A new DC link voltage boost scheme of IGBT inverters for wind energy extraction

This paper presents a new DC-link voltage boost method for adequate voltage coordination in grid-connected wind energy conversion inverter systems using insulated-gate bipolar transistors (IGBTs). The method provides a simple structure to solve DC-link voltage shortage problem at low winds by adding one switch between one of rectifier input legs and the middle point of the DC link reservoir capacitor. The switch, turned on at low winds, can boost the DC link voltage up to a double value compared to the situation without the switch. Consequently, a double voltage rectifier is used for this method. While the switch is turned off at high winds, the system brings the DC link voltage back to the normal to eliminate frequent overvoltage protection. The double voltage rectifier method can make more wind energy extraction at low winds than that without it. However, it brings an unsymmetrical operation to the turbine generator, thus resulting in a mechanical vibration of the wind turbine. To solve the unsymmetrical operation problem, a symmetrical double voltage rectifier is proposed. In this paper, both methods are described. The computer simulation results on both methods are presented.