EPE Association: EPE 2009 - Subtopic 05-6 - DS: 'Multi-Level Converters'

EPE 2009 - Subtopic 05-6 - DS: 'Multi-Level Converters'
You are here: EPE Documents > 01 - EPE & EPE ECCE Conference Proceedings > EPE 2009 - Conference > EPE 2009 - Topic 05: 'Hard Switching Converters and Control' > EPE 2009 - Subtopic 05-6 - DS: 'Multi-Level Converters'

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   A high-bandwidth high-power inverter
By Juan SABATE, Juan RIVAS, Paul SZCZESNY, Ljubisa STEVANOVIC [View]
[Download]

Abstract: This paper presents experimental results for the design of a high power voltage fed inverter and discusses the benefits of two technologies used in its implementation. The inverter design presented here finds application in procedures requiring accurate control of large fast-varying currents with minimal error. In the context of a 1 MVA voltage fed inverter, we experimentally demonstrate the advantages of combining high performance power modules with advanced cooling technologies. The power devices used combine conventional Silicon IGBTâ€™s with Silicon Carbide Schottky antiparallel diodes dramatically reducing switching losses in the system.

   Analysis of Dynamic Performance of Multilevel Modulators with Switching Pattern Restricted to Single Voltage Level Steps
By Ville NAUMANEN, Julius LUUKKO, Juha PYRHÃ–NEN, Pertti SILVENTOINEN [View]
[Download]

Abstract: Switching pattern in multilevel inverters has to be restricted to single voltage level steps to limit the overvoltages caused by the cable reflections and du/dt. This restriction affects not only the single-phase voltage pattern but the maximum allowed change of a voltage reference vector in three-phase operation and as a result also the maximum achievable frequency of the reference. These together can be perceived to determine the dynamical characteristic of the multilevel modulation schemes. Methods to determine the boundaries inside which these characteristics are valid are presented in this paper.

   Dead-time Compensation for Multilevel Cascaded H-bridge Converters with Novel Voltage Balancing
By Robert BETZ, Terry SUMMERS, Galina MIRZAEVA [View]
[Download]

Abstract: A novel capacitor voltage balancing algorithm for cascaded H-bridge converters can lead to undesirable voltage spikes at the output of the converter. This paper describes the voltage balancing algorithm and how it produces the voltage spikes. A simple and elegant solution is then developed and simulation results are presented to demonstrate its performance.

   Diode-clamped multilevel converters with integrable gate-driver power-supply circuits
By Sergio BUSQUETS-MONGE, Joan ROCABERT, Jean-Christophe CREBIER, Juan PERACAULA [View]
[Download]

Abstract: Recent contributions in pulse width modulations (PWM) for multilevel diode-clamped converters enable the use of these converters with passive front-ends, any number of levels, and small dc-link capacitors. Highly compact converters designs based on these topologies can be envisioned. However, the design of the gate-driver power-supply for the multiple controlled semiconductor devices remains an important issue to be addressed. This paper focuses on the design of such circuits and the analysis of the resulting multilevel converter performance. A simple circuit connected across each power switch and monolithically integrable within it is selected. These circuits lead to simple, compact, and efficient converter designs. The main issues arising from the operation of the multilevel converter with such circuits are analyzed, and both hardware and software solutions are proposed. In particular, a new PWM strategy is presented. Experimental results are provided verifying the good performance of all proposed solutions.

   Efficiency Comparison between a Hybrid Cascaded Connected Seven Level Converter and a Standard Cascaded Connected Seven Level Converter for STATCOM Applications
By Igor BARAIA, Jean-Luc THOMAS, Jon Andoni BARRENA, Josu GALARZA, Miguel Angel RODRIGUEZ [View]
[Download]

Abstract: This paper presents the dimensioning and comparison in terms of efficiency, cost and waveform quality of a Hybrid 7 Level converter and a Standard cascaded connected 7 Level converter for 26 MVA and 15 kV STATCOM applications. In addition, these converters are compared with commercially available 2 Level and 3 Level NPC VSCs.

   Fault-tolerant inverter for subsea applications
By Guy FLURY, Bernard GOLLENTZ, Christophe CONILH [View]
[Download]

Abstract: This paper investigates in a topology of medium voltage inverter retained to guarantee severe conditions concerning environmental and reliability requirements. This system is based on a standard three levels NPC (Neutral Point Clamped) drive [7] with redundant IGBT and can tolerate the on-state failure mode of the IGBT. Like this, in the operation mode the inverter has been designed to run in permanent condition with a failed IGBT in short circuit. The failed IGBT have been observed and analyzed in order to estimate the short circuit stability. On the other hand, the material improvement such as cooling unit, gate drive, control system and components sorting have been carried out to increase the design lifetime but will not be presented in this article. An experimental 200kVA mockup have been carried out and will be presented such as the significant results to qualify the principles.

   Feed-forward Compensation for Multilevel Cascaded H-bridge Statcoms
By Robert BETZ, Galina MIRZAEVA, Christopher TOWNSEND, Terry SUMMERS [View]
[Download]

Abstract: Multilevel Static Compensators (StatComs) offer significant advantages over traditional two level converter based StatComs. The cascaded H-bridge topology for multilevel StatComs is increasing becoming the topology of choice. This paper will address the problem of compensating for the non-ideal nature of the H-bridges so that accurate current control can be achieved with this topology using a predictive current controller.

   Four-Level Single-Leg Flying Capacitor Converter Voltage Balance Dynamics Analysis
By Boris REZNIKOV, Alex RUDERMAN [View]
[Download]

Abstract: Flying capacitor converter is an attractive multilevel converter choice due to its natural voltage balance property. Averaged voltage balance dynamics analytical research methods reported to date are essentially based on a frequency domain analysis. They require high mathematical skills and the solutions are not truly analytical and difficult to use in an everyday practice. In this paper, a straightforward time domain approach based on stitching of analytical solutions for consecutive switching intervals is applied to a four-level single-leg converter. Small parameter analysis yields physically meaningful simple accurate closed-form expressions for averaged oscillating voltage balance dynamics revealing the dependences of voltage balance frequency and time constant on load parameters, carrier frequency, and normalized DC PWM voltage command. Averaged voltage balance dynamics for AC PWM is obtained by averaging on AC fundamental period.

   Medium Voltage Three-level Converters for the Grid Connection of a Multi-MW Wind Turbine
By OSMAN S. SENTURK, LARS HELLE, STIG MUNK-NIELSEN, PEDRO RODRIGUEZ, REMUS TEODORESCU [View]
[Download]

Abstract: Three-level (3L) neutral point clamped (NPC), flying capacitor (FC), and H-bridge (HB) voltage source converters (VSCs) as a grid-side full-scale medium voltage (MV) converter are modeled, controlled, and simulated for the grid connection of a hypothetical 6MW wind turbine. Via the converter topological features and the simulation results demonstrating the converter performance, these three 3L-VSCs are discussed and compared in terms of power density and reliability, which can be considered as two of the most important criteria for the converters placed in wind turbine nacelles. Given the grid connection circuit (without capacitive switching ripple filters), the 3L-HB-VSC is expected to be superior with respect to power density and reliability over the 3L-NPC- and -FC-VSCs.

   Modeling of a Three Phase SPWM Multilevel VSI with Low THD Using Matlab/Simulink
By ILHAMI COLAK, Ramazan BAYINDIR , Gungor BAL, Ersan KABALCI [View]
[Download]

Abstract: Researches done based on basic inverter topologies show that multilevel inverters (MLIs) have many advantages, such as low power dissipation on power switches, low dv/dt ratios, low harmonic and low electromagnetic interference (EMI) outputs. The most common MLI topologies have been studied to define the most appropriate structure for Sinusoidal Pulse Width Modulation (SPWM) strategy. It is seen that cascaded H-bridges are the most convenient solution. The cascaded H-bridge cells have been constituted by IGBT semiconductors, and switched by the proposed 24-channel SPWM modulator to obtain 5-level output at the back-end of the 3-phase voltage source inverter (VSI). A modified 24 channels SPWM modulator that reduces output harmonics has been presented in this study to switch cascaded H-bridge cells of multilevel VSI. The designed multilevel VSI has a THDi ratio around at 0.1\% and a strong switching bandwidth up to 40 kHz, owing to its well designed modulator. The modeling operations are also examined in Matlab/Simulink to obtain a practical solution for threephase SPWM modulator. Various design steps and configurations have been considered to model the modulator and the success of modulator has been tested under several conditions such as increased modulation indexes and switching frequencies

   Multicarrier and Space Vector Modulation for Three-Phase NPC Converters: A Comparative Analysis
By Ivo PEREIRA, AntÃ³nio MARTINS [View]
[Download]

Abstract: The three-level neutral point clamped converter is one of the most important multilevel converters. Two important features of the neutral point clamped converter are the neutral point balance and the output voltage characteristics. Carrier and space vector Pulse-Width Modulation control methods efficiently manage the two issues. This paper analyses the voltage balancing problem and shows that a simple control loop maintains the voltage balance in different operating conditions. Besides simulation, the paper experimentally compares the two issues and shows that the two methods produce almost the same results.

   NEW ASYMMETRICAL HYBRID MULTILEVEL VOLTAGE INVERTER
By SAMIR AHMAD MUSSA, DOMINGO RUIZ-CABALLERO, LUIS MARTINEZ, REYNALDO RAMOS A [View]
[Download]

Abstract: This article presents the study and implementation of a new asymmetric hybrid voltage inverter, for high voltage applications. The proposed inverter employs two types of modulation in low and high frequency (sinusoidal PWM). Simulations and experiment results are provided showing the validity of the analyses. These were obtained using a low-voltage single-phase prototype that demonstrated its operation.

   Phase Leg Voltage Balancing of a Cascaded H-Bridge Converter Based STATCOM using Zero Sequence Injection
By Terrence SUMMERS, Robert BETZ, Galina MIRZAEVA [View]
[Download]

Abstract: In cascaded H-bridge wye and delta connected STATCOMs the phase leg capacitor voltages can diverge, even under ideal balanced voltage conditions, due to different leg losses and capacitor values. This paper presents a novel strategy for achieving phase leg voltage balance for wye and delta connected STATCOMs by making use of zero sequence injection into the STATCOM. The proposed strategy also makes the STATCOM leg voltages tolerant to terminal voltage imbalance.

   Pulse Width Modulation Scheme for the Modular Multilevel Converter
By Steffen ROHNER, Steffen BERNET, Marc HILLER, Rainer SOMMER [View]
[Download]

Abstract: The Modular Multilevel Converter (M2C) is an emerging and highly attractive multilevel converter topology for medium and high voltage applications. In this paper, a new pulse width modulation (PWM) scheme will be derived. For this pulse width modulation scheme, characteristic simulated waveforms are described and analyzed.

   Three-Level H-Bridge Flying Capacitor Converter Voltage Balance Dynamics Analysis
By Alex RUDERMAN, Boris REZNIKOV [View]
[Download]

Abstract: Flying capacitor converter is an attractive choice due to its natural voltage balance property. Voltage balance dynamics analytical research methods reported to date are essentially based on a frequency domain analysis. They require high mathematical skills and the solutions are not truly analytical and difficult to use in an everyday practice. In this paper, a straightforward time domain approach based on stitching of consecutive switching intervals analytical solutions is applied to an H-bridge three-level flying capacitor converter. Small parameter analysis yields simple accurate expressions for voltage balance time constants revealing their dependences on load parameters, carrier frequency, and normalized voltage command. Voltage balance dynamics for AC PWM is obtained by averaging DC PWM exponential term decay factors on AC fundamental period.

   Eighteen-Level Inverter Control with Minimum Switching Losses
By Mohamad N. Abdul Kadir; Saad Mekhilef [View]
[Download]

Abstract: A multilevel multistage inverter design and its corresponding control strategy are presented. The hybrid inverter has a high voltage stage composed of the six-switch conventional three phase inverter with its outputs connected in series to the outputs of three-level H-bridge medium and low voltage stages. The voltage ratio has been selected to form 18-level provide maximum number of uniform steps. The suggested control strategy has been developed to ensure minimum switching losses focusing on holding the higher voltage stage state as long as it is feasible. The reference voltage vector has been approximated to the nearest inverter voltage vector. A special definition of state zone has been introduced for the low voltage stage to enable the achievement of the reference vector with minimum error. The proposed control strategy has been tested and its short computational time and low memory requirement has been proven.

EPE 2009 - Subtopic 05-6 - DS: 'Multi-Level Converters'
You are here: EPE Documents > 01 - EPE & EPE ECCE Conference Proceedings > EPE 2009 - Conference > EPE 2009 - Topic 05: 'Hard Switching Converters and Control' > EPE 2009 - Subtopic 05-6 - DS: 'Multi-Level Converters'
	[return to parent folder]

	A high-bandwidth high-power inverter By Juan SABATE, Juan RIVAS, Paul SZCZESNY, Ljubisa STEVANOVIC	[View] [Download]
Abstract: This paper presents experimental results for the design of a high power voltage fed inverter and discusses the benefits of two technologies used in its implementation. The inverter design presented here finds application in procedures requiring accurate control of large fast-varying currents with minimal error. In the context of a 1 MVA voltage fed inverter, we experimentally demonstrate the advantages of combining high performance power modules with advanced cooling technologies. The power devices used combine conventional Silicon IGBTâ€™s with Silicon Carbide Schottky antiparallel diodes dramatically reducing switching losses in the system.

	Analysis of Dynamic Performance of Multilevel Modulators with Switching Pattern Restricted to Single Voltage Level Steps By Ville NAUMANEN, Julius LUUKKO, Juha PYRHÃ–NEN, Pertti SILVENTOINEN	[View] [Download]
Abstract: Switching pattern in multilevel inverters has to be restricted to single voltage level steps to limit the overvoltages caused by the cable reflections and du/dt. This restriction affects not only the single-phase voltage pattern but the maximum allowed change of a voltage reference vector in three-phase operation and as a result also the maximum achievable frequency of the reference. These together can be perceived to determine the dynamical characteristic of the multilevel modulation schemes. Methods to determine the boundaries inside which these characteristics are valid are presented in this paper.

	Dead-time Compensation for Multilevel Cascaded H-bridge Converters with Novel Voltage Balancing By Robert BETZ, Terry SUMMERS, Galina MIRZAEVA	[View] [Download]
Abstract: A novel capacitor voltage balancing algorithm for cascaded H-bridge converters can lead to undesirable voltage spikes at the output of the converter. This paper describes the voltage balancing algorithm and how it produces the voltage spikes. A simple and elegant solution is then developed and simulation results are presented to demonstrate its performance.

	Diode-clamped multilevel converters with integrable gate-driver power-supply circuits By Sergio BUSQUETS-MONGE, Joan ROCABERT, Jean-Christophe CREBIER, Juan PERACAULA	[View] [Download]
Abstract: Recent contributions in pulse width modulations (PWM) for multilevel diode-clamped converters enable the use of these converters with passive front-ends, any number of levels, and small dc-link capacitors. Highly compact converters designs based on these topologies can be envisioned. However, the design of the gate-driver power-supply for the multiple controlled semiconductor devices remains an important issue to be addressed. This paper focuses on the design of such circuits and the analysis of the resulting multilevel converter performance. A simple circuit connected across each power switch and monolithically integrable within it is selected. These circuits lead to simple, compact, and efficient converter designs. The main issues arising from the operation of the multilevel converter with such circuits are analyzed, and both hardware and software solutions are proposed. In particular, a new PWM strategy is presented. Experimental results are provided verifying the good performance of all proposed solutions.

	Efficiency Comparison between a Hybrid Cascaded Connected Seven Level Converter and a Standard Cascaded Connected Seven Level Converter for STATCOM Applications By Igor BARAIA, Jean-Luc THOMAS, Jon Andoni BARRENA, Josu GALARZA, Miguel Angel RODRIGUEZ	[View] [Download]
Abstract: This paper presents the dimensioning and comparison in terms of efficiency, cost and waveform quality of a Hybrid 7 Level converter and a Standard cascaded connected 7 Level converter for 26 MVA and 15 kV STATCOM applications. In addition, these converters are compared with commercially available 2 Level and 3 Level NPC VSCs.

	Fault-tolerant inverter for subsea applications By Guy FLURY, Bernard GOLLENTZ, Christophe CONILH	[View] [Download]
Abstract: This paper investigates in a topology of medium voltage inverter retained to guarantee severe conditions concerning environmental and reliability requirements. This system is based on a standard three levels NPC (Neutral Point Clamped) drive [7] with redundant IGBT and can tolerate the on-state failure mode of the IGBT. Like this, in the operation mode the inverter has been designed to run in permanent condition with a failed IGBT in short circuit. The failed IGBT have been observed and analyzed in order to estimate the short circuit stability. On the other hand, the material improvement such as cooling unit, gate drive, control system and components sorting have been carried out to increase the design lifetime but will not be presented in this article. An experimental 200kVA mockup have been carried out and will be presented such as the significant results to qualify the principles.

	Feed-forward Compensation for Multilevel Cascaded H-bridge Statcoms By Robert BETZ, Galina MIRZAEVA, Christopher TOWNSEND, Terry SUMMERS	[View] [Download]
Abstract: Multilevel Static Compensators (StatComs) offer significant advantages over traditional two level converter based StatComs. The cascaded H-bridge topology for multilevel StatComs is increasing becoming the topology of choice. This paper will address the problem of compensating for the non-ideal nature of the H-bridges so that accurate current control can be achieved with this topology using a predictive current controller.

	Four-Level Single-Leg Flying Capacitor Converter Voltage Balance Dynamics Analysis By Boris REZNIKOV, Alex RUDERMAN	[View] [Download]
Abstract: Flying capacitor converter is an attractive multilevel converter choice due to its natural voltage balance property. Averaged voltage balance dynamics analytical research methods reported to date are essentially based on a frequency domain analysis. They require high mathematical skills and the solutions are not truly analytical and difficult to use in an everyday practice. In this paper, a straightforward time domain approach based on stitching of analytical solutions for consecutive switching intervals is applied to a four-level single-leg converter. Small parameter analysis yields physically meaningful simple accurate closed-form expressions for averaged oscillating voltage balance dynamics revealing the dependences of voltage balance frequency and time constant on load parameters, carrier frequency, and normalized DC PWM voltage command. Averaged voltage balance dynamics for AC PWM is obtained by averaging on AC fundamental period.

	Medium Voltage Three-level Converters for the Grid Connection of a Multi-MW Wind Turbine By OSMAN S. SENTURK, LARS HELLE, STIG MUNK-NIELSEN, PEDRO RODRIGUEZ, REMUS TEODORESCU	[View] [Download]
Abstract: Three-level (3L) neutral point clamped (NPC), flying capacitor (FC), and H-bridge (HB) voltage source converters (VSCs) as a grid-side full-scale medium voltage (MV) converter are modeled, controlled, and simulated for the grid connection of a hypothetical 6MW wind turbine. Via the converter topological features and the simulation results demonstrating the converter performance, these three 3L-VSCs are discussed and compared in terms of power density and reliability, which can be considered as two of the most important criteria for the converters placed in wind turbine nacelles. Given the grid connection circuit (without capacitive switching ripple filters), the 3L-HB-VSC is expected to be superior with respect to power density and reliability over the 3L-NPC- and -FC-VSCs.

	Modeling of a Three Phase SPWM Multilevel VSI with Low THD Using Matlab/Simulink By ILHAMI COLAK, Ramazan BAYINDIR , Gungor BAL, Ersan KABALCI	[View] [Download]
Abstract: Researches done based on basic inverter topologies show that multilevel inverters (MLIs) have many advantages, such as low power dissipation on power switches, low dv/dt ratios, low harmonic and low electromagnetic interference (EMI) outputs. The most common MLI topologies have been studied to define the most appropriate structure for Sinusoidal Pulse Width Modulation (SPWM) strategy. It is seen that cascaded H-bridges are the most convenient solution. The cascaded H-bridge cells have been constituted by IGBT semiconductors, and switched by the proposed 24-channel SPWM modulator to obtain 5-level output at the back-end of the 3-phase voltage source inverter (VSI). A modified 24 channels SPWM modulator that reduces output harmonics has been presented in this study to switch cascaded H-bridge cells of multilevel VSI. The designed multilevel VSI has a THDi ratio around at 0.1\% and a strong switching bandwidth up to 40 kHz, owing to its well designed modulator. The modeling operations are also examined in Matlab/Simulink to obtain a practical solution for threephase SPWM modulator. Various design steps and configurations have been considered to model the modulator and the success of modulator has been tested under several conditions such as increased modulation indexes and switching frequencies

	Multicarrier and Space Vector Modulation for Three-Phase NPC Converters: A Comparative Analysis By Ivo PEREIRA, AntÃ³nio MARTINS	[View] [Download]
Abstract: The three-level neutral point clamped converter is one of the most important multilevel converters. Two important features of the neutral point clamped converter are the neutral point balance and the output voltage characteristics. Carrier and space vector Pulse-Width Modulation control methods efficiently manage the two issues. This paper analyses the voltage balancing problem and shows that a simple control loop maintains the voltage balance in different operating conditions. Besides simulation, the paper experimentally compares the two issues and shows that the two methods produce almost the same results.

	NEW ASYMMETRICAL HYBRID MULTILEVEL VOLTAGE INVERTER By SAMIR AHMAD MUSSA, DOMINGO RUIZ-CABALLERO, LUIS MARTINEZ, REYNALDO RAMOS A	[View] [Download]
Abstract: This article presents the study and implementation of a new asymmetric hybrid voltage inverter, for high voltage applications. The proposed inverter employs two types of modulation in low and high frequency (sinusoidal PWM). Simulations and experiment results are provided showing the validity of the analyses. These were obtained using a low-voltage single-phase prototype that demonstrated its operation.

	Phase Leg Voltage Balancing of a Cascaded H-Bridge Converter Based STATCOM using Zero Sequence Injection By Terrence SUMMERS, Robert BETZ, Galina MIRZAEVA	[View] [Download]
Abstract: In cascaded H-bridge wye and delta connected STATCOMs the phase leg capacitor voltages can diverge, even under ideal balanced voltage conditions, due to different leg losses and capacitor values. This paper presents a novel strategy for achieving phase leg voltage balance for wye and delta connected STATCOMs by making use of zero sequence injection into the STATCOM. The proposed strategy also makes the STATCOM leg voltages tolerant to terminal voltage imbalance.

	Pulse Width Modulation Scheme for the Modular Multilevel Converter By Steffen ROHNER, Steffen BERNET, Marc HILLER, Rainer SOMMER	[View] [Download]
Abstract: The Modular Multilevel Converter (M2C) is an emerging and highly attractive multilevel converter topology for medium and high voltage applications. In this paper, a new pulse width modulation (PWM) scheme will be derived. For this pulse width modulation scheme, characteristic simulated waveforms are described and analyzed.

	Three-Level H-Bridge Flying Capacitor Converter Voltage Balance Dynamics Analysis By Alex RUDERMAN, Boris REZNIKOV	[View] [Download]
Abstract: Flying capacitor converter is an attractive choice due to its natural voltage balance property. Voltage balance dynamics analytical research methods reported to date are essentially based on a frequency domain analysis. They require high mathematical skills and the solutions are not truly analytical and difficult to use in an everyday practice. In this paper, a straightforward time domain approach based on stitching of consecutive switching intervals analytical solutions is applied to an H-bridge three-level flying capacitor converter. Small parameter analysis yields simple accurate expressions for voltage balance time constants revealing their dependences on load parameters, carrier frequency, and normalized voltage command. Voltage balance dynamics for AC PWM is obtained by averaging DC PWM exponential term decay factors on AC fundamental period.

	Eighteen-Level Inverter Control with Minimum Switching Losses By Mohamad N. Abdul Kadir; Saad Mekhilef	[View] [Download]
Abstract: A multilevel multistage inverter design and its corresponding control strategy are presented. The hybrid inverter has a high voltage stage composed of the six-switch conventional three phase inverter with its outputs connected in series to the outputs of three-level H-bridge medium and low voltage stages. The voltage ratio has been selected to form 18-level provide maximum number of uniform steps. The suggested control strategy has been developed to ensure minimum switching losses focusing on holding the higher voltage stage state as long as it is feasible. The reference voltage vector has been approximated to the nearest inverter voltage vector. A special definition of state zone has been introduced for the low voltage stage to enable the achievement of the reference vector with minimum error. The proposed control strategy has been tested and its short computational time and low memory requirement has been proven.