This document summarizes the control of a single-stage three-phase buck-boost power factor correction rectifier. It begins with an abstract that describes advances in power electronics enabling more electric aircraft and the use of active power factor correction rectifiers for AC/DC conversion. It then provides background on traditional rectification methods, issues they present, and how active switched-mode converters address these issues. The document focuses on modeling and simulation of control strategies for a three-phase buck-boost topology, with the goal of developing a simple, fast, and reliable control strategy for these rectifiers in more electric aircraft.
Power Quality Enhancement in Wind Connected Grid System Interface Based On St...IJERA Editor
Wind energy has become one of the significant alternative renewable energy resources because of its abundance
and the strong drive for its commercialization. Dynamic electric load variations and wind velocity excursions
cause excessive changes in the prime mover kinetic energy and the corresponding electrical power injected into
the AC grid utility system. In this paper, a scheme based on the low cost static switched filter compensator
(SSFC) is presented for voltage sag/swell compensation, power factor improvement in distribution grid
networks with the dispersed wind energy interface. The SSFC scheme is based on an intermittent switching
process between two shunt capacitor banks to be one of them in parallel with the capacitor of a tuned arm filter.
Two regulators based on a tri- loop dynamic error driven inter-coupled weighted modified proportional-integralderivative
(PID) controller which is used to modulate the PWM.
The Static Switched Filter Compensation (SSFC) compensation scheme which enhances the system
power quality has been fully validated using MATLAB–Simulink. The effectiveness of this compensation
scheme approach is demonstrated using a study case of 3 bus system. Simulation results show that there is
improvement in harmonics reduction, voltage sag/swell compensation, power factor improvement at generator
bus, load bus, and infinite bus respectively
In this paper a grid interconnected system with wind energy source linked with a FACTs based SSFC device ( Static switched filter compensator ) at load for enhancing power quality is considered .Analysis is done for the proposed system by varying Carrier frequency over a wide range and observed system performance at all 3 busses wise Grid bus, Generator Bus and Load Bus. Two regulators are used to organize the FACTS SSFC-device, these are based on a tri-loop dynamic error obsessed inter-coupled input to VSC controller. Investigation is made in MATLAB/SIMULINK Environment for the proposed system ,it is observed that system performance in terms of percentage Total harmonic Distortion is satisfactory along with the Enhanced Power Quality.
Analysis of a High Efficiency Boost-Inverter with Back-up Battery Storage in ...irjes
paper, proposes an analysis and design of a high efficiency boost-inverter with bidirectional back-up battery storage in fuel cell. When low-voltage unregulated fuel cell (FC) output is conditioned to generate AC power, two stages are required: a boost stage and an inversion one. In this paper, the boost-inverter topology that achieves both boosting and inversion functions in a single-stage is used to develop an FC-based energy system which offers high conversion efficiency, low-cost and compactness. The proposed system incorporates additional battery-based energy storage and a DC-DC bi-directional converter to support instantaneous load changes. The output voltage of the boost-inverter is voltage-mode controlled and the DC-DC bidirectional converter is current-mode controlled. The load low frequency current ripple is supplied by the battery which minimizes the effects of such ripple being drawn directly from the FC itself. Analysis, simulation results are presented to confirm the operational performance of the proposed system.
A Single Phase to Three Phase PFC Half-Bridge Converter Using BLDC Drive with...IJERA Editor
In this paper, a buck half-bridge DC-DC converter is used as a single-stage power factor correction (PFC) converter for feeding a voltage source inverter (VSI) based permanent magnet brushless DC motor (BLDC) drive. The front end of this PFC converter is a diode bridge rectifier (DBR) fed from single-phase AC mains. The BLDC is used to drive a compressor load of an air conditioner through a three-phase VSI fed from a controlled DC link voltage. The speed of the compressor is controlled to achieve energy conservation using a concept of the voltage control at DC link proportional to the desired speed of the BLDC. Therefore the VSI is operated only as an electronic commutator of the BLDC. The stator current of the BLDC during step change of reference speed is controlled by a rate limiter for the reference voltage at DC link. The proposed BLDC drive with voltage control based PFC converter is designed, modeled and its performance is simulated in Matlab-Simulink environment for an air conditioner compressor driven through a 1.5 kW, 1500 rpm BLDC motor. The evaluation results of the proposed speed control scheme are presented to demonstrate an improved efficiency of the proposed drive system with PFC feature in wide range of the speed and an input AC voltage.
This paper presents an analysis of virtual-flux direct power control (VFDPC) technique for the three-phase pulse width modulation (PWM) ac-dc converter. The proposed VFDPC is developed by assuming the grid voltage and converter line filters quantities are related to a virtual three-phase ac motor. The controller works with less number of sensors by eliminating the voltage sensors used for measuring the three-phase grid voltage. The grid virtual flux which is proportional to the grid voltage will be estimated from the information of converter switching states, line current, and dc-link output voltage. Several analyses are performed in order to study the steady state and dynamic performance of the converter, particularly during the load and DC voltage output reference variations. The proportional integral (PI) controller at the outer voltage control loop of VFDPC is tuned properly and the entire PWM ac-dc converter system is simulated using MATLAB/Simulink to ensure the dc output voltage follow the desired output voltage under steady state and dynamic conditions. Ac-dc converter utilizing the proposed VFDPC is able to generate three-phase input current waveforms that are almost sinusoidal with low harmonics contents which is less than 5% and near unity power factor (pf) operation.
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.
DC Bus Voltage Switched Control Method for Three Phase Voltage Source PWM Rec...ijsrd.com
More electric aircraft referred to as the general move in the aerospace industry to increase the amount of electrically powered equipment on future aircraft. One of the most important kind of electric loads of the future more electric aircraft is the aircraft electric actuator but its power characteristics possesses rapidly varying nature in the wider range and constant power nature in the small signal sense. Due to the problem of varying nature of power characteristics the problem of flexible voltage regulation under dynamic loads arises. For solving this problem dc-bus voltage switched control method of three phase voltage source pwm rectifier is presented in this paper. Several linear controllers are designed on different operating points of the voltage source rectifier, and one controller is implemented according to certain switching law. The stability is checked by the common lyapunov function method. Simulation results showed the desired control performance is obtained. In comparison of classical PI controller the results of switched controller achieves considerable reduction in the dip and overshoot of the dc bus voltage under an aircraft’s electric actuator load.
Power Quality Enhancement in Wind Connected Grid System Interface Based On St...IJERA Editor
Wind energy has become one of the significant alternative renewable energy resources because of its abundance
and the strong drive for its commercialization. Dynamic electric load variations and wind velocity excursions
cause excessive changes in the prime mover kinetic energy and the corresponding electrical power injected into
the AC grid utility system. In this paper, a scheme based on the low cost static switched filter compensator
(SSFC) is presented for voltage sag/swell compensation, power factor improvement in distribution grid
networks with the dispersed wind energy interface. The SSFC scheme is based on an intermittent switching
process between two shunt capacitor banks to be one of them in parallel with the capacitor of a tuned arm filter.
Two regulators based on a tri- loop dynamic error driven inter-coupled weighted modified proportional-integralderivative
(PID) controller which is used to modulate the PWM.
The Static Switched Filter Compensation (SSFC) compensation scheme which enhances the system
power quality has been fully validated using MATLAB–Simulink. The effectiveness of this compensation
scheme approach is demonstrated using a study case of 3 bus system. Simulation results show that there is
improvement in harmonics reduction, voltage sag/swell compensation, power factor improvement at generator
bus, load bus, and infinite bus respectively
In this paper a grid interconnected system with wind energy source linked with a FACTs based SSFC device ( Static switched filter compensator ) at load for enhancing power quality is considered .Analysis is done for the proposed system by varying Carrier frequency over a wide range and observed system performance at all 3 busses wise Grid bus, Generator Bus and Load Bus. Two regulators are used to organize the FACTS SSFC-device, these are based on a tri-loop dynamic error obsessed inter-coupled input to VSC controller. Investigation is made in MATLAB/SIMULINK Environment for the proposed system ,it is observed that system performance in terms of percentage Total harmonic Distortion is satisfactory along with the Enhanced Power Quality.
Analysis of a High Efficiency Boost-Inverter with Back-up Battery Storage in ...irjes
paper, proposes an analysis and design of a high efficiency boost-inverter with bidirectional back-up battery storage in fuel cell. When low-voltage unregulated fuel cell (FC) output is conditioned to generate AC power, two stages are required: a boost stage and an inversion one. In this paper, the boost-inverter topology that achieves both boosting and inversion functions in a single-stage is used to develop an FC-based energy system which offers high conversion efficiency, low-cost and compactness. The proposed system incorporates additional battery-based energy storage and a DC-DC bi-directional converter to support instantaneous load changes. The output voltage of the boost-inverter is voltage-mode controlled and the DC-DC bidirectional converter is current-mode controlled. The load low frequency current ripple is supplied by the battery which minimizes the effects of such ripple being drawn directly from the FC itself. Analysis, simulation results are presented to confirm the operational performance of the proposed system.
A Single Phase to Three Phase PFC Half-Bridge Converter Using BLDC Drive with...IJERA Editor
In this paper, a buck half-bridge DC-DC converter is used as a single-stage power factor correction (PFC) converter for feeding a voltage source inverter (VSI) based permanent magnet brushless DC motor (BLDC) drive. The front end of this PFC converter is a diode bridge rectifier (DBR) fed from single-phase AC mains. The BLDC is used to drive a compressor load of an air conditioner through a three-phase VSI fed from a controlled DC link voltage. The speed of the compressor is controlled to achieve energy conservation using a concept of the voltage control at DC link proportional to the desired speed of the BLDC. Therefore the VSI is operated only as an electronic commutator of the BLDC. The stator current of the BLDC during step change of reference speed is controlled by a rate limiter for the reference voltage at DC link. The proposed BLDC drive with voltage control based PFC converter is designed, modeled and its performance is simulated in Matlab-Simulink environment for an air conditioner compressor driven through a 1.5 kW, 1500 rpm BLDC motor. The evaluation results of the proposed speed control scheme are presented to demonstrate an improved efficiency of the proposed drive system with PFC feature in wide range of the speed and an input AC voltage.
This paper presents an analysis of virtual-flux direct power control (VFDPC) technique for the three-phase pulse width modulation (PWM) ac-dc converter. The proposed VFDPC is developed by assuming the grid voltage and converter line filters quantities are related to a virtual three-phase ac motor. The controller works with less number of sensors by eliminating the voltage sensors used for measuring the three-phase grid voltage. The grid virtual flux which is proportional to the grid voltage will be estimated from the information of converter switching states, line current, and dc-link output voltage. Several analyses are performed in order to study the steady state and dynamic performance of the converter, particularly during the load and DC voltage output reference variations. The proportional integral (PI) controller at the outer voltage control loop of VFDPC is tuned properly and the entire PWM ac-dc converter system is simulated using MATLAB/Simulink to ensure the dc output voltage follow the desired output voltage under steady state and dynamic conditions. Ac-dc converter utilizing the proposed VFDPC is able to generate three-phase input current waveforms that are almost sinusoidal with low harmonics contents which is less than 5% and near unity power factor (pf) operation.
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.
DC Bus Voltage Switched Control Method for Three Phase Voltage Source PWM Rec...ijsrd.com
More electric aircraft referred to as the general move in the aerospace industry to increase the amount of electrically powered equipment on future aircraft. One of the most important kind of electric loads of the future more electric aircraft is the aircraft electric actuator but its power characteristics possesses rapidly varying nature in the wider range and constant power nature in the small signal sense. Due to the problem of varying nature of power characteristics the problem of flexible voltage regulation under dynamic loads arises. For solving this problem dc-bus voltage switched control method of three phase voltage source pwm rectifier is presented in this paper. Several linear controllers are designed on different operating points of the voltage source rectifier, and one controller is implemented according to certain switching law. The stability is checked by the common lyapunov function method. Simulation results showed the desired control performance is obtained. In comparison of classical PI controller the results of switched controller achieves considerable reduction in the dip and overshoot of the dc bus voltage under an aircraft’s electric actuator load.
This paper presented single DC bus single phase seven level cascaded H-bridge (CHB) inverter for multi-panel photovoltaic grid-connected applications. A single DC bus supplying flyback converters to produce DC link voltages for CHB cells is suggested. A balanced operation of CHB inverter cells is obtained irrespective to power unbalance occurred by individual maximum power point tracking boost converter of photovoltaic (PV) panels due to the non-uniform irradiation and partial shading. A DC bus voltage control system with addition of estimated DC bus ripple voltage to the reference is proposed to eliminate the second order harmonic contained in the feedback voltage of DC bus enabling to design high bandwidth of DC voltage control loop. This produces fast dynamic response, low total harmonic distortion (THD) of grid current and smaller DC bus capacitance. Mathematical modeling of bus voltage control system is presented. PSIM simulation program is used and the simulation results are obtained to validate the proposed control system.
Enhancement of Power System Dynamics Using a Novel Series Compensation SchemeIJMER
Phase imbalanced capacitive compensation is a “hybrid” series compensation scheme, where the
series capacitive compensation in one phase is created using a single-phase TCSC in series with a fixed capacitor
(Cc), and the other two phases are compensated by fixed series capacitors (C). The TCSC control is initially set
such that its equivalent compensations at the power frequency combined with the fixed capacitor yield a
resultant compensation equal to the other two phases. Thus, the phase balance is maintained at the power
frequency while at any other frequency, a phase imbalance is created. The effectiveness of the scheme in damping
power system oscillations for various network conditions, namely different system faults and tie-line power flows is
evaluated using the MATLAB/SIMULINK Software
An Improved UPQC Controller to Provide Grid-Voltage RegulationIJMTST Journal
In this paper presents an improved controller for the dual topology of the Unified Power Quality Conditioner (UPQC) extending its capability in power quality compensation, as well as in micro-grid applications. By the use of this controller, beyond the conventional UPQC power quality features including voltage sag/swell compensation, the iUPQC will also compensate reactive power support to regulate not only the load-bus voltage, but also the voltage at the grid-side bus. We can say, the iUPQC will work as a STATCOM at the grid side, while providing also the conventional UPQC compensations at the load terminal or micro-grid side. Experimental results are provided to verify the new functionality of the equipment.
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.
FIRING ANGLE SVC MODEL FOR ANALYZING THE PERFORMANCE OF TRANSMISSION NETWORK ...IAEME Publication
This paper deals with Power flow, which is necessary for any power system solution and carry
out a comprehensive study of the Newton- Raphson method of power flow analysis with and without
SVC. Voltage stability analysis is the major concern in order to operate any power system as
secured. This paper presents the investigation on N-R power flow enhancement of voltage stability
and power loss minimization with & without FACTS controllers such as Static Var Compensator
(SVC) device. The Static Var Compensator (SVC) provides a promising means to control power
flow in modern power systems. In this paper the Newton-Raphson is used to investigate its effect on
voltage profile and power system lossess with and without SVC in power system.. Simulations
investigate the effect of voltage magnitude and angle with and without SVC on the power flow of
the system. This survey article will be very much useful to the researchers for finding out the
relevant references in the field of Newton-Raphson power flow control with SVC in power systems.
In order to reach the above goals, these devices must be located optimally. In this paper the
Optimal placement of SVC is carried out by Voltage collapse Prediction Index (VCPI).The size of
the SVC is determined by suitable firing angle which reduces the losses in the system. Simulations
have been implemented in MATLAB Software and the IEEE 14 and IEEE 57-bus systems have been
used as case studies.
Power Quality Improvement of DC Drive by Reduction of Circulating Currentpaperpublications3
Abstract: The paper presents power quality improvement of DC drives by reduction of circulating current in parallal operation of active filters based on hysteresis current control. As it is a well-known fact that power quality determines the fitness of electrical power to consumer devices, hence an effort has been made to improve power quality in this work. Simulation with the help of MATLAB/Simulink has been done and results obtained are discussed in detail to verify the theoretical results. The multipulse converter was connected with DC drives and was run at no load condition to find out the transient and steady state performances. FFT analysis has been performed and Total Harmonic Distortion (THD) results obtained at different pulses are shown here.
Unified Power Quality Conditioner Model Based with Series and Shunt FiltersIAES-IJPEDS
With the increase of the complexion in the power distribution system, it is very possible that several kinds of power quality disturbances are happened in a power distribution system simultaneously.This paper proposes a unified power quality conditioner (UPQC) including a series and a shunt active power filter (APF) to compensate harmonics in both the distorted supply voltage and nonlinear load current. In the series APF control scheme, a proportional-integral (PI) controller, meanwhile a PI controller and are designed in the shunt APF control scheme to relieve harmonic currents produced by nonlinear loads. The DC voltage is maintained constant using Two degree of freedom proportional integral voltage controller (2DoFPI). The performance of the proposed UPQC is significantly improved compared to the conventional control strategy. The feasibility of the proposed UPQC control scheme is validated through the simulations.
A New Control Method for Grid-Connected PV System Based on Quasi-Z-Source Cas...IAES-IJPEDS
In this paper, a new control method for quasi-Z-source cascaded multilevel inverter based grid-connected photovoltaic (PV) system is proposed. The proposed method is capable of boosting the PV array voltage to a higher level and solves the imbalance problem of DC-link voltage in traditional cascaded H-bridge inverters. The proposed control system adjusts the grid injected current in phase with the grid voltage and achieves independent maximum power point tracking (MPPT) for the separate PV arrays. To achieve these goals, the proportional-integral (PI) controllers are employed for each module. For achieving the best performance, this paper presents an optimum approach to design the controller parameters using particle swarm optimization (PSO). The primary design goal is to obtain good response by minimizing the integral absolute error. Also, the transient response is guaranteed by minimizing the overshoot, settling time and rise time of the system response. The effectiveness of the new proposed control method has been verified through simulation studies based on a seven level quasi-Z- Source cascaded multilevel inverter.
Mitigation of Voltage Fluctuations in Power System Using STATCOMIJERA Editor
Wind energy being a renewable source of energy is enjoying a rapid growth globally. However, wind energy being an uncontrollable source of energy coupled with the fact that it uses distributed induction generators for power conversion poses a challenge in integrating a large scale wind-farm into a weak power system. An actual weak power system with two large Wind-Farms (WFs) coupled to it is introduced as part of this study. A model of this integrated system along with a STATCOM for steady state and dynamic impact study is developed in the MATLAB/Simulink environment. The power quality issues are highlighted and a centralized STATCOM is proposed to solve the issue of the voltage fluctuations in particular in addition to addressing the other issues. Based on the results obtained from the simulation, the system voltage control issues are analyzed and the location of STATCOM is assessed. Finally, a STATCOM control strategy for suppression of voltage fluctuations is presented.
The work presented in this paper is devoted to the control of a photovoltaic system connected to grid by a three level diode clamed inverter. A control structure based on three parts: dc link voltage control, power injected control and current control is proposed. In this work, the random PWM strategy is used to generate control signals for the multilevel inverter used us an interface to connect photovoltaic generators to the grid. Numerical simulations are performed using MATLAB / Simulink software, the simulation results for the proposed system indicate the performances of the proposed control structure, minimization of harmonics by the random PWM strategy applied and injection to the grid more active power by the multilevel inverter structure.
A Simple Strategy of Controlling a Balanced Voltage Capacitor in Single Phase...IAES-IJPEDS
The five-level inverter has been used for many applications in renewable energy systems. Even though its harmonic distortion was lower than the conventional two-level inverter. The five-level converter has some disadvantages such as increasing power semiconductor, complex pulse width modulation control methods, and problem with the voltage balancing of the capacitor. This paper aims to propose a modified five-level inverter based on sinusoidal pulse width modulation using phase shifted carrier to enhancing the capacitor voltage balancing. This modified five-level inverter reduces the overall cost and the complexity of the pulse width modulator. Thus making the proposed control system highly simple. The performance and its controller were validated by means of standard laboratory equipments. The analysis, simulation and implementation result showed better performance of five-level inverter.
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POWER STABILITY ANALYSIS OF A TRANSMISSION SYSTEM WITH A UNIFIED POWER FLOW C...IJITE
The unified power quality conditioner is the equipment used for regulated voltage distortion and voltage
unbalance in a power system. UPFC can enhance the power to flow through the transmission system by
controlling the power flow and voltage stability of the transmission line within their limits. This paper
presents a control scheme and Theoretical derivation of the unified power flow conditioner and the
simulation results are compared and contrasted in detail. UPFC is a combination of shunt Active and
series active power filters. UPFC contains a DC link capacitor in a single-phase voltage source inverter
with two back to back connected, three-phase three-wire and three-phase four-wire are arranged. The
fundamental target of this work is to determine the causes and impacts of power quality problems,
specifically voltage sag, voltage swell, power factor, and Total Harmonics Distortion (THD) and enhance
the power quality of a transmission system by UPFC based Transformative Intrinsic Algorithm (TIA). The
Simulation of the proposed method is developed by Mat lab Simulink software, and the simulation result
shows, the proposed method gives better solutions to control the power imbalance in the distribution
system with its cost-effectiveness.
Wind-Turbine Asynchronous Generator Synchronous Condenser with Excitation in ...IJMTST Journal
In this paper Standalone operation of a wind turbine generating system under fluctuating wind and variable load conditions is a difficult task. Moreover, high reactive power demand makes it more challenging due to the limitation of reactive capability of the wind generating system.The frequency is controlled by the Discrete Frequency Regulator block. This controller uses a standard three-phase Phase Locked Loop (PLL) system to measure the system frequency. The measured frequency is compared to the reference frequency to obtain the frequency error. This error is integrated to obtain the phase error. The phase error is then used by a Proportional-Differential (PD) controller to produce an output signal representing the required secondary load power. This signal is converted to an 8-bit digital signal controlling switching of the eight three-phase secondary loads. In order to minimize voltage disturbances, switching is performed at zero crossing of voltage.
Power Factor is a measure of how efficiently electrical power is consumed. In the ideal world Power Factor would be unity (or 1). Unfortunately in the real world Power Factor is reduced by highly inductive loads to 0.7 or less. This induction is caused by equipment such as lightly loaded electric motors and fluorescent lighting ballasts and welding sets, etc. Three phase power factor can be corrected using different approaches like sine wave control, vector control, single cycle control or Vienne Bridge Rectifier.
This paper presented single DC bus single phase seven level cascaded H-bridge (CHB) inverter for multi-panel photovoltaic grid-connected applications. A single DC bus supplying flyback converters to produce DC link voltages for CHB cells is suggested. A balanced operation of CHB inverter cells is obtained irrespective to power unbalance occurred by individual maximum power point tracking boost converter of photovoltaic (PV) panels due to the non-uniform irradiation and partial shading. A DC bus voltage control system with addition of estimated DC bus ripple voltage to the reference is proposed to eliminate the second order harmonic contained in the feedback voltage of DC bus enabling to design high bandwidth of DC voltage control loop. This produces fast dynamic response, low total harmonic distortion (THD) of grid current and smaller DC bus capacitance. Mathematical modeling of bus voltage control system is presented. PSIM simulation program is used and the simulation results are obtained to validate the proposed control system.
Enhancement of Power System Dynamics Using a Novel Series Compensation SchemeIJMER
Phase imbalanced capacitive compensation is a “hybrid” series compensation scheme, where the
series capacitive compensation in one phase is created using a single-phase TCSC in series with a fixed capacitor
(Cc), and the other two phases are compensated by fixed series capacitors (C). The TCSC control is initially set
such that its equivalent compensations at the power frequency combined with the fixed capacitor yield a
resultant compensation equal to the other two phases. Thus, the phase balance is maintained at the power
frequency while at any other frequency, a phase imbalance is created. The effectiveness of the scheme in damping
power system oscillations for various network conditions, namely different system faults and tie-line power flows is
evaluated using the MATLAB/SIMULINK Software
An Improved UPQC Controller to Provide Grid-Voltage RegulationIJMTST Journal
In this paper presents an improved controller for the dual topology of the Unified Power Quality Conditioner (UPQC) extending its capability in power quality compensation, as well as in micro-grid applications. By the use of this controller, beyond the conventional UPQC power quality features including voltage sag/swell compensation, the iUPQC will also compensate reactive power support to regulate not only the load-bus voltage, but also the voltage at the grid-side bus. We can say, the iUPQC will work as a STATCOM at the grid side, while providing also the conventional UPQC compensations at the load terminal or micro-grid side. Experimental results are provided to verify the new functionality of the equipment.
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.
FIRING ANGLE SVC MODEL FOR ANALYZING THE PERFORMANCE OF TRANSMISSION NETWORK ...IAEME Publication
This paper deals with Power flow, which is necessary for any power system solution and carry
out a comprehensive study of the Newton- Raphson method of power flow analysis with and without
SVC. Voltage stability analysis is the major concern in order to operate any power system as
secured. This paper presents the investigation on N-R power flow enhancement of voltage stability
and power loss minimization with & without FACTS controllers such as Static Var Compensator
(SVC) device. The Static Var Compensator (SVC) provides a promising means to control power
flow in modern power systems. In this paper the Newton-Raphson is used to investigate its effect on
voltage profile and power system lossess with and without SVC in power system.. Simulations
investigate the effect of voltage magnitude and angle with and without SVC on the power flow of
the system. This survey article will be very much useful to the researchers for finding out the
relevant references in the field of Newton-Raphson power flow control with SVC in power systems.
In order to reach the above goals, these devices must be located optimally. In this paper the
Optimal placement of SVC is carried out by Voltage collapse Prediction Index (VCPI).The size of
the SVC is determined by suitable firing angle which reduces the losses in the system. Simulations
have been implemented in MATLAB Software and the IEEE 14 and IEEE 57-bus systems have been
used as case studies.
Power Quality Improvement of DC Drive by Reduction of Circulating Currentpaperpublications3
Abstract: The paper presents power quality improvement of DC drives by reduction of circulating current in parallal operation of active filters based on hysteresis current control. As it is a well-known fact that power quality determines the fitness of electrical power to consumer devices, hence an effort has been made to improve power quality in this work. Simulation with the help of MATLAB/Simulink has been done and results obtained are discussed in detail to verify the theoretical results. The multipulse converter was connected with DC drives and was run at no load condition to find out the transient and steady state performances. FFT analysis has been performed and Total Harmonic Distortion (THD) results obtained at different pulses are shown here.
Unified Power Quality Conditioner Model Based with Series and Shunt FiltersIAES-IJPEDS
With the increase of the complexion in the power distribution system, it is very possible that several kinds of power quality disturbances are happened in a power distribution system simultaneously.This paper proposes a unified power quality conditioner (UPQC) including a series and a shunt active power filter (APF) to compensate harmonics in both the distorted supply voltage and nonlinear load current. In the series APF control scheme, a proportional-integral (PI) controller, meanwhile a PI controller and are designed in the shunt APF control scheme to relieve harmonic currents produced by nonlinear loads. The DC voltage is maintained constant using Two degree of freedom proportional integral voltage controller (2DoFPI). The performance of the proposed UPQC is significantly improved compared to the conventional control strategy. The feasibility of the proposed UPQC control scheme is validated through the simulations.
A New Control Method for Grid-Connected PV System Based on Quasi-Z-Source Cas...IAES-IJPEDS
In this paper, a new control method for quasi-Z-source cascaded multilevel inverter based grid-connected photovoltaic (PV) system is proposed. The proposed method is capable of boosting the PV array voltage to a higher level and solves the imbalance problem of DC-link voltage in traditional cascaded H-bridge inverters. The proposed control system adjusts the grid injected current in phase with the grid voltage and achieves independent maximum power point tracking (MPPT) for the separate PV arrays. To achieve these goals, the proportional-integral (PI) controllers are employed for each module. For achieving the best performance, this paper presents an optimum approach to design the controller parameters using particle swarm optimization (PSO). The primary design goal is to obtain good response by minimizing the integral absolute error. Also, the transient response is guaranteed by minimizing the overshoot, settling time and rise time of the system response. The effectiveness of the new proposed control method has been verified through simulation studies based on a seven level quasi-Z- Source cascaded multilevel inverter.
Mitigation of Voltage Fluctuations in Power System Using STATCOMIJERA Editor
Wind energy being a renewable source of energy is enjoying a rapid growth globally. However, wind energy being an uncontrollable source of energy coupled with the fact that it uses distributed induction generators for power conversion poses a challenge in integrating a large scale wind-farm into a weak power system. An actual weak power system with two large Wind-Farms (WFs) coupled to it is introduced as part of this study. A model of this integrated system along with a STATCOM for steady state and dynamic impact study is developed in the MATLAB/Simulink environment. The power quality issues are highlighted and a centralized STATCOM is proposed to solve the issue of the voltage fluctuations in particular in addition to addressing the other issues. Based on the results obtained from the simulation, the system voltage control issues are analyzed and the location of STATCOM is assessed. Finally, a STATCOM control strategy for suppression of voltage fluctuations is presented.
The work presented in this paper is devoted to the control of a photovoltaic system connected to grid by a three level diode clamed inverter. A control structure based on three parts: dc link voltage control, power injected control and current control is proposed. In this work, the random PWM strategy is used to generate control signals for the multilevel inverter used us an interface to connect photovoltaic generators to the grid. Numerical simulations are performed using MATLAB / Simulink software, the simulation results for the proposed system indicate the performances of the proposed control structure, minimization of harmonics by the random PWM strategy applied and injection to the grid more active power by the multilevel inverter structure.
A Simple Strategy of Controlling a Balanced Voltage Capacitor in Single Phase...IAES-IJPEDS
The five-level inverter has been used for many applications in renewable energy systems. Even though its harmonic distortion was lower than the conventional two-level inverter. The five-level converter has some disadvantages such as increasing power semiconductor, complex pulse width modulation control methods, and problem with the voltage balancing of the capacitor. This paper aims to propose a modified five-level inverter based on sinusoidal pulse width modulation using phase shifted carrier to enhancing the capacitor voltage balancing. This modified five-level inverter reduces the overall cost and the complexity of the pulse width modulator. Thus making the proposed control system highly simple. The performance and its controller were validated by means of standard laboratory equipments. The analysis, simulation and implementation result showed better performance of five-level inverter.
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POWER STABILITY ANALYSIS OF A TRANSMISSION SYSTEM WITH A UNIFIED POWER FLOW C...IJITE
The unified power quality conditioner is the equipment used for regulated voltage distortion and voltage
unbalance in a power system. UPFC can enhance the power to flow through the transmission system by
controlling the power flow and voltage stability of the transmission line within their limits. This paper
presents a control scheme and Theoretical derivation of the unified power flow conditioner and the
simulation results are compared and contrasted in detail. UPFC is a combination of shunt Active and
series active power filters. UPFC contains a DC link capacitor in a single-phase voltage source inverter
with two back to back connected, three-phase three-wire and three-phase four-wire are arranged. The
fundamental target of this work is to determine the causes and impacts of power quality problems,
specifically voltage sag, voltage swell, power factor, and Total Harmonics Distortion (THD) and enhance
the power quality of a transmission system by UPFC based Transformative Intrinsic Algorithm (TIA). The
Simulation of the proposed method is developed by Mat lab Simulink software, and the simulation result
shows, the proposed method gives better solutions to control the power imbalance in the distribution
system with its cost-effectiveness.
Wind-Turbine Asynchronous Generator Synchronous Condenser with Excitation in ...IJMTST Journal
In this paper Standalone operation of a wind turbine generating system under fluctuating wind and variable load conditions is a difficult task. Moreover, high reactive power demand makes it more challenging due to the limitation of reactive capability of the wind generating system.The frequency is controlled by the Discrete Frequency Regulator block. This controller uses a standard three-phase Phase Locked Loop (PLL) system to measure the system frequency. The measured frequency is compared to the reference frequency to obtain the frequency error. This error is integrated to obtain the phase error. The phase error is then used by a Proportional-Differential (PD) controller to produce an output signal representing the required secondary load power. This signal is converted to an 8-bit digital signal controlling switching of the eight three-phase secondary loads. In order to minimize voltage disturbances, switching is performed at zero crossing of voltage.
Power Factor is a measure of how efficiently electrical power is consumed. In the ideal world Power Factor would be unity (or 1). Unfortunately in the real world Power Factor is reduced by highly inductive loads to 0.7 or less. This induction is caused by equipment such as lightly loaded electric motors and fluorescent lighting ballasts and welding sets, etc. Three phase power factor can be corrected using different approaches like sine wave control, vector control, single cycle control or Vienne Bridge Rectifier.
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Power Factor is a measure of how efficiently electrical power is consumed. In the ideal world Power Factor would be unity (or 1). Unfortunately in the real world Power Factor is reduced by highly inductive loads to 0.7 or less. This induction is caused by equipment such as lightly loaded electric motors and fluorescent lighting ballasts and welding sets, etc. Three phase power factor can be corrected using different approaches like sine wave control, vector control, single cycle control or Vienne Bridge Rectifier.
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.
Analysis of a Single Stage Three Level Converter for a Wind Driven Self Excit...idescitation
In this project work, a three phase single stage three level Converter is
implemented for a wind energy conversion system. The proposed system is designed for a
three phase wind driven Self-Excited Induction Generator (SEIG). The SEIG output is
rectified with zero-dead band condition and the output of the converter is continuous. The
three level converter is designed and the performance characteristics are studied. The three
level converter is operated at a switching frequency of 50kHz to obtain a constant three level
output. The proposed model has been simulated in MATALAB Simulink. The hardware
prototype model is developed for a lower power rating and the results are compared.
The study made in this paper concerns the use of the voltage-oriented control (VOC) of three-phase pulse width modulation (PWM) rectifier with constant switching frequency. This control method, called voltage-oriented controlwith space vector modulation (VOC-SVM). The proposed control scheme has been founded on the transformation between stationary (α-β) and and synchronously rotating (d-q) coordinate system, it is based on two cascaded control loops so that a fast inner loop controls the grid current and an external loop DC-link voltage, while the DC-bus voltage is maintained at the desired level and ansured the unity power factor operation. So, the stable state performance and robustness against the load’s disturbance of PWM rectifiers are boths improved. The proposed scheme has been implemented and simulated in MATLAB/Simulink environment. The control system of the VOC-SVM strategy has been built based on dSPACE system with DS1104 controller board. The results obtained show the validity of the model and its control method. Compared with the conventional SPWM method, the VOC-SVM ensures high performance and fast transient response.
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.
Power Quality Improvement Using Cascaded H-Bridge Multilevel Inverter Based D...IJERA Editor
Cascaded multilevel configuration of the inverter has the advantage of its simplicity and modularity over the
configurations of the diode-clamped and flying capacitor multilevel inverters. This paper presents a threephase,
five-level and seven level cascaded multilevel voltage source inverter based active filter for power line
conditioning to improve power quality in the distribution network. The DSTATCOM helps to improve the
power factor and eliminate the Total Harmonics Distortion (THD) drawn from a Non-Liner Diode Rectifier
Load (NLDRL). The compensation process is based on concept of p-q theory. A CHB Inverter is considered for
shunt compensation of a 11 kV distribution system. Finally a level shifted PWM (LSPWM) and phase shifted
PWM (PSPWM) techniques are adopted to investigate the performance of CHB Inverter. The results are
obtained through Matlab/Simulink software package.
This paper introduces the modelling of a novel three phase AC-AC converter with indirect use of a capacitor as DC voltage link. The proposed converter has high efficiency because it uses Space Vector PWM (SVPWM) technique at both rectificier and inverter stages to operate the pulse width modulation in IGBT switches. The novel converter is equipped with a power factor control to shape the rectifier input current waveform to be sinusoidal and to be in phase with the input voltage. To keep the DC voltage stable, the converter utilizes PI controllers. Simulations are conducted for output voltage from 120 to 300 Volts with output frequency ranging from 30 Hz to 60 Hz. The simulation results show that the converter is able to maintain stable the DC voltage and current. Furthermore, the model demonstrates the benefits of proposed converter in terms of acquiring high input power factor and sinusoidal current waveform at the output side of the inverter.
dSPACE Implementation for a Fuzzy Logic Voltage Control using a Self-Excited ...IJECEIAES
The present work describes the analysis of a control scheme for keeping the RMS voltage output constant, the system is supplying by a self-excited induction generator with variable speed and load. A comparison is examined between simulation and experimental results using dSPACE board. The results are provided to verify the effectiveness of this approach and gives very high performance.
The paper describes the single stage AC-AC converter. This converter is a good alternative to quasi direct back to back converter. This single stage converter is called Matrix Converter. Matrix converter is an array of controlled semiconductor switches that connects three phase source to the three phase load. This converter provides bidirectional power flow, sinusoidal input and output waveforms and they have no dc link storage elements. Simulation model and results presented showing Venturini control method of matrix converter.
FC/PV Fed SAF with Fuzzy Logic Control for Power Quality EnhancementIJPEDS-IAES
In this paper, a Fuel cell (FC)/Photovoltaic cell (PV)/Battery operated three- phase Shunt Active power Filter (SAF) is proposed for improving the power quality at the utility side. Fuzzy based instantaneous p-q theory control is proposed for SAF. This SAF consists of Voltage Source PWM Converter (VSC) and a DC link capacitor supplied by a FC/PV/Battery. The filter provides harmonic mitigation with reactive power compensation and neutral compensation for loads at the Point of Common Coupling (PCC). A Single switch boost DC-DC converter connects the FC/PV/Battery with the VSC to maintain the load. The performance of the proposed SAF is tested in MATLAB/SIMULINK environment with Fuzzy logic controller (FLC). The controller maintains the DC link voltage based on the current reference generated by the p-q theory. The Hysteresis PWM current controller is employed to generate the gating pulses to the switches in VSC. The simulation results of the proposed SAF validate the effectiveness of FLC in power quality enhancement.
A Novel Power Factor Correction Rectifier for Enhancing Power QualityIJPEDS-IAES
In this paper, the disturbances in power system due to low quality of power
are discussed and a current injection method to maintain the sinusoidal input
current which will reduce the total current harmonic distortion (THD) as well
as improve the power factor nearer to unity is proposed. The proposed
method makes use of a novel controlled diode rectifier which involves the
use of bidirectional switches across the front-end rectifier and the operation
of the converter is fully analyzed. The main feature of the topology is low
cost, small size, high efficiency and simplicity, and is excellent for
retrofitting front-end rectifier of existing ac drives, UPS etc. A novel strategy
implementing reference compensation current depending on the load
harmonics and a control algorithm for three-phase three-level unity PF
rectifier which draws high quality sinusoidal supply currents and maintains
good dc link- voltage regulation under wide load variation. The proposed
technique can be applied as a retrofit to a variety of existing thyristor
converters which uses three bidirectional switches operating at low frequency
and a half-bridge inverter operating at high frequency .The total power
delivered to the load is processed by the injection network, the proposed
converter offers high efficiency and not only high power factor but also the
Total Harmonic Distortion is reduced. Theoretical analysis is verified by
digital simulation and a hardware proto type module is implemented in order
to confirm the feasibility of the proposed system. This scheme in general is
suitable for the common variable medium-to high-power level DC load
applications.
Comparative Study of Three Phase Grid Connected Photovoltaic Inverter Using P...IJPEDS-IAES
A comparative study of three phase grid connected photovoltaic (PV)
inverter using Proportional-Integral (PI) controller and Fuzzy logic controller
(FLC) is presented in this paper. Proposed three phase inverter with single DC
source employing three phase transformer for grid connected PV system
controlled by using space vector pulse width modulation (SVPWM) technique.
PI and FLC are used as current controller for regulating the current. Perturb and
observe maximum power point technique (MPPT) is used for tracking of
maximum power from the PV panel. Finally total harmonic distortion (THD)
comparison made between two controllers for validation of results.
Furthermore swithing losses of inverter are also presented. The simulation
results are obtained using MATLAB simulink.
Simulation of D-STATCOM to study Voltage Stability in Distribution systemijsrd.com
This paper presents the simulation of D-statcom to understand the improvement of voltage stability [1] of distribution system. The power circuits of the D-STATCOM and distribution networks are made up of simpower system blocks, while the control circuits made with the simulink blocks The STATCOM is applied to regulate transmission voltage to allow greater power flow in a voltage limited transmission network, in the same manner as a static var compensator (SVC), the STATCOM has further potential by giving an inherently faster response and greater output to a system with depressed voltage and offers improved quality of supply. The main applications of the STATCOM are; Distribution STATCOM (D-STATCOM) exhibits high speed control of reactive power to provide voltage stabilization and other type of system control. The DSTATCOM protects the utility transmission or distribution system from voltage sag and /or flicker caused by rapidly varying reactive current demand. During the transient conditions the D-STATCOM provides leading or lagging reactive power to active system stability, power factor correction and load balancing.
Push-Pull Converter Fed Three-Phase Inverter for Residential and Motor LoadIJPEDS-IAES
The proposed paper is an new approach for power conditioning of a PV
(photo-voltaic) cell array. The main objective is to investigate an approach to
provide and improve the delivered electric energy by means of power
conditioning structures with the use of alternative renewable resources
(ARRs) for remote rural residential or industrial non-linear loads. This
approach employs a series-combined connected boost and buck boost DCDC
converter for power conditioning of the dc voltage provided by a photovoltaic
array. The input voltage to the combined converters is 100 V
provided from two series connected PV cells, which is converted and
increased to 200 V at the dc output voltage. Series-combined connected
boost and buck-boost DC-DC converters operate alternatively. This helps to
reduce the input ripple current and provide the required 400 Vdc on a
sinusoidal PWM three-phase inverter. Analysis of the two series-combined
DC-DC converters is presented along with simulation results. Simulations of
the series-combined DC-DC converters are presented with an output DC
voltage of 200 V and a maximum output load of Po=600 W.
A Five – Level Integrated AC – DC ConverterIJTET Journal
This paper presents the implementation of a new five – level integrated AC – DC converter with high input power factor and reduced input current harmonics complied with IEC1000-3-2 harmonic standards for electrical equipments. The proposed topology is a combination of boost input power factor pre – regulator and five – level DC – DC converter. The single – stage PFC (SSPFC) approach used in this topology is an alternative solution to low – power and cost – effective applications.
This paper proposes a new voltage frequency converter (VFC) that converts both voltage and frequency to the required level of voltage and frequency in low voltage networks used in various countries. The proposed converter could be used as a universal power supply for sensitive AC loads. The converter is composed of, input voltage and frequency detection circuitry, full bridge boost rectifier and a DC to AC inverter. In addition, to improve the feasibility and performance of the converter, synchronous reference based PI (SRFPI) controller is adopted, where the system behaves similar to a DC-DC converter. The parameter selection of PI controller is done using a recent optimisation technique called Lightning Search Algorithm (LSA). The simulation of VFC is conducted in MATLAB/Simulink environment. The simulation results shows that LSA based PI controller provides better output voltage regulation with respect to the reference value under various load and input conditions.
In this paper, a new approach is proposed for keeping the RMS voltage output constant, the system is supplying by a self-excited induction generator (SEIG) driven by a controlled DC motor with variable speed and load. The scheme used in this paper is based on a classical Proportional-Integral regulator wich controls a SPWM switching. A MATLAB Simulink model of the system is developed to maintain the AC voltage at the desired value. Then a comparison is examined between simulation and experimental results using dSPACE board. The results are provided to verify the effectiveness of this approach and it gives very high performance.
A Integrated Technique of SIDO PFC Fly back Converter in power systemIJMTST Journal
Energy saving is the major international efforts to control down the global warming .Power electronics based devices has being improving day by day for saving the electrical energy in the power grids. The govt. of India is also contributing several projects based on energy conservation. The Designing of a single-inductor dual output (SIDO) fly-back power factor correction (PFC) converter is proposed, in which the PFC and power conversion are done at the same time, multiplexing of a single-inductor is implemented through which each output can be regulated independently. The converter will be operating under in critical conduction mode (CRM). A SIDO PFC converter is a system of dual efficient DC output obtained from the AC source, it can also be replaced by solar panel and our system is capable of running a dc motor also, fly back converter can be used in both ac-dc and dc-dc conversion process. The efficiency along with power factor, total harmonic distortion (THD), settling time and output accuracy of this converter will be improved by implementing the neural network as controllers in the system
A Integrated Technique of SIDO PFC Fly back Converter in power system
Latex_Final_Bryan_F
1. Control of a Single-Stage Three-Phase Buck-Boost
Power Factor Correction Rectifier
Bryan P. Faulkner
The Bradley Department
of Electrical & Computer Engineering
Virginia Tech
Blacksburg, Virginia 24060
Email: bryanf81@vt.edu
Abstract—Advances in Power Electronics are enabling More
Electric Aircraft (MEA) to replace pneumatic systems with elec-
trical systems. Active Power Factor Correction (PFC) rectifiers
are used for AC/DC conversion, to maintain unity input power
factor. Traditional three-phase variable voltage and variable
frequency AC/DC rectification methodologies used with airplane
generators implement passive diode bridges and large DC link
capacitors. While useful, these rectifiers have several drawbacks
such as higher harmonics in the input current, poor input power
factor operation, input voltage source disturbances, and lack
output voltage regulation. To alleviate these problems, high-speed
power semiconductor devices have facilitated the development
of active switched-mode AC/DC converters that are controlled
by pulse width modulation (PWM) techniques. A single-stage
PWM-based AC/DC converter topology, which has received
limited attention and is the focus of this summer research
effort, is the three-phase buck-boost-type PFC converter. As
preliminary work, literature reviews relevant to the MEA thrust,
of aircraft electrical systems and power electronic principles,
were conducted. Once the necessary background information was
grasped, simulation and modeling of buck-boost control strategies
began. Ideally, the novel results produced during this summer
2015 REU, at the University of Maryland, will lead to a greater
acceptance of the buck-boost converter in future More Electric
Aircraft.
I. INTRODUCTION
Traditional three-phase variable voltage and variable fre-
quency AC/DC rectification methodologies in airplane genera-
tors utilize passive diode bridges and large DC link capacitors.
Passive diode-bridge based rectifiers result in higher harmonics
in the input current, poor input power factor operation, input
voltage source disturbances, and lack output voltage regu-
lation [1]. To alleviate these problems, recent progresses in
high-speed, power semiconductor devices have facilitated the
development of active switched-mode AC/DC converters that
are controlled by pulse width modulation (PWM) techniques.
The dominant topologies for active, single-stage PWM-based
AC/DC conversion are boost-type [1-2] and buck-type [3-4]
rectifiers. Three-phase, buck-boost-type, power factor correc-
tion (PFC) converters have received limited attention.
The three-phase buck-boost-type AC-DC converter topology
proposed in [5] has drawbacks such as discontinuous current
conduction mode operation, an excessive amount of power
semiconductor devices, and low conversion efficiency. The
buck-boost control strategies proposed in [6-7] need 2200µF
output capacitors (a capacitance value that is over four times
greater than the required output capacitor, used in this paper
- 500µF). To improve upon existing strategies, and to offer
a novel solution without any of the previously mentioned
drawbacks, this paper proposes a new control strategy utilizing
the input currents and output voltage of the converter using
only a single Proportional-Integral (PI) controller. The PI
compensator was designed and implemented to stabilize the
voltage loop of the system. The main objective of the control
strategy is to make the input current controller as fast and as
robust as possible, to ultimately produce high quality input
currents (low THD percentage and unity power factor). This
control structure excels in two separate areas: (1) obtaining
a fast and robust input current response (with high power
factor quality); and (2) achieving a steady state response in
a significantly less amount of settling time, under a step
change in load or reference output voltage, as compared to
conventional PI current compensators. Simply put, the control
strategy put forth in this research thrust is simple, fast, and
reliable and is perfectly suited for implementation in the active
three-phase buck-boost rectifiers of the future.
II. MORE ELECTRIC AIRCRAFT
A. Electrical Power Generation in the Boeing 777
The Boeing 777 electrical system is comprised of two
independent electrical systems: the main and the backup.
The main system involves two engine-driven integrated drive
generators, a generator driven by the auxiliary power unit
(APU), three generator control units, and a bus power control
unit [8].
In order to provide for redundant contingencies, in case
of failure, a backup electrical system is included with every
aircraft. Included in the backup design are two-engine driven
generators and one inverter/control unit. When all of the
systems/redundancy plans are considered, as a whole, they
are equivalent to a three-engine plane (the 777 only has two
physical engines); essentially, the 777 has one backup engine.
The specifications of the power generation of the 777 are noted
in Table I [8].
2. Fig. 1. Comparison of Single-Phase and Three-Phase Signals
B. Electrical Power Generation in the Boeing 787
The Boeing 787 electrical system is of a hybrid voltage
design. The system is comprised of six generators: two per
engine, and two per APU, operating at 235 VAC. Additionally,
ground power receptacles are included in the system design for
airplane servicing on the ground without the use of the APU.
All of the systems generators are directly connected to the
engine gearboxes and can be operated at a variable frequency
(360 to 800 hertz), that is proportional to the engine speed.
Characteristics of the Boeing 787 hybrid voltage system are
noted in Table I [9].
TABLE I
ELECTRICAL SYSTEM COMPARISON BETWEEN THE BOEING 777 AND THE
787
Characteristic Boeing 777 Boeing 787
AC Voltage* 115 VAC 115 VAC & 235 VAC
DC Voltage 28 VDC 28 VDC & ± 270 VDC
Operating Frequency 400 Hz 360-800 Hz
*Phase-to-Neutral RMS
C. No-Bleed Architecture
The new 235 VAC and the ± 270 VDC voltage types stem
from the new no-bleed electrical architecture, on the Boeing
787. The new architecture method results in an expanded
electrical system that is capable of generating twice as much
electricity as previous Boeing airplane models [9]. In previous
aircraft, bleed-air systems, were pneumatic air intake and
compressor systems that would provide electric power to
various airplane components; i.e. air-conditioning packs and
wing anti-ice systems, among many others [9]. With the
new 787 no-bleed architecture, which moves away from the
previous pneumatic school of thought, to the electrical, Boeing
is hoping to achieve the following [9]: (1) Fuel savings of
about 3% (2) extract as much as 35% less power from the
engines; (3) increased performance of the Auxiliary Power
Unit (APU), due to a simpler, all electric APU design; (4)
more efficient engine cycles; and (5) more efficient secondary
power extraction, power transfer, and energy usage.
III. LITERATURE REVIEW
A. Single-Phase and Three-Phase Power
Illustrated in Fig. 1, is a comparison between a single-phase
voltage, versus a three-phase voltage. A single phase signal
only has one sinusoidal value (i.e. one AC voltage, or one AC
current. For example,
V = A · cos(ωt) (1)
where A is the maximum amplitude of the single-phase
sinusoid and ω is the angular frequency.
A three-phase signal, on the other hand, the bottom graph
of Fig. 1, is composed of three separate signals, with the same
maximum amplitude and angular frequency each 120° apart.
For example, please see Eqs. (2)-(4).
Va = A · cos(ωt) (2)
Vb = A · cos(ωt − 120°) (3)
Vc = A · cos(ωt + 120°) (4)
In similar fashion to the single-phase signal, A is the same
maximum amplitude and is the same angular frequency, across
all of the sinusoids.
Another significant difference between single-phase, and
three-phase signals, is power. A single-phase signal allows
power to fall three times every cycle. A three-phase signal
delivers a constant power supply to a load.
B. Converter Topologies
1) Step-Down (Buck) Topology: The basic topology of an
AC/DC buck-type three-phase rectifier is shown in Fig. 2.
The three-phase buck-type topology forces the output voltage
to be smaller (buck) than the input voltage; contingent upon
appropriate circuit element values and duty ratio, D.
The converter includes a three-phase input voltage source
followed by three series inductors, a capacitor bank, six
switches {S1 − S6} with voltage blocking capabilities (that
can be implemented using either MOSFETs or IGBTs), six
diodes {D1 − D6}, an output inductor (LDC), and an output
filter capacitor (Co). The output inductor helps to minimize
the output current ripple, and acts as a constant current-source
(iDC). The output filter capacitor helps to minimize the output
voltage ripple, and acts as a constant voltage source (VDC) [2].
2) Step-Up (Boost) Topology: The basic topology of an
AC/DC boost-type three-phase rectifier is shown in Fig. 3.
The three-phase boost-type topology forces the output voltage
to be greater (boost) than the input voltage; contingent upon
appropriate circuit element values and duty ratio, D.
The converter includes a three-phase input voltage source
followed by three series inductors, six switches {S1 − S6}
with voltage blocking capabilities (that can be implemented
using either MOSFETs or IGBTs), and an output filter
capacitor (Co). The three series inductors following the input
three-phase source aid in boosting the input voltage and
filter the input current, thus reducing the current harmonic
3. levels. The output filter capacitor helps to minimize the output
voltage ripple, and acts as a constant voltage source (VDC)[2].
3) Step-Down, Step-Up (Buck-Boost) Topology: The basic
topology of an AC/DC buck-boost type three-phase rectifier is
shown in Fig. 4. This topology resembles a buck-type rectifier
at the input voltage, see Fig. 2, and is similar to a DC/DC buck-
boost converter towards the output. The three-phase buck-
boost-type topology allows for the output voltage to either
be greater (boost) or smaller (buck) than the input voltage,
depending upon various circuit element values and duty ratio,
D.
The converter includes a three-phase input voltage source
followed by three series inductors, a capacitor bank, six
switches {S1 − S6} with voltage blocking capabilities (that
can be implemented using either MOSFETs or IGBTs), seven
diodes {D1 − D7}, an output inductor (LDC), and an output
filter capacitor (Co). The output inductor helps to minimize
the output current ripple, and acts as a constant current-source
(I). The output filter capacitor helps to minimize the output
voltage ripple, and acts as a constant voltage source (VDC)
[2].
i1,avg(t) =
D2
Ts
2L
· v1(t) (5)
As is shown in Eq. (5), there is a perfect linear relationship
between i1,avg(t) and v1(t), demonstratiing that the Buck-
Boost topology, theoretically, has excellent, intrinsic PFC
properties [10].
Fig. 2. Step-Down (Buck) Rectifier Topology
Fig. 3. Step-Up (Boost) Rectifier Topology
Fig. 4. Step-Down, Step-Up (Buck-Boost) Rectifier Topology
C. Total Harmonic Distortion
Total Harmonic Distortion is based upon the Fourier ex-
pansion of nonsinusoidal waveforms. The THD of a distorted
current waveform, is defined by the following equation [11]:
THD =
h=hmax
h=2
Ih
I1
2 1/2
(6)
where Ik is the amplitude of the h-th order current harmonic,
I1 is the fundamental frequency of the waveform (50 or 60 Hz
component), and hmax is the maximum number of harmonics
to be included ( 40-50 on average). THD can also be a
performance indicator for distorted voltages. It is common
to multiply the THD by 100% to obtain a percentage of
distortion. Using Ik, Irms can be defined [11]:
Irms =
h=hmax
h=1
I2
h
1/2
(7)
Additionally, the relationship between current THD and rms
current can be derived [11]:
Irms = I1 1 + (THD)2 (8)
Using this relationship the power-factor definition can take
harmonic currents into account, only knowing the THD of the
current [11]:
λ =
P
S
=
I1 · cos(φ)
Irms
=
cos(φ)
1 + (THD)2
(9)
.
D. Pulse-Width Modulation
Pulse-Width Modulation (PWM) is a method used to control
output voltage, at a constant switching frequency (hence, a
constant switching time period (Ts = ton+toff), while adjusting
the on-duration of a switch. In this method the ratio of the on
duration to the switching time period, known as the switch
duty ratio (D), is varied [12].
4. Fig. 5. Space vector representation of three-phase converter
E. Space Vector Pulse-Width Modulation
Space Vector PWM (SVPWM), like PWM, also controls
average voltage output; however, SVPWM does so without a
constant switching frequency.
As shown Fig. 5, the objective of the SVPWM technique
is to approximate the reference voltage vector (V ∗
) instanta-
neously by combining the switching states corresponding to
the basic space vectors {V0, V1, V2, V3, V4, V5, V6, V7} [11].
The two following equations are used to implement
SVPWM [11]:
d1 · V1 + d2 · V2 = V ∗
(10)
including the zero vector, d0
d0 + d1 + d2 = 1. (11)
SVPWM, when applied to a three-phase
converter, allows for 8 possible switching states
{pnn, ppn, npn, npp, nnp, pnp, ppp, nnn}. Examples of
the npp and the nnp switching states, applied to a Buck-
Boost Converter are illustrated in Fig. 6 and Fig. 7 respectively
[11].
The SVPWM technique also allows for a smaller percentage
of Total Harmonic Distortion (THD), mentioned in section
III.C, for our system [11].
F. State-Space Averaging
State-space averaging techniques ease computational efforts
on digital signal processors, and linearize systems around
certain operating points. State-space averaging methods were
implemented in this research project as a means to control
the rectification process, due to the fact that the voltage and
current transients reach steady state with less oscillation than
other methods; zero-order approximations, as an example, are
more oscillatory [13]
Fig. 7. Buck-Boost Topology in the npp (V4) switching state
Fig. 8. Buck-Boost Topology in the nnp (V5) switching state
IV. CONTROL STRATEGY
In the following analyses, the following nomenclature is
used:
D duty ratio
I current across inductor LDC
Co output capacitor voltage
VMN voltage across inductor LDC
VDC output voltage
R resistance
From state-space averaging techniques, discussed in Section
II.F, the transfer function obtained for the three-phase buck-
boost-type rectifier in Fig. 4 is as follows [2]:
Gvd(s) =
Vo(s)
d(s)
=
−(I · LDC · R)s + [VDC(1 − D) + VMN (D − 1)]R
(R · LDC · Co)s2 + L · s + (D2 + 1 − 2D)R
.
(12)
The transfer function in Eg. (12) has a zero shown in Eq. (13):
s =
VDC(1 − D) + VMN (D − 1)
I · LDC
. (13)
As the zero indicates, in Eq. (13), the DC/DC converter is a
non-minimum phase system [1]. A zero is located in the right
half plane when VDC > VMN . Conversely, a zero is located
in the left half plane when VDC < VMN . If a right half zero
occurs in a system, the dynamic response in output voltage
and input current is significantly slower, in comparison to a
system with a left half zero and similar gain response. Due
5. Fig. 6. Control Structure of the Single-Stage, Three-Phase Buck-Boost AC/DC Converter
to the nature of the zero, the control circuit of the rectifier is
difficult to tune and is best suited for operation only in a given
region. However, since LC low pass filters must be designed
to allow for faster input current dynamics, rather than output
voltage dynamics, it is necessary to separate the dynamics of
the input current from the output voltage.
Additionally, the control strategy presented in Fig. 8 is
implemented using Space Vector Pulse-Width Modulation
(SVPWM) techniques, as discussed in section III.E to
generate switching pulses for the converter. Complementary
pulses were generated with a dead-band. Park Transforms
(ABC/dq0) and Clark Transforms (ABC/αβ) are also uti-
lized. The equations for Park and Clarke Transforms are shown
in Eq. (14) and Eq. (15), respectively.
ud
uq
u0
=
2
3
cos(ωt) cos(ωt − 2π
3 ) cos(ωt + 2π
3 )
− sin(ωt) − sin(ωt − 2π
3 ) − sin(ωt − 2π
3 )
1
2
1
2
1
2
ua
ub
uc
.
(14)
uα
uβ
u0
=
2
3 −1
3 −1
3
0 1√
3
− 1√
3
1
3
1
3
1
3
ua
ub
uc
.
(15)
V. SIMULATION RESULTS
The converter in this work has been simulated with an
input voltage of 230V (phase-neutral RMS) at 400 Hz; these
specifications were chosen, as they are typically used for
the Regulated Transformer Rectifier Unit (RTRU) in next-
generation More-Electric-Aircraft (MEA).
The simulation of this work was performed in MATLAB-
Simulink. Fig. 9 provides the simulation results of the con-
verter in both buck and boost mode, and also validates the
PFC operation with voltage regulation of the converter (as the
voltage and current sinusoids are in-phase).
During the simulation, at 50 ms, the output voltage refer-
ence, V ∗
DC, is decreased from 700V (boost-mode) to 400V
(buck-mode). The 2% settling time of the output DC voltage
is 7 ms with our proposed control. The settling time of the
control system proposed in this work is faster as compared
to a system with multiple PI controllers that takes 20ms to
reach 2% settling band. As Fig. 9 demonstrates, the proposed
control is able to achieve a unity PFC operation, and 2.3%
input current THD.
VI. CONCLUSION
The Transportation Electrification Research Experience for
Undergraduates offered an excellent opportunity to become
introduced to the field of power electronics and the ad-
vancements of the More Electric Aircraft (MEA). As pre-
liminary work, literature reviews relevant to the MEA thrust,
of aircraft electrical systems and power electronic principles,
were conducted. Once the necessary background information
was grasped, simulation and modeling of buck-boost control
strategies began.
Fig. 9. (a) DC output reference voltage; (b) DC link voltage (V) with our
proposed control and PI compensator; (c) Phase A current (A) with our
proposed control and PI compensator (d) Phase A input voltage.
6. The proposed controller presented in this work is capable
of stabilizing the single-stage three-phase buck-boost AC/DC
Rectifier with PFC operation at a rated power condition, while
undergoing a step change in either output voltage or load
power.
This body of research is under review for possible publica-
tion for the fall of 2015. Ideally, the novel results produced
during this summer research effort will lead to a greater
acceptance of the buck-boost converter in future More Electric
Aircraft.
ACKNOWLEDGMENT
I would like to thank my Research Advisor, Dr. Alireza
Khaligh for the opportunity to conduct research related to
Transportation Electrification, this summer. I would also like
to thank Dr. Khaligh, my Graduate Research Mentor, Ayan
Mallik, and all members of the Power Electronics, Energy
Harvesting and Renewable Energies Laboratory at the Univer-
sity of Maryland-College Park for their ever-present support,
encouragement, and guidance.
This work has been supported through the National Science
Foundation grant number EEC 1263063, REU Site: Summer
Engineering Research Experiences in Transportation Electrifi-
cation, which is gratefully acknowledged.
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