EPE Association: EPE 2009 - Subtopic 06-5: 'Converter Control, Current / Voltage Control'

EPE 2009 - Subtopic 06-5: 'Converter Control, Current / Voltage Control'
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 06-5: 'Converter Control, Current / Voltage Control'

   [return to parent folder]

   A New Approach to Design High Performance Current Controllers for Grid Connected Voltage Source Converters
By Carlos RAMOS, António MARTINS, Adriano CARVALHO [View]
[Download]

Abstract: The usual approach to design the two current controllers for a grid-connected voltage source converter is to design the two compensation controllers for the direct path and use a feed forward component to compensate the coupling. However, this term can lead to significant errors since the associated parameters can change in time. A controller that can directly handle this coupling term is the best approach to maintain high performance levels. The paper presents a methodology to design a current controller based on the concept of a controller in the complex domain. The complex controller is obtained using the pole placement method and its extension to high order systems is discussed. Simulation and experimental results are presented, clearly demonstrating the validity of the design approach.

   Comparison of high dynamic current tracking methods for multiswitching systems
By Maria Stefania CARMELI, Gabrio SUPERTI-FURGA, Francesco CASTELLI-DEZZA [View]
[Download]

Abstract: Multiconverter configurations, consisting of cascaded or parallel connections of small-size units are usually used for high-power applications. This paper discusses and compares three different current tracking strategies based on the Predictive Smart Modulation algorithm (PSM) applied to a multiconverter configuration. Simulation results are presented.

   Coordinated Control for Grid Connected Power Electronic Converters under the presence of Voltage Dips and Harmonics
By Aritz MILICUA, Szymon PIASECKI, Malgorzata BOBROWSKA, Krzysztof RAFAL, Gonzalo ABAD [View]
[Download]

Abstract: In this paper, the joined reactive power compensator and active filter functionality, of a grid connected two level Voltage Source Converter (VSC), is explored. This VSC, fulfills two different objectives: Compensate current harmonics demanded by non-linear loads (active filter application) and exchange reactive power with a grid subjected to balanced and unbalanced dips. For that purpose, a coordinated control structure is proposed based on Dual Vector Current Controllers (DVCC). In addition, by means of detailed simulation and experimental results, the proposed control structure is validated under different operation conditions.

   Cross Voltage Control with Inner Hysteresis Current Control for Multi-output Boost Converter
By ALIREZA NAMI, FIRUZ ZARE, GHOSH ARINDAM, FREDE BLAABJERG [View]
[Download]

Abstract: Multi-output boost (MOB) converter is a novel DC-DC converter unlike the regular boost converter, has the ability to share its total output voltage and to have different series output voltage from a given duty cycle for low and high power applications. In this paper, discrete voltage control with inner hysteresis current control loop has been proposed to keep the simplicity of the control law for the double-output MOB converter, which can be implemented by a combination of analogue and logical ICs or simple microcontroller to constrain the output voltages of MOB converter at their reference voltages against variation in load or input voltage. The salient features of the proposed control strategy are simplicity of implementation and ease to extend to multiple outputs in the MOB converter. Simulation and experimental results are presented to show the validity of control strategy.

   Design and Analysis of a Solar Converter with Minimized Energy Storage
By Bjoern WITTIG, Wulf Toke FRANKE, Friedrich W. FUCHS [View]
[Download]

Abstract: Solar converters to feed the energy from the solar module into the AC grid consist of a DC/DC and a three phase DC/AC converter decoupled by a capacitor in the DC link which is to be minimized. A current fed instead of a voltage fed full bridge DC/DC converter is chosen and leads to a higher efficiency. Furthermore undesirable voltage spikes can be avoided by the use of this topology. This paper presents a control concept without additional sensors to reduce the DC link capacity in solar converters and its analysis. Two different analytical methods to determine a minimal DC link capacity are explained. The proposed control method to reduce the voltage deviation in the DC link can be implemented without additional sensors in most of solar converter applications. It can also be adapted to other DC/AC converter applications like converter systems for fuel cells. Laboratory measurements confirm the simulation results.

   Digital Repetitive Control of a Three-Phase Flat-Top-Modulated Grid Tie Solar Inverter
By Stefan ENGEL, Klaus RIGBERS, Rik W. DE DONCKER [View]
[Download]

Abstract: Grid connected solar inverters are used to feed energy generated by a photovoltaic generator into the mains. High efficiency is a major requirement. Furthermore a low total harmonic distortion (THD) of the output current is needed to comply with regulations. This paper presents the control for a new highly efficient inverter topology. Due to disturbances of the grid voltage and non-linear effects such as dead-time effects in the output stage of the inverter, the output current is distorted, especially when using small output inductors. Furthermore, the investigated inverter is operated with 120° flat-top modulation to improve efficiency. However, this modulation scheme in combination with an LCL output filter leads to higher THD. As the current distortion is periodic with the grid voltage, a repetitive learning controller can be used to compensate it. In this paper, the design of a vector control including a repetitive controller is outlined. The results of the implementation of the control algorithm on hardware are presented.

   Direct Power Control Based Indirect AC to AC Power Conversion System
By Toshihiko NOGUCHI, akira SATO [View]
[Download]

Abstract: This paper describes a novel control strategy of a direct-power-control based indirect matrix converter. The key of this strategy is direct selection of a switching state of the indirect matrix converter on the basis of instantaneous power errors. A relationship between the instantaneous power and the switching state of the indirect matrix converter is theoretically analyzed, which is essential to compose a switching-state-table. Effectiveness of the proposed technique is examined through several experimental tests, using a 1.6-kW prototype. As a result, unity power factor operation is achieved by the proposed method, and the output currents are confirmed to be sinusoidal waveforms without large distortion.

   Flux-Based Multivariable Control of a Three-Phase Active Front End Feeding a 16.7-Hz Single-Phase Load
By Carsten HEISING, Martin OETTMEIER, Matthias GORSKI, Volker STAUDT, Andreas STEIMEL [View]
[Download]

Abstract: Actually, AC 16.7-Hz railway grids are fed via back-to-back converters from the public grid. A fluxbased multivariable control for the three-phase-side converter is presented, which takes the resonant circuit of the single-phase-side converter into account, leading to excellent stationary and dynamic behaviour.

   Fuzzy Logic Control of the Cross Connected Intermediate Level (CCIL)Voltage Source Inverter
By Toufann CHAUDHURI, Alfred RUFER [View]
[Download]

Abstract: The Cross Connected Intermediate Level (CCIL) Voltage Source Inverter Topology was first introduced in 2007 [1]. The idea behind this novel multilevel topology is to explore the area of reduced number of component topologies producing large number of voltage levels. Mathematical modeling of the electrical circuit for the understanding and the control of the capacitor voltage has proven to be less intuitive and rather complex. A model based on graphical representation of the currents, modulation index and voltage levels was developed. It allowed having a good intuitive understanding on how to control the capacitor voltage. In this paper, a regulation scheme for the voltage control of the unsupplied phase capacitor voltage of the topology is proposed, based on a graphical model and using a fuzzy logic control strategy.

   GENERALIZED INSTANTANEOUS REACTIVE POWER THEORY IN POLY-PHASE POWER SYSTEMS
By REYES HERRERA, PATRICIO SALMERÓN, JESUS VAZQUEZ, SALVADOR LITRÁN, ALEJANDRO PÉREZ [View]
[Download]

Abstract: The systematic use of Active Power Filters, APFs, to compensate nonlinear loads, has extended the use of the instantaneous reactive power theory. Originally, the p-q theory appeared; it obtained constant instantaneous power in the source side after compensation. Later, other formulations have been developed. They have allowed different compensation objectives to be obtained. Nevertheless, all of them can only be applied to three-phase systems, i.e. those formulations frameworks can not be used to establish control strategies in poly-phase systems. This paper presents a new approach, based on geometric algebra, which can be applied to multiphase systems. A new tensor product is introduced that allows the operative definition of the instantaneous reactive power tensor and its derived instantaneous reactive current component. In addition, in this paper a new concept of instantaneous power multivector is introduced which allows the instantaneous reactive power theory to be encoded in an analog way as single-phase systems analysis. The new expressions are applied to a practical multi-phase system. Power and current terms are calculated and the associated waveforms are presented. Results corroborate the correspondence with the traditional electric power theory

   High Performance Hybrid Control for Buck Converters
By Angelica MENDOZA, Ilse CERVANTES, Francisco PEREZ-PINAL [View]
[Download]

Abstract: In this paper a hybrid control for buck converters is proposed that is able to guarantee voltage tracking and maximum voltage and current ripple simultaneously. The controller is based on the piece-wise model of the converter and it works by switching on or off once a set of performance surfaces is reached. The controller provides global attractiveness and asymptotic stability to a bounded set.

   Model Predictive Control of Cascaded H-Bridge Multilevel Inverters
By Patricio CORTES, Alan WILSON, Samir KOURO, Jose RODRIGUEZ, Haitham ABU-RUB [View]
[Download]

Abstract: This paper presents a Model Predictive Current Control strategy for a multilevel cascaded inverter. A simple discrete model is used to predict the behavior of the system for each possible voltage vector generated by the inverter. The voltage vector that minimizes a cost function is selected and applied during a whole sampling interval. The cost function measures the load current error. Due to the large number of voltage vectors, voltage levels per phase and switching states in a multilevel cascaded inverter, high amount of calculations is needed in order to make predictions. This makes difficult the implementation of this control strategy in a standard control platform. A modified control strategy that considerably reduces the number of calculations is proposed and validated with simulation results using a Cascaded H-Bridge multilevel inverter.

   New Algorithmic Modulation Strategy for Cascaded H-Bridge Inverters with IGCT Burst Capability Monitoring and Excellent Performance
By Timo CHRIST, Bernd ORLIK [View]
[Download]

Abstract: The paper presents a new modulation strategy for cascaded H-bridge inverters which allows easy integration of device specific safety features like IGCT burst capability monitoring. It is compared to PWM using a simulation model of an unusual configuration for a 10kV medium voltage inverter using just three cascaded cells per phase. The general structure of the cascaded H-bridge inverter and key data of the simulation model, which includes thermal characteristics, is described. The pulse width modulator is explained including details particular to cascaded H-bridge inverters. The new modulation strategy is outlined briefly, more detail being used to show how burst capability monitoring for IGCTs is implemented. In the performance comparisons, which were done using simulation models in which only the used modulators differ, efficiency, total harmonic distortion, loss and temperature distribution among cells and the share of output power contributed by each cell were analyzed. The results reveal improved partial load efficiency due to reduced switching frequency for the new modulator. Harmonic distortion is much improved; particularly at elevated frequencies up to 200Hz and at low power. Power distribution is quite uniform although the algorithm does not contain any measures to achieve balancing of equal DC-link voltage cells because it was designed for asymmetrical converter configurations.

   Optimal Design of Output Filter Capacitor for Peak Current Mode Control Converter with First-Order Response
By Abe SEIYA, Masahito SHOYAMA, Tamotsu NINOMIYA [View]
[Download]

Abstract: The synchronous buck converter is generally used as basic circuit for low-voltage application such as POL. The buck converter with peak current mode control has first-order response depending on the power-stage or controller design. Therefore the overshoot and undershoot don’t appear in transient response. This feature is the chief advantage of peak current mode control. However, there is no example of the design that employed this feature efficiently. So far, we have performed various discussions about transient response of buck converter with peak current mode control. From various discussions, we have found that the voltage variation at transient time does not depend on the output capacitance on buck converter with peak current mode control. This paper discusses the optimal design of the output filter capacitor for first-order response on buck converter with peak current mode control.

   Predictive Current Controller for a Power Factor Correction Boost Converter Operating in Mixed Conduction Mode
By Leandro ROGGIA, José Eduardo BAGGIO, José Renes PINHEIRO [View]
[Download]

Abstract: This paper proposes a digital predictive current controller applied to a power factor correction boost converter rated to a wide range of output power, operating in mixed conduction mode with fixed switching frequency. The current controller comprises two predictive model based control laws (one for the continuous and another for the discontinuous conduction mode) and an operation mode selection algorithm, which is responsible to detect the operation mode and select the respective control law. The paper explains in details both the current control laws and the selection algorithm. The design of the inductor and capacitor are also presented. The proposed control scheme has been implemented using a low cost microcontroller. Experimental results are provided to show the performance and validate the proposed PFC boost converter control system.

   The Control of NPC Grid Connected Converter for Interfacing to Unbalanced DC Link Loads
By Edward CHRISTOPHER, Mark SUMNER [View]
[Download]

Abstract: A novel control scheme for Neutral Point Clamped converters is presented, which allows interfacing of two unbalanced DC sources or loads to the ac grid. Multivariable control provides power matching for each DC link, under unbalanced DC loading conditions. Due to operation with unequal DC link capacitor voltages feedforward compensation is used to minimise the even harmonics caused in the supply current. An analytical method is derived which uses system parameters and loading to deduce the limits of control over the capacitor voltages. Experimental and simulation results are given showing the control performance.

EPE 2009 - Subtopic 06-5: 'Converter Control, Current / Voltage Control'
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 06-5: 'Converter Control, Current / Voltage Control'
	[return to parent folder]

	A New Approach to Design High Performance Current Controllers for Grid Connected Voltage Source Converters By Carlos RAMOS, António MARTINS, Adriano CARVALHO	[View] [Download]
Abstract: The usual approach to design the two current controllers for a grid-connected voltage source converter is to design the two compensation controllers for the direct path and use a feed forward component to compensate the coupling. However, this term can lead to significant errors since the associated parameters can change in time. A controller that can directly handle this coupling term is the best approach to maintain high performance levels. The paper presents a methodology to design a current controller based on the concept of a controller in the complex domain. The complex controller is obtained using the pole placement method and its extension to high order systems is discussed. Simulation and experimental results are presented, clearly demonstrating the validity of the design approach.

	Comparison of high dynamic current tracking methods for multiswitching systems By Maria Stefania CARMELI, Gabrio SUPERTI-FURGA, Francesco CASTELLI-DEZZA	[View] [Download]
Abstract: Multiconverter configurations, consisting of cascaded or parallel connections of small-size units are usually used for high-power applications. This paper discusses and compares three different current tracking strategies based on the Predictive Smart Modulation algorithm (PSM) applied to a multiconverter configuration. Simulation results are presented.

	Coordinated Control for Grid Connected Power Electronic Converters under the presence of Voltage Dips and Harmonics By Aritz MILICUA, Szymon PIASECKI, Malgorzata BOBROWSKA, Krzysztof RAFAL, Gonzalo ABAD	[View] [Download]
Abstract: In this paper, the joined reactive power compensator and active filter functionality, of a grid connected two level Voltage Source Converter (VSC), is explored. This VSC, fulfills two different objectives: Compensate current harmonics demanded by non-linear loads (active filter application) and exchange reactive power with a grid subjected to balanced and unbalanced dips. For that purpose, a coordinated control structure is proposed based on Dual Vector Current Controllers (DVCC). In addition, by means of detailed simulation and experimental results, the proposed control structure is validated under different operation conditions.

	Cross Voltage Control with Inner Hysteresis Current Control for Multi-output Boost Converter By ALIREZA NAMI, FIRUZ ZARE, GHOSH ARINDAM, FREDE BLAABJERG	[View] [Download]
Abstract: Multi-output boost (MOB) converter is a novel DC-DC converter unlike the regular boost converter, has the ability to share its total output voltage and to have different series output voltage from a given duty cycle for low and high power applications. In this paper, discrete voltage control with inner hysteresis current control loop has been proposed to keep the simplicity of the control law for the double-output MOB converter, which can be implemented by a combination of analogue and logical ICs or simple microcontroller to constrain the output voltages of MOB converter at their reference voltages against variation in load or input voltage. The salient features of the proposed control strategy are simplicity of implementation and ease to extend to multiple outputs in the MOB converter. Simulation and experimental results are presented to show the validity of control strategy.

	Design and Analysis of a Solar Converter with Minimized Energy Storage By Bjoern WITTIG, Wulf Toke FRANKE, Friedrich W. FUCHS	[View] [Download]
Abstract: Solar converters to feed the energy from the solar module into the AC grid consist of a DC/DC and a three phase DC/AC converter decoupled by a capacitor in the DC link which is to be minimized. A current fed instead of a voltage fed full bridge DC/DC converter is chosen and leads to a higher efficiency. Furthermore undesirable voltage spikes can be avoided by the use of this topology. This paper presents a control concept without additional sensors to reduce the DC link capacity in solar converters and its analysis. Two different analytical methods to determine a minimal DC link capacity are explained. The proposed control method to reduce the voltage deviation in the DC link can be implemented without additional sensors in most of solar converter applications. It can also be adapted to other DC/AC converter applications like converter systems for fuel cells. Laboratory measurements confirm the simulation results.

	Digital Repetitive Control of a Three-Phase Flat-Top-Modulated Grid Tie Solar Inverter By Stefan ENGEL, Klaus RIGBERS, Rik W. DE DONCKER	[View] [Download]
Abstract: Grid connected solar inverters are used to feed energy generated by a photovoltaic generator into the mains. High efficiency is a major requirement. Furthermore a low total harmonic distortion (THD) of the output current is needed to comply with regulations. This paper presents the control for a new highly efficient inverter topology. Due to disturbances of the grid voltage and non-linear effects such as dead-time effects in the output stage of the inverter, the output current is distorted, especially when using small output inductors. Furthermore, the investigated inverter is operated with 120° flat-top modulation to improve efficiency. However, this modulation scheme in combination with an LCL output filter leads to higher THD. As the current distortion is periodic with the grid voltage, a repetitive learning controller can be used to compensate it. In this paper, the design of a vector control including a repetitive controller is outlined. The results of the implementation of the control algorithm on hardware are presented.

	Direct Power Control Based Indirect AC to AC Power Conversion System By Toshihiko NOGUCHI, akira SATO	[View] [Download]
Abstract: This paper describes a novel control strategy of a direct-power-control based indirect matrix converter. The key of this strategy is direct selection of a switching state of the indirect matrix converter on the basis of instantaneous power errors. A relationship between the instantaneous power and the switching state of the indirect matrix converter is theoretically analyzed, which is essential to compose a switching-state-table. Effectiveness of the proposed technique is examined through several experimental tests, using a 1.6-kW prototype. As a result, unity power factor operation is achieved by the proposed method, and the output currents are confirmed to be sinusoidal waveforms without large distortion.

	Flux-Based Multivariable Control of a Three-Phase Active Front End Feeding a 16.7-Hz Single-Phase Load By Carsten HEISING, Martin OETTMEIER, Matthias GORSKI, Volker STAUDT, Andreas STEIMEL	[View] [Download]
Abstract: Actually, AC 16.7-Hz railway grids are fed via back-to-back converters from the public grid. A fluxbased multivariable control for the three-phase-side converter is presented, which takes the resonant circuit of the single-phase-side converter into account, leading to excellent stationary and dynamic behaviour.

	Fuzzy Logic Control of the Cross Connected Intermediate Level (CCIL)Voltage Source Inverter By Toufann CHAUDHURI, Alfred RUFER	[View] [Download]
Abstract: The Cross Connected Intermediate Level (CCIL) Voltage Source Inverter Topology was first introduced in 2007 [1]. The idea behind this novel multilevel topology is to explore the area of reduced number of component topologies producing large number of voltage levels. Mathematical modeling of the electrical circuit for the understanding and the control of the capacitor voltage has proven to be less intuitive and rather complex. A model based on graphical representation of the currents, modulation index and voltage levels was developed. It allowed having a good intuitive understanding on how to control the capacitor voltage. In this paper, a regulation scheme for the voltage control of the unsupplied phase capacitor voltage of the topology is proposed, based on a graphical model and using a fuzzy logic control strategy.

	GENERALIZED INSTANTANEOUS REACTIVE POWER THEORY IN POLY-PHASE POWER SYSTEMS By REYES HERRERA, PATRICIO SALMERÓN, JESUS VAZQUEZ, SALVADOR LITRÁN, ALEJANDRO PÉREZ	[View] [Download]
Abstract: The systematic use of Active Power Filters, APFs, to compensate nonlinear loads, has extended the use of the instantaneous reactive power theory. Originally, the p-q theory appeared; it obtained constant instantaneous power in the source side after compensation. Later, other formulations have been developed. They have allowed different compensation objectives to be obtained. Nevertheless, all of them can only be applied to three-phase systems, i.e. those formulations frameworks can not be used to establish control strategies in poly-phase systems. This paper presents a new approach, based on geometric algebra, which can be applied to multiphase systems. A new tensor product is introduced that allows the operative definition of the instantaneous reactive power tensor and its derived instantaneous reactive current component. In addition, in this paper a new concept of instantaneous power multivector is introduced which allows the instantaneous reactive power theory to be encoded in an analog way as single-phase systems analysis. The new expressions are applied to a practical multi-phase system. Power and current terms are calculated and the associated waveforms are presented. Results corroborate the correspondence with the traditional electric power theory

	High Performance Hybrid Control for Buck Converters By Angelica MENDOZA, Ilse CERVANTES, Francisco PEREZ-PINAL	[View] [Download]
Abstract: In this paper a hybrid control for buck converters is proposed that is able to guarantee voltage tracking and maximum voltage and current ripple simultaneously. The controller is based on the piece-wise model of the converter and it works by switching on or off once a set of performance surfaces is reached. The controller provides global attractiveness and asymptotic stability to a bounded set.

	Model Predictive Control of Cascaded H-Bridge Multilevel Inverters By Patricio CORTES, Alan WILSON, Samir KOURO, Jose RODRIGUEZ, Haitham ABU-RUB	[View] [Download]
Abstract: This paper presents a Model Predictive Current Control strategy for a multilevel cascaded inverter. A simple discrete model is used to predict the behavior of the system for each possible voltage vector generated by the inverter. The voltage vector that minimizes a cost function is selected and applied during a whole sampling interval. The cost function measures the load current error. Due to the large number of voltage vectors, voltage levels per phase and switching states in a multilevel cascaded inverter, high amount of calculations is needed in order to make predictions. This makes difficult the implementation of this control strategy in a standard control platform. A modified control strategy that considerably reduces the number of calculations is proposed and validated with simulation results using a Cascaded H-Bridge multilevel inverter.

	New Algorithmic Modulation Strategy for Cascaded H-Bridge Inverters with IGCT Burst Capability Monitoring and Excellent Performance By Timo CHRIST, Bernd ORLIK	[View] [Download]
Abstract: The paper presents a new modulation strategy for cascaded H-bridge inverters which allows easy integration of device specific safety features like IGCT burst capability monitoring. It is compared to PWM using a simulation model of an unusual configuration for a 10kV medium voltage inverter using just three cascaded cells per phase. The general structure of the cascaded H-bridge inverter and key data of the simulation model, which includes thermal characteristics, is described. The pulse width modulator is explained including details particular to cascaded H-bridge inverters. The new modulation strategy is outlined briefly, more detail being used to show how burst capability monitoring for IGCTs is implemented. In the performance comparisons, which were done using simulation models in which only the used modulators differ, efficiency, total harmonic distortion, loss and temperature distribution among cells and the share of output power contributed by each cell were analyzed. The results reveal improved partial load efficiency due to reduced switching frequency for the new modulator. Harmonic distortion is much improved; particularly at elevated frequencies up to 200Hz and at low power. Power distribution is quite uniform although the algorithm does not contain any measures to achieve balancing of equal DC-link voltage cells because it was designed for asymmetrical converter configurations.

	Optimal Design of Output Filter Capacitor for Peak Current Mode Control Converter with First-Order Response By Abe SEIYA, Masahito SHOYAMA, Tamotsu NINOMIYA	[View] [Download]
Abstract: The synchronous buck converter is generally used as basic circuit for low-voltage application such as POL. The buck converter with peak current mode control has first-order response depending on the power-stage or controller design. Therefore the overshoot and undershoot don’t appear in transient response. This feature is the chief advantage of peak current mode control. However, there is no example of the design that employed this feature efficiently. So far, we have performed various discussions about transient response of buck converter with peak current mode control. From various discussions, we have found that the voltage variation at transient time does not depend on the output capacitance on buck converter with peak current mode control. This paper discusses the optimal design of the output filter capacitor for first-order response on buck converter with peak current mode control.

	Predictive Current Controller for a Power Factor Correction Boost Converter Operating in Mixed Conduction Mode By Leandro ROGGIA, José Eduardo BAGGIO, José Renes PINHEIRO	[View] [Download]
Abstract: This paper proposes a digital predictive current controller applied to a power factor correction boost converter rated to a wide range of output power, operating in mixed conduction mode with fixed switching frequency. The current controller comprises two predictive model based control laws (one for the continuous and another for the discontinuous conduction mode) and an operation mode selection algorithm, which is responsible to detect the operation mode and select the respective control law. The paper explains in details both the current control laws and the selection algorithm. The design of the inductor and capacitor are also presented. The proposed control scheme has been implemented using a low cost microcontroller. Experimental results are provided to show the performance and validate the proposed PFC boost converter control system.

	The Control of NPC Grid Connected Converter for Interfacing to Unbalanced DC Link Loads By Edward CHRISTOPHER, Mark SUMNER	[View] [Download]
Abstract: A novel control scheme for Neutral Point Clamped converters is presented, which allows interfacing of two unbalanced DC sources or loads to the ac grid. Multivariable control provides power matching for each DC link, under unbalanced DC loading conditions. Due to operation with unequal DC link capacitor voltages feedforward compensation is used to minimise the even harmonics caused in the supply current. An analytical method is derived which uses system parameters and loading to deduce the limits of control over the capacitor voltages. Experimental and simulation results are given showing the control performance.