EPE Association: EPE 2018 - DS2f: Renewable Energy Systems I

EPE 2018 - DS2f: Renewable Energy Systems I
You are here: EPE Documents > 01 - EPE & EPE ECCE Conference Proceedings > EPE 2018 ECCE Europe - Conference > EPE 2018 - Topic 05: Renewable Energy Power Systems > EPE 2018 - DS2f: Renewable Energy Systems I

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   A Low-Voltage Ride-Through Control Strategy for Two-Stage T-Type Three-Level Photovoltaic Inverters Limiting DC-Link Overvoltage and Grid-Side Overcurrent
By Xu CHEN [View]
[Download]

Abstract: To ensure the stable operation of grid-connected photovoltaic (PV) generation systems when grid voltage dips, the grid-connected inverters are required to have the low-voltage ride-through (LVRT) capability. Based on a two-stage grid-connected inverter which consists of a boost converter and a T-type three-level inverter, the effects of symmetric and asymmetric grid voltage dips on the PV grid-connected system with conventional control strategy is analyzed, and the conclusion that the main incentives of LVRT failure are dc-link overvoltage and grid-side overcurrent is drawn. In this paper, an improved control strategy to avoid LVRT failure for the two-stage grid-connected inverter is proposed. For grid synchronization under grid voltage dip, a dual second-order generalized integrator (DSOGI) pre-filtered based phase-locked loop is adopted. According to PV voltage control scheme during LVRT, a modified PV voltage reference generation method is interpreted, which can make the PV panels work at the point where the power balance is automatically achieved, and thus the dc-link overvoltage is limited. Then a full feedforward of point of common coupling (PCC) voltage is introduced, which can not only limit the overshoot of the grid-side current, but also eliminate its negative-sequence component under an asymmetric voltage dip. By using the proposed control strategies, the LVRT failure can be successfully avoided and the LVRT requirements can be met. The simulation results verify the effectiveness of these control strategies.

   Active Ripple Compensation Port for Single Phase Transformerless Photovoltaic Inverter
By Nachiketa DESHMUKH [View]
[Download]

Abstract: Transformerless topologies for grid feeding solar photovoltaic (PV) inverter have several advantagesincluding low cost, low weight and high efficiency. The instantaneous power to the grid pulsates atdouble the grid frequency. An energy storage element is needed to supply oscillatory component of power such that the PV power can be decoupled from the grid power. This is usually done using Aluminium Electrolytic Capacitors (AECs) of large value. Though AECs are appealing due to their high volumetric efficiency and low cost, they have low reliability and limited current ripple capability. This limits the life expectancy of PV inverter and reduces its reliability. This paper explores active power decoupling technique for transformerless PV inverter topology with leakage current suppression. The reduction in capacitance requirement enables use of high reliability ceramic or film capacitors. The proposed ripple compensation port achieves dual function of decoupling pulsating power and boosting dc-link voltage, in case of low solar PV voltage. The working principle of the circuit is discussed and validated with help of simulations in MATLAB/Simulink software package.

   Control Strategies for Modular Grid-tied DMPPT Systems Integrating Photovoltaic Generation and Battery Storage at Module Level
By Ramón LÓPEZ-ERAUSKIN [View]
[Download]

Abstract: This manuscript presents new control strategies for PV and battery integrated Distributed maximumpower point tracking (DMPPT) systems. The presented system shows increased performance underlarge mismatching conditions thanks to the adopted strategies: (i) an adaptive DC-bus voltage extendsthe MPPT operating range of the converters dedicated to control single photovoltaic panels and (ii) theintegration of batteries at module-level further compensates the output voltage level of the converters.A novel output voltage estimation is presented as well, providing full control of the converters' outputvoltages with reduced sensing circuitry. In addition, a sequential control that coordinates PV voltagesand the DC-bus voltage is addressed, as a first step to suitably couple the distributed and the centraltracking of the system.

   Grid-tied Modular and Scalable Photovoltaic Distributed Maximum Power Point Tracking System with Storage at Module Level Using Non-Isolated Three-Port Converter
By Ander GONZÁLEZ [View]
[Download]

Abstract: In this manuscript a new modular PV and storage system for grid-tied applications is presented. Eachmodule comprises a PV panel, a small battery pack and a power converter. The system is able to performdistributed MPPT at panel level with enlarged operating conditions thanks to the added storage.Different strategies to enlarge the MPPT capability are presented along with simulations that show theireffectiveness.

   Low Loss Converter System Applied for Series Connected Wind Farm by New Modulation Control
By Naoki KAWABATA [View]
[Download]

Abstract: Modified Trapezoidal Modulation is applied for voltage source converter (VSC) used for wind powergeneration. It reduces the switching loss of the VSC. The simulation feasibility study of the induction generatorsystem has shown that the cost of the converter system can be reduced. The MTM is effective to reduce theswitching loss in the VSC used for exciting the induction generator. The reduction of the total loss inthe VSC is about 30\%. However the generation of harmonic components may have some negativeeffects. They generate the torque ripple in the induction generator and may cause the fatigue collapsefrom the repeated oscillation of the shaft. In the previous investigation, the fixed value of the _ can befound to reduce the torque ripple. This paper shows that the existence of the PFC converter and othercircuits cause the change of the condition depending on the value of _ and the slip s of the inductiongenerator. It is shown by the simulation, that there are the optimum variables, _ and s.

   Novel High-Voltage High-Power DC-DC Converter for Offshore Wind Farms
By Takaharu ISHIBASHI [View]
[Download]

Abstract: This paper deals with offshore wind system with DC collector grid, in which a high-voltage (HV) DC-DC converter is utilized between the DC collector gird and HVDC transmission line. This study is focused on the circuit configuration of the HV DC-DC converter. Conventionally, a modular multilevel converter (MMC) is used for AC-DC conversion in HVDC systems. However, adopting the MMC topology for the HV DC-DC converter cannot achieve high efficiency because of hard switching. This paper proposes a novel configuration of a 1-GW ±25-kV/±350-kV dual-active bridge DC-DC converter for offshore wind system, which comprises two series-connected IGBTs to reduce the transformer weight and increase the efficiency. The proposed configuration can achieve the efficiency of 98.5\%.

   On-site Performance of a 3.4 MW Type 4 Wind Turbine During Grid Faults
By Pedro CATALÁN [View]
[Download]

Abstract: This paper addresses the capability of the 3.4MW SENVION wind turbine for providing an active power and dynamic voltage control during grid faults by injecting active and reactive currents, both in positive and negative sequence. The proposed control scheme complies with the most cutting-edge requirements of the grid codes, with a totally sequence-independent current control. The on-site performance of the FC NES 3.XM 3400LV2LSWC INGECONW is shown, as well as the effects current injection has on the grid voltage during the fault.

   Reliability Analysis of Micro-Inverter considering PV Panel Variations and Degradation Rates
By Elizaveta LIIVIK [View]
[Download]

Abstract: This paper analyzes the impact of PV module variations on the micro-inverter reliability. The evaluation results show a significant deviation in the micro-inverter reliability for different PV modules. Moreover, the PV module degradation impacts are also taken into consideration in the reliability assessment. Such information can be used to reduce the cost of the final designed micro-inverter and better match the PV application.

   The role of hydrogen, battery-electric vehicles and heat as flexibility option in future energy systems
By Kay BAREISS [View]
[Download]

Abstract: In this article we aim at understanding the role of different flexibility options in the future German energy supply system dominated by volatile renewable energy production. Specifically, the options power-to-heat (P2H) and power-to-gas (P2G) are contrasted with a possible flexibility added by a grid optimized charging and discharging process of battery electric vehicles (BEV). The basic assumptions are oriented on scenarios for the German energy supply of the year 2050, with an overall CO2-reduction of 80\% and 95\% with respect to 1990.

   Validation of a Wind Turbine Harmonic Model based on the Generic Type 4 Wind Turbine Standard
By Carlos RUIZ [View]
[Download]

Abstract: This paper presents the development and validation of a Wind Turbine (WT) harmonic model forharmonic analysis in power systems. For that purpose and based on standard WT generic models,some changes and the implementation of additional structures are proposed to represent the influenceof the wind turbine in the frequency domain. The validation of the model is done with a comparisonbetween the results obtained from the WT harmonic model implemented in Matlab/Simulink and anexperimental platform. The experimental results are performed on a test bench with a downscaleversion of the INGECON WIND MV100 commercial converter of Ingeteam manufacturer. Theharmonic emission is tested for two modulation strategies, the typical CB-PWM and a newsynchronous SHE-PWM based modulation. The results show good agreement between the model andthe real converter.

   Voltage Doubler Rectifier Application for an Isolated Photovoltaic Boost Converter
By Yusuke ZUSHI [View]
[Download]

Abstract: A boost module that consists of a phase shifted full bridge and a voltage doubler rectifier with a filter inductor is proposed. The investigation clarified the best trade-off between the efficiency and the output power as well as between the maximum output power and the boost ratio for photovoltaic application.

EPE 2018 - DS2f: Renewable Energy Systems I
You are here: EPE Documents > 01 - EPE & EPE ECCE Conference Proceedings > EPE 2018 ECCE Europe - Conference > EPE 2018 - Topic 05: Renewable Energy Power Systems > EPE 2018 - DS2f: Renewable Energy Systems I
	[return to parent folder]

	A Low-Voltage Ride-Through Control Strategy for Two-Stage T-Type Three-Level Photovoltaic Inverters Limiting DC-Link Overvoltage and Grid-Side Overcurrent By Xu CHEN	[View] [Download]
Abstract: To ensure the stable operation of grid-connected photovoltaic (PV) generation systems when grid voltage dips, the grid-connected inverters are required to have the low-voltage ride-through (LVRT) capability. Based on a two-stage grid-connected inverter which consists of a boost converter and a T-type three-level inverter, the effects of symmetric and asymmetric grid voltage dips on the PV grid-connected system with conventional control strategy is analyzed, and the conclusion that the main incentives of LVRT failure are dc-link overvoltage and grid-side overcurrent is drawn. In this paper, an improved control strategy to avoid LVRT failure for the two-stage grid-connected inverter is proposed. For grid synchronization under grid voltage dip, a dual second-order generalized integrator (DSOGI) pre-filtered based phase-locked loop is adopted. According to PV voltage control scheme during LVRT, a modified PV voltage reference generation method is interpreted, which can make the PV panels work at the point where the power balance is automatically achieved, and thus the dc-link overvoltage is limited. Then a full feedforward of point of common coupling (PCC) voltage is introduced, which can not only limit the overshoot of the grid-side current, but also eliminate its negative-sequence component under an asymmetric voltage dip. By using the proposed control strategies, the LVRT failure can be successfully avoided and the LVRT requirements can be met. The simulation results verify the effectiveness of these control strategies.

	Active Ripple Compensation Port for Single Phase Transformerless Photovoltaic Inverter By Nachiketa DESHMUKH	[View] [Download]
Abstract: Transformerless topologies for grid feeding solar photovoltaic (PV) inverter have several advantagesincluding low cost, low weight and high efficiency. The instantaneous power to the grid pulsates atdouble the grid frequency. An energy storage element is needed to supply oscillatory component of power such that the PV power can be decoupled from the grid power. This is usually done using Aluminium Electrolytic Capacitors (AECs) of large value. Though AECs are appealing due to their high volumetric efficiency and low cost, they have low reliability and limited current ripple capability. This limits the life expectancy of PV inverter and reduces its reliability. This paper explores active power decoupling technique for transformerless PV inverter topology with leakage current suppression. The reduction in capacitance requirement enables use of high reliability ceramic or film capacitors. The proposed ripple compensation port achieves dual function of decoupling pulsating power and boosting dc-link voltage, in case of low solar PV voltage. The working principle of the circuit is discussed and validated with help of simulations in MATLAB/Simulink software package.

	Control Strategies for Modular Grid-tied DMPPT Systems Integrating Photovoltaic Generation and Battery Storage at Module Level By Ramón LÓPEZ-ERAUSKIN	[View] [Download]
Abstract: This manuscript presents new control strategies for PV and battery integrated Distributed maximumpower point tracking (DMPPT) systems. The presented system shows increased performance underlarge mismatching conditions thanks to the adopted strategies: (i) an adaptive DC-bus voltage extendsthe MPPT operating range of the converters dedicated to control single photovoltaic panels and (ii) theintegration of batteries at module-level further compensates the output voltage level of the converters.A novel output voltage estimation is presented as well, providing full control of the converters' outputvoltages with reduced sensing circuitry. In addition, a sequential control that coordinates PV voltagesand the DC-bus voltage is addressed, as a first step to suitably couple the distributed and the centraltracking of the system.

	Grid-tied Modular and Scalable Photovoltaic Distributed Maximum Power Point Tracking System with Storage at Module Level Using Non-Isolated Three-Port Converter By Ander GONZÁLEZ	[View] [Download]
Abstract: In this manuscript a new modular PV and storage system for grid-tied applications is presented. Eachmodule comprises a PV panel, a small battery pack and a power converter. The system is able to performdistributed MPPT at panel level with enlarged operating conditions thanks to the added storage.Different strategies to enlarge the MPPT capability are presented along with simulations that show theireffectiveness.

	Low Loss Converter System Applied for Series Connected Wind Farm by New Modulation Control By Naoki KAWABATA	[View] [Download]
Abstract: Modified Trapezoidal Modulation is applied for voltage source converter (VSC) used for wind powergeneration. It reduces the switching loss of the VSC. The simulation feasibility study of the induction generatorsystem has shown that the cost of the converter system can be reduced. The MTM is effective to reduce theswitching loss in the VSC used for exciting the induction generator. The reduction of the total loss inthe VSC is about 30\%. However the generation of harmonic components may have some negativeeffects. They generate the torque ripple in the induction generator and may cause the fatigue collapsefrom the repeated oscillation of the shaft. In the previous investigation, the fixed value of the _ can befound to reduce the torque ripple. This paper shows that the existence of the PFC converter and othercircuits cause the change of the condition depending on the value of _ and the slip s of the inductiongenerator. It is shown by the simulation, that there are the optimum variables, _ and s.

	Novel High-Voltage High-Power DC-DC Converter for Offshore Wind Farms By Takaharu ISHIBASHI	[View] [Download]
Abstract: This paper deals with offshore wind system with DC collector grid, in which a high-voltage (HV) DC-DC converter is utilized between the DC collector gird and HVDC transmission line. This study is focused on the circuit configuration of the HV DC-DC converter. Conventionally, a modular multilevel converter (MMC) is used for AC-DC conversion in HVDC systems. However, adopting the MMC topology for the HV DC-DC converter cannot achieve high efficiency because of hard switching. This paper proposes a novel configuration of a 1-GW ±25-kV/±350-kV dual-active bridge DC-DC converter for offshore wind system, which comprises two series-connected IGBTs to reduce the transformer weight and increase the efficiency. The proposed configuration can achieve the efficiency of 98.5\%.

	On-site Performance of a 3.4 MW Type 4 Wind Turbine During Grid Faults By Pedro CATALÁN	[View] [Download]
Abstract: This paper addresses the capability of the 3.4MW SENVION wind turbine for providing an active power and dynamic voltage control during grid faults by injecting active and reactive currents, both in positive and negative sequence. The proposed control scheme complies with the most cutting-edge requirements of the grid codes, with a totally sequence-independent current control. The on-site performance of the FC NES 3.XM 3400LV2LSWC INGECONW is shown, as well as the effects current injection has on the grid voltage during the fault.

	Reliability Analysis of Micro-Inverter considering PV Panel Variations and Degradation Rates By Elizaveta LIIVIK	[View] [Download]
Abstract: This paper analyzes the impact of PV module variations on the micro-inverter reliability. The evaluation results show a significant deviation in the micro-inverter reliability for different PV modules. Moreover, the PV module degradation impacts are also taken into consideration in the reliability assessment. Such information can be used to reduce the cost of the final designed micro-inverter and better match the PV application.

	The role of hydrogen, battery-electric vehicles and heat as flexibility option in future energy systems By Kay BAREISS	[View] [Download]
Abstract: In this article we aim at understanding the role of different flexibility options in the future German energy supply system dominated by volatile renewable energy production. Specifically, the options power-to-heat (P2H) and power-to-gas (P2G) are contrasted with a possible flexibility added by a grid optimized charging and discharging process of battery electric vehicles (BEV). The basic assumptions are oriented on scenarios for the German energy supply of the year 2050, with an overall CO2-reduction of 80\% and 95\% with respect to 1990.

	Validation of a Wind Turbine Harmonic Model based on the Generic Type 4 Wind Turbine Standard By Carlos RUIZ	[View] [Download]
Abstract: This paper presents the development and validation of a Wind Turbine (WT) harmonic model forharmonic analysis in power systems. For that purpose and based on standard WT generic models,some changes and the implementation of additional structures are proposed to represent the influenceof the wind turbine in the frequency domain. The validation of the model is done with a comparisonbetween the results obtained from the WT harmonic model implemented in Matlab/Simulink and anexperimental platform. The experimental results are performed on a test bench with a downscaleversion of the INGECON WIND MV100 commercial converter of Ingeteam manufacturer. Theharmonic emission is tested for two modulation strategies, the typical CB-PWM and a newsynchronous SHE-PWM based modulation. The results show good agreement between the model andthe real converter.

	Voltage Doubler Rectifier Application for an Isolated Photovoltaic Boost Converter By Yusuke ZUSHI	[View] [Download]
Abstract: A boost module that consists of a phase shifted full bridge and a voltage doubler rectifier with a filter inductor is proposed. The investigation clarified the best trade-off between the efficiency and the output power as well as between the maximum output power and the boost ratio for photovoltaic application.