EPE Association: EPE 2021 - Dialogue session - Renewable Energy Power Systems

EPE 2021 - Dialogue session - Renewable Energy Power Systems
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 - Dialogue session - Renewable Energy Power Systems

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   A three-phase transformerless Boost inverter for the reduction of common-mode leakage current in photovoltaic applications
By Georgios ORFANOUDAKIS [View]
[Download]

Abstract: Three-phase transformerless photovoltaic (PV) inverters with PV voltage step-up capability are widely used for integrating PV generation to the electric grid. A known issue with transformerless topologies is the generation of common-mode (CM) ground leakage currents. Several inverter topologies and modulation strategies have been proposed to suppress the CM currents below the limits set by relative standards. The proposed inverter topologies commonly have increased component count and lower efficiency than conventional three-phase inverters, while their modified modulation strategies commonly result in lower output voltage quality and DC-bus voltage utilization. This paper presents a new three-phase Boost PV inverter topology which achieves CM leakage current suppression by modifying the Boost converter instead of the three-phase inverter stage. The topology is formed simply with the addition of one diode in the Boost stage. The added diode losses have a minor effect on the overall conversion efficiency, while the inverter can be modulated with conventional modulation strategies, thus retaining a high output voltage/current quality. The structure and operating principle of the proposed topology are presented, and its effectiveness with respect to CM current suppression is demonstrated through simulation results in MATLAB/Simulink.

   Boost-in-the-Loop for Real-time Evaluation of Wind Turbines Based on PMSG
By Shahin HEDAYATI KIA [View]
[Download]

Abstract: This article studies the development of a boost-in-the-loop facility with the main aim of real-time evaluating of wind turbines having passive generator-side power converters in their systems. It relies on the implementation of some parts of the wind turbine structure models namely the wind turbine blades, the wind generator, and the three-phase diode-bridge rectifier in a real-time system. A programmable DC power supply connects the output voltage of diode-bridge, provided by the real-time model, to a one-level hardware boost converter where this latter supplies a resistive load. Furthermore, a maximum power point tracking algorithm is proposed and validated through experiments where the results illustrate the efficacy of the developed power-hardware-in-the-loop system.

   Clustering of electrical generators in a multirotor wind turbine with inertia emulation
By Rui ALVES [View]
[Download]

Abstract: An innovative control scheme of a multirotor wind turbine (MRWT) based on N parallelpermanent magnet synchronous generators connected to a single back-to-back converter ispresented, aiming at an overall cost and weight reduction of the system. This control solutionis based on the MPPT mode of operation, to maximize power extraction when in below ratedwind speed, together with standard vector current control. An inertia emulation controller wasadded to the model to provide primary frequency control to the network. Various simulationswere carried out to validate the model considering five rotors. Furthermore, a comparisonbetween the system behaviour and power extraction is performed against a MRWT withdedicated converters for each generator. Inertia emulation is also reproduced. Low voltage ridethroughwas validated by means of simulations. It was concluded that the clusteringconfiguration is robust and might be a suitable solution for a MRWT.

   Common mode voltage impact on wind turbine main shaft bearing
By Jian ZHAO [View]
[Download]

Abstract: Main shaft bearing is an important part of the wind turbine rotating system. But the bearing voltage, which is the voltage between the bearing and the main shaft, is the main reason for the downtime of the main shaft bearing. That is induced by the fast switching device of the converter and may cause bearing damage and electromagnetic interference (EMI) problems. Base on the practical test result of bearing current, common-mode voltage (CMV) of the converters is considered as the main source. In this paper, a circuit model is proposed to model the CMVtransmission path to the main shaft bearing. For further verification, a downsize wind turbine is built up in lab condition, different tests are launched to verify and improve the model.

   Development of Power Leveling System with Hybrid Energy Storage of LiB and FW
By Hiromi MORITA [View]
[Download]

Abstract: This paper proposed that a method of dividing the compensated power reference value for each energy storage system for the power leveling system using multiple energy storage systems used for the photovoltaic power generation system. This proposed method is effective for a power leveling system consisting of an energy storage system such as LiB whose output is small for its capacity and an energy storage system such as FW whose capacity is small for its output. The main purpose of controlling state of charge is to reduce the state of charge of energy storage systems, such as FW, which have a small capacity for the output, reaching the upper and lower limits of compensation. The fluctuation suppression effect obtained by demonstration test was 2.9×10^(-2), a decrease of 81 \% less than when nothing was done.

   EMI Filter Performance for Photovoltaic Applications Considering Termination Impedances
By Duc-Thanh DO [View]
[Download]

Abstract: This paper proposes an analytical approach to investigate attenuation characteristics for the performance of electromagnetic interference (EMI) filters. Since source and load impedances are unknown, effect of its degradation can only be observed by output measurement data. Based on a definition of insertion loss (see CISPR 17) and experimental data, the performance of propagation path can be analyzed. This approach can also predict possible variation of actual attenuation following termination impedances and parasitic components. Based on comprehensive results, mitigation disturbance can be used to clarify the EMI filter performance for small-scale photovoltaic applications.

   Impact of the total dc-link voltage ripple on the grid-side harmonics of a 3LNPC back-to-back converter employed in a medium voltage WECS
By Ioannis TSOUMAS [View]
[Download]

Abstract: The operation of two back-to-back three-level neutral point clamped (3LNPC) converters employed in a medium voltage (MV) wind energy conversion system (WECS) is analytically investigated. In particular, the harmonics that appear on the primary winding of the grid-side transformer due to oscillation of the dc-link voltage of the converters.

   Low-Frequency ripple influence in the P&O MPPT dynamics response applied in the single-stage DABSR DC-AC converter for interfacing PV to single-phase grid
By Daniel CHAVEZ ORIHUELA [View]
[Download]

Abstract: This paper proposes a novel strategy of control and modulation in an isolated single-stage Dual Active Bridge Series-Resonant (DABSR) DC-AC converter specifically for solar photovoltaic arrays connected to a single-phase grid (PV2SPG). The Perturb and Observe (P&O) maximum power point tracking (MPPT) algorithm is implemented and analyzed considering the influence of the low-frequency ripple on the PV side. Aiming to compensate the PV voltage, which varies with the temperature, a duty ratio (DR) control is introduced. Besides, the power flow is controlled by phase shift modulation. The DC-AC converter is compared with an analogous DABSR DC-DC converter that does not have the low-frequency ripple problem to validate the proposed control and modulation. The result simulations validate the proposed control and modulation.

   Scan-Dual-Mode Maximum Power Point Tracking Scheme for PV Systems Under Partially Shaded Conditions
By Rosalie ROUPHAEL [View]
[Download]

Abstract: The growing use of photovoltaic (PV) systems in urban environment and on all types of buildings forces their optimisation in terms of energy harvesting, complexity and cost. Solutions for this compromising issue target source/charge adaptation problem (DC/DC converters) and controller's command method (maximum power point tracking MPPT techniques). Besides, PV panels implementation has met another obstacle: shadows. The presence of non-uniform irradiation introduces additional MPPT difficulties such as having multiple local maximum power points (LMPPs). This paper proposes a novel MPPT technique for PV systems under partially shaded conditions. The algorithm controls a quadratic boost converter that presents the advantage of higher voltage gain ratio along with lower switching loss and voltage stress. First, a hybrid between an adaptive step P&O and an output voltage stabilization is developed as a new MPPT method for rapidly changing insolations. Then, a quick scan is included in a repetitive MPPT cycle to ensure tracking the global maximum (GMPP) among all local maxima.The architecture and the command algorithm boat the advantages of guaranteed effectiveness, high accuracy and robustness without additional advanced circuits or calculations. The efficiency and performance of the proposed method are proved for different shadow patterns considering all GMPP positions in MATLAB/Simulink environment.

EPE 2021 - Dialogue session - Renewable Energy Power Systems
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 - Dialogue session - Renewable Energy Power Systems
	[return to parent folder]

	A three-phase transformerless Boost inverter for the reduction of common-mode leakage current in photovoltaic applications By Georgios ORFANOUDAKIS	[View] [Download]
Abstract: Three-phase transformerless photovoltaic (PV) inverters with PV voltage step-up capability are widely used for integrating PV generation to the electric grid. A known issue with transformerless topologies is the generation of common-mode (CM) ground leakage currents. Several inverter topologies and modulation strategies have been proposed to suppress the CM currents below the limits set by relative standards. The proposed inverter topologies commonly have increased component count and lower efficiency than conventional three-phase inverters, while their modified modulation strategies commonly result in lower output voltage quality and DC-bus voltage utilization. This paper presents a new three-phase Boost PV inverter topology which achieves CM leakage current suppression by modifying the Boost converter instead of the three-phase inverter stage. The topology is formed simply with the addition of one diode in the Boost stage. The added diode losses have a minor effect on the overall conversion efficiency, while the inverter can be modulated with conventional modulation strategies, thus retaining a high output voltage/current quality. The structure and operating principle of the proposed topology are presented, and its effectiveness with respect to CM current suppression is demonstrated through simulation results in MATLAB/Simulink.

	Boost-in-the-Loop for Real-time Evaluation of Wind Turbines Based on PMSG By Shahin HEDAYATI KIA	[View] [Download]
Abstract: This article studies the development of a boost-in-the-loop facility with the main aim of real-time evaluating of wind turbines having passive generator-side power converters in their systems. It relies on the implementation of some parts of the wind turbine structure models namely the wind turbine blades, the wind generator, and the three-phase diode-bridge rectifier in a real-time system. A programmable DC power supply connects the output voltage of diode-bridge, provided by the real-time model, to a one-level hardware boost converter where this latter supplies a resistive load. Furthermore, a maximum power point tracking algorithm is proposed and validated through experiments where the results illustrate the efficacy of the developed power-hardware-in-the-loop system.

	Clustering of electrical generators in a multirotor wind turbine with inertia emulation By Rui ALVES	[View] [Download]
Abstract: An innovative control scheme of a multirotor wind turbine (MRWT) based on N parallelpermanent magnet synchronous generators connected to a single back-to-back converter ispresented, aiming at an overall cost and weight reduction of the system. This control solutionis based on the MPPT mode of operation, to maximize power extraction when in below ratedwind speed, together with standard vector current control. An inertia emulation controller wasadded to the model to provide primary frequency control to the network. Various simulationswere carried out to validate the model considering five rotors. Furthermore, a comparisonbetween the system behaviour and power extraction is performed against a MRWT withdedicated converters for each generator. Inertia emulation is also reproduced. Low voltage ridethroughwas validated by means of simulations. It was concluded that the clusteringconfiguration is robust and might be a suitable solution for a MRWT.

	Common mode voltage impact on wind turbine main shaft bearing By Jian ZHAO	[View] [Download]
Abstract: Main shaft bearing is an important part of the wind turbine rotating system. But the bearing voltage, which is the voltage between the bearing and the main shaft, is the main reason for the downtime of the main shaft bearing. That is induced by the fast switching device of the converter and may cause bearing damage and electromagnetic interference (EMI) problems. Base on the practical test result of bearing current, common-mode voltage (CMV) of the converters is considered as the main source. In this paper, a circuit model is proposed to model the CMVtransmission path to the main shaft bearing. For further verification, a downsize wind turbine is built up in lab condition, different tests are launched to verify and improve the model.

	Development of Power Leveling System with Hybrid Energy Storage of LiB and FW By Hiromi MORITA	[View] [Download]
Abstract: This paper proposed that a method of dividing the compensated power reference value for each energy storage system for the power leveling system using multiple energy storage systems used for the photovoltaic power generation system. This proposed method is effective for a power leveling system consisting of an energy storage system such as LiB whose output is small for its capacity and an energy storage system such as FW whose capacity is small for its output. The main purpose of controlling state of charge is to reduce the state of charge of energy storage systems, such as FW, which have a small capacity for the output, reaching the upper and lower limits of compensation. The fluctuation suppression effect obtained by demonstration test was 2.9×10^(-2), a decrease of 81 \% less than when nothing was done.

	EMI Filter Performance for Photovoltaic Applications Considering Termination Impedances By Duc-Thanh DO	[View] [Download]
Abstract: This paper proposes an analytical approach to investigate attenuation characteristics for the performance of electromagnetic interference (EMI) filters. Since source and load impedances are unknown, effect of its degradation can only be observed by output measurement data. Based on a definition of insertion loss (see CISPR 17) and experimental data, the performance of propagation path can be analyzed. This approach can also predict possible variation of actual attenuation following termination impedances and parasitic components. Based on comprehensive results, mitigation disturbance can be used to clarify the EMI filter performance for small-scale photovoltaic applications.

	Impact of the total dc-link voltage ripple on the grid-side harmonics of a 3LNPC back-to-back converter employed in a medium voltage WECS By Ioannis TSOUMAS	[View] [Download]
Abstract: The operation of two back-to-back three-level neutral point clamped (3LNPC) converters employed in a medium voltage (MV) wind energy conversion system (WECS) is analytically investigated. In particular, the harmonics that appear on the primary winding of the grid-side transformer due to oscillation of the dc-link voltage of the converters.

	Low-Frequency ripple influence in the P&O MPPT dynamics response applied in the single-stage DABSR DC-AC converter for interfacing PV to single-phase grid By Daniel CHAVEZ ORIHUELA	[View] [Download]
Abstract: This paper proposes a novel strategy of control and modulation in an isolated single-stage Dual Active Bridge Series-Resonant (DABSR) DC-AC converter specifically for solar photovoltaic arrays connected to a single-phase grid (PV2SPG). The Perturb and Observe (P&O) maximum power point tracking (MPPT) algorithm is implemented and analyzed considering the influence of the low-frequency ripple on the PV side. Aiming to compensate the PV voltage, which varies with the temperature, a duty ratio (DR) control is introduced. Besides, the power flow is controlled by phase shift modulation. The DC-AC converter is compared with an analogous DABSR DC-DC converter that does not have the low-frequency ripple problem to validate the proposed control and modulation. The result simulations validate the proposed control and modulation.

	Scan-Dual-Mode Maximum Power Point Tracking Scheme for PV Systems Under Partially Shaded Conditions By Rosalie ROUPHAEL	[View] [Download]
Abstract: The growing use of photovoltaic (PV) systems in urban environment and on all types of buildings forces their optimisation in terms of energy harvesting, complexity and cost. Solutions for this compromising issue target source/charge adaptation problem (DC/DC converters) and controller's command method (maximum power point tracking MPPT techniques). Besides, PV panels implementation has met another obstacle: shadows. The presence of non-uniform irradiation introduces additional MPPT difficulties such as having multiple local maximum power points (LMPPs). This paper proposes a novel MPPT technique for PV systems under partially shaded conditions. The algorithm controls a quadratic boost converter that presents the advantage of higher voltage gain ratio along with lower switching loss and voltage stress. First, a hybrid between an adaptive step P&O and an output voltage stabilization is developed as a new MPPT method for rapidly changing insolations. Then, a quick scan is included in a repetitive MPPT cycle to ensure tracking the global maximum (GMPP) among all local maxima.The architecture and the command algorithm boat the advantages of guaranteed effectiveness, high accuracy and robustness without additional advanced circuits or calculations. The efficiency and performance of the proposed method are proved for different shadow patterns considering all GMPP positions in MATLAB/Simulink environment.