EPE Association: EPE 1999 - Topic 02c: Multilevel and Matrix Converters

EPE 1999 - Topic 02c: Multilevel and Matrix Converters
You are here: EPE Documents > 01 - EPE & EPE ECCE Conference Proceedings > EPE 1999 - Conference > EPE 1999 - Topic 02: POWER ELECTRONICS CONVERTER CIRCUITS > EPE 1999 - Topic 02c: Multilevel and Matrix Converters

   [return to parent folder]

   A New Carrierwave-Based SVPWM for Multilevel H-Bridge Inverter
By D-W. Kang; Y-H. Lee; B-S. Suh; C-H. Choi; D-S. Hyun [View]
[Download]

Abstract: H-bridge multilevel inverters have been focused on in recent years and selected as the power inverter in serveral high voltage and high power applications. This paper proposes a new pulse width modulation (PWM) method for the multilevel H-bridge inverter systems. the proposed PWM method is a carrierwave-based space vector PWM method that utilizes the phase voltage redundancies of the inverter to make both the switch and conduction loss of the devices equal one another. We describe the new PWM method in detail and the effectiveness of the new PWM method is verified by the simulation and experimental results.

   A Simple Neutral Point Control for Three Level PWM Rectifiers
By J. Rodríguez; D. Rodríguez; C. Silva; E. Wiechmann [View]
[Download]

Abstract: This paper presents the modelling, analysis and control of a three-level PWM rectifier working with vector modulation. Specifically, this paper identifies the unbalance generated by the different conduction states and proposes a very simple method to achieve balanced capacitor voltages by using the redundant vectors in the modulation, depending on the polarity of the voltage difference and the direction of power flow. Simulation results confirm the conclusions of the analytical study.

   Analysis and Simulation of Three-Level Voltage Source Inverters and its Application to Flywheel Energy Storage Systems
By I. J. Iglesias; A. Agudo; M. Lafoz [View]
[Download]

Abstract: This paper describes the analysis and simulation (by means of SaberÆÊ simulator) of a threelevel voltage source inverter (VSI) to be used into a Flywheel Energy Storage (FES) System. The inverter drives a permanent magnet synchronous motor. A high speed (up to 30.000 rpm) and a very low THD current motor are required. To achieve this high speed value, a high output frequency (up to 1000 Hz) is necessary; a two-level conventional VSI would require an unacceptable switching frequency to comply with current harmonic distortion requirements. By this reason, three-level inverter topology appears as a good solution because it is capable of generating high frequency and low THD output currents with an acceptable switching frequency (around 6 kHz.). Two different switching strategies for the three-level VSI are analysed and compared in this paper: Space Vector Modulation (SVM) and Natural Sampling Modulation. Developed simulations have shown that three-level topology can fulfil all the above mentioned requirements.

   Asymmetric Multilevel Converter for High Resolution Voltage Phasor Generation
By A. Rufer; M. Veenstra [View]
[Download]

Abstract: Recent publications on so called multilevel inverters deal with series connected cells, mainly developed for the increase of the output-voltage magnitude, in order to meet the classical design levels of medium size motors in the lower megawatt power range. In all well known multilevel topologies, generally a regular or symmetric voltage share over all partial sourceshas been chosen, with as main goal a better use of the individual silicon devices regarding the possible blocking properties. The definition of the resulting output voltage has generally been sufficient due to the high number of series connected cells. In the proposed solution, the main efforts are set to the aspect of getting a higher resulotion of the voltage phasor, in relation with the use of motors with strongly reduced leakage inductances. Together with the specification of a limited current harmonic content, even the frequency of the fundamental component is an important parameter. One application field will be the variable speed drives for ultra-speed kinetic energy storage.

   Bi-Directional Switch Commutation for Matrix Converters
By L. Empringham; P. Wheeler; J. Clare [View]
[Download]

Abstract: This paper deals with the problem of current commutation in matrix converters. Existing strategies are reviewed. An improved implementation of a semi-soft snubberless commutation method is presented. This method employs current detection within intelligent gate drive circuits for each bi-directional cell. Each cell communicates with the other cells to provide accurate current direction information. The problems with other methods at low currents are overcome. Experimental results verifying the method are presented.

   Control Strategies for a Hybrid Seven-level Inverter
By R. Lund; M. D. Manjrekar; P. Steimer; T. A. Lipo [View]
[Download]

Abstract: This paper is devoted to the investigation of control techniques applicable for seven-level 4.16 kV hybrid inverter. A detailed analysis of a hybrid modulation technique, which incorporates stepped synthesis in conjunction with variable pulse width of the consecutive steps, is included. In addition, variations of multicarrier Pulse Width Modulation (PWM) techniques related to the disposition and phase shifting and their comparative evaluation is presented in this paper. The performance attributes of conventional techniques such as staircase modulation and programmed PWM are assessed and optimization of switching angles to minimize the harmonic distortion at different modulation depths is discussed. Operating principles, spectral structure and other practical issues are studied. Computer simulations accompanied with experimental results are presented in the paper.

   Drive Control Timing in Soft-Switched Nested-Cell Inverters
By F.R. Dijkhuizen; J. L. Duarte [View]
[Download]

Abstract: A method is presented to provide soft diode-to-transistor commutations in a three-level nested-cell inverter, on the basis of an additional auxiliary pole. In order to limit the maximum peak current through the auxiliary circuit, while keeping a wide margin of pulse-width modulation, gating signals for the main and auxiliary switches are updated dynamically, by taking the output load current and duty-cycle into account. To this purpose, design considerations for the additional components are also given. The generation of accurate switching times is described, being validated by practical data.

   Dynamic Control and Voltage Balance of Multilevel Converters: Large Signal One-Cycle Response
By R. H. Wilkinson; T. A. Meynard; F. Richardeau; J. H. R. Enslin [View]
[Download]

Abstract: Multilevel converters were first introduced to increase the power rating of converters using available semiconductors [5]. Using these converters allows a reduction in the size of the filtering elements. This affects the dynamic response of the converter. In this paper, the authors discuss the problems encountered in obtaining a bandwidth, approaching the switching frequency of the multilevel converter. Possible solutions are also proposed for dynamic voltage balance of the capacitors.

   Five Level Flying Capacitor Converter - Capacitor Voltage Balancing
By M. F. Escalante; J.-C. Vannier [View]
[Download]

Abstract: This paper deals with the control of the voltage of the capacitors in a 5-level flying capacitor converter. This type of converter takes advantage of the series connection of low voltage power semiconductor devices in order to handle high voltages. Its key feature is the utilisation of clamping capacitors in order to equally split the total volateb between the power semiconductor devices and at the same time having at the output several voltage levels. However, keeping the capacitor voltages at their right values is a well-known constraint of this converter. In this paper we present a logic approach based on the redundancy of the switching states in order to balance the voltage of the capacitors in a 5-level flying capacitor converter. Simulation results are presented to demonstrate the validity of the balancing logic presented.

   Multilevel Converters - A Survey
By R. Teodorescu; F. Blaabjerg; J. K. Pedersen; E. Cengelci; S. U. Sulistijo; B. O. Woo; P. Enjeti [View]
[Download]

Abstract: Multilevel power converter technology is a recent alternative that address high power medium voltage applications requirements. This paper surveys the most popular topologies and modulation strategies used in multilevel power conversion, focussing on a novel Triphase Cascaded (TC) VSI that uses three standard triphase IGBT PWM inverter modules along with an 0.33 p.u. output transformer. A comparative analyse in terms of rating and complexity is carried out for the most common multilevel topologies with reference to the GTO Current Source Inverters (CSI). Computer simulations using SABER as well as practical experiments analyze the characteristics of this new topology in a typical medium-voltage adjustable speed drive (ASD).

   Performance of a Two Steps Commutated Matrix Converter for AC-Variable Speed Drives
By M. Ziegler; W. Hofmann [View]
[Download]

Abstract: This paper deals with the problem of snubberless commutation in matrix converters. Based on a two steps commutation strategy with optimised switching patterns a simple hysteresis current control is implemented which guaranties a safe control of bidirectional switches with seperated internal conduction paths for each current direction.

   SVPWM for Small Fluctuation of Neutral Point Current in High Index Modulation Region of the Three-level Inverter
By R.-Y. Kim; Y.-H. Lee; D.-S. Hyun [View]
[Download]

Abstract: The diode clamped three-level VSI has been widely used in high-capacity high-performance AC drive applications. There exists an inherent problem that is the variation of neutral point voltage in dc link capacitor bank of three-level inverter. This paper describes the analysis of the neutral point current of the diode clamped three-level inverter and the improved space-vector based PWM strategy to consider the switching frequency and to minimize the neutral point current in spite of high modulation index region and low power factor. It contributes to decrease the capacitance of dc link capacitor bank and to increase the neutral point voltage controllable region. Especially, even if second (or even) order harmonic is induced in load current (at this situation, it was investigated that the general control method can not suppress the neutral point voltage variation), this PWM can provide effective control method to supress the neutral point voltage variation. Various simulation results by means of Matlab/Simulink are presented to verify the proposed PWM.

   Transformer Assisted PWM Zero Voltage Switching Pole Inverter and its Applications to Multilevel Inverters
By X. Yuan; I. Barbi; H. Stemmler [View]
[Download]

Abstract: This paper reports a newly proposed transformer assisted PWM zero voltage switching pole inverter technique. This technique is comprehensively compared with the Auxiliary-Resonant-Commutated-Pole-Inverter (ARCPI) technique, advantages and limiotations of both circuits are outlined. Applications of this technique to the diode clamping multilevel inverter and the capacitor clamping multilevel inverter are discussed. Relevant test results from a 7kW half bridge Neural-Point-Clamped (NPC) inverter and a 3 kW half bridge three-level capacitor clamping inverter are given.

   Voltage Space Vectors of Multilevel Inverters
By Oguchi Kuniomi; Toshiharu Karaki; Nobukazu Hoshi [View]
[Download]

Abstract: The relationship among voltage-levels of three-phase inverters, numbers of different space vectors of output voltages, and coupling schemes of double inverters is presented. It is shown that a harmonic canceling reactor-coupled system can produce a large number of space vectors of output voltages. An application example of the space vectors to pulse width modulation is also described.

   Wide-Bandwidth Current-Source Interleaved Converter
By J. S. Batchvarov; J. L. Duarte; M. A. M. Hendrix [View]
[Download]

Abstract: In this paper, a novel method for control of interleaved converters with variable switching frequency is presented. It is based on cycle-by-cycle measurements of the switching period and calculation of the needed phase shift by means of analog circuitry. A control circuit is developed ensuring low phase error, high bandwidth and high reliability. Simply adding more modules with minimum additional modifications can easily extend the system's power capability. In case of failure of one or more modules, the phase shift can be automatically corrected, maintaining minimum ripple amplitude. Short design considerations are given in order to prevent some possible drawbacks. Finally, simulation and experimental results are presented for verification. As an application example, a welding converter based on interleaved modules is presented showing promising results for achieving a high quality current source.

EPE 1999 - Topic 02c: Multilevel and Matrix Converters
You are here: EPE Documents > 01 - EPE & EPE ECCE Conference Proceedings > EPE 1999 - Conference > EPE 1999 - Topic 02: POWER ELECTRONICS CONVERTER CIRCUITS > EPE 1999 - Topic 02c: Multilevel and Matrix Converters
	[return to parent folder]

	A New Carrierwave-Based SVPWM for Multilevel H-Bridge Inverter By D-W. Kang; Y-H. Lee; B-S. Suh; C-H. Choi; D-S. Hyun	[View] [Download]
Abstract: H-bridge multilevel inverters have been focused on in recent years and selected as the power inverter in serveral high voltage and high power applications. This paper proposes a new pulse width modulation (PWM) method for the multilevel H-bridge inverter systems. the proposed PWM method is a carrierwave-based space vector PWM method that utilizes the phase voltage redundancies of the inverter to make both the switch and conduction loss of the devices equal one another. We describe the new PWM method in detail and the effectiveness of the new PWM method is verified by the simulation and experimental results.

	A Simple Neutral Point Control for Three Level PWM Rectifiers By J. Rodríguez; D. Rodríguez; C. Silva; E. Wiechmann	[View] [Download]
Abstract: This paper presents the modelling, analysis and control of a three-level PWM rectifier working with vector modulation. Specifically, this paper identifies the unbalance generated by the different conduction states and proposes a very simple method to achieve balanced capacitor voltages by using the redundant vectors in the modulation, depending on the polarity of the voltage difference and the direction of power flow. Simulation results confirm the conclusions of the analytical study.

	Analysis and Simulation of Three-Level Voltage Source Inverters and its Application to Flywheel Energy Storage Systems By I. J. Iglesias; A. Agudo; M. Lafoz	[View] [Download]
Abstract: This paper describes the analysis and simulation (by means of SaberÆÊ simulator) of a threelevel voltage source inverter (VSI) to be used into a Flywheel Energy Storage (FES) System. The inverter drives a permanent magnet synchronous motor. A high speed (up to 30.000 rpm) and a very low THD current motor are required. To achieve this high speed value, a high output frequency (up to 1000 Hz) is necessary; a two-level conventional VSI would require an unacceptable switching frequency to comply with current harmonic distortion requirements. By this reason, three-level inverter topology appears as a good solution because it is capable of generating high frequency and low THD output currents with an acceptable switching frequency (around 6 kHz.). Two different switching strategies for the three-level VSI are analysed and compared in this paper: Space Vector Modulation (SVM) and Natural Sampling Modulation. Developed simulations have shown that three-level topology can fulfil all the above mentioned requirements.

	Asymmetric Multilevel Converter for High Resolution Voltage Phasor Generation By A. Rufer; M. Veenstra	[View] [Download]
Abstract: Recent publications on so called multilevel inverters deal with series connected cells, mainly developed for the increase of the output-voltage magnitude, in order to meet the classical design levels of medium size motors in the lower megawatt power range. In all well known multilevel topologies, generally a regular or symmetric voltage share over all partial sourceshas been chosen, with as main goal a better use of the individual silicon devices regarding the possible blocking properties. The definition of the resulting output voltage has generally been sufficient due to the high number of series connected cells. In the proposed solution, the main efforts are set to the aspect of getting a higher resulotion of the voltage phasor, in relation with the use of motors with strongly reduced leakage inductances. Together with the specification of a limited current harmonic content, even the frequency of the fundamental component is an important parameter. One application field will be the variable speed drives for ultra-speed kinetic energy storage.

	Bi-Directional Switch Commutation for Matrix Converters By L. Empringham; P. Wheeler; J. Clare	[View] [Download]
Abstract: This paper deals with the problem of current commutation in matrix converters. Existing strategies are reviewed. An improved implementation of a semi-soft snubberless commutation method is presented. This method employs current detection within intelligent gate drive circuits for each bi-directional cell. Each cell communicates with the other cells to provide accurate current direction information. The problems with other methods at low currents are overcome. Experimental results verifying the method are presented.

	Control Strategies for a Hybrid Seven-level Inverter By R. Lund; M. D. Manjrekar; P. Steimer; T. A. Lipo	[View] [Download]
Abstract: This paper is devoted to the investigation of control techniques applicable for seven-level 4.16 kV hybrid inverter. A detailed analysis of a hybrid modulation technique, which incorporates stepped synthesis in conjunction with variable pulse width of the consecutive steps, is included. In addition, variations of multicarrier Pulse Width Modulation (PWM) techniques related to the disposition and phase shifting and their comparative evaluation is presented in this paper. The performance attributes of conventional techniques such as staircase modulation and programmed PWM are assessed and optimization of switching angles to minimize the harmonic distortion at different modulation depths is discussed. Operating principles, spectral structure and other practical issues are studied. Computer simulations accompanied with experimental results are presented in the paper.

	Drive Control Timing in Soft-Switched Nested-Cell Inverters By F.R. Dijkhuizen; J. L. Duarte	[View] [Download]
Abstract: A method is presented to provide soft diode-to-transistor commutations in a three-level nested-cell inverter, on the basis of an additional auxiliary pole. In order to limit the maximum peak current through the auxiliary circuit, while keeping a wide margin of pulse-width modulation, gating signals for the main and auxiliary switches are updated dynamically, by taking the output load current and duty-cycle into account. To this purpose, design considerations for the additional components are also given. The generation of accurate switching times is described, being validated by practical data.

	Dynamic Control and Voltage Balance of Multilevel Converters: Large Signal One-Cycle Response By R. H. Wilkinson; T. A. Meynard; F. Richardeau; J. H. R. Enslin	[View] [Download]
Abstract: Multilevel converters were first introduced to increase the power rating of converters using available semiconductors [5]. Using these converters allows a reduction in the size of the filtering elements. This affects the dynamic response of the converter. In this paper, the authors discuss the problems encountered in obtaining a bandwidth, approaching the switching frequency of the multilevel converter. Possible solutions are also proposed for dynamic voltage balance of the capacitors.

	Five Level Flying Capacitor Converter - Capacitor Voltage Balancing By M. F. Escalante; J.-C. Vannier	[View] [Download]
Abstract: This paper deals with the control of the voltage of the capacitors in a 5-level flying capacitor converter. This type of converter takes advantage of the series connection of low voltage power semiconductor devices in order to handle high voltages. Its key feature is the utilisation of clamping capacitors in order to equally split the total volateb between the power semiconductor devices and at the same time having at the output several voltage levels. However, keeping the capacitor voltages at their right values is a well-known constraint of this converter. In this paper we present a logic approach based on the redundancy of the switching states in order to balance the voltage of the capacitors in a 5-level flying capacitor converter. Simulation results are presented to demonstrate the validity of the balancing logic presented.

	Multilevel Converters - A Survey By R. Teodorescu; F. Blaabjerg; J. K. Pedersen; E. Cengelci; S. U. Sulistijo; B. O. Woo; P. Enjeti	[View] [Download]
Abstract: Multilevel power converter technology is a recent alternative that address high power medium voltage applications requirements. This paper surveys the most popular topologies and modulation strategies used in multilevel power conversion, focussing on a novel Triphase Cascaded (TC) VSI that uses three standard triphase IGBT PWM inverter modules along with an 0.33 p.u. output transformer. A comparative analyse in terms of rating and complexity is carried out for the most common multilevel topologies with reference to the GTO Current Source Inverters (CSI). Computer simulations using SABER as well as practical experiments analyze the characteristics of this new topology in a typical medium-voltage adjustable speed drive (ASD).

	Performance of a Two Steps Commutated Matrix Converter for AC-Variable Speed Drives By M. Ziegler; W. Hofmann	[View] [Download]
Abstract: This paper deals with the problem of snubberless commutation in matrix converters. Based on a two steps commutation strategy with optimised switching patterns a simple hysteresis current control is implemented which guaranties a safe control of bidirectional switches with seperated internal conduction paths for each current direction.

	SVPWM for Small Fluctuation of Neutral Point Current in High Index Modulation Region of the Three-level Inverter By R.-Y. Kim; Y.-H. Lee; D.-S. Hyun	[View] [Download]
Abstract: The diode clamped three-level VSI has been widely used in high-capacity high-performance AC drive applications. There exists an inherent problem that is the variation of neutral point voltage in dc link capacitor bank of three-level inverter. This paper describes the analysis of the neutral point current of the diode clamped three-level inverter and the improved space-vector based PWM strategy to consider the switching frequency and to minimize the neutral point current in spite of high modulation index region and low power factor. It contributes to decrease the capacitance of dc link capacitor bank and to increase the neutral point voltage controllable region. Especially, even if second (or even) order harmonic is induced in load current (at this situation, it was investigated that the general control method can not suppress the neutral point voltage variation), this PWM can provide effective control method to supress the neutral point voltage variation. Various simulation results by means of Matlab/Simulink are presented to verify the proposed PWM.

	Transformer Assisted PWM Zero Voltage Switching Pole Inverter and its Applications to Multilevel Inverters By X. Yuan; I. Barbi; H. Stemmler	[View] [Download]
Abstract: This paper reports a newly proposed transformer assisted PWM zero voltage switching pole inverter technique. This technique is comprehensively compared with the Auxiliary-Resonant-Commutated-Pole-Inverter (ARCPI) technique, advantages and limiotations of both circuits are outlined. Applications of this technique to the diode clamping multilevel inverter and the capacitor clamping multilevel inverter are discussed. Relevant test results from a 7kW half bridge Neural-Point-Clamped (NPC) inverter and a 3 kW half bridge three-level capacitor clamping inverter are given.

	Voltage Space Vectors of Multilevel Inverters By Oguchi Kuniomi; Toshiharu Karaki; Nobukazu Hoshi	[View] [Download]
Abstract: The relationship among voltage-levels of three-phase inverters, numbers of different space vectors of output voltages, and coupling schemes of double inverters is presented. It is shown that a harmonic canceling reactor-coupled system can produce a large number of space vectors of output voltages. An application example of the space vectors to pulse width modulation is also described.

	Wide-Bandwidth Current-Source Interleaved Converter By J. S. Batchvarov; J. L. Duarte; M. A. M. Hendrix	[View] [Download]
Abstract: In this paper, a novel method for control of interleaved converters with variable switching frequency is presented. It is based on cycle-by-cycle measurements of the switching period and calculation of the needed phase shift by means of analog circuitry. A control circuit is developed ensuring low phase error, high bandwidth and high reliability. Simply adding more modules with minimum additional modifications can easily extend the system's power capability. In case of failure of one or more modules, the phase shift can be automatically corrected, maintaining minimum ripple amplitude. Short design considerations are given in order to prevent some possible drawbacks. Finally, simulation and experimental results are presented for verification. As an application example, a welding converter based on interleaved modules is presented showing promising results for achieving a high quality current source.