EPE Association: EPE 2007 - Subtopic 06-6 - DS: Converter control sets and modulation strategies

EPE 2007 - Subtopic 06-6 - DS: Converter control sets and modulation strategies
You are here: EPE Documents > 01 - EPE & EPE ECCE Conference Proceedings > EPE 2007 - Conference > EPE 2007 - Topic 06: 'Modulation strategies and specific control methods for static converter' > EPE 2007 - Subtopic 06-6 - DS: Converter control sets and modulation strategies

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   A new modulation technique for a three phase PWM buck rectifier
By PAVLOU Konstantinos; MANIAS Stefanos; KALETSANOS Athanasios; MANOLAS Iakovos [View]
[Download]

Abstract: In this paper a novel modulation technique for a three phase buck rectifier is presented and analyzed. The proposed control technique compared to the conventional control techniques exhibits a higher true power factor while providing an equivalent dynamic response. The dynamic performance of the proposed control technique is checked experimentally in a d.c. motor drive system and the results are compared to those of the classical current space vector technique. The experimental validation illustrates that the technique introduced improves significantly the input line current THD factor and achieves a greater power factor with respect to the conventional method even in cases involving important motor torque variations.

   A Novel Space Vector Modulation Control Strategy for Three-leg Four-Wire Voltage Source Inverters
By MOHD Alaa; ORTJOHANN Egon; HAMSIC Nedzad [View]
[Download]

Abstract: One of the desirable characteristics of inverters in three-phase systems is the ability to feed unbalanced loads with voltage and frequency nominal values. This paper introduces an innovative control method in combination with a three dimensional space vector modulation (3D-SVM) control strategy. It is able to feed grids with unbalanced loads while reducing the switching frequency losses. The results from this study show that the developed control scheme in combination with three-leg four-wire inverters can carry out the grid feeding requirements under extreme unbalanced load conditions efficiently.

   A Selective Harmonic Elimination system for restoring and equalising DC link voltages in a multilevel active rectifier
By CLARE Jon; WATSON Alan; WHEELER Patrick [View]
[Download]

Abstract: This paper presents a reduced switching frequency, Selective Harmonic Elimination technique for balancing DC link capacitor voltages in a cascaded H-bridge multilevel rectifier. The method controls power flow through the individual cells of the converter in an attempt to ensure that the DC link capacitor voltages for the cells converge, even when unbalanced loads are attached. Simulation and experimental results are presented to show the functionality and operation of the proposed technique.

   A Simple Feedback for Parrallel Operation of Current Controlled Inverters involved in UPS
By LE CLAIRE Jean-Claude; LEMBROUCK GrÃ©gory [View]
[Download]

Abstract: Thanks to the use of a novel modulation strategy, the inverters of a voltage source converter are under accurate current controls. Thanks to this strategy, the inverter gains are known. Then, the system open loop transfer function is deduced and a simple PID controller permits to target a good behaviour and a stable operation of the multi-inverter structure which could be involved in an UPS.

   A simpler and faster method for SVM implementation
By PABLO Santiago De; REY Alexis B.; HERRERO Luis C.; RUIZ JosÃ© M. [View]
[Download]

Abstract: Space Vector Modulation is perhaps the common technique mostly applied to drive three-phase voltage-source inverters. During every switching period it calculates three duty cycles in order to generate a suitable pulse sequence. This paper presents a new, faster and, most important, simpler method to compute these time values without using either trigonometric functions or even Clarke or Park transformations. The result is a light-weight algorithm easier to implement in small digital signal processors or microcontrollers. The relationship between SVM and PWM is also explained.

   Algorithm Evaluation for the Optimal Selection of the Space Vector Voltage using DPC in Power Systems
By VIOLA Julio; BUENO Alexander; RESTREPO Jose; ALLER Jose M. [View]
[Download]

Abstract: This work presents the experimental evaluation for a new scheme of Optimal Vector Selection (OVS) in Direct Power Control (DPC) for a three-phase rectifier without the use of switch selection tables. The OVS is physically implemented using a software configurable test rig (Platform III). Additional states were added to the standard seven space vectors obtained with a three-phase inverter bridge using Space Vector Modulation (SVM) in order to reduce the hysteresis band of the power controller. Normal operation, model parameter fit, regenerative behavior and comparisons between two different sets of vectors are analyzed.

   ANALYSIS AND COMPENSATION METHODS OF DEAD-TIME EFFECTS IN A PWM AC CHOPPER
By MEYNARD Thierry; COUGO Bernardo [View]
[Download]

Abstract: This paper presents the generation of "dead-time" in switching signals of a PWM AC chopper. It also presents the effects of dead-time in the output voltage of such converters. Comparisons between the effects of dead-time in inverters and in the PWM AC chopper are made. An open-loop compensation method is proposed and verified.

   Buck-Boost Impedance Networks
By GOH Ailian; GAO Feng; LOH Poh Chiang; BLAABJERG Frede [View]
[Download]

Abstract: Most inverters designed to date can only perform either voltage-buck or boost operation with buck-boost mode usually attained by introducing additional active semiconductor devices and passive components to the inverters. Although effective, adding active switches will complicate the inverter control, and push up the overall system costs. Therefore, alternative topological solutions are of interest, and should preferably be implemented using only passive LC elements and diodes, connected as unique impedance networks. A number of possible network configurations are now investigated in this paper, and are respectively named as Z-source, H-source, EZ-source and their respective "inverted" variants. The presented impedance networks can either be used with a traditional voltage-source or current-source inverter, and can either be powered by a voltage or current source. All impedance networks are shown to produce the same voltage gain under the same operating conditions, but structurally, they have their respective advantages and disadvantages, which are thoroughly described throughout the paper. Experimental results captured using a laboratory prototype are also presented for confirming the practicalities and performances of the described impedance networks.

   Energy Generation System Behaviour using a Clocked Fuzzy Peak Current Control
By BIZON Nicu [View]
[Download]

Abstract: In this paper is analyzed by simulations the nonlinear phenomena in the boost converter used as power interface into the energy generation system (EGS). Transition to chaos in one or more stages depends on the initial conditions and the bifurcation diagrams with the reference current as the variable parameter have been reported. The simulation results show that the EGS without large energy storage device (ESD) shift to chaos as the parameter is modified. Two kind of the peak current controller are used. The proposed fuzzy peak current controller provides better dynamic response, robustness against system uncertainty disturbances, and an implicit stability proof.

   FIVE-PHASE INVERTER MODULATION STRATEGY FOR HIGH PERFORMANCE MOTOR DRIVES: ANALYSIS OF THE VOLTAGE LIMIT
By ZARRI Luca; SERRA Giovanni; TANI Angelo; MILANESI Filippo; CASADEI Domenico [View]
[Download]

Abstract: In this paper the problem of the modulation strategy of a five-phase inverter is completely solved using the Duty-Cycle Space Vector approach. Furthermore, the inverter voltage limit, under different operating conditions, with sinusoidal or non-sinusoidal output currents, is determined. The analytical approach is confirmed by experimental tests.

   Introduction and Evaluation of Novel Multi-level Carrier-Based PWM Strategies Using a Generalized Algorithm
By RADAN Ahmad; DAVARI FAR Mehrdad; DANESHI FAR Zahra [View]
[Download]

Abstract: A multilevel Carrier-Based Pulse Width Modulation (CB-PWM) strategy has M-1 carriers which can be differently selected from several aspects. The specifications and allocation of carriers strongly affect the converter performances. While investigating the influence of different types of carriers on the converter performances in frame of a general algorithm, the paper introduces some novel strategies and compares them with the already known methods.

   Real-Time Performance Testing of a 3Ï† VSWM Inverter-Fed Induction Motor
By RAHMAN Mohammed; SALEH Saleh [View]
[Download]

Abstract: This paper presents a real-time performance testing of a three-phase (3Ï†) voltage-source (VS) six-pulse wavelet-modulated (WM) inverter-fed induction motor (IM). The proposed modulation technique is based on a set of three scale-based linearly-combined scaling functions shifted by 2Ï€ 3 â—¦ from each other. These scaling functions are employed to sample three reference-modulating signals, each corresponds to one phase, in a non-uniform recurrent manner. Moreover, these scaling functions have dual synthesis scaling functions that are responsible for reconstructing the three continuous-time (CT) referencemodulating signals from their non-uniform recurrent samples. The reconstruction processes are carried out by the three synthesis scaling functions to achieve 180-degrees conduction mode of the 3Ï† six-pulse inverter. The proposed wavelet modulation technique is realized through a Turboâˆ’C code that is executed by a dSPACE ds1102 DSP board to generate switching pulses to activate the inverter six IGBT switches. The IGBT inverter supplies a 1 hp, 1750 RPM, 208 V, 60 Hz, Y-connected 3Ï† squirrel-cage induction motor that is tested for several speeds. These test results demonstrate robust performance, simple implementation, significant dynamic responses and high ability to maintain high quality outputs.

   Research on Eliminating Common-mode Voltage of Cascaded Medium-voltage Variable Frequency Driver with Phase-difference SVPWM
By LU Jiaming; CHEN Bin; NI Xijun; YANG Zhenyu; ZHAO Jianfeng [View]
[Download]

Abstract: For application to cascaded multi-level inverter, three phase-difference SVM (PD-SVM) schemes based on left and right bridge vectors are proposed firstly. For these three schemes, equivalent SPWM components are deduced, and unipolarity or bipolarity of output waveforms is analyzed. Use sampling time staggered SVM (STS-SVM) for reference, improved PD-SVM-STS PD-SVM can be applied to cascaded medium-voltage variable speed driver (MV-VSD). The mechanism of eliminating two sorts of CMV by one of improved PD-SVM schemes-STS 2π/3 PD-SVM is analyzed in detail. Through the simulation results in the end, this modulation scheme can effectively eliminate CMV without reducing the utilization of the dc voltage excessively in contrast with conventional 3d-order harmonic injection SPWM.

   Space vector modulation of nine-phase voltage source inverters based on three-phase decomposition
By GRANDI Gabriele; SERRA Giovanni; TANI Angelo [View]
[Download]

Abstract: A new space vector modulation (SVM) technique having a full and independent control of the multiple voltage space vectors of a nine-phase voltage source inverter (VSI) is presented in this paper. The proposed approach is based on the concept of system decomposition, leading to the modulation of three three-phase VSIs. The resulting SVM corresponds to standard SVM for each three-phase VSI in the case of a nine-phase load with three insulated central points, whereas the additional modulation of the zero-sequence component is introduced for each three-phase VSI in the case of a nine-phase load with a single central point. The modulation limits are investigated and the analytical developments are proved by a complete set of simulation results.

   Synchronous Balanced Control of Cascaded Two-Level Inverters with Separated DC-Sources
By PROFUMO Francesco; OLESCHUK Valentin [View]
[Download]

Abstract: The paper presents results of dissemination of novel method of synchronized pulsewidth modulation (PWM) for wide-range control of dual inverter-fed motor drives with power balancing capability between dc-links. This drive topology includes two insulated dc sources (with equal or different voltages), feeding two standard three-phase inverters, connected with an open-end winding induction motor. Algorithms of synchronized PWM provide both continuous synchronization of the phase voltage of the induction motor and required sharing of the output power between two dc sources. Special attention has been given to analysis of operation of the drive system with synchronized PWM in the zone of overmodulation. Simulations give the behavior of dual inverter-fed systems with continuous and discontinuous versions of synchronized pulsewidth modulation in both undermodulation and overmodulation control ranges. The spectra of the motor phase voltages do not contain even harmonics and sub-harmonics during the whole control range for any ratio between the switching and fundamental frequencies, which is especially important for the medium/high power systems.

   The self-switching management principle applied toactive bidirectional switches
By SIEMASZKO Daniel; DE NOVAES Yales; RUFER Alfred; BARRADE Philippe [View]
[Download]

Abstract: The self-switching principle is a synthesis of synchronous type switching and switch inner protection mechanisms. Both switch ON and switch OFF are performed on the base of current and voltage measurement across the switch. Applied to an active bidirectional device, it may give complete autonomy to the switch. On the basis of those principles, the synthesis of an autonomous bidirectional free-wheeling path for an AC/AC buck converter is implemented with active switches. This paper introduces the current/ voltage state representation in order to illustrate the experimental switching mechanisms. As a further application, the automatic triac is synthesized for a bipolar AC/DC half-bridge converter.

   Three-Phase Multi-Level PWM Rectifier Multi-Carrier Discontinuous Voltage Modulation Strategy
By RUDERMAN Alex [View]
[Download]

Abstract: Multi-level PWM rectifier requires fewer semiconductor switches compared with its bidirectional multi-level converter counterpart. Though three-level (multi-level) PWM rectifiers are known for more than 10 years, no multi-level PWM rectifier carrier based voltage modulation strategies were reported so far. After multi-level PWM rectifier topologies introduction and classification, the paper presents a three-phase multi-level PWM rectifier phase shifted multi-carrier voltage modulation strategy based on appropriate discontinuous voltage commands transformation. Suggested formalism naturally allows derivation of a multi-level PWM rectifier voltage amplitude (modulation index) vs. voltage-current phase angle operation envelope without making use of space vector calculus. PWM rectifier operation envelope becomes less restrictive with levels count increase and full utilization. Suggested approach is not limited to a three-phase case and is applicable to a general multi-phase case.

EPE 2007 - Subtopic 06-6 - DS: Converter control sets and modulation strategies
You are here: EPE Documents > 01 - EPE & EPE ECCE Conference Proceedings > EPE 2007 - Conference > EPE 2007 - Topic 06: 'Modulation strategies and specific control methods for static converter' > EPE 2007 - Subtopic 06-6 - DS: Converter control sets and modulation strategies
	[return to parent folder]

	A new modulation technique for a three phase PWM buck rectifier By PAVLOU Konstantinos; MANIAS Stefanos; KALETSANOS Athanasios; MANOLAS Iakovos	[View] [Download]
Abstract: In this paper a novel modulation technique for a three phase buck rectifier is presented and analyzed. The proposed control technique compared to the conventional control techniques exhibits a higher true power factor while providing an equivalent dynamic response. The dynamic performance of the proposed control technique is checked experimentally in a d.c. motor drive system and the results are compared to those of the classical current space vector technique. The experimental validation illustrates that the technique introduced improves significantly the input line current THD factor and achieves a greater power factor with respect to the conventional method even in cases involving important motor torque variations.

	A Novel Space Vector Modulation Control Strategy for Three-leg Four-Wire Voltage Source Inverters By MOHD Alaa; ORTJOHANN Egon; HAMSIC Nedzad	[View] [Download]
Abstract: One of the desirable characteristics of inverters in three-phase systems is the ability to feed unbalanced loads with voltage and frequency nominal values. This paper introduces an innovative control method in combination with a three dimensional space vector modulation (3D-SVM) control strategy. It is able to feed grids with unbalanced loads while reducing the switching frequency losses. The results from this study show that the developed control scheme in combination with three-leg four-wire inverters can carry out the grid feeding requirements under extreme unbalanced load conditions efficiently.

	A Selective Harmonic Elimination system for restoring and equalising DC link voltages in a multilevel active rectifier By CLARE Jon; WATSON Alan; WHEELER Patrick	[View] [Download]
Abstract: This paper presents a reduced switching frequency, Selective Harmonic Elimination technique for balancing DC link capacitor voltages in a cascaded H-bridge multilevel rectifier. The method controls power flow through the individual cells of the converter in an attempt to ensure that the DC link capacitor voltages for the cells converge, even when unbalanced loads are attached. Simulation and experimental results are presented to show the functionality and operation of the proposed technique.

	A Simple Feedback for Parrallel Operation of Current Controlled Inverters involved in UPS By LE CLAIRE Jean-Claude; LEMBROUCK GrÃ©gory	[View] [Download]
Abstract: Thanks to the use of a novel modulation strategy, the inverters of a voltage source converter are under accurate current controls. Thanks to this strategy, the inverter gains are known. Then, the system open loop transfer function is deduced and a simple PID controller permits to target a good behaviour and a stable operation of the multi-inverter structure which could be involved in an UPS.

	A simpler and faster method for SVM implementation By PABLO Santiago De; REY Alexis B.; HERRERO Luis C.; RUIZ JosÃ© M.	[View] [Download]
Abstract: Space Vector Modulation is perhaps the common technique mostly applied to drive three-phase voltage-source inverters. During every switching period it calculates three duty cycles in order to generate a suitable pulse sequence. This paper presents a new, faster and, most important, simpler method to compute these time values without using either trigonometric functions or even Clarke or Park transformations. The result is a light-weight algorithm easier to implement in small digital signal processors or microcontrollers. The relationship between SVM and PWM is also explained.

	Algorithm Evaluation for the Optimal Selection of the Space Vector Voltage using DPC in Power Systems By VIOLA Julio; BUENO Alexander; RESTREPO Jose; ALLER Jose M.	[View] [Download]
Abstract: This work presents the experimental evaluation for a new scheme of Optimal Vector Selection (OVS) in Direct Power Control (DPC) for a three-phase rectifier without the use of switch selection tables. The OVS is physically implemented using a software configurable test rig (Platform III). Additional states were added to the standard seven space vectors obtained with a three-phase inverter bridge using Space Vector Modulation (SVM) in order to reduce the hysteresis band of the power controller. Normal operation, model parameter fit, regenerative behavior and comparisons between two different sets of vectors are analyzed.

	ANALYSIS AND COMPENSATION METHODS OF DEAD-TIME EFFECTS IN A PWM AC CHOPPER By MEYNARD Thierry; COUGO Bernardo	[View] [Download]
Abstract: This paper presents the generation of "dead-time" in switching signals of a PWM AC chopper. It also presents the effects of dead-time in the output voltage of such converters. Comparisons between the effects of dead-time in inverters and in the PWM AC chopper are made. An open-loop compensation method is proposed and verified.

	Buck-Boost Impedance Networks By GOH Ailian; GAO Feng; LOH Poh Chiang; BLAABJERG Frede	[View] [Download]
Abstract: Most inverters designed to date can only perform either voltage-buck or boost operation with buck-boost mode usually attained by introducing additional active semiconductor devices and passive components to the inverters. Although effective, adding active switches will complicate the inverter control, and push up the overall system costs. Therefore, alternative topological solutions are of interest, and should preferably be implemented using only passive LC elements and diodes, connected as unique impedance networks. A number of possible network configurations are now investigated in this paper, and are respectively named as Z-source, H-source, EZ-source and their respective "inverted" variants. The presented impedance networks can either be used with a traditional voltage-source or current-source inverter, and can either be powered by a voltage or current source. All impedance networks are shown to produce the same voltage gain under the same operating conditions, but structurally, they have their respective advantages and disadvantages, which are thoroughly described throughout the paper. Experimental results captured using a laboratory prototype are also presented for confirming the practicalities and performances of the described impedance networks.

	Energy Generation System Behaviour using a Clocked Fuzzy Peak Current Control By BIZON Nicu	[View] [Download]
Abstract: In this paper is analyzed by simulations the nonlinear phenomena in the boost converter used as power interface into the energy generation system (EGS). Transition to chaos in one or more stages depends on the initial conditions and the bifurcation diagrams with the reference current as the variable parameter have been reported. The simulation results show that the EGS without large energy storage device (ESD) shift to chaos as the parameter is modified. Two kind of the peak current controller are used. The proposed fuzzy peak current controller provides better dynamic response, robustness against system uncertainty disturbances, and an implicit stability proof.

	FIVE-PHASE INVERTER MODULATION STRATEGY FOR HIGH PERFORMANCE MOTOR DRIVES: ANALYSIS OF THE VOLTAGE LIMIT By ZARRI Luca; SERRA Giovanni; TANI Angelo; MILANESI Filippo; CASADEI Domenico	[View] [Download]
Abstract: In this paper the problem of the modulation strategy of a five-phase inverter is completely solved using the Duty-Cycle Space Vector approach. Furthermore, the inverter voltage limit, under different operating conditions, with sinusoidal or non-sinusoidal output currents, is determined. The analytical approach is confirmed by experimental tests.

	Introduction and Evaluation of Novel Multi-level Carrier-Based PWM Strategies Using a Generalized Algorithm By RADAN Ahmad; DAVARI FAR Mehrdad; DANESHI FAR Zahra	[View] [Download]
Abstract: A multilevel Carrier-Based Pulse Width Modulation (CB-PWM) strategy has M-1 carriers which can be differently selected from several aspects. The specifications and allocation of carriers strongly affect the converter performances. While investigating the influence of different types of carriers on the converter performances in frame of a general algorithm, the paper introduces some novel strategies and compares them with the already known methods.

	Real-Time Performance Testing of a 3Ï† VSWM Inverter-Fed Induction Motor By RAHMAN Mohammed; SALEH Saleh	[View] [Download]
Abstract: This paper presents a real-time performance testing of a three-phase (3Ï†) voltage-source (VS) six-pulse wavelet-modulated (WM) inverter-fed induction motor (IM). The proposed modulation technique is based on a set of three scale-based linearly-combined scaling functions shifted by 2Ï€ 3 â—¦ from each other. These scaling functions are employed to sample three reference-modulating signals, each corresponds to one phase, in a non-uniform recurrent manner. Moreover, these scaling functions have dual synthesis scaling functions that are responsible for reconstructing the three continuous-time (CT) referencemodulating signals from their non-uniform recurrent samples. The reconstruction processes are carried out by the three synthesis scaling functions to achieve 180-degrees conduction mode of the 3Ï† six-pulse inverter. The proposed wavelet modulation technique is realized through a Turboâˆ’C code that is executed by a dSPACE ds1102 DSP board to generate switching pulses to activate the inverter six IGBT switches. The IGBT inverter supplies a 1 hp, 1750 RPM, 208 V, 60 Hz, Y-connected 3Ï† squirrel-cage induction motor that is tested for several speeds. These test results demonstrate robust performance, simple implementation, significant dynamic responses and high ability to maintain high quality outputs.

	Research on Eliminating Common-mode Voltage of Cascaded Medium-voltage Variable Frequency Driver with Phase-difference SVPWM By LU Jiaming; CHEN Bin; NI Xijun; YANG Zhenyu; ZHAO Jianfeng	[View] [Download]
Abstract: For application to cascaded multi-level inverter, three phase-difference SVM (PD-SVM) schemes based on left and right bridge vectors are proposed firstly. For these three schemes, equivalent SPWM components are deduced, and unipolarity or bipolarity of output waveforms is analyzed. Use sampling time staggered SVM (STS-SVM) for reference, improved PD-SVM-STS PD-SVM can be applied to cascaded medium-voltage variable speed driver (MV-VSD). The mechanism of eliminating two sorts of CMV by one of improved PD-SVM schemes-STS 2π/3 PD-SVM is analyzed in detail. Through the simulation results in the end, this modulation scheme can effectively eliminate CMV without reducing the utilization of the dc voltage excessively in contrast with conventional 3d-order harmonic injection SPWM.

	Space vector modulation of nine-phase voltage source inverters based on three-phase decomposition By GRANDI Gabriele; SERRA Giovanni; TANI Angelo	[View] [Download]
Abstract: A new space vector modulation (SVM) technique having a full and independent control of the multiple voltage space vectors of a nine-phase voltage source inverter (VSI) is presented in this paper. The proposed approach is based on the concept of system decomposition, leading to the modulation of three three-phase VSIs. The resulting SVM corresponds to standard SVM for each three-phase VSI in the case of a nine-phase load with three insulated central points, whereas the additional modulation of the zero-sequence component is introduced for each three-phase VSI in the case of a nine-phase load with a single central point. The modulation limits are investigated and the analytical developments are proved by a complete set of simulation results.

	Synchronous Balanced Control of Cascaded Two-Level Inverters with Separated DC-Sources By PROFUMO Francesco; OLESCHUK Valentin	[View] [Download]
Abstract: The paper presents results of dissemination of novel method of synchronized pulsewidth modulation (PWM) for wide-range control of dual inverter-fed motor drives with power balancing capability between dc-links. This drive topology includes two insulated dc sources (with equal or different voltages), feeding two standard three-phase inverters, connected with an open-end winding induction motor. Algorithms of synchronized PWM provide both continuous synchronization of the phase voltage of the induction motor and required sharing of the output power between two dc sources. Special attention has been given to analysis of operation of the drive system with synchronized PWM in the zone of overmodulation. Simulations give the behavior of dual inverter-fed systems with continuous and discontinuous versions of synchronized pulsewidth modulation in both undermodulation and overmodulation control ranges. The spectra of the motor phase voltages do not contain even harmonics and sub-harmonics during the whole control range for any ratio between the switching and fundamental frequencies, which is especially important for the medium/high power systems.

	The self-switching management principle applied toactive bidirectional switches By SIEMASZKO Daniel; DE NOVAES Yales; RUFER Alfred; BARRADE Philippe	[View] [Download]
Abstract: The self-switching principle is a synthesis of synchronous type switching and switch inner protection mechanisms. Both switch ON and switch OFF are performed on the base of current and voltage measurement across the switch. Applied to an active bidirectional device, it may give complete autonomy to the switch. On the basis of those principles, the synthesis of an autonomous bidirectional free-wheeling path for an AC/AC buck converter is implemented with active switches. This paper introduces the current/ voltage state representation in order to illustrate the experimental switching mechanisms. As a further application, the automatic triac is synthesized for a bipolar AC/DC half-bridge converter.

	Three-Phase Multi-Level PWM Rectifier Multi-Carrier Discontinuous Voltage Modulation Strategy By RUDERMAN Alex	[View] [Download]
Abstract: Multi-level PWM rectifier requires fewer semiconductor switches compared with its bidirectional multi-level converter counterpart. Though three-level (multi-level) PWM rectifiers are known for more than 10 years, no multi-level PWM rectifier carrier based voltage modulation strategies were reported so far. After multi-level PWM rectifier topologies introduction and classification, the paper presents a three-phase multi-level PWM rectifier phase shifted multi-carrier voltage modulation strategy based on appropriate discontinuous voltage commands transformation. Suggested formalism naturally allows derivation of a multi-level PWM rectifier voltage amplitude (modulation index) vs. voltage-current phase angle operation envelope without making use of space vector calculus. PWM rectifier operation envelope becomes less restrictive with levels count increase and full utilization. Suggested approach is not limited to a three-phase case and is applicable to a general multi-phase case.