EPE Association: EPE 2016 - DS2e: Standard and Advanced Control Techniques for Power Converters

EPE 2016 - DS2e: Standard and Advanced Control Techniques for Power Converters
You are here: EPE Documents > 01 - EPE & EPE ECCE Conference Proceedings > EPE 2016 ECCE Europe - Conference > EPE 2016 - Topic 03: Measurement and Control > EPE 2016 - DS2e: Standard and Advanced Control Techniques for Power Converters

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   Advanced Control Method for VSC-HVDC Systems Connected to Weak Grids
By Omar JASIM [View]
[Download]

Abstract: This paper proposes a novel control method for modular multilevel converter (MMC) based high voltage direct current (HVDC) power transmission system connected to a very weak or strong AC system under balanced or unbalanced operating conditions. The control concept is developed based on no need for phase-locked loop (PLL) where the voltage source converter (VSC) is controlled directly in ABC frame. The proposed control scheme regulates the instantaneous active and reactive power independently at the Point of Common coupling (PCC). A Multi-Input-Multi-Output (MIMO) state space model has been derived in ABC frame for the MMC converter. An enhanced outer loop is presented for achieving a smooth transition between weak and strong AC network by providing reactive power support to the AC voltage at PCC and exchanging maximum amount of active power within the converter rating limits. Moreover, the controller is designed to tolerate for computational delays. The effectiveness of the proposed control is validated by simulations results.

   Capacitor voltage balance performance comparison of MMC-STATCOM using NLC and PS-PWM strategies during negative sequence current injection
By Heverton PEREIRA [View]
[Download]

Abstract: This paper addresses the modular multilevel converter applied as a static synchronous compensator. The mainobjective of this work is to compare the converter performance considering two different submodule capacitorvoltage balancing strategies: nearest level control and phase-shifted pulse width modulation, during positive andnegative sequence current injection. Results of a 15 MVA MMC STATCOM show that the nearest level controlstrategy has lower average switching frequency compared to the phase-shifted pulse width modulation strategy,considering comparable submodule capacitance voltage ripple.

   Carrier-based PWM with Minimum Infinity Norm for Overmodulation Area of Five-Phase Converters
By Tomas KOMRSKA [View]
[Download]

Abstract: Overmodulation area of five-phase converters is covered by space vector PWM methods above all. The paper proposes a carrier-based PWM modulator employing the minimum infinity-norm method which is able to synthesize an arbitrary voltage vector in both, aß and xy planes, respectively, which is advantageous besides the linear modulation area in the overmodulation zone as well. Thanks to the proposed optimization, the modulator is able to achieve a competitive modulation index in the overmodulation area while attenuating undesired harmonics.

   Control of Switching Frequency for Modular Multilevel Converters by a Variable Hysteresis Band Modulation
By Sascha KUBERA [View]
[Download]

Abstract: The average switching frequency of the Modular Multilevel Converter (MMC) is a characteristic system parameter, which affects the losses of the converter system. Several investigations were done to reduce the switching frequency by applying different modulation strategies. Up to now the switching frequency is always an indirect and random outcome of the modulator and it is not directly controlled.Based on the known techniques for two-level converters a method is proposed to control the switching frequency in steady state operation of a MMC by varying the hysteresis band of the modulator. This allows design calculations with a well-defined average switching frequency, because the control guarantees the desired switching frequency in steady state operation.Simulation results from PSCAD/EMTDC show the proper work of the control loop in a HVDC transmission system model.

   Local Vector Current Controller and Current Clamp Minimisation
By Robert BETZ [View]
[Download]

Abstract: This paper presents the Local Vector Control (LVC) algorithm that is applicable to power electronic systems. This controller does not differentiate between linear or non-linear systems and can operate, without change, in stationary or rotating reference frames. The performance of this current controller with particular emphasis on current clamp minimisation will be the paper's focus. A comparison between the LVC, PI and predictive dead-beat current controllers (PCC) is presented.

   LQ Control of Single-phase Converter with LCL Filter with Partially Observed State
By Stepan BLAHA [View]
[Download]

Abstract: A linear-quadratic controller of a single-phase converter with LCL filter is designed. Since the full state is not directly observed, we design several observation models of the system and apply the Kalman filtering theory to obtain observes. In the tested configuration, we obtained good performance of the controller even with one voltage and one current sensor.

   Method for balancing capacitors voltages on split DC-links
By Douglas PAPPIS [View]
[Download]

Abstract: A technique to actively balance the voltages on series-connected capacitors designated to split DC sources whose loads comprise power converters is presented. It performs such balancing dynamically, enabling the voltage equalization even for small capacitors under wide power and voltages ranges. Proposal consists on lightly controlling the power of one input capacitor for each pair, measuring their voltage difference and, based upon that, generating a single control signal. Thereby, it then controls the power drained individually from that capacitor, whilst the total load remains being supplied by the whole pair. The performance of the proposed capacitor voltage balancing control loop has been demonstrated by means of experimental results of a 300 V - 6 kW bipolar-buck (330 V - 1500 V supply).

   Model Predictive Control of Dual Inverter Respecting Temperature Limits of IGBTs
By Martin VOTAVA [View]
[Download]

Abstract: This paper deals with a new control system based on finite control set model predictive control designed for a dual voltage source inverter. The proposed control systems deals with three objectives, the first one is the output current control depending on the load current demands, the second part of the control system is balancing of power losses among the semiconductor devices using redundant switching states of the converter and the third part of the control system is dedicated for the thermal limitation and protection of the semiconductor devices. This protection is performed by power losses limitation calculated by a designed thermal model of the semiconductor devices using the measured temperature of the device baseplate. A simplified thermal network model is used for the converter output power limitation during its operation depending on the semiconductor temperature. The thermal protection of the semiconductor devices is ensured in two ways: (i) by reduction of the switching frequency, (ii) by reduction of the maximum output current. These control system parts are employed in a new multicritera cost function proposal which is described in detail.

   Model predictive current reference calculation for single-phase VSCs
By Joan-Marc RODRIGUEZ-BERNUZ [View]
[Download]

Abstract: This paper presents a model predictive strategy to generate optimal reference signals for single-phaseinverters. The reference signal is obtained from an optimisation problem, which can hold multiple objectivesand constraints over a defined time horizon. Specifically, the proposed strategy is designed to tradeoff harmonic distortion for instantaneous DC bus voltage ripple regulation without exceeding physicalsystem limitations.

   Spectrum Calculation Method for a Boost Converter with Chaotic PWM
By ZHICHANG YANG [View]
[Download]

Abstract: In this paper, an analytical calculation method of chaotic spectrum for DC-DC converters under CPWM is firstly proposed based on Fourier series. The proposed method can be employed to precisely calculate the spectrum of PWM waveforms under CPWM. Simulation and experimental results both verify the correctness of the proposed spectrum calculation method.

EPE 2016 - DS2e: Standard and Advanced Control Techniques for Power Converters
You are here: EPE Documents > 01 - EPE & EPE ECCE Conference Proceedings > EPE 2016 ECCE Europe - Conference > EPE 2016 - Topic 03: Measurement and Control > EPE 2016 - DS2e: Standard and Advanced Control Techniques for Power Converters
	[return to parent folder]

	Advanced Control Method for VSC-HVDC Systems Connected to Weak Grids By Omar JASIM	[View] [Download]
Abstract: This paper proposes a novel control method for modular multilevel converter (MMC) based high voltage direct current (HVDC) power transmission system connected to a very weak or strong AC system under balanced or unbalanced operating conditions. The control concept is developed based on no need for phase-locked loop (PLL) where the voltage source converter (VSC) is controlled directly in ABC frame. The proposed control scheme regulates the instantaneous active and reactive power independently at the Point of Common coupling (PCC). A Multi-Input-Multi-Output (MIMO) state space model has been derived in ABC frame for the MMC converter. An enhanced outer loop is presented for achieving a smooth transition between weak and strong AC network by providing reactive power support to the AC voltage at PCC and exchanging maximum amount of active power within the converter rating limits. Moreover, the controller is designed to tolerate for computational delays. The effectiveness of the proposed control is validated by simulations results.

	Capacitor voltage balance performance comparison of MMC-STATCOM using NLC and PS-PWM strategies during negative sequence current injection By Heverton PEREIRA	[View] [Download]
Abstract: This paper addresses the modular multilevel converter applied as a static synchronous compensator. The mainobjective of this work is to compare the converter performance considering two different submodule capacitorvoltage balancing strategies: nearest level control and phase-shifted pulse width modulation, during positive andnegative sequence current injection. Results of a 15 MVA MMC STATCOM show that the nearest level controlstrategy has lower average switching frequency compared to the phase-shifted pulse width modulation strategy,considering comparable submodule capacitance voltage ripple.

	Carrier-based PWM with Minimum Infinity Norm for Overmodulation Area of Five-Phase Converters By Tomas KOMRSKA	[View] [Download]
Abstract: Overmodulation area of five-phase converters is covered by space vector PWM methods above all. The paper proposes a carrier-based PWM modulator employing the minimum infinity-norm method which is able to synthesize an arbitrary voltage vector in both, aß and xy planes, respectively, which is advantageous besides the linear modulation area in the overmodulation zone as well. Thanks to the proposed optimization, the modulator is able to achieve a competitive modulation index in the overmodulation area while attenuating undesired harmonics.

	Control of Switching Frequency for Modular Multilevel Converters by a Variable Hysteresis Band Modulation By Sascha KUBERA	[View] [Download]
Abstract: The average switching frequency of the Modular Multilevel Converter (MMC) is a characteristic system parameter, which affects the losses of the converter system. Several investigations were done to reduce the switching frequency by applying different modulation strategies. Up to now the switching frequency is always an indirect and random outcome of the modulator and it is not directly controlled.Based on the known techniques for two-level converters a method is proposed to control the switching frequency in steady state operation of a MMC by varying the hysteresis band of the modulator. This allows design calculations with a well-defined average switching frequency, because the control guarantees the desired switching frequency in steady state operation.Simulation results from PSCAD/EMTDC show the proper work of the control loop in a HVDC transmission system model.

	Local Vector Current Controller and Current Clamp Minimisation By Robert BETZ	[View] [Download]
Abstract: This paper presents the Local Vector Control (LVC) algorithm that is applicable to power electronic systems. This controller does not differentiate between linear or non-linear systems and can operate, without change, in stationary or rotating reference frames. The performance of this current controller with particular emphasis on current clamp minimisation will be the paper's focus. A comparison between the LVC, PI and predictive dead-beat current controllers (PCC) is presented.

	LQ Control of Single-phase Converter with LCL Filter with Partially Observed State By Stepan BLAHA	[View] [Download]
Abstract: A linear-quadratic controller of a single-phase converter with LCL filter is designed. Since the full state is not directly observed, we design several observation models of the system and apply the Kalman filtering theory to obtain observes. In the tested configuration, we obtained good performance of the controller even with one voltage and one current sensor.

	Method for balancing capacitors voltages on split DC-links By Douglas PAPPIS	[View] [Download]
Abstract: A technique to actively balance the voltages on series-connected capacitors designated to split DC sources whose loads comprise power converters is presented. It performs such balancing dynamically, enabling the voltage equalization even for small capacitors under wide power and voltages ranges. Proposal consists on lightly controlling the power of one input capacitor for each pair, measuring their voltage difference and, based upon that, generating a single control signal. Thereby, it then controls the power drained individually from that capacitor, whilst the total load remains being supplied by the whole pair. The performance of the proposed capacitor voltage balancing control loop has been demonstrated by means of experimental results of a 300 V - 6 kW bipolar-buck (330 V - 1500 V supply).

	Model Predictive Control of Dual Inverter Respecting Temperature Limits of IGBTs By Martin VOTAVA	[View] [Download]
Abstract: This paper deals with a new control system based on finite control set model predictive control designed for a dual voltage source inverter. The proposed control systems deals with three objectives, the first one is the output current control depending on the load current demands, the second part of the control system is balancing of power losses among the semiconductor devices using redundant switching states of the converter and the third part of the control system is dedicated for the thermal limitation and protection of the semiconductor devices. This protection is performed by power losses limitation calculated by a designed thermal model of the semiconductor devices using the measured temperature of the device baseplate. A simplified thermal network model is used for the converter output power limitation during its operation depending on the semiconductor temperature. The thermal protection of the semiconductor devices is ensured in two ways: (i) by reduction of the switching frequency, (ii) by reduction of the maximum output current. These control system parts are employed in a new multicritera cost function proposal which is described in detail.

	Model predictive current reference calculation for single-phase VSCs By Joan-Marc RODRIGUEZ-BERNUZ	[View] [Download]
Abstract: This paper presents a model predictive strategy to generate optimal reference signals for single-phaseinverters. The reference signal is obtained from an optimisation problem, which can hold multiple objectivesand constraints over a defined time horizon. Specifically, the proposed strategy is designed to tradeoff harmonic distortion for instantaneous DC bus voltage ripple regulation without exceeding physicalsystem limitations.

	Spectrum Calculation Method for a Boost Converter with Chaotic PWM By ZHICHANG YANG	[View] [Download]
Abstract: In this paper, an analytical calculation method of chaotic spectrum for DC-DC converters under CPWM is firstly proposed based on Fourier series. The proposed method can be employed to precisely calculate the spectrum of PWM waveforms under CPWM. Simulation and experimental results both verify the correctness of the proposed spectrum calculation method.