The steady growth of installed wind power together with the upscaling of the single wind turbine power capability has pushed the research and development of power converters toward full-scale power conversion, lowered cost pr kW, increased power density, and also the need for higher reliability. In this paper, power converter technologies are reviewed with focus on existing ones and on those that have potential for higher power but which have not been yet adopted due to the important risk associated with the high-power industry. The power converters are classified into single- and multicell topologies, in the latter case with attention to series connection and parallel connection either electrical or magnetic ones (multiphase/windings machines/transformers). It is concluded that as the power level increases in wind turbines, medium-voltage power converters will be a dominant power converter configuration, but continuously cost and reliability are important issues to be addressed.

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Power Electronics Converters for Wind Turbine Systems

The steady growth of installed wind power which reached 200 GW capacity in 2010, together with the up-scaling of the single wind turbine power capability - 7 MW's has been announced by manufacturers - has pushed the research and development of power converters towards full scale power conversion, lowered cost pr kW, and increased power density and the need for higher reliability. Substantial efforts are made to comply with the more stringent grid codes, especially grid faults ride-through and reactive power injection, which challenges power converter topologies, because the need for crowbar protection and/or power converter over-rating has been seen in the case of a doubly-fed induction generator. In this paper, power converter technologies are reviewed with focus on single/multi-cell power converter topologies. Further, case studies on the Low Voltage Ride Through demand to power converter technology are presented including a discussion on reliability. It is concluded that as the power level increases in wind turbines, medium voltage power converters will be a dominant power converter configuration.

/pdf/power-electronics-converters-for-wind-turbine-systems-3onpe4kum9.pdf

Power electronics converters for wind turbine systems

In the field of wind energy generation particular interest has been focused in recent years on distributed generation through small wind-turbines (power unit 200 kW) because of their limited size and lower environmental impact. The field of small generation was dominated by the use of asynchronous generators directly connected to the grid, while recently permanent magnet synchronous generators (PMSG) with power converter, either partially or fully controlled, became popular. This paper reviews the control issues related to these small wind-turbine systems: generator torque control, speed/position estimation, pitch control, braking chopper control, dc/dc converter control, and grid converter control. Specific issues for small wind-turbines arise in the wind energy extraction optimization and limitation and in the innovative concept of “universal” wind-turbine operation, that leads these system to operate grid-connected, standalone or in load supporting mode.

A Survey of Control Issues in PMSG-Based Small Wind-Turbine Systems

The growing trends in wind energy technology are motivating the researchers to work in this area with the aim towards the optimization of the energy extraction from the wind and the injection of the quality power into the grid. Over the last few years, wind generators based on permanent magnet synchronous machines (PMSMs) are becoming the most popular solution for the modern wind energy conversion systems (WECSs). This paper presents a concise review of the grid-integrated WECSs employing permanent magnet synchronous generators (PMSGs). It reviews the trends in converter topologies, control methodologies, and methods for maximum energy extraction in PMSG based WECSs, which have been reported in various research literatures primarily in reputed research journals and transactions during last few years. It also presents an overview to the grid interconnection issues related to output power smoothing and reactive power control in addition to fault-ride-through (FRT) and grid support capabilities of PMSG based WECSs. This review article will serve the researchers working in the area of grid-integrated PMSG based WECSs in the exploration of trends, developments and challenges in the past research works and in finding out the relevant references for their research work.

Grid-integrated permanent magnet synchronous generator based wind energy conversion systems: A technology review

This paper proposes the use of a three-phase high-frequency semicontrolled rectifier for wind energy conversion systems based on permanent magnet generators. The main advantages of the topology are: simplicity, since all active switches are connected to a common point, robustness, as short-circuit through a leg is not possible, and high efficiency due to reduced number of elements. As a disadvantage, higher but acceptable total harmonic distortion of the generator currents results. The complete operation of the converter and theoretical analysis are presented. Additionally, a single-phase pulsewidth modulation inverter is also employed in the grid connection. Experimental results on 5-kW prototype are presented and discussed.

A Three-Phase High-Frequency Semicontrolled Rectifier for PM WECS

The wind energy system presented in this paper uses a permanent magnet generator connected to a three- phase semi-controlled rectifier. Although an acceptable THD and power factor result, the proposed converter is simple, cheaper, and robust. Additionally, a single-phase PWM inverter is also employed in the grid connection. The inverter uses a double hysteresis in the control of the current injected in the grid, what implies reduced switching losses. Analysis and partial experimental results are presented for a 5 kW prototype. At the final version of this paper, a more detailed theoretical analysis, simulation results, as well as experimental results at rated power are supposed to be presented.

A variable speed wind energy conversion system connected to the grid for small wind generator

This paper presents the theoretical analysis of the three-phase zero voltage switching pulsewidth modulation dc-dc converter associated with a double Wye connected rectifier, delta primary, using a special switching scheme in order to maintain equilibrium among the currents through the output filters. The operating stages are described and the simulation and experimental results of a 6-kW prototype are presented

A Three-Phase ZVS PWM DC–DC Converter Associated With a Double-Wye Connected Rectifier, Delta Primary

In this paper it is proposed a new topology of three-phase controlled rectifier feasible for high power wind energy conversion systems (WECS). This rectifier is based on the bridgeless rectifier, uses six wires of the generator, and allows the operation with high power factor, increasing the generator efficiency. One Cycle Control (OCC), which avoids the need of sinusoidal reference signals, was used in the rectifier control. This study is then concerned with the operation principle and experimental results obtained from a 5 kVA prototype.

A novel three-phase rectifier with high power factor for wind energy conversion systems

The study of a topology resulting from the combination of two forward structures attached to a single transformer core is presented in this paper, as a dual active bridge converter is obtained. In order to reduce the switching losses and the electromagnetic interference, a soft commutation cell, which provides zero-voltage commutation of the main switches for the entire load range, is implemented. Besides, the auxiliary switches are zero-current turned on and zero-current, zero-voltage turned off. This converter reduces the voltage over the main switches to half of the input voltage, employing only four switches and an additional transformer winding when compared to the full-bridge converter. The analysis of the circuit is carried out, and experimental results obtained from a prototype are also presented to support the theoretical assumptions.

Carlos Elmano de Alencar e Silva

Papers

A Three-Phase High-Frequency Semicontrolled Rectifier for PM WECS

A variable speed wind energy conversion system connected to the grid for small wind generator

A Three-Phase ZVS PWM DC–DC Converter Associated With a Double-Wye Connected Rectifier, Delta Primary

A novel three-phase rectifier with high power factor for wind energy conversion systems

Analysis, Design, and Experimentation of a Double Forward Converter With Soft Switching Characteristics for All Switches