EPE Association: EPE 2016 - DS1f: Wind Energy System

EPE 2016 - DS1f: Wind Energy System
You are here: EPE Documents > 01 - EPE & EPE ECCE Conference Proceedings > EPE 2016 ECCE Europe - Conference > EPE 2016 - Topic 05: Renewable Energy Power Systems > EPE 2016 - DS1f: Wind Energy System

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   A High-Power DC-DC Converter based Dual Active Bridge for MVDC Grids on Offshore Wind Farms
By YOUNGSIL LEE [View]
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Abstract: This paper presents the steady-state analysis of a high power step-up DC-DC converter based three-phase dual active bridge (3DAB) for use as a medium voltage (MV) DC-DC collector of offshore wind farms. An optimization procedure for a high-power medium frequency transformer is explained and moreover, a design of an optimal control phase shift angle is explained and verified through simulation. The comparisons with two scenarios are presented: 4MW converters for power conversion from low dc voltage (LVDC) of the wind turbine output terminal to 40kV MVDC grid of offshore wind farms. The proposed 3DAB DC-DC converter is investigated for the given scenarios in terms of losses of the semi-conductors and the magnetic part as well as the quantity of semi-conductors.

   Analysis of the Influence of Different Cable Modelling for DC Series Offshore Wind Farm
By Haibo ZHANG [View]
[Download]

Abstract: In this paper, a dc series offshore wind farm with an onshore modular multilevel converter (MMC) is presented with consideration of different cable models. Normally, the dc cable is represented either by a small capacitance or by pi-sections, which implies that the frequency-dependent effects of the HVDC cable is neglected. One should be carefully when using these cable models for high frequency simulations, especially for dc seires offshore wind farm, whose topology forms a resonance circuit and consequently, accurate model of cable should be adopted to correctly represent the transient characteristic of the HVDC transmission system. This paper shows that the two most common lumped parameter types of DC cable model: small capacitance and pi-section model are unable to provide equivalent damping effect as the Wideband cable model or universal line model (ULM). The Wideband model is suitable for EMT analysis while its distributed parameters make it impossible to be transferred into a state-space representation.This paper first introduces the topology of a DC series offshore wind farm. Then the resonance characteristic of the wind farm topology is analysed based on different cable models. Finally the offshore wind farm is simulated with these three types of cable models and controlled by modular multilevel converter (MMC).

   Characterization of diode valve in medium voltage DC/DC converter for wind turbines
By CATALIN DINCAN [View]
[Download]

Abstract: This paper proposes a methodology for characterization of medium voltage (MV), medium frequency (MF) rectifier diode valve. The intended application is for 10MW dc/dc converters used in DC offshore wind turbines. Sensitivity to semiconductor component parameter variation, snubber component tolerance, influence of temperature and stray capacitance are analyzed. It is concluded that the largest impact on sensitivity is given by reverse recovery charge variation and differences of temperature between adjacent devices.

   Modularity in Wind Turbine Generator Systems - Opportunities and Challenges
By Udai SHIPURKAR [View]
[Download]

Abstract: Although the reliability of wind turbines have improved over time, there is still considerable interest inimproving their availability. As the generator system has a sizeable contribution to the overall failure ratesof turbines, it is important to consider methods of reducing the effects of these failures on the availabilityof turbines. This paper examines modular concepts for wind turbine generator systems from the point ofview of increasing the availability of wind turbines. It explores the modularities possible in wind turbinegenerator systems at different layers, i.e. the functional and the physical layer. The paper also attempts tohighlight some opportunities and challenges in including modularity in these layers.

   Reduced Distortion and Increased Availability in Wind Turbines Through Load Dependent Operation of Parallel Inverter Units with Variable DC Link Voltage
By Johannes ADLER [View]
[Download]

Abstract: A new control concept for inverter systems in wind turbines is proposed. Thereby only as many parallel connected inverter units as needed are activated to feed in the momentary generated power into the grid. Each inverter unit is equipped with an individual controller without additional communication between the inverter units. The load dependent activation and deactivation of inverter units is controlled by the use of a variable DC link voltage. The proposed control strategy reduces the total harmonic distortion in part load operation significantly and adds additional redundancy in case of failures in any of the inverter units to the whole inverter system. Arising zero sequence currents between the inverter units are effectively reduced by controlling the switching frequencies of the inverter units. The new control strategy is studied for three parallel connected grid sided inverter units in simulations as well as on a 20.7 kVA laboratory test setup.

   Self-excitation systems of a synchronous generator with a bipolar and unipolar PWM DC-DC converters
By Anait GRIGORYAN [View]
[Download]

Abstract: Models of Synchronous Generators with PWM DC-DC converter and Self-Excitation Systems have been designed. Calculations have shown that the unipolar PWM DC-DC converter in some modes shortly excludes from the voltage regulation process. The bipolar PWM converter effectively affects the generator and consequently enhances the system operation speed. The bipolar PWM converter uses the energy recovery in exciter as a short-circuit protection. The unipolar DC-DC converter uses explosive fuse and dumping resistor as a short-circuit protection.

   Six-Phase Active PWM Rectifier with Synchronous Frame Reference Control
By SAMIR AHMAD MUSSA [View]
[Download]

Abstract: Poly-phase systems have been used for many years in machines and recently in wind power generations. Typically, this system employs diode rectifiers, however, it may be improved employing active rectifier. Considering it, this paper proposesa six-phase active rectifier topology controlled in synchronous frame reference. Results were validated by simulation.

   The Application of the Modular Multilevel Matrix Converter in High-Power Wind Energy Conversion Systems
By Matias DIAZ [View]
[Download]

Abstract: The trend in wind turbines has shown an ongoing power rating growth, reaching sizes up to 10 MW. Multilevel converters have therefore become a favourable solution for Multi-MW Wind Energy Conversion Systems (WECSs), due to high efficiency, reliability, controllability and the ability to reach high power/voltage ratings. Moreover, stringent grid codes to regulate the connection of WECSs to the electrical networks have been developed in countries with a high penetration of wind energy. In this context, this paper introduces the novel application of the Modular Multilevel Matrix Converter for interfacing Multi-MW Wind Turbines to provide decoupled input-output regulation, variable speed operation and fulfilment of modern grid codes.

EPE 2016 - DS1f: Wind Energy System
You are here: EPE Documents > 01 - EPE & EPE ECCE Conference Proceedings > EPE 2016 ECCE Europe - Conference > EPE 2016 - Topic 05: Renewable Energy Power Systems > EPE 2016 - DS1f: Wind Energy System
	[return to parent folder]

	A High-Power DC-DC Converter based Dual Active Bridge for MVDC Grids on Offshore Wind Farms By YOUNGSIL LEE	[View] [Download]
Abstract: This paper presents the steady-state analysis of a high power step-up DC-DC converter based three-phase dual active bridge (3DAB) for use as a medium voltage (MV) DC-DC collector of offshore wind farms. An optimization procedure for a high-power medium frequency transformer is explained and moreover, a design of an optimal control phase shift angle is explained and verified through simulation. The comparisons with two scenarios are presented: 4MW converters for power conversion from low dc voltage (LVDC) of the wind turbine output terminal to 40kV MVDC grid of offshore wind farms. The proposed 3DAB DC-DC converter is investigated for the given scenarios in terms of losses of the semi-conductors and the magnetic part as well as the quantity of semi-conductors.

	Analysis of the Influence of Different Cable Modelling for DC Series Offshore Wind Farm By Haibo ZHANG	[View] [Download]
Abstract: In this paper, a dc series offshore wind farm with an onshore modular multilevel converter (MMC) is presented with consideration of different cable models. Normally, the dc cable is represented either by a small capacitance or by pi-sections, which implies that the frequency-dependent effects of the HVDC cable is neglected. One should be carefully when using these cable models for high frequency simulations, especially for dc seires offshore wind farm, whose topology forms a resonance circuit and consequently, accurate model of cable should be adopted to correctly represent the transient characteristic of the HVDC transmission system. This paper shows that the two most common lumped parameter types of DC cable model: small capacitance and pi-section model are unable to provide equivalent damping effect as the Wideband cable model or universal line model (ULM). The Wideband model is suitable for EMT analysis while its distributed parameters make it impossible to be transferred into a state-space representation.This paper first introduces the topology of a DC series offshore wind farm. Then the resonance characteristic of the wind farm topology is analysed based on different cable models. Finally the offshore wind farm is simulated with these three types of cable models and controlled by modular multilevel converter (MMC).

	Characterization of diode valve in medium voltage DC/DC converter for wind turbines By CATALIN DINCAN	[View] [Download]
Abstract: This paper proposes a methodology for characterization of medium voltage (MV), medium frequency (MF) rectifier diode valve. The intended application is for 10MW dc/dc converters used in DC offshore wind turbines. Sensitivity to semiconductor component parameter variation, snubber component tolerance, influence of temperature and stray capacitance are analyzed. It is concluded that the largest impact on sensitivity is given by reverse recovery charge variation and differences of temperature between adjacent devices.

	Modularity in Wind Turbine Generator Systems - Opportunities and Challenges By Udai SHIPURKAR	[View] [Download]
Abstract: Although the reliability of wind turbines have improved over time, there is still considerable interest inimproving their availability. As the generator system has a sizeable contribution to the overall failure ratesof turbines, it is important to consider methods of reducing the effects of these failures on the availabilityof turbines. This paper examines modular concepts for wind turbine generator systems from the point ofview of increasing the availability of wind turbines. It explores the modularities possible in wind turbinegenerator systems at different layers, i.e. the functional and the physical layer. The paper also attempts tohighlight some opportunities and challenges in including modularity in these layers.

	Reduced Distortion and Increased Availability in Wind Turbines Through Load Dependent Operation of Parallel Inverter Units with Variable DC Link Voltage By Johannes ADLER	[View] [Download]
Abstract: A new control concept for inverter systems in wind turbines is proposed. Thereby only as many parallel connected inverter units as needed are activated to feed in the momentary generated power into the grid. Each inverter unit is equipped with an individual controller without additional communication between the inverter units. The load dependent activation and deactivation of inverter units is controlled by the use of a variable DC link voltage. The proposed control strategy reduces the total harmonic distortion in part load operation significantly and adds additional redundancy in case of failures in any of the inverter units to the whole inverter system. Arising zero sequence currents between the inverter units are effectively reduced by controlling the switching frequencies of the inverter units. The new control strategy is studied for three parallel connected grid sided inverter units in simulations as well as on a 20.7 kVA laboratory test setup.

	Self-excitation systems of a synchronous generator with a bipolar and unipolar PWM DC-DC converters By Anait GRIGORYAN	[View] [Download]
Abstract: Models of Synchronous Generators with PWM DC-DC converter and Self-Excitation Systems have been designed. Calculations have shown that the unipolar PWM DC-DC converter in some modes shortly excludes from the voltage regulation process. The bipolar PWM converter effectively affects the generator and consequently enhances the system operation speed. The bipolar PWM converter uses the energy recovery in exciter as a short-circuit protection. The unipolar DC-DC converter uses explosive fuse and dumping resistor as a short-circuit protection.

	Six-Phase Active PWM Rectifier with Synchronous Frame Reference Control By SAMIR AHMAD MUSSA	[View] [Download]
Abstract: Poly-phase systems have been used for many years in machines and recently in wind power generations. Typically, this system employs diode rectifiers, however, it may be improved employing active rectifier. Considering it, this paper proposesa six-phase active rectifier topology controlled in synchronous frame reference. Results were validated by simulation.

	The Application of the Modular Multilevel Matrix Converter in High-Power Wind Energy Conversion Systems By Matias DIAZ	[View] [Download]
Abstract: The trend in wind turbines has shown an ongoing power rating growth, reaching sizes up to 10 MW. Multilevel converters have therefore become a favourable solution for Multi-MW Wind Energy Conversion Systems (WECSs), due to high efficiency, reliability, controllability and the ability to reach high power/voltage ratings. Moreover, stringent grid codes to regulate the connection of WECSs to the electrical networks have been developed in countries with a high penetration of wind energy. In this context, this paper introduces the novel application of the Modular Multilevel Matrix Converter for interfacing Multi-MW Wind Turbines to provide decoupled input-output regulation, variable speed operation and fulfilment of modern grid codes.