EPE Association: EPE 2021 - Power Electronics in Renewables

EPE 2021 - Power Electronics in Renewables
You are here: EPE Documents > 01 - EPE & EPE ECCE Conference Proceedings > EPE 2021 ECCE Europe - Conference > EPE 2021 - Topic 06: Grids, Smart Grids, AC & DC > EPE 2021 - Power Electronics in Renewables

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   A Parallel Voltage Source Converter and Diode Rectifier PMSM Drive Concept for Decoupling the Thermal Cycles in the Machine-Side Converter of an Airborne Wind E
By Bakr BAGABER [View]
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Abstract: Pumping cycle (PC) Airborne wind energy systems (AWES) are novel wind turbines capable of fostering wind fields at high altitudes. The unique load profile of PC-AWES creates strong thermal cycles within the machine-side voltage source converter (VSC) which affect its lifetime. In this work, a novel drive concept comprising a voltage source converter paralleled with a passive diode rectifier (DR) is proposed to decouple and reduce the impact of those thermal cycles. The results suggest that this approach combined with an adjusted flight control of the kite and a reduced switching frequency can scale down the required IGBT chip area for a target lifetime of 20 years by 63\%, and the diode chip area by 18\%. The losses at nominal load are also reduced by 30\%.

   Full-SiC Flying Capacitor Boost Converter for 1500 V multi-string PV inverter
By Gaëtan PEREZ [View]
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Abstract: Flying capacitor converters are not widely used in PV applications, however they could bring interesting performances. The design of a three-level flying capacitor DC/DC converter is then studied in this paper, the objective being the realization of the first stage (20 kW DC/DC booster) of a two stages 1500 VOC multi-string inverter. The efficiency being critical for both stages in order not to penalize the overall efficiency, technical choices leading to the DC/DC converter realization have been conducted to reach a high peak efficiency (sup.99.5\%). The analytical calculations in this paper have shown that the use of SiC devices allows to reach high efficiencies with higher power densities (higher switching frequency) than with Si devices. The realization of a full-SiC 2x 20 kW DC/DC converter is discussed in this paper, the peak efficiency of 99.55\% experimentally measured is in accordance with our predictions.

   High Step-Up Converter for Regeneration of Photovoltaic Cells Affected by Potential Induced Degradation
By Alex MIRTCHEV [View]
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Abstract: In this paper a high step-up AC-DC converter is proposed, for regenerating photovoltaic (PV) cells that have been degraded due to the Potential Induced Degradation (PID) phenomenon. A description of the PID is presented and the fundamental technique to counteract the phenomenon is explained. A practical, easy and safe solution is suggested, using a power converter, with multiple output voltage stages for universal use in photovoltaic (PV) parks of different scale. Moreover, with the proposed plug & play solution the PID effect can be artificially created, to study the degradation effect under controlled conditions. Experimental tests with maximum output voltage of 1kV were conducted to verify the proof-of-concept, both in creating as well as reverting the PID phenomenon.

   Synchronous Reference Frame current control of Aalborg-type PV inverters
By Georgios ORFANOUDAKIS [View]
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Abstract: Transformerless photovoltaic (PV) inverters with voltage step-up capability are currently the preferred interface for integrating PV generation to a single phase of the electric grid. Among the different topologies employed for such inverters, dual-mode time-sharing topologies offer high conversion efficiencies, but present control challenges that can result in significant grid current distortion. Existing control approaches operate in the stationary reference frame and use different controllers for the Buck and Boost modes of operation. This paper presents a new current control approach for Aalborg-type Buck in Buck, Boost in Boost PV inverters, which operates in the Synchronous Reference Frame and uses a common controller for Buck and Boost operation. The proposed method achieves high output current quality even at unfavourable conditions of low PV voltage and/or power levels. Simulation results in MATLAB-Simulink are presented to illustrate that it can reduce the Total Harmonic Distortion (THD) of the grid current by two to three times as compared to the existing alternative.

EPE 2021 - Power Electronics in Renewables
You are here: EPE Documents > 01 - EPE & EPE ECCE Conference Proceedings > EPE 2021 ECCE Europe - Conference > EPE 2021 - Topic 06: Grids, Smart Grids, AC & DC > EPE 2021 - Power Electronics in Renewables
	[return to parent folder]

	A Parallel Voltage Source Converter and Diode Rectifier PMSM Drive Concept for Decoupling the Thermal Cycles in the Machine-Side Converter of an Airborne Wind E By Bakr BAGABER	[View] [Download]
Abstract: Pumping cycle (PC) Airborne wind energy systems (AWES) are novel wind turbines capable of fostering wind fields at high altitudes. The unique load profile of PC-AWES creates strong thermal cycles within the machine-side voltage source converter (VSC) which affect its lifetime. In this work, a novel drive concept comprising a voltage source converter paralleled with a passive diode rectifier (DR) is proposed to decouple and reduce the impact of those thermal cycles. The results suggest that this approach combined with an adjusted flight control of the kite and a reduced switching frequency can scale down the required IGBT chip area for a target lifetime of 20 years by 63\%, and the diode chip area by 18\%. The losses at nominal load are also reduced by 30\%.

	Full-SiC Flying Capacitor Boost Converter for 1500 V multi-string PV inverter By Gaëtan PEREZ	[View] [Download]
Abstract: Flying capacitor converters are not widely used in PV applications, however they could bring interesting performances. The design of a three-level flying capacitor DC/DC converter is then studied in this paper, the objective being the realization of the first stage (20 kW DC/DC booster) of a two stages 1500 VOC multi-string inverter. The efficiency being critical for both stages in order not to penalize the overall efficiency, technical choices leading to the DC/DC converter realization have been conducted to reach a high peak efficiency (sup.99.5\%). The analytical calculations in this paper have shown that the use of SiC devices allows to reach high efficiencies with higher power densities (higher switching frequency) than with Si devices. The realization of a full-SiC 2x 20 kW DC/DC converter is discussed in this paper, the peak efficiency of 99.55\% experimentally measured is in accordance with our predictions.

	High Step-Up Converter for Regeneration of Photovoltaic Cells Affected by Potential Induced Degradation By Alex MIRTCHEV	[View] [Download]
Abstract: In this paper a high step-up AC-DC converter is proposed, for regenerating photovoltaic (PV) cells that have been degraded due to the Potential Induced Degradation (PID) phenomenon. A description of the PID is presented and the fundamental technique to counteract the phenomenon is explained. A practical, easy and safe solution is suggested, using a power converter, with multiple output voltage stages for universal use in photovoltaic (PV) parks of different scale. Moreover, with the proposed plug & play solution the PID effect can be artificially created, to study the degradation effect under controlled conditions. Experimental tests with maximum output voltage of 1kV were conducted to verify the proof-of-concept, both in creating as well as reverting the PID phenomenon.

	Synchronous Reference Frame current control of Aalborg-type PV inverters By Georgios ORFANOUDAKIS	[View] [Download]
Abstract: Transformerless photovoltaic (PV) inverters with voltage step-up capability are currently the preferred interface for integrating PV generation to a single phase of the electric grid. Among the different topologies employed for such inverters, dual-mode time-sharing topologies offer high conversion efficiencies, but present control challenges that can result in significant grid current distortion. Existing control approaches operate in the stationary reference frame and use different controllers for the Buck and Boost modes of operation. This paper presents a new current control approach for Aalborg-type Buck in Buck, Boost in Boost PV inverters, which operates in the Synchronous Reference Frame and uses a common controller for Buck and Boost operation. The proposed method achieves high output current quality even at unfavourable conditions of low PV voltage and/or power levels. Simulation results in MATLAB-Simulink are presented to illustrate that it can reduce the Total Harmonic Distortion (THD) of the grid current by two to three times as compared to the existing alternative.