EPE Association: EPE 2009 - Subtopic 06-4 - DS: 'Converter Control Sets and Modulation Strategies'

EPE 2009 - Subtopic 06-4 - DS: 'Converter Control Sets and Modulation Strategies'
You are here: EPE Documents > 01 - EPE & EPE ECCE Conference Proceedings > EPE 2009 - Conference > EPE 2009 - Topic 06: 'Modulation Strategies and Specific Control Methods for Static Converter' > EPE 2009 - Subtopic 06-4 - DS: 'Converter Control Sets and Modulation Strategies'

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   A graphical method for SVM duty cycles computation. Application on two-level and multi-level inverters.
By Santiago de PABLO, Alexis B. REY, Luis C. HERRERO, Fernando MARTINEZ [View]
[Download]

Abstract: A graphical method, easy to understand and easy to implement, has been developed for two-level and multi-level Space Vector Modulation. Switching sequences can be computed with no need of solving neither multi-variable inverse problems nor expensive trigonometric functions. Proposed method has been validated through simulations and physical implementations.

   A Novel Control Strategy for Optimal Inverter Switching Frequency Associated with Minimal Current Ripple Using Single Step Predictive Current Control
By Thomas WOLBANK, Ronald STUMBERGER, Alois LECHNER, Jürgen MACHL [View]
[Download]

Abstract: The common trend in converter development is to increase the drive system performance with simultaneous consideration of cost reduction by operating the whole drive at its thermal limit. For this purpose all system components are, for short durations, even stressed above their rated values. Because thermal losses have to be well balanced it is necessary to adjust inverter switching frequency to its optimum value depending on the point of operation. By varying the inverter switching frequency the distribution of overall inverter losses between conduction and switching losses can be influenced. This control however implies the possibility of adjusting the inverter switching frequency online dependent on the point of operation. In this paper a new control strategy for controlling the switching frequency near its optimum by using a predictive fixed step current controller is presented. By influencing the switching decision using a weighting factor, the resulting inverter switching frequency can be modified. Hence operating the whole drive system with optimum performance with respect to both, the power devices as well as the ac machine losses is possible. The performance of the proposed method is investigated by simulation. Measurements results verify the accuracy in adapting the switching frequency to the optimum value depending on the point of operation.

   A novel pulsewidth modulation to operate a bidirectional two-stage dc-ac converter with high-frequency isolation in discontinuous conduction mode for photovolta
By Montserrat MATA-DUMENJO, Sergio BUSQUETS-MONGE, Jaume DIEST-YUS, Mireia BARENYS-ESPADALER, Joan ROCABERT-DELGADO, Joan SALAET- PEREIRA [View]
[Download]

Abstract: This paper presents a novel modulation for a two-stage dc-ac power converter with high-frequency isolation installed in a photovoltaic stand-alone system. The presented modulation, which is designed for the converter discontinuous conduction mode of operation, solves the problem of connection to a grid, and permits a bidirectional power flow. In this document is described the modulation strategy and some simulation and experimental results are presented.

   A Phase Shift Selective Harmonic Elimination Method for balancing capacitor voltages in aseven level Cascaded H-Bridge Rectifier
By Alan WATSON, Patrick WHEELER, Jon CLARE [View]
[Download]

Abstract: This paper presents a low switching frequency, Selective Harmonic Elimination (SHE) modulation method which may be applied to a Cascaded H-Bridge Active Rectifier. The method is based on a decoupled scheme where the modulation index of each H-Bridge cell is controlled independently to enable complete control of power flow through the converter. The method utilises a phase shift between the AC side cell voltages to achieve the required cell power balancing but with reduced distortion in the output waveform when compared with previously presented methods. Practical results from a laboratory based prototype converter are presented to validate the analysis. Although presented for a single phase topology the method can be applied to a three phase converter.

   Active Self-Switching Methods for Emerging Monolithic Bidirectional Switches Applied to Diode-Less Converters
By Daniel SIEMASZKO, Alfred RUFER [View]
[Download]

Abstract: This paper presents a recently introduced switching principle for emerging monolithic bidirectional devices. Based on the hypothesis that those switches may overcome conventional diode type solutions in power converters, an active self-switching process becomes compulsory. Its principle relies on the measurement of both voltage and current polarity, in order to allow a natural switching as commonly used in matrix conversion. A self-switching method, implemented close to the switch, allows the detection of both short-circuits and open circuits. The accuracy of the presented system is experimented and validated in a 1kVA buck converter where the free-wheeling path is performed by a synthesized diode. The results that are discussed in this paper open a new perspective by introducing the principle of a so-called bidirectional diode as well as the commutation of sources of a similar nature.

   Analysis and Comparison of 3D-SVM Schemes for Flying-Capacitor Multi-Level Inverters
By Michael WAITE, Li ZHANG [View]
[Download]

Abstract: The paper presents a comparative study of three different 3D-SVM techniques for the control of flying-capacitor multi-level inverters under both balanced and unbalanced operating conditions. Simulation results show that Direct 3D-SVM is the most efficient in computational effort. Application of this scheme to a three-level FCMI is simulated using the Alternative Transients Program (ATP). Output performance and features are highlighted.

   Control Strategies and Inverter Topologies for Stabilization of DC Grids in Embedded Systems
By Nicolas PATIN [View]
[Download]

Abstract: Compactness is a key constraint for embedded equipments design. The main issue concerns DC link capacitors, which must maintain a good DC voltage quality. However, their size is too high when classical PWM strategies are used. In this paper, two adapted techniques are compared with uncertain or varying grid parameters.

   Direct Control Strategy for a Flying Capacitor Converter
By Ana M. LLOR, François DEFAY, Maurice FADEL [View]
[Download]

Abstract: In this paper, a direct control of a flying capacitor inverter is proposed. This control allows to limit the number of commutations in a switching period with the use of a pre-calculated output voltage profile. A predictive control is made for the 3 phases 4 levels inverter in a active filtering operation. The advantages of this direct control is to reduce the switching frequency of the IGBTs, to use only a threshold voltage detector for flying capacitor voltages and to define offline pre-calculated switching tables. Experimental results for an active power filter application validate the performances of this control for static and dynamic conditions.

   DISCONTINUOUS MODULATION OF MULTI-PHASE INVERTER-FED AC MOTORS
By Sandor HALASZ [View]
[Download]

Abstract: Different types of discontinuous PWMs of multiphase inverter-fed ac motors are investigated from point of view of ac motor harmonic losses. The derived expressions for computation of the generalized loss-factors and its components are given for different phase number and for all the investigated PWM methods. It is shown that the discontinuous PWM of multiphase system cannot be as successful as that for the case of three-phase system. Therefore in comparison with continuous PWMs the discontinuous ones have no advantages in case of phase number more than 9. However, the stator harmonic current losses are slightly higher while the rotor harmonic current losses are considerably lower than those in case of three-phase system. At the same time for the phase number over 7 a sensible broadening of the linear voltage control region is impossible for any PWM method. The theoretical derived expressions for stator and rotor losses (derived for infinite value of switching frequency, MATCAD program) are checked by results of direct computation for a finite value of switching frequency (MATLAB program) as well by simulations.

   Dual-PDM Control for Parallel Resonant Inverter
By Abdelhalim SANDALI, ahmed CHERITI [View]
[Download]

Abstract: The application of Pulse Density Modulation (PDM) control to a rectifier - series resonant inverter set makes it possible to implement an ac/ac converter with good performances (size and efficiency). However its power factor decreases when the load power varies. We propose a Dual-PDM control strategy adapted to a rectifier – parallel resonant inverter set. This converter is obtained by application of the rules of the duality to a series-resonant-inverter. The main interests of this converter are a self power factor correction and a step-up load power. Dual-PDM control law is defined and converter modeling is carried out. Results are validated by simulation.

   Elimination of Harmonic Spikes using Second-Order Space Dithered Sigma-Delta Modulation
By Kyo-Beum LEE, Seo-Hyeong KIM [View]
[Download]

Abstract: This paper proposes second-order SDSDM (Space Dithered Sigma-Delta Modulation) to suppress the harmonic spikes in power conversion. PWM (Pulse Width Modulation) normally operates with a fixed switching frequency, which causes power spectrum to be concentrated at multiples of the switching frequency. The proposed scheme is confirmed in the DC/DC converter. The experimental results show that the proposed method provides improved performance in reducing harmonic spikes caused by PWM while maintaining the low current ripples.

   HPS Lamp Control by Signal Injection of Approaching Frequency to Avoid Acoustic Resonances: Application to an LCC Circuit
By LABO CHHUN, Pascal MAUSSION, Sounil BHOSLE, Georges ZISSIS [View]
[Download]

Abstract: The supply of high intensity discharge (HID) lamp at high frequency provides important benefits in ballast optimization. However, in certain frequency range, the lamp is disturbed by the acoustic resonance (AR) which can lead to lamp arc fluctuation, extinction and lamp destruction in the worst case. This paper presents a novel approach of lamp control based on the injection of signals of approaching frequencies to avoid acoustic resonances in high pressure sodium (HPS) lamps operating under high frequency condition. The injected signals are confined within a selective band, so the lamp can be operated by a simple LCC half-bridge inverter based on the PWM modulation. The advantages in this strategy remain in the simplicity of the ballast structure and the independent control of injected signal parameters. Furthermore, additional adjacent frequency signals can still be injected without modifying the ballast structure or the PWM scheme in order to improve the AR avoidance. The simulation and experimental results are also presented in this paper.

   Improvement of Z-source inverter properties using advanced PWM methods
By Jacek RABKOWSKI [View]
[Download]

Abstract: This paper describes improvement of the Z-source inverter (ZSI) properties possible due to advanced PWM methods. Switching conditions and distribution of semiconductor power losses in the ZSI are analyzed in reference to Voltage Source Inverter and Boost Converter system. Two new PWM methods are proposed, including Asymmetric Optimized Switching Type (AOST) with efficiency improvement by 2,7\%. Considerations are illustrated with datasheet based calculations, simulation results and test of the Z-source inverter 2,5kVA laboratory model.

   Modulation of Three Phase Rectifier in Connection With PMSG for Maximum Energy Extraction
By Dimosthenis PEFTITSIS, Georgios ADAMIDIS [View]
[Download]

Abstract: This paper presents a Maximum Power Point Tracking (MPPT) method which is applied on a Wind Turbine with Permanent Magnet Synchronous Generator (PMSG). A three-phase Switched Mode Rectifier (SMR) is connected with the three phase output of the PMSG. The SMR employs a modulation strategy which is based on the Space Vector Modulation (SVM) technique. Thus, the three phase input voltage is divided in six equal intervals with respect to the zero crossing of the phase voltage and only two switches are switching in each one. A duty ratio D is introduced for each switch and is able to vary by ΔD in order to control the peak current through each phase. By controlling the three phase currents, it is possible to adjust the rotational speed of the PMSG and consequently the extracted power. The “Hill Climbing” algorithm has been used for achieving operation on the Maximum Power Point (MPP). The whole system has been designed and simulated using Matlab/Simulink and simulation results are shown for a variety of ΔD. Finally, a short discussion about the results is given.

   New Method of Direct Torque Control for Three-level Voltage Inverter
By Petr CHLEBIS, Petr MORAVCIK, Petr SIMONIK [View]
[Download]

Abstract: This paper presents a new Method of control based on Direct Torque Control (DTC) strategy. This method is designed to be applied in the control of Induction Motors (IM) fed with a three-level Voltage Source Inverter (VSI). This type of inverter has several advantages in comparison with standard two-level VSI, such as a greater number of levels in the output voltage waveforms, lower dV/dt, less harmonic distortion in voltage and current waveforms and lower switching frequencies. In the new method, torque and stator flux errors are used together with the stator flux angular frequency to generate a reference voltage vector. Further, practical application and operation of designed converters are documented on experimental results.

   Resonant frequency tracking control by using one CT for high frequency inverter
By Hiroyasu KIFUNE [View]
[Download]

Abstract: This paper presents a novel resonant frequency tracking control method for the full bridge type high frequency inverter. The proposed method uses only one AC current transformer though a general PLL as a frequency control method uses 2 current or potential transformers. Furthermore, the high frequency inverter system does not need to employ an active converter to control the DC bus voltage for the output power regulation although the inverter system using PLL has to have an active converter. Accordingly, the inverter that installs the proposed control method can control the operation frequency adequate and regulate the output power by one converter system. Hence, the high frequency inverter that is used for changing reactance load like an induction heating load can be simplified by introducing the proposed frequency control method. The operation principle is illustrated with a sample of block diagram. Simulation is implemented to estimate the control method and its results show a good performance for tuning the operation frequency to the resonant frequency. In addition, the control method is installed in an actual inverter for high power induction heating application. Observed and measured results verify the performance of the proposed frequency control method.

   Robust Space Vector Modulation with Minimum Distortions
By Radiy BEKBUDOV [View]
[Download]

Abstract: The strategy of conventional space vector modulation (SVM) is based on the assumption of ideal power commutations. In reality, the power commutations are under switching disturbances that leads to the appearance of distortions into the output current. The reduction of the current distortions is available due to obtaining the robustness of SVM based on redundancy. The robust SVM with minimum distortions is presented in this paper.

   Single-Phase AC/AC Buck-Boost Converter with Single-Phase Matrix Topology
By Minh-Khai NGUYEN, Young-Gook JUNG, Young-Cheol LIM [View]
[Download]

Abstract: This paper deals with a new family of single-phase AC/AC buck-boost converter based on single-phase matrix topology. The proposed converter provides a wider range of output AC voltage in which the output voltage can be bucked and in-phase/out-of-phase with the input voltage; and the output voltage can be boosted and in-phase/out-of-phase with the input voltage. A commutation strategy is employed to realize snubberless operation. The operating principles, circuit analysis and experimental results based on TMS320F2812 DSP are presented.

EPE 2009 - Subtopic 06-4 - DS: 'Converter Control Sets and Modulation Strategies'
You are here: EPE Documents > 01 - EPE & EPE ECCE Conference Proceedings > EPE 2009 - Conference > EPE 2009 - Topic 06: 'Modulation Strategies and Specific Control Methods for Static Converter' > EPE 2009 - Subtopic 06-4 - DS: 'Converter Control Sets and Modulation Strategies'
	[return to parent folder]

	A graphical method for SVM duty cycles computation. Application on two-level and multi-level inverters. By Santiago de PABLO, Alexis B. REY, Luis C. HERRERO, Fernando MARTINEZ	[View] [Download]
Abstract: A graphical method, easy to understand and easy to implement, has been developed for two-level and multi-level Space Vector Modulation. Switching sequences can be computed with no need of solving neither multi-variable inverse problems nor expensive trigonometric functions. Proposed method has been validated through simulations and physical implementations.

	A Novel Control Strategy for Optimal Inverter Switching Frequency Associated with Minimal Current Ripple Using Single Step Predictive Current Control By Thomas WOLBANK, Ronald STUMBERGER, Alois LECHNER, Jürgen MACHL	[View] [Download]
Abstract: The common trend in converter development is to increase the drive system performance with simultaneous consideration of cost reduction by operating the whole drive at its thermal limit. For this purpose all system components are, for short durations, even stressed above their rated values. Because thermal losses have to be well balanced it is necessary to adjust inverter switching frequency to its optimum value depending on the point of operation. By varying the inverter switching frequency the distribution of overall inverter losses between conduction and switching losses can be influenced. This control however implies the possibility of adjusting the inverter switching frequency online dependent on the point of operation. In this paper a new control strategy for controlling the switching frequency near its optimum by using a predictive fixed step current controller is presented. By influencing the switching decision using a weighting factor, the resulting inverter switching frequency can be modified. Hence operating the whole drive system with optimum performance with respect to both, the power devices as well as the ac machine losses is possible. The performance of the proposed method is investigated by simulation. Measurements results verify the accuracy in adapting the switching frequency to the optimum value depending on the point of operation.

	A novel pulsewidth modulation to operate a bidirectional two-stage dc-ac converter with high-frequency isolation in discontinuous conduction mode for photovolta By Montserrat MATA-DUMENJO, Sergio BUSQUETS-MONGE, Jaume DIEST-YUS, Mireia BARENYS-ESPADALER, Joan ROCABERT-DELGADO, Joan SALAET- PEREIRA	[View] [Download]
Abstract: This paper presents a novel modulation for a two-stage dc-ac power converter with high-frequency isolation installed in a photovoltaic stand-alone system. The presented modulation, which is designed for the converter discontinuous conduction mode of operation, solves the problem of connection to a grid, and permits a bidirectional power flow. In this document is described the modulation strategy and some simulation and experimental results are presented.

	A Phase Shift Selective Harmonic Elimination Method for balancing capacitor voltages in aseven level Cascaded H-Bridge Rectifier By Alan WATSON, Patrick WHEELER, Jon CLARE	[View] [Download]
Abstract: This paper presents a low switching frequency, Selective Harmonic Elimination (SHE) modulation method which may be applied to a Cascaded H-Bridge Active Rectifier. The method is based on a decoupled scheme where the modulation index of each H-Bridge cell is controlled independently to enable complete control of power flow through the converter. The method utilises a phase shift between the AC side cell voltages to achieve the required cell power balancing but with reduced distortion in the output waveform when compared with previously presented methods. Practical results from a laboratory based prototype converter are presented to validate the analysis. Although presented for a single phase topology the method can be applied to a three phase converter.

	Active Self-Switching Methods for Emerging Monolithic Bidirectional Switches Applied to Diode-Less Converters By Daniel SIEMASZKO, Alfred RUFER	[View] [Download]
Abstract: This paper presents a recently introduced switching principle for emerging monolithic bidirectional devices. Based on the hypothesis that those switches may overcome conventional diode type solutions in power converters, an active self-switching process becomes compulsory. Its principle relies on the measurement of both voltage and current polarity, in order to allow a natural switching as commonly used in matrix conversion. A self-switching method, implemented close to the switch, allows the detection of both short-circuits and open circuits. The accuracy of the presented system is experimented and validated in a 1kVA buck converter where the free-wheeling path is performed by a synthesized diode. The results that are discussed in this paper open a new perspective by introducing the principle of a so-called bidirectional diode as well as the commutation of sources of a similar nature.

	Analysis and Comparison of 3D-SVM Schemes for Flying-Capacitor Multi-Level Inverters By Michael WAITE, Li ZHANG	[View] [Download]
Abstract: The paper presents a comparative study of three different 3D-SVM techniques for the control of flying-capacitor multi-level inverters under both balanced and unbalanced operating conditions. Simulation results show that Direct 3D-SVM is the most efficient in computational effort. Application of this scheme to a three-level FCMI is simulated using the Alternative Transients Program (ATP). Output performance and features are highlighted.

	Control Strategies and Inverter Topologies for Stabilization of DC Grids in Embedded Systems By Nicolas PATIN	[View] [Download]
Abstract: Compactness is a key constraint for embedded equipments design. The main issue concerns DC link capacitors, which must maintain a good DC voltage quality. However, their size is too high when classical PWM strategies are used. In this paper, two adapted techniques are compared with uncertain or varying grid parameters.

	Direct Control Strategy for a Flying Capacitor Converter By Ana M. LLOR, François DEFAY, Maurice FADEL	[View] [Download]
Abstract: In this paper, a direct control of a flying capacitor inverter is proposed. This control allows to limit the number of commutations in a switching period with the use of a pre-calculated output voltage profile. A predictive control is made for the 3 phases 4 levels inverter in a active filtering operation. The advantages of this direct control is to reduce the switching frequency of the IGBTs, to use only a threshold voltage detector for flying capacitor voltages and to define offline pre-calculated switching tables. Experimental results for an active power filter application validate the performances of this control for static and dynamic conditions.

	DISCONTINUOUS MODULATION OF MULTI-PHASE INVERTER-FED AC MOTORS By Sandor HALASZ	[View] [Download]
Abstract: Different types of discontinuous PWMs of multiphase inverter-fed ac motors are investigated from point of view of ac motor harmonic losses. The derived expressions for computation of the generalized loss-factors and its components are given for different phase number and for all the investigated PWM methods. It is shown that the discontinuous PWM of multiphase system cannot be as successful as that for the case of three-phase system. Therefore in comparison with continuous PWMs the discontinuous ones have no advantages in case of phase number more than 9. However, the stator harmonic current losses are slightly higher while the rotor harmonic current losses are considerably lower than those in case of three-phase system. At the same time for the phase number over 7 a sensible broadening of the linear voltage control region is impossible for any PWM method. The theoretical derived expressions for stator and rotor losses (derived for infinite value of switching frequency, MATCAD program) are checked by results of direct computation for a finite value of switching frequency (MATLAB program) as well by simulations.

	Dual-PDM Control for Parallel Resonant Inverter By Abdelhalim SANDALI, ahmed CHERITI	[View] [Download]
Abstract: The application of Pulse Density Modulation (PDM) control to a rectifier - series resonant inverter set makes it possible to implement an ac/ac converter with good performances (size and efficiency). However its power factor decreases when the load power varies. We propose a Dual-PDM control strategy adapted to a rectifier – parallel resonant inverter set. This converter is obtained by application of the rules of the duality to a series-resonant-inverter. The main interests of this converter are a self power factor correction and a step-up load power. Dual-PDM control law is defined and converter modeling is carried out. Results are validated by simulation.

	Elimination of Harmonic Spikes using Second-Order Space Dithered Sigma-Delta Modulation By Kyo-Beum LEE, Seo-Hyeong KIM	[View] [Download]
Abstract: This paper proposes second-order SDSDM (Space Dithered Sigma-Delta Modulation) to suppress the harmonic spikes in power conversion. PWM (Pulse Width Modulation) normally operates with a fixed switching frequency, which causes power spectrum to be concentrated at multiples of the switching frequency. The proposed scheme is confirmed in the DC/DC converter. The experimental results show that the proposed method provides improved performance in reducing harmonic spikes caused by PWM while maintaining the low current ripples.

	HPS Lamp Control by Signal Injection of Approaching Frequency to Avoid Acoustic Resonances: Application to an LCC Circuit By LABO CHHUN, Pascal MAUSSION, Sounil BHOSLE, Georges ZISSIS	[View] [Download]
Abstract: The supply of high intensity discharge (HID) lamp at high frequency provides important benefits in ballast optimization. However, in certain frequency range, the lamp is disturbed by the acoustic resonance (AR) which can lead to lamp arc fluctuation, extinction and lamp destruction in the worst case. This paper presents a novel approach of lamp control based on the injection of signals of approaching frequencies to avoid acoustic resonances in high pressure sodium (HPS) lamps operating under high frequency condition. The injected signals are confined within a selective band, so the lamp can be operated by a simple LCC half-bridge inverter based on the PWM modulation. The advantages in this strategy remain in the simplicity of the ballast structure and the independent control of injected signal parameters. Furthermore, additional adjacent frequency signals can still be injected without modifying the ballast structure or the PWM scheme in order to improve the AR avoidance. The simulation and experimental results are also presented in this paper.

	Improvement of Z-source inverter properties using advanced PWM methods By Jacek RABKOWSKI	[View] [Download]
Abstract: This paper describes improvement of the Z-source inverter (ZSI) properties possible due to advanced PWM methods. Switching conditions and distribution of semiconductor power losses in the ZSI are analyzed in reference to Voltage Source Inverter and Boost Converter system. Two new PWM methods are proposed, including Asymmetric Optimized Switching Type (AOST) with efficiency improvement by 2,7\%. Considerations are illustrated with datasheet based calculations, simulation results and test of the Z-source inverter 2,5kVA laboratory model.

	Modulation of Three Phase Rectifier in Connection With PMSG for Maximum Energy Extraction By Dimosthenis PEFTITSIS, Georgios ADAMIDIS	[View] [Download]
Abstract: This paper presents a Maximum Power Point Tracking (MPPT) method which is applied on a Wind Turbine with Permanent Magnet Synchronous Generator (PMSG). A three-phase Switched Mode Rectifier (SMR) is connected with the three phase output of the PMSG. The SMR employs a modulation strategy which is based on the Space Vector Modulation (SVM) technique. Thus, the three phase input voltage is divided in six equal intervals with respect to the zero crossing of the phase voltage and only two switches are switching in each one. A duty ratio D is introduced for each switch and is able to vary by ΔD in order to control the peak current through each phase. By controlling the three phase currents, it is possible to adjust the rotational speed of the PMSG and consequently the extracted power. The “Hill Climbing” algorithm has been used for achieving operation on the Maximum Power Point (MPP). The whole system has been designed and simulated using Matlab/Simulink and simulation results are shown for a variety of ΔD. Finally, a short discussion about the results is given.

	New Method of Direct Torque Control for Three-level Voltage Inverter By Petr CHLEBIS, Petr MORAVCIK, Petr SIMONIK	[View] [Download]
Abstract: This paper presents a new Method of control based on Direct Torque Control (DTC) strategy. This method is designed to be applied in the control of Induction Motors (IM) fed with a three-level Voltage Source Inverter (VSI). This type of inverter has several advantages in comparison with standard two-level VSI, such as a greater number of levels in the output voltage waveforms, lower dV/dt, less harmonic distortion in voltage and current waveforms and lower switching frequencies. In the new method, torque and stator flux errors are used together with the stator flux angular frequency to generate a reference voltage vector. Further, practical application and operation of designed converters are documented on experimental results.

	Resonant frequency tracking control by using one CT for high frequency inverter By Hiroyasu KIFUNE	[View] [Download]
Abstract: This paper presents a novel resonant frequency tracking control method for the full bridge type high frequency inverter. The proposed method uses only one AC current transformer though a general PLL as a frequency control method uses 2 current or potential transformers. Furthermore, the high frequency inverter system does not need to employ an active converter to control the DC bus voltage for the output power regulation although the inverter system using PLL has to have an active converter. Accordingly, the inverter that installs the proposed control method can control the operation frequency adequate and regulate the output power by one converter system. Hence, the high frequency inverter that is used for changing reactance load like an induction heating load can be simplified by introducing the proposed frequency control method. The operation principle is illustrated with a sample of block diagram. Simulation is implemented to estimate the control method and its results show a good performance for tuning the operation frequency to the resonant frequency. In addition, the control method is installed in an actual inverter for high power induction heating application. Observed and measured results verify the performance of the proposed frequency control method.

	Robust Space Vector Modulation with Minimum Distortions By Radiy BEKBUDOV	[View] [Download]
Abstract: The strategy of conventional space vector modulation (SVM) is based on the assumption of ideal power commutations. In reality, the power commutations are under switching disturbances that leads to the appearance of distortions into the output current. The reduction of the current distortions is available due to obtaining the robustness of SVM based on redundancy. The robust SVM with minimum distortions is presented in this paper.

	Single-Phase AC/AC Buck-Boost Converter with Single-Phase Matrix Topology By Minh-Khai NGUYEN, Young-Gook JUNG, Young-Cheol LIM	[View] [Download]
Abstract: This paper deals with a new family of single-phase AC/AC buck-boost converter based on single-phase matrix topology. The proposed converter provides a wider range of output AC voltage in which the output voltage can be bucked and in-phase/out-of-phase with the input voltage; and the output voltage can be boosted and in-phase/out-of-phase with the input voltage. A commutation strategy is employed to realize snubberless operation. The operating principles, circuit analysis and experimental results based on TMS320F2812 DSP are presented.