EPE Association: EPE 2013 - LS1d: Converter Control, Current/Voltage Control

EPE 2013 - LS1d: Converter Control, Current/Voltage Control
You are here: EPE Documents > 01 - EPE & EPE ECCE Conference Proceedings > EPE 2013 ECCE Europe - Conference > EPE 2013 - Topic 06: Modulation strategies and specific control methods for static converters > EPE 2013 - LS1d: Converter Control, Current/Voltage Control

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   Comparison of Linear and Predictive Control Employing Different Current Reference Strategies for Unbalance Voltage Sources
By Salvador REVELO, Cesar SILVA [View]
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Abstract: This paper presents a comparison between a linear Proportional-Integral (PI) controller and a Finite Set Model Predictive Control (FS-MPC) for current control references in unbalance voltage conditions. Instantaneous active reactive control (IARC), balance positive sequence control (BPSC) and positive negative sequence control (PNSC) current references are evaluated. Experimental results are shown for the PNSC strategy and are compared with the simulation results. The current harmonic distortion in presence of unbalanced voltage is assessed.

   Impact of Modulation Schemes on the Power Capability of High Power Converters with Low Pulse Ratios
By Jie SHEN, Stefan SCHROEDER, Hanno STAGGE, Rik W. DE DONCKER [View]
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Abstract: The design of modulation schemes at low pulse ratios is a known topic. However, most of previous work has focused on Optimized Pulse Patterns, e.g. Selective Harmonic Elimination (SHE). For industrial applications, standard carrier modulators are still highly attractive in many cases. Unfortunately, few papers presented insightful studies on carrier modulators at extremely low pulse ratios. This paper covers this gap. At extremely low pulse ratios, several special phenomena of carrier modulators are observed. Their mechanisms are explained in detail. Moreover, a quantitative comparison between different carrier-based modulation schemes is presented. Based on that, several design criteria for modulators at low pulse ratios are proposed at the end.

   Self-commissioning Notch Filter for Active Damping in Three Phase LCL-filter Based Grid Converters
By Rafael PENA-ALZOLA, Marco LISERRE, Frede BLAABJERG, Tamas KEREKES [View]
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Abstract: LCL-filters are used to mitigate the harmonic current content in grid converters. The LCL-filter resonancemust be damped in order to avoid stability problems in the current control. Active damping avoidsresistors at the expense of increased control complexity. Large grid impedance variations can challengethe LCL-filter stability. Active damping by using a notch filter on the reference voltage for the modulatoris simple to implement and does not require additional sensors. With the notch frequency tuned for theresonant frequency the voltage reference does not contain any component susceptible of exciting theLCL-filter. However, the notch filter tuning requires considerable design effort and the variations in theresonance frequency limit the LCL-filter robustness. This paper proposes a simple tuning procedure forthe notch filter that results in proper robustness. In order to cope with the grid inductance variations itis proposed to estimate the resonance frequency by means of Fourier analysis. The Goertzel algorithm,instead of the FFT, is used to reduce the calculation and memory requirements. Thus, the proposedself-commissioning notch filter results robust and consumes little computational resources. Finally, theanalysis is validated with both simulation and experiments.

   Space-Vector-Modulated Three-level Z-source Hybrid Direct AC-AC Power Converter
By Francis EFFAH, Alan WATSON, Pat WHEELER, Jon CLARE, Liliana DE-LILLO [View]
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Abstract: The addition of Z-source components into the “source” of standard converters enables a boost function-ality without the need for additional switch. This relatively recent conversion concept can be extendedto the three-level two-stage matrix converter by inserting a single Z-source network into its intermediatedc-link. The topology formed is, therefore, physically not very different. However, its modulation isnot very straightforward if advantages like voltage buck-boost flexibility, minimum commutation count,and sinusoidal supply and load quantities are to be achieved simultaneously. This paper presents theprinciples of operation and the modified space vector modulation strategy that can achieve the above-mentioned advantages of the three-level Z-source hybrid direct ac-ac power converter as an attractivetopological alternative for ac-ac buck-boost energy conversion. The findings presented here have beenverified in simulations while experimental validation is currently under development.

EPE 2013 - LS1d: Converter Control, Current/Voltage Control
You are here: EPE Documents > 01 - EPE & EPE ECCE Conference Proceedings > EPE 2013 ECCE Europe - Conference > EPE 2013 - Topic 06: Modulation strategies and specific control methods for static converters > EPE 2013 - LS1d: Converter Control, Current/Voltage Control
	[return to parent folder]

	Comparison of Linear and Predictive Control Employing Different Current Reference Strategies for Unbalance Voltage Sources By Salvador REVELO, Cesar SILVA	[View] [Download]
Abstract: This paper presents a comparison between a linear Proportional-Integral (PI) controller and a Finite Set Model Predictive Control (FS-MPC) for current control references in unbalance voltage conditions. Instantaneous active reactive control (IARC), balance positive sequence control (BPSC) and positive negative sequence control (PNSC) current references are evaluated. Experimental results are shown for the PNSC strategy and are compared with the simulation results. The current harmonic distortion in presence of unbalanced voltage is assessed.

	Impact of Modulation Schemes on the Power Capability of High Power Converters with Low Pulse Ratios By Jie SHEN, Stefan SCHROEDER, Hanno STAGGE, Rik W. DE DONCKER	[View] [Download]
Abstract: The design of modulation schemes at low pulse ratios is a known topic. However, most of previous work has focused on Optimized Pulse Patterns, e.g. Selective Harmonic Elimination (SHE). For industrial applications, standard carrier modulators are still highly attractive in many cases. Unfortunately, few papers presented insightful studies on carrier modulators at extremely low pulse ratios. This paper covers this gap. At extremely low pulse ratios, several special phenomena of carrier modulators are observed. Their mechanisms are explained in detail. Moreover, a quantitative comparison between different carrier-based modulation schemes is presented. Based on that, several design criteria for modulators at low pulse ratios are proposed at the end.

	Self-commissioning Notch Filter for Active Damping in Three Phase LCL-filter Based Grid Converters By Rafael PENA-ALZOLA, Marco LISERRE, Frede BLAABJERG, Tamas KEREKES	[View] [Download]
Abstract: LCL-filters are used to mitigate the harmonic current content in grid converters. The LCL-filter resonancemust be damped in order to avoid stability problems in the current control. Active damping avoidsresistors at the expense of increased control complexity. Large grid impedance variations can challengethe LCL-filter stability. Active damping by using a notch filter on the reference voltage for the modulatoris simple to implement and does not require additional sensors. With the notch frequency tuned for theresonant frequency the voltage reference does not contain any component susceptible of exciting theLCL-filter. However, the notch filter tuning requires considerable design effort and the variations in theresonance frequency limit the LCL-filter robustness. This paper proposes a simple tuning procedure forthe notch filter that results in proper robustness. In order to cope with the grid inductance variations itis proposed to estimate the resonance frequency by means of Fourier analysis. The Goertzel algorithm,instead of the FFT, is used to reduce the calculation and memory requirements. Thus, the proposedself-commissioning notch filter results robust and consumes little computational resources. Finally, theanalysis is validated with both simulation and experiments.

	Space-Vector-Modulated Three-level Z-source Hybrid Direct AC-AC Power Converter By Francis EFFAH, Alan WATSON, Pat WHEELER, Jon CLARE, Liliana DE-LILLO	[View] [Download]
Abstract: The addition of Z-source components into the “source” of standard converters enables a boost function-ality without the need for additional switch. This relatively recent conversion concept can be extendedto the three-level two-stage matrix converter by inserting a single Z-source network into its intermediatedc-link. The topology formed is, therefore, physically not very different. However, its modulation isnot very straightforward if advantages like voltage buck-boost flexibility, minimum commutation count,and sinusoidal supply and load quantities are to be achieved simultaneously. This paper presents theprinciples of operation and the modified space vector modulation strategy that can achieve the above-mentioned advantages of the three-level Z-source hybrid direct ac-ac power converter as an attractivetopological alternative for ac-ac buck-boost energy conversion. The findings presented here have beenverified in simulations while experimental validation is currently under development.