When combined with 3D convolution and deep curriculum learning optimization (CLO), itsignificantly improves
the immunity of models against localized universal attacks by up to 40%. We evaluate our proposed approach
using contemporary CNN architectures and the modified Canadian Institute for Advanced Research (CIFAR-10
and CIFAR-100) and ImageNet Large Scale Visual Recognition Challenge (ILSVRC12) datasets, showcasing
accuracy improvements over previous techniques. The results indicate that the combination of the volumetric
input and curriculum learning holds significant promise for mitigating adversarial attacks without necessitating
adversary training.
Welcome to WIPAC Monthly the magazine brought to you by the LinkedIn Group Water Industry Process Automation & Control.
In this month's edition, along with this month's industry news to celebrate the 13 years since the group was created we have articles including
A case study of the used of Advanced Process Control at the Wastewater Treatment works at Lleida in Spain
A look back on an article on smart wastewater networks in order to see how the industry has measured up in the interim around the adoption of Digital Transformation in the Water Industry.
Cosmetic shop management system project report.pdfKamal Acharya
Buying new cosmetic products is difficult. It can even be scary for those who have sensitive skin and are prone to skin trouble. The information needed to alleviate this problem is on the back of each product, but it's thought to interpret those ingredient lists unless you have a background in chemistry.
Instead of buying and hoping for the best, we can use data science to help us predict which products may be good fits for us. It includes various function programs to do the above mentioned tasks.
Data file handling has been effectively used in the program.
The automated cosmetic shop management system should deal with the automation of general workflow and administration process of the shop. The main processes of the system focus on customer's request where the system is able to search the most appropriate products and deliver it to the customers. It should help the employees to quickly identify the list of cosmetic product that have reached the minimum quantity and also keep a track of expired date for each cosmetic product. It should help the employees to find the rack number in which the product is placed.It is also Faster and more efficient way.
Cosmetic shop management system project report.pdf
[1_CV] Model Predictive Control Method for Modular Multilevel Converter Applications
1. The 11th SEATUC Symposium
1
MODEL PREDICTIVE CONTROL METHOD FOR MODULAR
MULTILEVEL CONVERTER APPLICATION
Tran Hung Cuong(1), Tran Trong Minh(2), Hoang Thanh Nam(2)
(1)Hong Duc University, Viet Nam
(2)Ha Noi University of Science and Technology, Viet Nam
Email: tranhungcuong@hdu.edu.vn
ABSTRACT
This paper proposes a Model Predictive Control
(MPC) method for Modular-Multilevel-Converter
(MMC) applications for connect renewable energy
sources. Modular multilevel converter has some
advantages in comparison with conventional multilevel
converters such as: scalable to different power and
voltage levels; expandable to any number of voltage
steps with low total harmonic distortion; only one DC
bus voltage input is used; transformerless. To control the
MMC system properly, the ac current, circulating
current, and submodule (SM) capacitor voltage are taken
into consideration. However, the applications of control
methods to ensure the normal operation of the inverter
MMC is difficult, especially voltage balance over
capacitors. This paper deals with an application of
Model Predictive Control and an energy balancing
algorithm for a modular multilevel converter to solve the
voltage balance problem. The proposed method has
significantly reduced the switching frequency and
produced output voltage with very low total harmonic
distortion at the AC side of the converter.
KEYWORDS: Modular multilever converter, energy
balancing algorithm.
1. INTRODUCTION
Multilevel converters receive increasing attentions in
recent years due to the demands of high power and high
voltage applications for connect renewable energy
sources [1]. Among the existing multilevel converters,
diode-clamped and cascaded H-bridge (CHB) multilevel
converters are the most widely used [5]. For medium-
voltage (2.3, 3.3, and 4.16 kV) applications, three level
neutral-point-clamped (NPC) topology is a good solution
[7], but some problems exist while extending NPC
converter to higher voltage levels, such as mass clamping
diodes and the voltage imbalance of dc-link capacitors
[8]. For applications with voltage higher than 6 kV,
CHB multilevel inverters are commonly used [7], [9],
[10]. Recently, a new multilevel topology gains more and
more attentions in high-voltage applications: modular
multilevel converter [10]. It is regarded as one of the
next-generation high-voltage multilevel converters
without line-frequency transformers [12]. The MMC is
suitable for high-voltage power conversion due to its
modular structure, simple voltage scaling, and common
dc bus [11]. However, it also has some drawbacks, such
as voltage imbalance of floating capacitors and acute
voltage fluctuation at low frequency [12]. This paper
proposes a Model Predictive Control (MPC) method for
Modular-Multilevel-Converter (MMC). Model Predictive
Control or MPC was first introduced in 1960s . It has
more complex calculations compared to classical linear
controllers, while it provides faster controller with higher
accuracy and stability. From 1980s, the idea of MPC in
power electronics applications was introduced although
lack of the fast processors at that time, limited its
applications only to low switching frequencies. Due to
invention of fast and powerful processors such as DSP
and FPGA, the power electronics industry could take the
advantages of MPC strategy in practice. Many papers
have studied a finite MPC method to control the power
converter. In the MPC method, first, the future values are
predicted on the basis of the switch states, and then the
final switch state is decided in a way to minimize the cost
function. The cost function is designed according to the
control goal, cost function may include a control goal,
such as switching frequency reduction, improve total
harmonic distortion (THD)[2], common-mode voltage
reduction, and current ripple reduction in order to control
the power converter[3]. The proposed control method
applied the cost function to control the ac current,
circulating current, and SM capacitor voltage balancing.
This paper proposes an MPC method with a reduced
number of considered states for ac-side current control.
The details are described by the following parts. In
Section 2, the system structure and operating principles
of the MMC are introduced. Section 3 analyzes
mathematical model of a dc-ac MMC and derives
discrete mathematical models of variables for the MPC
strategy. Section 4 presents the design of control system.
in Section 5, simulations studies analyses are carried out
in the Matlab/Simulink software. Conclusions are
summarized in Section 6.
2. The 11th SEATUC Symposium
2
2. THE DC-AC MODULAR MULTILEVEL
CONVERTER
2.1 Structure Modular Multilevel Converter
Modular Multilevel Converter is an AC to DC
converter topology that was first introduced in 2003 [9].
It is very suitable for high power-high voltage, high -
power applications especially applications for connect
renewable energy sources. In this section, a brief
description of MMC topology and its operation
principles will be presented. MMC topology will be
explained as well as its advantages and disadvantages
comparing it with high power Voltage Source Converters
(VSC) shown in Fig. 1.
vupa
vlowa
l
r
l
r
iupa
ilowa
va
vb
vc
iz
0
SMn+1
SM2n
Idc
ia L R ea
LOAD
D1
D2
S1
S2
C
SM1
SMn
Fig 1. Topology of the (n+1) level MMC connected to a
typical load
A three-phase (n+1)-level MMC has three upper and
three lower arms that are all identical (Fig. 1). Each arm
has been made of a specific number (n) of units named
Sub-modules (SMs) and a small inductor (l) which is
called arm inductor. Each SM has been made of a series
connected of two IGBT/diode parallel combinations and
a precharged capacitor in parallel with them (Fig. 2).
D1
D2
S1
S2
C
i
VSM
Fig 2. Sub-module cỉcuit
The main purpose of using arm inductor is limiting
AC current when a short circuit occurs at the DC-line
[6]. Hence, high di/dt which is dangerous for equipment
can be controlled and minimized by this inductor.
Although it is very useful during fault, it does not
contribute to the normal operation of MMC because the
internal arm currents are flowing continuously. Voltage
sharing between switches is important for high voltage
converters. Sometimes especially during the switching
time, harmful high voltages may destroy the power
switches or at least shorten their life time. The SMs’
capacitors have solved this problem by maintaining the
voltage level across the switches to a certain value.
Moreover, MMC provides the advantage of scalability,
modularity and high power quality. Another remarkable
feature of using MMC in high power applications is that
there is no need of input transformer to adjust the voltage
in contrast with the conventional converters. As a result,
the elimination of the transformer itself and its cooling
equipment that are usually large in size and weight will
lead to saving money and space. Furthermore, the input
filter installations, which are necessary for classical
converters, are not needed when using MMC. When
using VSC, a DC-line capacitor is needed to keep the
voltage constant and the stored energy in this capacitor
may result in extremely high surge currents during short
circuit occurrence [8]. There is no need for this capacitor
in MMC installations.
MMC operates in lower switching frequency than
VSC. Therefore, switching power loss is less. This
feature makes MMC an appropriate converter for high
power applications. However, MMCs are more
expensive and complicated than VSCs and controlling
them is more difficult. A big challenge regarding MMC
controlling is how to keep the capacitor voltages around
the initial value that is equal to 𝑉𝑑𝑐/𝑛
2.2 Sub-Module operating principles
In order to create the desired output voltage at the
MMC terminals, the controller command the switches in
SMs to be turned on or off. Regarding SM circuit in Fig.
2, there are two complementary switching states: S1 is on
and S2 is off and S2 is on and S1 is off. It is not allowed
to turn on both switches simultaneously, because the
capacitor voltage will be totally discharged and afterward
it becomes useless. By considering the switching states,
four different working states can be made based on the
current direction:
S1
S2
S1
S2
S1
S2
S1
S2
ON
OFF
OFF
ON
ON
OFF
OFF
ON
1) 4)2) 3)
Fig 3. Sub-Module operating principles
1) S1 is OFF and S2 is ON: The current (i) will pass
through S2 , VSM will be zero (IGBT on-state voltage
drop is assumed to be zero) and the capacitor is
bypassed.
3. The 11th SEATUC Symposium
3
2) S1 is ON and S2 is OFF: In this case the current (i)
will pass through D1 and capacitor will be charged and
VSM = VC . The voltage of the arm, in which the SM is
placed, will increase one step.
3) S1 is ON and S2 is OFF: The controller will turn on
S1 in order to connect the capacitor to the circuit and
increase the arm voltage on step. In this state, the
capacitor is discharged and VSM=VC.
4) S1 is OFF and S2 is ON: In this state, D2 is turned on
and i will pass through it. The capacitor will be bypassed
and VSM = 0.
In this report, the term “turned on” SM means that
its capacitor is connected and the term “turned off” SM
means a bypassed capacitor. Charging and discharging of
capacitors depend on the currents direction.
2.3 Working principles of MMC
In normal operation of MMC, all of the capacitors are
charged up to its nominal value 𝑉𝑑𝑐/𝑛. In order to reach
this value, [9] has proposed to turn on one SM of a leg
and turn off the rest of SMs in that leg that are 2n-1 SMs.
When the capacitor is charged up, it should be turned off
by the controller command and the next SM should be
turned on. All of the capacitors will be energized
individually one after another. This process has been
shown in Fig. 3. However, it is not possible to charge
them by the main voltage source, because applying a
high step voltage to the capacitors will lead to extremely
high currents. As a consequence, an external voltage
source with lower DC voltage level is needed [12]. As a
better charging method, adding a resistor to the arms has
been proposed by [11]. By using this method, there will
be no need for any external voltage source and there is
no loss due to the resistors in the normal operation. The
controller should only provide the connection and
disconnection of the resistors when needed. When all of
the capacitors have been charged, the controller sends
turning on and off signals to SMs to create an AC
voltage from a DC source or vice versa. At each
sampling time, only half of the total number of SMs in
each phase is on (n SMs).Therefore, the total number of
the connected capacitors from upper arm and lower arm
together is equal to n at any instant. For example, if all of
the n upper SMs are on, all of the lower arm SMs should
be off. So, the AC-line voltage level will be minimum:
.
2 2
dc dc dc
ac
V V V
v n
n
(1)
And reversely, if all of the lower arm SMs are on,
the AC-line voltage level will be maximum:
0.
2 2
dc dc dc
ac
V V V
v
n
(2)
Therefore, AC-bus voltage can vary between -𝑉 𝑑𝑐/2
and +𝑉 𝑑𝑐 /2 with the steps of +𝑉𝑑𝑐/𝑛. Each arm of
MMC represents a controllable voltage source. AC-line
voltage increases by turning off upper arm SMs and
simultaneously turning on the same number of SMs in
the lower arm. However, it is better to increase and
decrease the voltage one step at each switching time to
have a smooth voltage waveform. Charging or
discharging of the capacitors depends on the current
direction as explained in section 2.1.
2.4. MMC control requirements
The following aspects from control point of view are
very important to transfer desired power with maximum
efficiency and minimum voltage and current harmonics:
1. Controlled variable reference tracking Depending on
the main controlled variable that can be output voltage or
current, the control scheme should be able to create the
turning on and turning off signals to make the required
output voltage and current with minimum error with their
reference signals.
2. Keeping the capacitor voltages balanced
As mentioned earlier, if SM is going to be turned on
or off, depending on the current direction, its capacitor
will be charged or discharged; so, it will be more or less
than 𝑉𝑑𝑐/n. The value of voltage variation obviously
depends on the capacitance value and the on-time
duration of SM. In high switching frequency, on-time
duration of Sub-𝑛. Modules is short; therefore, voltage
balancing is not critical. By the way, the control scheme
should consider it carefully to stabilize the voltage of
capacitors in its limitations especially in low switching
frequencies.
3. Circulating current minimization During the operation
of MMC, in addition to the AC side and DC side currents
there are three pure AC high frequency circulating
currents [13].The main reason behind these currents is
the voltage variation (ripple) of capacitors during
charging and discharging period [13]. These circulating
currents have no effect on the DC or AC side of MMC
and no power transfer occurs due to them. However, they
have a significant impact on the rating values of the
MMC components, SMs capacitor ripples and converter
loss [13]. Hence, the circulating current should be
minimized by the controller as much as possible.
In the next chapter, FSC-MPC will be applied to
MMC and it will be proved that it can handle all of the
above control challenges.
3. MATHEMATICAL MODEL OF MMC
The circuit model of a three-phase DC-AC MMC
has been demonstrated in Fig. 4. It is connected to the
utility grid or motor as a load. In this study, the loss in
Sub Modules and arm inductors has been modeled with a
small resistor (r) connected in series with them [3,13].
The resistivity of DC source and DC line has been
neglected. The load is three sets of series-connected
inductor (L), resistor (R) and voltage source (e) in star
shape. The voltage source has 50 Hz frequency. Each
arm of MMC represents a controllable voltage source
called 𝑣 𝑢𝑝𝑗 and 𝑣𝑙𝑜𝑤𝑗 [9], which are the sum of SMs
output voltages (VSM) of upper arm and lower arm in
phase j (a, b or c).
4. The 11th SEATUC Symposium
4
As shown in Fig. 1, 𝑣𝑡𝑗 is the representation of pole
voltages with respect to 𝑉𝑑𝑐/𝑛 point O. By assuming
that each capacitor voltage is ideally equal to and
neglecting the voltage drop across arm inductor and
resistor, 𝑣𝑡𝑗 can be calculated by:
(3)
Where 𝑛 𝑢𝑝𝑗 and 𝑛𝑙𝑜𝑤𝑗 are the number of upper and
lower SMs that have been turned on. Total number of on
SMs in each phase of MMC is:
upj lowjn n n (4)
According to [7, 11 and 13], the upper and lower
arm currents (𝑖 𝑢𝑝𝑗 and 𝑖𝑙𝑜𝑤𝑗) can be calculated by:
3 2
jdc
upj zj
iI
i i (5)
3 2
jdc
lowj zj
iI
i i (6)
Where 𝐼 𝑑𝑐 is the dc component of the dc line
current, 𝑖𝑗 is the output phase current and 𝑖 𝑧𝑗 is the
circulating current flowing through phase j. These
equations mean that the arm currents consist of three
main components with different frequencies: 1. zero
frequency current (Idc) that is its dc offset 2. 50 Hz
current (ij) that is transferring power to the load 3. 100
Hz circulating current (if capacitor voltages are balanced
and the circulating current is minimized very well).
According to Fig 1 and by applying Kirchhoff law, the
mathematical equations can be described as follows.
2
upj jdc
upj upj j j
di diV
v l ri Ri L e
dt dt
(7)
2
lowj jdc
lowj lowj j j
di diV
v l ri Ri L e
dt dt
(8)
Phase currents 𝑖𝑗 can be calculated by subtracting
Eq.6 from Eq.5 and the circulating currents 𝑖 𝑧𝑗 can be
found by adding Eq.5 and Eq.6.
j upj lowji i i (9)
21
2 3
dc
zj upj lowj
I
i i i
(10)
By subtracting Eq.8 from Eq.7 and replacing Eq.9,
the main first order differential equation (Eq.12) that can
be used to predict the phase currents will appear:
2 2 2 0
upj lowj j
upj lowj upj lowj j j
d i i di
v v l r i i Ri L e
dt dt
(11)
1
2 2
2
j
upj lowj j j
di
v v r R i e
dt l L
(12)
In order to predict the second controlled variable, i.e.
the circulating current, Eq.7 and Eq.8 should be added.
.
upj lowj
dc upj lowj upj lowj
d i i
V v v l r i i
dt
(13)
And Eq.10 should be replaced into the above
equation:
1 2
2
2 3
zj
dc upj lowj zj dc
di
V v v ri rI
dt l
(14)
For simplification, the DC line current is assumed to
be constant (𝑑𝐼 𝑑𝑐/𝑑𝑡 = 0).
The third and last controlled variable is the capacitor
voltages that can be calculated by
cij mjdv i
dt C
(15)
Where i = 1,2,..,2n is the SM number and 𝑖 𝑚𝑗 can be
zero if SM is off, or 𝑖 𝑢𝑝𝑗 if SM is located in the upper
arm or 𝑖𝑙𝑜𝑤𝑗 if SM is located in the lower arm.
4. PROPOSED MPC STRATEGY BASED ON THE
MATHEMATICAL MODEL OF THE MMC
4.1. Introduction of Model Predictive Control
The operating principle of MPC is based on the cost
function can contain different linear function and depend
on the characteristics of each system [8].
Converter LoadCost function
minimization
Controled
variables
prediction
Sxref(k+1)
x(k)
MPC controller
Fig 4. The control lock diagram of MMC
Where x(k) is the controlled variables. Based on the
discrete model of system (load and converter), the
current values of the controlled variables x(k) are used to
predict their future values x(k+1) for all N possible
switching states. All the predicted values of the
controlled variables x(k+1) are compared with their
reference values xref(k+1) in the cost function
minimization block. Finally, the switching state (S) that
minimizes the cost function will be selected as the next
switching state and it will be applied to the converter.
The procedure of switching state selection has been
shown in Fig 5; tk is presenting the current state, tk+1 and
tk+2 are the next time steps. The sampling time is Ts.
Assume that the MPC is applied to a converter with
three possible switching states (x1, x2 and x3) and the
reference is constant in a short period of time. The cost
function is defined as the distance between the controlled
variable and its reference value that should be minimized
in order to track the reference. The controlled variable at
the next step time is predicted for all the switching states,
but choosing x3 provides the least distance to the
2
lowj upj
tj dc
n n
v V
n
5. The 11th SEATUC Symposium
5
reference value xref ; as a result, it will be applied to the
converter at time tk+1. Subsequently, all the process will
be shifted one step forward. By repeating the procedure
once again for tk+2 will be selected due to its minimum
distance with xref . Thus, the whole procedure will be
repeated again.
Ts Ts
x
xref(k)
tk tk+1
tk+2
t
x1(k+1)
x3(k+1)
x2(k+1)
x2(k+2)
x1(k+2)
x3(k+2)
x(k)
Fig 5. MPC operating principle
Mô hình MPC áp dụng cho bộ biến đổi điện tử công
suất được bắt đầu bằng các biến rời rạc như dòng điện,
điện áp… hàm mục tiêu phải được xác định theo hành vi
mong muốn của BBĐ. Tại mỗi thời điểm lấy mẫu, hàm
mục tiêu sẽ tính tất cả các trạng thái chuyển mạch có thể
cho chu kỳ trích mẫu tiếp theo dựa trên các trạng thái
hiện tại. Sau đó, các trạng thái tối ưu sẽ được lựa chọn để
áp dụng cho bộ chuyển đổi. Để thiết kế bộ điều khiển
MPC cho bộ biến đổi điện tử công suất ta thực hiện ba
giai đoạn: Lấy mô hình rời rạc của hệ thống theo các dẫn
xuất biến điều khiển để có thể dự đoán trong tương lai;
Xác định tất cả các trạng thái chuyển mạch có thể cho
chuyển đổi và mối quan hệ của chúng với các biến khác;
Xác định hàm mục tiêu để tính các giá trị tối ưu đại diện
cho hành vi mong muốn của hệ thống.
4.2. MPC strategy of the MMC
This Section proposes a MPC strategy to control the
ac-side currents, regulate the SMs capacitor voltages, and
eliminate/minimize circulating currents. The proposed
MPC strategy is based on the following steps:
• Development of a discrete-time model of the system
for one-step forward prediction of an MMC variables.
• Definition of a cost function associated with control
objectives.
• Evaluation of the defined cost function for all
possible switching states of the converter and selection of
the best switching state that minimizes the cost function.
FCS-MPC can fulfill all the MMC control requirements
simultaneously and very well. By defining a proper cost
function, it can make the output currents to follow their
references, keep the capacitor voltages in a balanced
position around 𝑉𝑑𝑐/n and minimize the circulating
currents as much as possible. In a single-phase (n+1)-
level MMC, the total possible switching states are:
2
2 !
! 2 !
n
n
n
n C
n n n
(16)
Consequently, for a three-phase one it will be equal
to 𝑁3
. For example, a 3-level MMC has totally 63
= 216
switching states. This number is important because the
controller speed depends directly to it. Cost function
calculation process repeats for all the switching states
and then, the one that minimizes the cost function will be
selected to be applied at the next switching instant.
As mentioned earlier, there are three controlled
variables regarding MMC; output AC currents, capacitor
voltages and circulating currents. In order to predict the
one-step ahead value of the controlled variables, Eq.11,
14 and 15 should be discretized by one of the Euler
methods. As the system model accuracy is very
important for the controller performance, midpoint Euler
method is selected. However, the system model based on
both backward and forward Euler methods will be
calculated and used for a single phase 3-level MMC.
AC-Side Current Control: The objective of current
control is to regulate the MMC ac-side currents at their
reference values, i.e., reference current tracking. Based
on Eq.11 and assuming a sampling period of Ts, the
discrete-time model of the MMC ac-side current, with an
Euler approximation of the current derivative, is deduced
as:
2
(
2 2 . 2
2
( )) (17)
2
lowj s upj s
j s
s j s
j s j
s
v t T v t T
i t T
T l L R i t T
l L
e t T i t
T
Predicted current, ij(t) is the measured ac-side
current, and esj(t + Ts) is the estimated grid voltage at the
low-voltage side of the transformer which is
approximated by the measured value of esj(t). vupa(t+Ts)
and vlowa(t+Ts) are the predicted arm voltages which can
be calculated based on adding up the one-step forward
predicted capacitor voltages, or directly the sampled
capacitor voltages of the predicted switched-on SMs in
upper and lower arms, respectively.
In the next step of designing FCS-MPC, a cost
function should be defined in order to force the output
AC currents to track their references, keep the capacitor
voltages balanced (i.e. around the nominal value 𝑉𝑑𝑐/𝑛)
and minimize the circulating currents. It should be
mentioned that the total switching states [
3
2N n
nC ]
of a three-phase MMC are three identical sets. Therefore,
it is better and simpler to design three identical
controller’ codes to work in parallel instead of writing
one code for considering all of them; therefore, each
phase is controlled by their own cost function separately
and at the same time with the other two phases.
j jref s j sJ i t T i t T (18)
Where ijref is the reference current and ij(t+Ts)
obtained from Eq.17 is the next-step predicted current.
Ideally, the cost function Jj reaches its minimum value at
zero if the ac-side currents track their reference values.
6. The 11th SEATUC Symposium
6
This condition is used as a basis for the ac-side current
control. Within each sampling period, Jj is calculated and
evaluated for all possible switching states of the MMC.
The switching state which results in the minimum value
for Eq.18, is the best switching state for the next
switching cycle. For simplicity, 𝑖𝑗𝑟𝑒𝑓(t+Ts) is
approximated with 𝑖𝑗𝑟𝑒𝑓(t) in high sampling frequency.
Capacitor Voltages Balancing: Based on Eq.15, the
next step predicted value of the capacitor voltage,
Vcij(t+Ts), is calculated by :
m
Cij s Cij s
i t
V t T V t T
C
for an on-state SM (19a)
Cij s CijV t T V t for an off-state SM (19b)
Where im(t) = iupj(t) for the SMs in the upper arm
and im(t) = ilowj(t) for the SMs in the lower arm. To carry
out the voltage balancing task, the MPC strategy assigns
an additional cost to the capacitor voltage balancing task.
This is achieved by including an additional term,
associated with the voltage deviations of the SMs
capacitor voltages from their reference values, in the
original cost function. Consequently, the cost function Jj
is modified to:
' dc
j j C Cij s
i
V
J J V t T
n
(20)
Where λC is a weighing factor and is tuned based on
the cost contribution assigned to the capacitor voltages
deviations. The procedure to determine λC is based on the
empirical method presented in [11].
Circulating Current Control: To reduce the SMs
Capacitor voltage ripples and converter losses and to
avoid the overrated design of the MMC components, the
circulating currents are required to be
eliminated/minimized. Based on Eq.14, the discrete-time
model of the circulating currents is deduced as:
2
s
zj s dc lowj s upj s zj
T
i t T V v t T v t T i t
l
(21)
The MPC strategy aims at eliminating/minimizing
the circulating current by adding a third term, associated
with the circulating current, to the original cost function,
as follows:
'' '
j j j Z Zj sJ J J i t T (22)
Where λz is a weighing factor and is tuned based on
the design requirements or control objectives.
The MPC strategy evaluates the cost function J’’
for
all possible switching states of phase j and selects the
state which results in the minimum value for J’’
, as the
desired switching state. From the above analysis,
interpolation algorithm of the system control as follows:
Evaluate the cost function
based on (22)
No
Yes
Yes
No
Updete the switching state
Apply the selected switching state Sj
Measured
Calculate ij(t+Ts), Vcij(t+Ts), and izj(t+Ts)
based on (17),(19), and (21) for Sj(K)
Fig 6. Block fiagram of the per-phase MPC strategy for
the MMC
5. SIMULATION RESULTS
This section evaluates the performance of a five-level
gridconnected MMC system of Fig. 1 that operates based
on the proposed MPC strategy. The simulation studies
are conducted in the MATLAB/SIMMULINK
environment to demonstrate the performance of the
proposed MPC strategy in terms of capacitor voltages
balancing, circulating current elimination capabilities,
and power control which is based on current control. The
system parameters are given in Table 1.
Table 1. Parameters of the study system of Fig 1.
Vdc
f 50Hz
r
l
R 2
L 0.02
EXPERIMENT
7. The 11th SEATUC Symposium
7
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