EPE Association: EPE 2001 - Topic 02c: Multilevel and Matrix Converters

EPE 2001 - Topic 02c: Multilevel and Matrix Converters
You are here: EPE Documents > 01 - EPE & EPE ECCE Conference Proceedings > EPE 2001 - Conference > EPE 2001 - Topic 02: POWER ELECTRONICS CONVERTER CIRCUITS > EPE 2001 - Topic 02c: Multilevel and Matrix Converters

   [return to parent folder]

   A Double Connected Voltage Source Three-phase Diode Rectifier
By S. Masukawa; S. Iida [View]
[Download]

Abstract: In this paper, a novel method for reducing harmonics involved in ac line currents of a double connected voltage source three-phase diode rectifier is proposed. This proposed method is based on a conventional 12-step diode rectifier. By adding an auxiliary circuit composed of a single-phase transformer and four diodes on the dc side, input voltage waveforms in the proposed circuit can output almost 24-step voltages, which correspond to the conventional 24-step diode rectifier. In this paper, circuit performances of the proposed method are discussed by analyzing waveforms, and optimum parameters are derived. Then effects on harmonics reductions can be clarified by experimental results.

   A new linear method for neutral point compensation in the NPC Inverter
By A.Scaglia G. Mazzorin [View]
[Download]

Abstract: The paper describes, through a theoretical analysis, the phenomena causing in an NPC inverter the neutral point voltage to deviate from the ideal value, due to unbalance between the voltages of the two capacitor banks of the D.C. Bus. The authors give the equations that permit to calculate such deviation in different operating conditions, for both the dipolar and the unipolar modulation methods. By this analysis arises that the neutral point voltage is influenced by non perfect circuit symmetry and modulation method. In effect the neutral point voltage shows a deviation due to the unbalance between the capacitor banks of the DC link. Besides, during the unipolar modulation it appears a third harmonic ripple that is not present during the dipolar modulation. The authors deal with the problem of the compensation of the neutral point deviation and propose a new solution based on a linear method. A closed loop system compensates the neutral point voltage deviation and a particular procedure based on an open loop structure control reduces the third harmonic ripple. These procedures have been implemented and tested on 9MVA NPC Inverter with active front end as reported in this paper.

   A new range of medium voltage multilevel inverter-drives with floating
By G. Beinhold; R. Jakob; M. Nahrstaedt [View]
[Download]

Abstract: An air cooled medium voltage drive family called “SYMPHONY” based on IGBT modules and floating capacitor topology is described. The harmonic content of both, input and output current is very low, due to 18 pulse input and 4-level voltage output. Beside principal explanations to introduce the solution, the clearly arranged design is described, leading to high reliability, because of a low number of components and low cost of maintenance. A closer look is given to the key components like “partial discharge free low inductance bus bars”, “gating power supply” and the “floating capacitor module”.

   Advanced Control of a Three-Level Voltage Source Converter Drive with
By Joachim Böcker; J. Janning; H. Jebenstreit [View]
[Download]

Abstract: A high dynamic control system for the Alspa VDM 7000 medium voltage drive was implemented, which provides fast torque response times of a few milliseconds despite the typically low switching frequency of GTO thyristors that is necessary to achieve high efficiency. The drive system consists of a three-level voltage source converter with active front-end and a synchronous motor. The drive has most recently been applied for a main strip mill. It provides a maximum of 8.3 MW mechanical power with a rated motor voltage of 3 kV. Besides motor torque as the main control objective, the control system has to comply with a number of additional objectives and constraints like DC link voltage regulation and balancing, current and torque harmonics, motor flux and excitation.

   Analytical equations for three level NPC converters
By G. Tomta; R. Nilsen [View]
[Download]

Abstract: Equations for calculating losses in components analytically in a three level NPC converter are presented. The formulas are designed for high switching frequency of more than 10 times the fundamental frequency. The formulas are tested with simulations in Krean and Saber and are proved useful as tools in design of a NPC converter.

   Application of a new IGBT Module for Matrixconverter
By M. Bruckmann; O. Simon; W. Springmann; M. Münzer; M. Loddenkötter [View]
[Download]

Abstract: For more than twenty years, Matrix topology has been discussed on technical conferences, but up to now only few authors have discussed the realisation of a feasible technical solution for the power section of that type of converter. In this paper, for the first time the application of a new complete all in one IGBT module incorporating the full switch matrix in a powerstage for matrixconverter is presented. Experimental results of a laboratory prototype in regular and critical conditions demonstrate the feasibility of the concept. It is concluded that some of the open questions dealing with reliability and manufacturability can be considered as solved.

   ARCP multicell inverter - Efficiency measurement by opposition method
By C. Turpin; F. Richardeau; T. Meynard; F. Forest [View]
[Download]

Abstract: A high power ARCP multicell inverter is presented. The opposition method is used to measure and to compare the losses between hard-switching and soft-switching multicell inverters. This original method is presented and analysed. The aim is to show the benefits of soft-switching techniques applied to the multicell inverters.

   Characteristics of a Five-level Double Converter for IM Drive
By T. Ishida; T. Miyamoto; K. Matsuse; K. Sasagawa; L. Huang [View]
[Download]

Abstract: In this paper, two kinds of control strategies for a three-phase five-level double converter are described on the assumption that the converter is applied to the induction motor drive system. The purposes of the proposed control strategies are to correct voltage imbalance of the dc-bus capacitors, to keep the input power factor at near unity, and to achieve adjustable-speed drive. Characteristics of the converter operated by each of the two control strategies are examined and the validity is verified by experiments using a 3.7 kW induction motor.

   Commutation Phenomena in Direct AC-AC Converters
By M. Bland; J. Clare; P. Wheeler; L. Empringham [View]
[Download]

Abstract: The characteristics of all possible commutations in a matrix converter topology using two or four step commutation are studied and explained. Waveforms obtained from two bi-directional switches commutating current between two input phases are presented and the commutation phenomena are explained. Comparisons between PSPICE circuit simulations of the commutation and practical results are made.

   development of a multilevel converter model of variation
By C. Saudemont; J. P. Cambronne; C. Rombaut [View]
[Download]

Abstract: The optimal running of multilevel converters depends on their capacitor voltage balance. The model of variation we develop in this paper is an analytical way to understand the capacitor charge phenomena. This work is based, on the one hand on equation stemming from the study of the multicell chopper and on the other hand on the control of it. The support of this work is the four cell chopper.

   DTC using Matrix Converters: Improvement of the Input Line Current
By D. Casadei; M. Matteini; G. Serra; A. Tani; F. Blaabjerg [View]
[Download]

Abstract: In this paper a new control method that allows the application of matrix converters in Direct Torque Control (DTC) of induction machines is presented. Thanks to the matrix converter topology, this control method allows, under the constraint of unity input power factor, the generation of the voltage vectors required to implement the direct torque control of induction machines. Despite of the major complexity of the matrix converter structure compared to traditional Voltage Source Inverters (VSI), the proposed control algorithm is simple and robust. The appropriate switching configuration of the matrix converter is selected using a switching table defined on the basis of three hysteresis controllers applied to stator flux, electromagnetic torque and input power factor. Numerical and experimental results are carried out and analysed, showing the feasibility of the proposed drive system. Finally, a modified control strategy for the input power factor that reduces the harmonic content of the input line current is proposed and verified by numerical simulations.

   Generalized Asymmetric Multilevel Converter for High Power Conversion
By J. Song-Manguelle; S. Mariethoz; M. Veenstra; A. Rufer [View]
[Download]

Abstract: This paper is focused on a general design principle of a uniform step multilevel converter, with K series-connected full bridges inverters per phase. A new design terminology is proposed and analytical relationships are established. The DC-voltage sources supplying partial inverters are supposed to be rationally unbalanced. The corresponding “Asymmetrical” topology provides more flexibility to the designer, and can generate a large number of levels (any odd number from 2K+1 to 3K) without increasing the number of H-bridges. Simulation results and experimental tests shown the reliability of the design approach suggested.

   High power multilevel voltage sourced converters for ...
By P. G. Kamp ; M. Wolf; R. Gruber; R. Schuster [View]
[Download]

Abstract: A new 45 MVA voltage source DC-link converter unit for the traction power supply of high speed trains has been developed. The design criteria concerning the special requirements and different topologies of the power circuit are discussed. Special attention is paid to the advantages of the converter unit block and to the protection circuits.

   Matrix converter synchronous motor drive
By R. Havrila; B. Dobroucky; P. Balazovic [View]
[Download]

Abstract: The paper presents analysis, simulation and practical realisation of the space vector modulated threephase to three-phase matrix converter with input power factor correction. The modulation algorithm is derived from desired transfer functions, using the indirect transfer function approach and applied using DSP. The control algorithm was tested under passive R-L load and active, disc synchronous motor in closed loop. The resultant output and input currents are to be sinusoidal with controllable input power factor.

   Modelling and Control of a Flying-Capacitor Inverter
By S. J. Watkins; L. Zhang [View]
[Download]

Abstract: This paper presents the results of an investigation into the variation in the output voltage quality of a flying-capacitor inverter under staircase angle control. The trade-offs between capacitor size, power device voltage rating and output voltage quality are assessed through simulation. A general mathematical model for an N-level inverter is used for circuit operation analysis and its results are compared with those from a Simulink circuit simulation. The computer model allows a thorough investigation of all possible switching pattern permutations that produce the desired sinusoidal output and maintain steady state capacitor voltage balancing. Results show that the total harmonic distortion in a sinusoidal synthesised output can be minimised by the correct selection of the switching mode sequence.

   Multilevel Converter with 2 Stage-Conversion
By C. Chabert; A. Rufer [View]
[Download]

Abstract: The use of electrical equipment in rail and ship transportation is bound to consideration on mass and size, particularly because of conventional low frequency transformers. On this paper, an optimized multilevel converter with medium frequency transformer is presented. It allows to adapt voltage from primary generators (6.6kV) to service use (440V). From a pseudo continuous model of the converter, we present a method to improve its working and to define a corresponding operating domain.

   Power Devices and DC-Bus Voltage Utilization in NPDC Inverters
By M. E. Santos; S. M. Silva; B. J. Cardoso Filho [View]
[Download]

Abstract: In this paper PWM methods for neutral point diode clamped three-level inverters are analyzed focusing on power devices and DC-bus voltage utilization. For each PWM scheme considered, the conduction and switching losses are computed for all devices as a function of the modulation indexes and of the load power factor. Several modulation strategies are characterized in terms of DC-bus voltage utilization, total harmonic distortion of the output voltage and losses in the power devices. Simulation results are included to illustrate the impact of the PWM strategies in the inverter design.

   Robust Two-Level and Multilevel PWM AC Choppers
By E. Lefeuvre; T. Meynard; P. Viarouge [View]
[Download]

Abstract: The authors present a new single-phase PWM two-level AC chopper based on conventional commutation cells. The simple switching pattern and the standard Voltage Source Inverter-type commutation of the switches provide a high safety of operation. A multilevel AC converter derived from the basic structure is also presented. The multilevel structure increases the voltage attainable with standard power semiconductors.

   Sliding Mode Control of Matrix Converters with Lead-Lag Power Factor
By S. Ferreira Pinto; J. Fernando Silva [View]
[Download]

Abstract: This work presents the design of robust sliding mode controllers for three-phase ac-ac matrix converters, in order to guarantee output sinusoidal waveforms and leading or lagging input power factor. Matrix converters may be useful in several applications, such as ac drives. In fact, this is the best known application for matrix converters, which, in this case, operate mostly with unity input power factor. However, for other applications, such as static VAR compensators (SVC) or phase shifters a fully controllable input power factor is useful. A control method is proposed which ensures that the output voltage and input current track their references, guaranteeing the desired power factor. The obtained results show that sliding mode controllers guarantee an on-line control of the matrix converter output voltages, with leading or lagging input power factor.

   Stacked Multicell Converter (SMC): Structure and control
By G. Gateau; T.A. Meynard; H. Foch [View]
[Download]

Abstract: A new topology of multilevel converter is presented in this paper. This new topology called Stacked Multicell Converter (SMC) allows to increase the number of voltage levels compared with the standard flying capacitor multicell converter while decreasing the energy stored in the converter. The topology consists of a hybrid association of commutation cells allowing to share the bus voltage over several switches, and also to improve significantly the output waveforms of the converter (increased number of levels and increased apparent switching frequency). The topology, the corresponding modulator and the basic operation are detailed. In a third part, explanations about the control of the SMC converter are given. Simulations and experimental results obtained on a 50kVA experimental set-up are presented.

   switching behaviour of a generalized diode-clamped converter.
By P. Bartholomeüs; P. Le Moigne [View]
[Download]

Abstract: This paper presents a generalized diode-clamped converter for high voltage applications. The concept and the working principle are presented. This converter is not used in the multilevel mode; thanks to an association of a low power diode array and a particular switching sequence, it allows for a dynamic equalization of the transistor voltages. A prototype (1000V/20A) has been developed in order to study the dynamic behavior during the transistor switching. Experimental results highlight several over-voltage problems during the Switching-ON of the transistors. These problems are analyzed and solutions are proposed. Finally the good behavior of this kind of converter is proved.

   Theoretical And Practical Limits In Mpc Multilevel Inverters
By M. Marchesoni; P. Tenca [View]
[Download]

Abstract: DC-link capacitor voltages in Multi-Point-Clamped (MPC) converters must be actively controlled to achieve a correct voltage sharing. This works demonstrates that no balancing strategy does exist that is able to guarantee a correct functioning in all the operating conditions, if single MPC inverters or rectifiers are considered. The analytical work that has been done to determine the theoretical limits related to a correct converter behaviour is presented. In addition, a balancing control strategy that has been based on the developed theory is described and a lot of almost theoretical and practical results are presented.

   Theory of Vector Modulation for Matrix Converters
By O. Simon; M. Braun [View]
[Download]

Abstract: Although space vector modulation techniques for matrix converters have been introduced already, a closed theory for describing the possible output voltage and input current for any modulation scheme has not been presented yet. This paper contains the derivation of two simple equations, one for the output voltage, one for the input current, which are the transfer functions of the matrix converter. The complicated control of the matrix converter is reduced to methods known from dc link converters.

   Three-level Inverter with hysteresis current control
By M. Lafoz; I.J. Iglesias; C. Veganzones [View]
[Download]

Abstract: This paper presents the simulation results of a Double Three Level Voltage Source Inverter controlled by means of a double current hysteresis band technique. The presented control strategy will be applied to a 1.2 MW three-level VSI to drive a multipole Permanent Magnet Synchronous Generator in a Wind-Generation Plant. A current strategy is chosen for this application in order to control the electromagnetic torque in the generator and the power factor at the front-end inverter. The neutral point voltage control, which is one of the critical aspects in this kind of topology, can be easily achieved by means of progressive variation of the hysteresis bands limits.

   Topology and Balance Control of Medium Voltage Multilevel Drives
By C. Keller; R. Jakob; S. Salama [View]
[Download]

Abstract: The paper presents a new reliable series connection technique of power semiconductor devices using the floating capacitor multilevel topology. For improved dynamic voltage sharing of the series connected devices floating capacitors with much smaller capacitance values are used than those used by the standard floating capacitor topology. A simple voltage sharing control strategy which does not need neither high dynamic voltage measuring devices nor fast signal signal processing will be presented.

   Which topology for a multilevel inverter?
By C. Bodel; P. Delarue; R. Bausiere [View]
[Download]

Abstract: For given conditions of source and sink, there are many possible multilevel converter structures. In order to give the designer some clues, it is of special interest to analyse the consequences of various converter associations upon power switch losses or reactive component sizing for given values of DC-voltage source, power supplied to the load and output current harmonic quality. This paper deals specially with comparison on the basis of output filter inductance sizing.

EPE 2001 - Topic 02c: Multilevel and Matrix Converters
You are here: EPE Documents > 01 - EPE & EPE ECCE Conference Proceedings > EPE 2001 - Conference > EPE 2001 - Topic 02: POWER ELECTRONICS CONVERTER CIRCUITS > EPE 2001 - Topic 02c: Multilevel and Matrix Converters
	[return to parent folder]

	A Double Connected Voltage Source Three-phase Diode Rectifier By S. Masukawa; S. Iida	[View] [Download]
Abstract: In this paper, a novel method for reducing harmonics involved in ac line currents of a double connected voltage source three-phase diode rectifier is proposed. This proposed method is based on a conventional 12-step diode rectifier. By adding an auxiliary circuit composed of a single-phase transformer and four diodes on the dc side, input voltage waveforms in the proposed circuit can output almost 24-step voltages, which correspond to the conventional 24-step diode rectifier. In this paper, circuit performances of the proposed method are discussed by analyzing waveforms, and optimum parameters are derived. Then effects on harmonics reductions can be clarified by experimental results.

	A new linear method for neutral point compensation in the NPC Inverter By A.Scaglia G. Mazzorin	[View] [Download]
Abstract: The paper describes, through a theoretical analysis, the phenomena causing in an NPC inverter the neutral point voltage to deviate from the ideal value, due to unbalance between the voltages of the two capacitor banks of the D.C. Bus. The authors give the equations that permit to calculate such deviation in different operating conditions, for both the dipolar and the unipolar modulation methods. By this analysis arises that the neutral point voltage is influenced by non perfect circuit symmetry and modulation method. In effect the neutral point voltage shows a deviation due to the unbalance between the capacitor banks of the DC link. Besides, during the unipolar modulation it appears a third harmonic ripple that is not present during the dipolar modulation. The authors deal with the problem of the compensation of the neutral point deviation and propose a new solution based on a linear method. A closed loop system compensates the neutral point voltage deviation and a particular procedure based on an open loop structure control reduces the third harmonic ripple. These procedures have been implemented and tested on 9MVA NPC Inverter with active front end as reported in this paper.

	A new range of medium voltage multilevel inverter-drives with floating By G. Beinhold; R. Jakob; M. Nahrstaedt	[View] [Download]
Abstract: An air cooled medium voltage drive family called “SYMPHONY” based on IGBT modules and floating capacitor topology is described. The harmonic content of both, input and output current is very low, due to 18 pulse input and 4-level voltage output. Beside principal explanations to introduce the solution, the clearly arranged design is described, leading to high reliability, because of a low number of components and low cost of maintenance. A closer look is given to the key components like “partial discharge free low inductance bus bars”, “gating power supply” and the “floating capacitor module”.

	Advanced Control of a Three-Level Voltage Source Converter Drive with By Joachim Böcker; J. Janning; H. Jebenstreit	[View] [Download]
Abstract: A high dynamic control system for the Alspa VDM 7000 medium voltage drive was implemented, which provides fast torque response times of a few milliseconds despite the typically low switching frequency of GTO thyristors that is necessary to achieve high efficiency. The drive system consists of a three-level voltage source converter with active front-end and a synchronous motor. The drive has most recently been applied for a main strip mill. It provides a maximum of 8.3 MW mechanical power with a rated motor voltage of 3 kV. Besides motor torque as the main control objective, the control system has to comply with a number of additional objectives and constraints like DC link voltage regulation and balancing, current and torque harmonics, motor flux and excitation.

	Analytical equations for three level NPC converters By G. Tomta; R. Nilsen	[View] [Download]
Abstract: Equations for calculating losses in components analytically in a three level NPC converter are presented. The formulas are designed for high switching frequency of more than 10 times the fundamental frequency. The formulas are tested with simulations in Krean and Saber and are proved useful as tools in design of a NPC converter.

	Application of a new IGBT Module for Matrixconverter By M. Bruckmann; O. Simon; W. Springmann; M. Münzer; M. Loddenkötter	[View] [Download]
Abstract: For more than twenty years, Matrix topology has been discussed on technical conferences, but up to now only few authors have discussed the realisation of a feasible technical solution for the power section of that type of converter. In this paper, for the first time the application of a new complete all in one IGBT module incorporating the full switch matrix in a powerstage for matrixconverter is presented. Experimental results of a laboratory prototype in regular and critical conditions demonstrate the feasibility of the concept. It is concluded that some of the open questions dealing with reliability and manufacturability can be considered as solved.

	ARCP multicell inverter - Efficiency measurement by opposition method By C. Turpin; F. Richardeau; T. Meynard; F. Forest	[View] [Download]
Abstract: A high power ARCP multicell inverter is presented. The opposition method is used to measure and to compare the losses between hard-switching and soft-switching multicell inverters. This original method is presented and analysed. The aim is to show the benefits of soft-switching techniques applied to the multicell inverters.

	Characteristics of a Five-level Double Converter for IM Drive By T. Ishida; T. Miyamoto; K. Matsuse; K. Sasagawa; L. Huang	[View] [Download]
Abstract: In this paper, two kinds of control strategies for a three-phase five-level double converter are described on the assumption that the converter is applied to the induction motor drive system. The purposes of the proposed control strategies are to correct voltage imbalance of the dc-bus capacitors, to keep the input power factor at near unity, and to achieve adjustable-speed drive. Characteristics of the converter operated by each of the two control strategies are examined and the validity is verified by experiments using a 3.7 kW induction motor.

	Commutation Phenomena in Direct AC-AC Converters By M. Bland; J. Clare; P. Wheeler; L. Empringham	[View] [Download]
Abstract: The characteristics of all possible commutations in a matrix converter topology using two or four step commutation are studied and explained. Waveforms obtained from two bi-directional switches commutating current between two input phases are presented and the commutation phenomena are explained. Comparisons between PSPICE circuit simulations of the commutation and practical results are made.

	development of a multilevel converter model of variation By C. Saudemont; J. P. Cambronne; C. Rombaut	[View] [Download]
Abstract: The optimal running of multilevel converters depends on their capacitor voltage balance. The model of variation we develop in this paper is an analytical way to understand the capacitor charge phenomena. This work is based, on the one hand on equation stemming from the study of the multicell chopper and on the other hand on the control of it. The support of this work is the four cell chopper.

	DTC using Matrix Converters: Improvement of the Input Line Current By D. Casadei; M. Matteini; G. Serra; A. Tani; F. Blaabjerg	[View] [Download]
Abstract: In this paper a new control method that allows the application of matrix converters in Direct Torque Control (DTC) of induction machines is presented. Thanks to the matrix converter topology, this control method allows, under the constraint of unity input power factor, the generation of the voltage vectors required to implement the direct torque control of induction machines. Despite of the major complexity of the matrix converter structure compared to traditional Voltage Source Inverters (VSI), the proposed control algorithm is simple and robust. The appropriate switching configuration of the matrix converter is selected using a switching table defined on the basis of three hysteresis controllers applied to stator flux, electromagnetic torque and input power factor. Numerical and experimental results are carried out and analysed, showing the feasibility of the proposed drive system. Finally, a modified control strategy for the input power factor that reduces the harmonic content of the input line current is proposed and verified by numerical simulations.

	Generalized Asymmetric Multilevel Converter for High Power Conversion By J. Song-Manguelle; S. Mariethoz; M. Veenstra; A. Rufer	[View] [Download]
Abstract: This paper is focused on a general design principle of a uniform step multilevel converter, with K series-connected full bridges inverters per phase. A new design terminology is proposed and analytical relationships are established. The DC-voltage sources supplying partial inverters are supposed to be rationally unbalanced. The corresponding “Asymmetrical” topology provides more flexibility to the designer, and can generate a large number of levels (any odd number from 2K+1 to 3K) without increasing the number of H-bridges. Simulation results and experimental tests shown the reliability of the design approach suggested.

	High power multilevel voltage sourced converters for ... By P. G. Kamp ; M. Wolf; R. Gruber; R. Schuster	[View] [Download]
Abstract: A new 45 MVA voltage source DC-link converter unit for the traction power supply of high speed trains has been developed. The design criteria concerning the special requirements and different topologies of the power circuit are discussed. Special attention is paid to the advantages of the converter unit block and to the protection circuits.

	Matrix converter synchronous motor drive By R. Havrila; B. Dobroucky; P. Balazovic	[View] [Download]
Abstract: The paper presents analysis, simulation and practical realisation of the space vector modulated threephase to three-phase matrix converter with input power factor correction. The modulation algorithm is derived from desired transfer functions, using the indirect transfer function approach and applied using DSP. The control algorithm was tested under passive R-L load and active, disc synchronous motor in closed loop. The resultant output and input currents are to be sinusoidal with controllable input power factor.

	Modelling and Control of a Flying-Capacitor Inverter By S. J. Watkins; L. Zhang	[View] [Download]
Abstract: This paper presents the results of an investigation into the variation in the output voltage quality of a flying-capacitor inverter under staircase angle control. The trade-offs between capacitor size, power device voltage rating and output voltage quality are assessed through simulation. A general mathematical model for an N-level inverter is used for circuit operation analysis and its results are compared with those from a Simulink circuit simulation. The computer model allows a thorough investigation of all possible switching pattern permutations that produce the desired sinusoidal output and maintain steady state capacitor voltage balancing. Results show that the total harmonic distortion in a sinusoidal synthesised output can be minimised by the correct selection of the switching mode sequence.

	Multilevel Converter with 2 Stage-Conversion By C. Chabert; A. Rufer	[View] [Download]
Abstract: The use of electrical equipment in rail and ship transportation is bound to consideration on mass and size, particularly because of conventional low frequency transformers. On this paper, an optimized multilevel converter with medium frequency transformer is presented. It allows to adapt voltage from primary generators (6.6kV) to service use (440V). From a pseudo continuous model of the converter, we present a method to improve its working and to define a corresponding operating domain.

	Power Devices and DC-Bus Voltage Utilization in NPDC Inverters By M. E. Santos; S. M. Silva; B. J. Cardoso Filho	[View] [Download]
Abstract: In this paper PWM methods for neutral point diode clamped three-level inverters are analyzed focusing on power devices and DC-bus voltage utilization. For each PWM scheme considered, the conduction and switching losses are computed for all devices as a function of the modulation indexes and of the load power factor. Several modulation strategies are characterized in terms of DC-bus voltage utilization, total harmonic distortion of the output voltage and losses in the power devices. Simulation results are included to illustrate the impact of the PWM strategies in the inverter design.

	Robust Two-Level and Multilevel PWM AC Choppers By E. Lefeuvre; T. Meynard; P. Viarouge	[View] [Download]
Abstract: The authors present a new single-phase PWM two-level AC chopper based on conventional commutation cells. The simple switching pattern and the standard Voltage Source Inverter-type commutation of the switches provide a high safety of operation. A multilevel AC converter derived from the basic structure is also presented. The multilevel structure increases the voltage attainable with standard power semiconductors.

	Sliding Mode Control of Matrix Converters with Lead-Lag Power Factor By S. Ferreira Pinto; J. Fernando Silva	[View] [Download]
Abstract: This work presents the design of robust sliding mode controllers for three-phase ac-ac matrix converters, in order to guarantee output sinusoidal waveforms and leading or lagging input power factor. Matrix converters may be useful in several applications, such as ac drives. In fact, this is the best known application for matrix converters, which, in this case, operate mostly with unity input power factor. However, for other applications, such as static VAR compensators (SVC) or phase shifters a fully controllable input power factor is useful. A control method is proposed which ensures that the output voltage and input current track their references, guaranteeing the desired power factor. The obtained results show that sliding mode controllers guarantee an on-line control of the matrix converter output voltages, with leading or lagging input power factor.

	Stacked Multicell Converter (SMC): Structure and control By G. Gateau; T.A. Meynard; H. Foch	[View] [Download]
Abstract: A new topology of multilevel converter is presented in this paper. This new topology called Stacked Multicell Converter (SMC) allows to increase the number of voltage levels compared with the standard flying capacitor multicell converter while decreasing the energy stored in the converter. The topology consists of a hybrid association of commutation cells allowing to share the bus voltage over several switches, and also to improve significantly the output waveforms of the converter (increased number of levels and increased apparent switching frequency). The topology, the corresponding modulator and the basic operation are detailed. In a third part, explanations about the control of the SMC converter are given. Simulations and experimental results obtained on a 50kVA experimental set-up are presented.

	switching behaviour of a generalized diode-clamped converter. By P. Bartholomeüs; P. Le Moigne	[View] [Download]
Abstract: This paper presents a generalized diode-clamped converter for high voltage applications. The concept and the working principle are presented. This converter is not used in the multilevel mode; thanks to an association of a low power diode array and a particular switching sequence, it allows for a dynamic equalization of the transistor voltages. A prototype (1000V/20A) has been developed in order to study the dynamic behavior during the transistor switching. Experimental results highlight several over-voltage problems during the Switching-ON of the transistors. These problems are analyzed and solutions are proposed. Finally the good behavior of this kind of converter is proved.

	Theoretical And Practical Limits In Mpc Multilevel Inverters By M. Marchesoni; P. Tenca	[View] [Download]
Abstract: DC-link capacitor voltages in Multi-Point-Clamped (MPC) converters must be actively controlled to achieve a correct voltage sharing. This works demonstrates that no balancing strategy does exist that is able to guarantee a correct functioning in all the operating conditions, if single MPC inverters or rectifiers are considered. The analytical work that has been done to determine the theoretical limits related to a correct converter behaviour is presented. In addition, a balancing control strategy that has been based on the developed theory is described and a lot of almost theoretical and practical results are presented.

	Theory of Vector Modulation for Matrix Converters By O. Simon; M. Braun	[View] [Download]
Abstract: Although space vector modulation techniques for matrix converters have been introduced already, a closed theory for describing the possible output voltage and input current for any modulation scheme has not been presented yet. This paper contains the derivation of two simple equations, one for the output voltage, one for the input current, which are the transfer functions of the matrix converter. The complicated control of the matrix converter is reduced to methods known from dc link converters.

	Three-level Inverter with hysteresis current control By M. Lafoz; I.J. Iglesias; C. Veganzones	[View] [Download]
Abstract: This paper presents the simulation results of a Double Three Level Voltage Source Inverter controlled by means of a double current hysteresis band technique. The presented control strategy will be applied to a 1.2 MW three-level VSI to drive a multipole Permanent Magnet Synchronous Generator in a Wind-Generation Plant. A current strategy is chosen for this application in order to control the electromagnetic torque in the generator and the power factor at the front-end inverter. The neutral point voltage control, which is one of the critical aspects in this kind of topology, can be easily achieved by means of progressive variation of the hysteresis bands limits.

	Topology and Balance Control of Medium Voltage Multilevel Drives By C. Keller; R. Jakob; S. Salama	[View] [Download]
Abstract: The paper presents a new reliable series connection technique of power semiconductor devices using the floating capacitor multilevel topology. For improved dynamic voltage sharing of the series connected devices floating capacitors with much smaller capacitance values are used than those used by the standard floating capacitor topology. A simple voltage sharing control strategy which does not need neither high dynamic voltage measuring devices nor fast signal signal processing will be presented.

	Which topology for a multilevel inverter? By C. Bodel; P. Delarue; R. Bausiere	[View] [Download]
Abstract: For given conditions of source and sink, there are many possible multilevel converter structures. In order to give the designer some clues, it is of special interest to analyse the consequences of various converter associations upon power switch losses or reactive component sizing for given values of DC-voltage source, power supplied to the load and output current harmonic quality. This paper deals specially with comparison on the basis of output filter inductance sizing.