EPE Association: EPE 2007 - Subtopic 05-5 - DS: Multilevel converter topologies

EPE 2007 - Subtopic 05-5 - DS: Multilevel converter topologies
You are here: EPE Documents > 01 - EPE & EPE ECCE Conference Proceedings > EPE 2007 - Conference > EPE 2007 - Topic 05: 'Hard switching converters and control' > EPE 2007 - Subtopic 05-5 - DS: Multilevel converter topologies

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   A Back to Back Multilevel Converter for Driving Low Inductance Brushless AC Machines
By FOSTER Martin; MINSHULL Steve; BINGHAM Chris; STONE Dave [View]
[Download]

Abstract: Traditionally, multilevel converters are utilised in medium voltage applications, allowing the dc-link voltage to exceed the switch maximum blocking voltage. Here, their application to control high-efficiency brushless permanent magnet synchronous machines exhibiting low phase inductance is explored, the relative advantages being shown to include reduced current ripple and improved harmonic spectrum. A cost benefit analysis is included along with experimental results from a prototype 5-level back-to-back converter.

   A Five-Level Inverter Scheme with Common-Mode Voltage Elimination by Cascading Conventional Two-Level and Three-Level NPC Inverters for an Induction Motor Drive
By MONDAL Gopal; TEKWANI Pragneshkumar; LEVI Emil; K Gopakumar [View]
[Download]

Abstract: Common-mode voltage generated by the PWM inverter causes shaft voltage, bearing current and ground leakage current in induction motor drive system, resulting in an early motor failure. This paper presents a common-mode elimination scheme for a five-level inverter with reduced power circuit complexity. The proposed scheme is realised by cascading conventional two-level and conventional NPC three-level inverters in conjunction with an open-end winding three-phase induction motor drive and the common-mode voltage (CMV) elimination is achieved by using only switching states that result in zero CMV, for the entire modulation range.

   A New On-line Approach for Determining Conducting Angles in Multilevel Cascaded Inverters
By NGUYEN VAN Nho; SAITO Yoshifuru; LE MINH Phuong; PHAN QUOC Dzung [View]
[Download]

Abstract: An on-line approach for calculating of conducting angles for a multilevel cascaded inverter is presented. The proposed method is a combination of equal voltage-second area and superposition principles. The conducting angle for each voltage level can be determined so that the fundamental component of the output voltage waveform of each H- bridge inverter unit musts accord with each voltage-second area of the reference voltage waveform. This approach can be suitable for calculating of switching angles for any level of multilevel inverter, particularly in case of unequal DC sources. To demonstrate the validity of the proposed method, a simulation study has been done using Matlab/ Simulink.

   Active rectifier design and advanced control for medium voltage
By FLURY Guy; GOLLENTZ Bernard; SIALA Sami [View]
[Download]

Abstract: The paper present the active rectifier design and control for a medium voltage inverter. The considered inverter for the study is a three levels neutral clamped IGBT inverter for a voltage of 3300Vrms and a nominal current of 1800Arms. The particularities of such a system are the limited high frequency current harmonics generated to the supply and the perfect management of control limitations. To reach this goal an active damping control of the sinus filter is chosen in addition to a classic vector control. The filter design must take into account the control and the harmonics current considerations. To illustrate the performance, simulation and test bench results will be presented.

   An adaptive hysteresis current control for a five-level inverter for active power filters
By ZABIHI Sasan; ZARE Firuz; LEDWICH Gerard [View]
[Download]

Abstract: In most high-performance application of voltage source pulse-width modulation inverters, current control is an essential part of the overall control system. In this paper a novel adaptive hysteresis current control technique based on time and magnitude error for a single phase five-level inverter with flying-capacitor topology used in an Active Power Filter (APF) is proposed.

   Analysis of Carrier PWM Method for Common Mode Elimination in Multilevel Inverters
By NHO Nguyen Van; LEE Hong-Hee [View]
[Download]

Abstract: The paper introduces a universal carrier PWM technique for eliminating common mode voltage in multilevel inverters. The correlation between carrier PWM and space vector PWM will be also presented. Switching state sequence can be described in a nominal switching diagram. A linear overmodulation is also included.

   CURRENT DEMAND OF HIGH PERFORMANCE INVERTERS FOR RENEWABLE
By ANTUNES Fernando; SCHMID JÃ¼rgen; DAHER Sergio [View]
[Download]

Abstract: This paper points out that versatile stand-alone renewable energy systems demand on at least one robust battery inverter. Despite of the employed system configuration, it is shown that the battery inverter should be capable to practically support all load demand. In practice, improved characteristics of reliability, surge power capability and efficiency are essential to guarantee long term and flexible operation for such systems. In addition, it is shown that these inverters can be optimized by considering the typical load profile commonly found in stand-alone applications. It is shown that multilevel topologies can be very suitable for these applications due to their inherent high efficiency and robustness. A prototype of 3 kVA was implemented and it has proved itself to be robust. Peak efficiency of 96.0\% was achieved: value that is higher than similar high performance inverters currently available in the market.

   Development of a 1.2MVA Active Front End Using Parallel Industrial Units
By CLAERBOUT James; GODBERSEN Jens [View]
[Download]

Abstract: Danfoss Drives A/S has developed a 1.2MVA Active Front End (AFE). The purpose with this development was to realize a high power AFE as a study object. Secondly the AFE was integrated into a new dynamometer and engaged in testing of high power motor inverters in an engineering laboratory environment. The AFE was used to supply power to a 1500HP adjustable speed drive used for the dynamometer. The development was made with tight constraints: A limited time frame was available, and the design chosen must assure immediate successful operation. The scope of this paper is to present some of the considerations done during the design phase and to present the achieved system performance of the final system.

   Fault-Tolerant Hybrid Four-Leg Multilevel Converter
By ZARAGOZA Jordi; IBANEZ Pedro; POU Josep; MARTIN Jose Luis; CEBALLOS Salvador; ROBLES Eider [View]
[Download]

Abstract: In this paper a modification of the Neutral-Point-Clamped (NPC) converter, in which a fourth leg has been added, is presented. The main aim of this additional leg is to increase the reliability of the converter and thereby allow it to continue operating when a breakdown in one of the IGBTs occurs. In addition, during normal fault-free operation, the fourth leg also guarantees a correct control of the neutral point voltage, removing completely the low frequency voltage oscillations. A simple and computationally efficient control scheme is proposed for this purpose.

   Modular pulsed generator for kV and kHz applications based on forward converters association
By REDONDO Luis; SILVA JosÃ©; MARGATO Elmano [View]
[Download]

Abstract: The operation of a modular generator topology, developed for kHz and kV pulsed applications, is presented. The proposed generator uses individual modules each one consisting of a pulse circuit based on a modified forward converter topology, with the secondary windings series connected, delivering a fraction of the total voltage. A laboratorial prototype with three 5 kV modules, 800 V semiconductor switches and 1:10 step-up transformers has been assembled. The first experimental results of this modular generator are presented and discussed. The circuit has 80 \% efficiency and is capable of delivering, into resistive loads, -15 kV / 1 A pulses with 5 s width, 10 kHz frequency, with less than 1 s pulse rise time.

   Multi-level Converter Dimensioning with Structure and Losses Consideration for DFACTS Applications
By LE PELLETER Erwan; SCHANEN Jean-Luc; JEANNIN Pierre-Olivier; FREY David [View]
[Download]

Abstract: Due to electrical system's deregulation and subventions given by authorities for renewable energy, there is a multiplication of Distributed Generation (DG) connected to low and medium voltage grids. This increases the number of intermittent power exchanges. To maximize the penetration of DG it is necessary to use new grid's exploitation schemes. Series connected power electronics devices connected to looped or meshed distribution grids called Distributed Flexible Alternating Current Transmission Systems (DFACTS) could bring optimal functioning by dynamic Ohm's law to realize optimal share of power flows and also to limit short-circuit currents. So far uses of FACTS and DFACTS have been limited because they were suffering from reliability, high maintenance costs and losses. Losses are mainly due to switches commutations and make them not very attractive, especially for FACTS based on the Voltage Source Converter (VSC). This paper proposes a method to find the most adapted multi-level converter structure configuration and switch by considering the IGBT parameters and the commutation conditions.

   Multilevel converters for UPS applications: comparison and implementation
By MUNK-NIELSEN Stig; CASADEI Domenico; LEGA Alberto; BLAABJERG Frede [View]
[Download]

Abstract: In this paper the possibility to use multilevel converters in UPS applications is discussed. Three different converter topologies, i.e. the three-level diode-clamped, the four-level diode-clamped and the four-level Multi Point Clamped (MPC) have been firstly compared by simulation simulations to find out their efficiency. The Simulink environment has been used, together with Plecs toolbox, to obtain a fast simulation including conduction and switching losses in the components. The MPC turned out to be the converter with the highest efficiency among the three considered and it was implemented to prove the simulation result with some experimental tests. Furthermore, two switching tables for the MPC converter have been implemented and compared in order to minimize the voltage spikes across the switches during the commutations.

   Operational Analysis and Modulation Control of Three-Level Z-Source Inverters With Enhanced Output Waveform Quality
By LOH Poh Chiang; BLAABJERG Frede; LIM Sok Wei; GAO Feng [View]
[Download]

Abstract: Three-level Z-source inverters are recent single-stage topological solutions proposed for buck-boost energy conversion with all favorable advantages of three-level switching retained. Despite their proven buck-boost capability, existing three-level Z-source inverters are either too costly with numerous passive LC elements needed or poor in spectral quality if the "reduced element count" (REC) variant is used. Instead of being constrained by the tradeoff, this paper proposes an alternative three-level Z-source topological and control combination that can produce optimal output waveform quality, while using lesser passive LC elements. Through detailed operational analysis, new operating modes of the REC Z-source inverters are identified, which when inserted appropriately to the inverter state sequence, will always produce the desired voltage transfer gain with minimized commutation count and optimized three-level switching. For conceptual verification, an optimally controlled laboratory prototype was constructed and tested with a set of results captured and presented in a later section of the paper.

   Performance Evaluation of Buck-Boost Three-Level Inverters with Topological and Modulation Development
By BLAABJERG Frede; LOH Poh Chiang; GAO Feng; TEODORESCU Remus; VILATHGAMUWA D Mahinda [View]
[Download]

Abstract: This paper proposes a series of buck-boost three-level inverters for neutral-point-clamped (NPC) and dc-link-cascaded (DCLC) topologies using the SEPIC-derived front-end circuits with the bidirectional operation capability which can be modulated using either phase disposition (PD) or alternative phase opposition disposition (APOD) modulation scheme. To achieve the optimized harmonic performance corresponding to the PD modulation, the buck-boost three-level inverter is designed with two special voltage boost circuitries. For further minimizing the component count, only one voltage boost circuitry is assumed to regulate the dc-link voltage with the designed APOD modulation adopted. By separately controlling the switching signals of upper full-bridge in the dc-link cascaded inverter, the voltage boost circuitry can be simplified with single dc switch, which significantly reduces whole system cost and switching losses. All theoretical findings have been verified experimentally using laboratory prototypes.

   Simplifying Approach for Analysis of Space-Vector PWM for Three-Phase and Multiphase Converters
By PROFUMO Francesco; OLESCHUK Valentin; TENCONI Alberto [View]
[Download]

Abstract: Direct time-domain approach, which is characterized by the simplicity and clarity, is proposed for the study and design of algorithms of voltage space-vector modulation for basic topologies of the three-phase two-level and three-level inverters, and five-phase voltage source inverters. This approach is based on the detailed consideration of switching state sequences of inverters (with the corresponding duty-cycles), which are integrated characteristics of space-vector-based schemes and versions of pulsewidth modulation (PWM). It also permits providing of continuous synchronization of output voltage waveforms of converters during the whole control range, including overmodulation zone.

   Space Vector Modulation Extended to Voltage Source Converters With Multiple Legs in Parallel
By GABE Ivan Jorge; DA COSTA Jean Patric; PINHEIRO Humberto; JASGULSKI Igor; STEFANELLO Marcio [View]
[Download]

Abstract: This paper extends the space vector (SV) modulation to Voltage Source Converters (VSC) with multiple legs in parallel. Multiple legs voltage source converters are strong candidates for low voltage high power applications, such as wind power systems wherethe converter has to handle high currents. The main advantages of the proposed modulation are: (i) minimization of the total harmonic distortion (THD) of the output current or reduction the filter size; (ii) decoupling the output current control loops from the current sharing control loops. In addition the well-known features of the SV modulation such as the full utilization of the DC bus voltage and the possibility of minimization of switching losses can also be achieved. Finally, experimental results from a three phase multiple legs converter are presented to support the analysis carried out as well as to demonstrate the performance of the proposed SV modulation. Furthermore, experimental results are also presented to compare the proposed SV modulation with a conventional PWM with triangular phase-shift.

   Three-Level Quadratic Non-Insulated Basic DC-DC Converters
By DE NOVAES Yales Romulo; BARBI Ivo; BOTTARELLI Marlos Gatti; RUFER Alfred [View]
[Download]

Abstract: This paper presents a family of three transformerless converters (buck, boost and buck-boost) with two specific characteristics: the quadratic static gain as a function of the duty cycle ratio, and the division of the higher voltage level between the two switches. Because of that they are called "three-level quadratic converters", or TLQ converters. All of them are composed by two diodes, two active switches, two inductors and two capacitors. A specific modulation strategy based on concentric pulses is presented. Based on it, they are able to convert the input voltage with a ratio that the basic converters could not. The proposed converters are mostly attractive for applications in which a wide voltage ratio is desired, like fuel cells, for instance. The commutation cell common to them is shown, as the main waveforms, equations and output characteristics. Experimental results are presented to confirm the theory.

EPE 2007 - Subtopic 05-5 - DS: Multilevel converter topologies
You are here: EPE Documents > 01 - EPE & EPE ECCE Conference Proceedings > EPE 2007 - Conference > EPE 2007 - Topic 05: 'Hard switching converters and control' > EPE 2007 - Subtopic 05-5 - DS: Multilevel converter topologies
	[return to parent folder]

	A Back to Back Multilevel Converter for Driving Low Inductance Brushless AC Machines By FOSTER Martin; MINSHULL Steve; BINGHAM Chris; STONE Dave	[View] [Download]
Abstract: Traditionally, multilevel converters are utilised in medium voltage applications, allowing the dc-link voltage to exceed the switch maximum blocking voltage. Here, their application to control high-efficiency brushless permanent magnet synchronous machines exhibiting low phase inductance is explored, the relative advantages being shown to include reduced current ripple and improved harmonic spectrum. A cost benefit analysis is included along with experimental results from a prototype 5-level back-to-back converter.

	A Five-Level Inverter Scheme with Common-Mode Voltage Elimination by Cascading Conventional Two-Level and Three-Level NPC Inverters for an Induction Motor Drive By MONDAL Gopal; TEKWANI Pragneshkumar; LEVI Emil; K Gopakumar	[View] [Download]
Abstract: Common-mode voltage generated by the PWM inverter causes shaft voltage, bearing current and ground leakage current in induction motor drive system, resulting in an early motor failure. This paper presents a common-mode elimination scheme for a five-level inverter with reduced power circuit complexity. The proposed scheme is realised by cascading conventional two-level and conventional NPC three-level inverters in conjunction with an open-end winding three-phase induction motor drive and the common-mode voltage (CMV) elimination is achieved by using only switching states that result in zero CMV, for the entire modulation range.

	A New On-line Approach for Determining Conducting Angles in Multilevel Cascaded Inverters By NGUYEN VAN Nho; SAITO Yoshifuru; LE MINH Phuong; PHAN QUOC Dzung	[View] [Download]
Abstract: An on-line approach for calculating of conducting angles for a multilevel cascaded inverter is presented. The proposed method is a combination of equal voltage-second area and superposition principles. The conducting angle for each voltage level can be determined so that the fundamental component of the output voltage waveform of each H- bridge inverter unit musts accord with each voltage-second area of the reference voltage waveform. This approach can be suitable for calculating of switching angles for any level of multilevel inverter, particularly in case of unequal DC sources. To demonstrate the validity of the proposed method, a simulation study has been done using Matlab/ Simulink.

	Active rectifier design and advanced control for medium voltage By FLURY Guy; GOLLENTZ Bernard; SIALA Sami	[View] [Download]
Abstract: The paper present the active rectifier design and control for a medium voltage inverter. The considered inverter for the study is a three levels neutral clamped IGBT inverter for a voltage of 3300Vrms and a nominal current of 1800Arms. The particularities of such a system are the limited high frequency current harmonics generated to the supply and the perfect management of control limitations. To reach this goal an active damping control of the sinus filter is chosen in addition to a classic vector control. The filter design must take into account the control and the harmonics current considerations. To illustrate the performance, simulation and test bench results will be presented.

	An adaptive hysteresis current control for a five-level inverter for active power filters By ZABIHI Sasan; ZARE Firuz; LEDWICH Gerard	[View] [Download]
Abstract: In most high-performance application of voltage source pulse-width modulation inverters, current control is an essential part of the overall control system. In this paper a novel adaptive hysteresis current control technique based on time and magnitude error for a single phase five-level inverter with flying-capacitor topology used in an Active Power Filter (APF) is proposed.

	Analysis of Carrier PWM Method for Common Mode Elimination in Multilevel Inverters By NHO Nguyen Van; LEE Hong-Hee	[View] [Download]
Abstract: The paper introduces a universal carrier PWM technique for eliminating common mode voltage in multilevel inverters. The correlation between carrier PWM and space vector PWM will be also presented. Switching state sequence can be described in a nominal switching diagram. A linear overmodulation is also included.

	CURRENT DEMAND OF HIGH PERFORMANCE INVERTERS FOR RENEWABLE By ANTUNES Fernando; SCHMID JÃ¼rgen; DAHER Sergio	[View] [Download]
Abstract: This paper points out that versatile stand-alone renewable energy systems demand on at least one robust battery inverter. Despite of the employed system configuration, it is shown that the battery inverter should be capable to practically support all load demand. In practice, improved characteristics of reliability, surge power capability and efficiency are essential to guarantee long term and flexible operation for such systems. In addition, it is shown that these inverters can be optimized by considering the typical load profile commonly found in stand-alone applications. It is shown that multilevel topologies can be very suitable for these applications due to their inherent high efficiency and robustness. A prototype of 3 kVA was implemented and it has proved itself to be robust. Peak efficiency of 96.0\% was achieved: value that is higher than similar high performance inverters currently available in the market.

	Development of a 1.2MVA Active Front End Using Parallel Industrial Units By CLAERBOUT James; GODBERSEN Jens	[View] [Download]
Abstract: Danfoss Drives A/S has developed a 1.2MVA Active Front End (AFE). The purpose with this development was to realize a high power AFE as a study object. Secondly the AFE was integrated into a new dynamometer and engaged in testing of high power motor inverters in an engineering laboratory environment. The AFE was used to supply power to a 1500HP adjustable speed drive used for the dynamometer. The development was made with tight constraints: A limited time frame was available, and the design chosen must assure immediate successful operation. The scope of this paper is to present some of the considerations done during the design phase and to present the achieved system performance of the final system.

	Fault-Tolerant Hybrid Four-Leg Multilevel Converter By ZARAGOZA Jordi; IBANEZ Pedro; POU Josep; MARTIN Jose Luis; CEBALLOS Salvador; ROBLES Eider	[View] [Download]
Abstract: In this paper a modification of the Neutral-Point-Clamped (NPC) converter, in which a fourth leg has been added, is presented. The main aim of this additional leg is to increase the reliability of the converter and thereby allow it to continue operating when a breakdown in one of the IGBTs occurs. In addition, during normal fault-free operation, the fourth leg also guarantees a correct control of the neutral point voltage, removing completely the low frequency voltage oscillations. A simple and computationally efficient control scheme is proposed for this purpose.

	Modular pulsed generator for kV and kHz applications based on forward converters association By REDONDO Luis; SILVA JosÃ©; MARGATO Elmano	[View] [Download]
Abstract: The operation of a modular generator topology, developed for kHz and kV pulsed applications, is presented. The proposed generator uses individual modules each one consisting of a pulse circuit based on a modified forward converter topology, with the secondary windings series connected, delivering a fraction of the total voltage. A laboratorial prototype with three 5 kV modules, 800 V semiconductor switches and 1:10 step-up transformers has been assembled. The first experimental results of this modular generator are presented and discussed. The circuit has 80 \% efficiency and is capable of delivering, into resistive loads, -15 kV / 1 A pulses with 5 s width, 10 kHz frequency, with less than 1 s pulse rise time.

	Multi-level Converter Dimensioning with Structure and Losses Consideration for DFACTS Applications By LE PELLETER Erwan; SCHANEN Jean-Luc; JEANNIN Pierre-Olivier; FREY David	[View] [Download]
Abstract: Due to electrical system's deregulation and subventions given by authorities for renewable energy, there is a multiplication of Distributed Generation (DG) connected to low and medium voltage grids. This increases the number of intermittent power exchanges. To maximize the penetration of DG it is necessary to use new grid's exploitation schemes. Series connected power electronics devices connected to looped or meshed distribution grids called Distributed Flexible Alternating Current Transmission Systems (DFACTS) could bring optimal functioning by dynamic Ohm's law to realize optimal share of power flows and also to limit short-circuit currents. So far uses of FACTS and DFACTS have been limited because they were suffering from reliability, high maintenance costs and losses. Losses are mainly due to switches commutations and make them not very attractive, especially for FACTS based on the Voltage Source Converter (VSC). This paper proposes a method to find the most adapted multi-level converter structure configuration and switch by considering the IGBT parameters and the commutation conditions.

	Multilevel converters for UPS applications: comparison and implementation By MUNK-NIELSEN Stig; CASADEI Domenico; LEGA Alberto; BLAABJERG Frede	[View] [Download]
Abstract: In this paper the possibility to use multilevel converters in UPS applications is discussed. Three different converter topologies, i.e. the three-level diode-clamped, the four-level diode-clamped and the four-level Multi Point Clamped (MPC) have been firstly compared by simulation simulations to find out their efficiency. The Simulink environment has been used, together with Plecs toolbox, to obtain a fast simulation including conduction and switching losses in the components. The MPC turned out to be the converter with the highest efficiency among the three considered and it was implemented to prove the simulation result with some experimental tests. Furthermore, two switching tables for the MPC converter have been implemented and compared in order to minimize the voltage spikes across the switches during the commutations.

	Operational Analysis and Modulation Control of Three-Level Z-Source Inverters With Enhanced Output Waveform Quality By LOH Poh Chiang; BLAABJERG Frede; LIM Sok Wei; GAO Feng	[View] [Download]
Abstract: Three-level Z-source inverters are recent single-stage topological solutions proposed for buck-boost energy conversion with all favorable advantages of three-level switching retained. Despite their proven buck-boost capability, existing three-level Z-source inverters are either too costly with numerous passive LC elements needed or poor in spectral quality if the "reduced element count" (REC) variant is used. Instead of being constrained by the tradeoff, this paper proposes an alternative three-level Z-source topological and control combination that can produce optimal output waveform quality, while using lesser passive LC elements. Through detailed operational analysis, new operating modes of the REC Z-source inverters are identified, which when inserted appropriately to the inverter state sequence, will always produce the desired voltage transfer gain with minimized commutation count and optimized three-level switching. For conceptual verification, an optimally controlled laboratory prototype was constructed and tested with a set of results captured and presented in a later section of the paper.

	Performance Evaluation of Buck-Boost Three-Level Inverters with Topological and Modulation Development By BLAABJERG Frede; LOH Poh Chiang; GAO Feng; TEODORESCU Remus; VILATHGAMUWA D Mahinda	[View] [Download]
Abstract: This paper proposes a series of buck-boost three-level inverters for neutral-point-clamped (NPC) and dc-link-cascaded (DCLC) topologies using the SEPIC-derived front-end circuits with the bidirectional operation capability which can be modulated using either phase disposition (PD) or alternative phase opposition disposition (APOD) modulation scheme. To achieve the optimized harmonic performance corresponding to the PD modulation, the buck-boost three-level inverter is designed with two special voltage boost circuitries. For further minimizing the component count, only one voltage boost circuitry is assumed to regulate the dc-link voltage with the designed APOD modulation adopted. By separately controlling the switching signals of upper full-bridge in the dc-link cascaded inverter, the voltage boost circuitry can be simplified with single dc switch, which significantly reduces whole system cost and switching losses. All theoretical findings have been verified experimentally using laboratory prototypes.

	Simplifying Approach for Analysis of Space-Vector PWM for Three-Phase and Multiphase Converters By PROFUMO Francesco; OLESCHUK Valentin; TENCONI Alberto	[View] [Download]
Abstract: Direct time-domain approach, which is characterized by the simplicity and clarity, is proposed for the study and design of algorithms of voltage space-vector modulation for basic topologies of the three-phase two-level and three-level inverters, and five-phase voltage source inverters. This approach is based on the detailed consideration of switching state sequences of inverters (with the corresponding duty-cycles), which are integrated characteristics of space-vector-based schemes and versions of pulsewidth modulation (PWM). It also permits providing of continuous synchronization of output voltage waveforms of converters during the whole control range, including overmodulation zone.

	Space Vector Modulation Extended to Voltage Source Converters With Multiple Legs in Parallel By GABE Ivan Jorge; DA COSTA Jean Patric; PINHEIRO Humberto; JASGULSKI Igor; STEFANELLO Marcio	[View] [Download]
Abstract: This paper extends the space vector (SV) modulation to Voltage Source Converters (VSC) with multiple legs in parallel. Multiple legs voltage source converters are strong candidates for low voltage high power applications, such as wind power systems wherethe converter has to handle high currents. The main advantages of the proposed modulation are: (i) minimization of the total harmonic distortion (THD) of the output current or reduction the filter size; (ii) decoupling the output current control loops from the current sharing control loops. In addition the well-known features of the SV modulation such as the full utilization of the DC bus voltage and the possibility of minimization of switching losses can also be achieved. Finally, experimental results from a three phase multiple legs converter are presented to support the analysis carried out as well as to demonstrate the performance of the proposed SV modulation. Furthermore, experimental results are also presented to compare the proposed SV modulation with a conventional PWM with triangular phase-shift.

	Three-Level Quadratic Non-Insulated Basic DC-DC Converters By DE NOVAES Yales Romulo; BARBI Ivo; BOTTARELLI Marlos Gatti; RUFER Alfred	[View] [Download]
Abstract: This paper presents a family of three transformerless converters (buck, boost and buck-boost) with two specific characteristics: the quadratic static gain as a function of the duty cycle ratio, and the division of the higher voltage level between the two switches. Because of that they are called "three-level quadratic converters", or TLQ converters. All of them are composed by two diodes, two active switches, two inductors and two capacitors. A specific modulation strategy based on concentric pulses is presented. Based on it, they are able to convert the input voltage with a ratio that the basic converters could not. The proposed converters are mostly attractive for applications in which a wide voltage ratio is desired, like fuel cells, for instance. The commutation cell common to them is shown, as the main waveforms, equations and output characteristics. Experimental results are presented to confirm the theory.