Research On Excitation System Technology Of Doubly-fed Wind Power Generator

In recent years, wind power has drawn increasing attention, while the double-fed wind power generation attracts more attention because of its superior to traditional wind power generation. Because of wind energy has randomness and instability, so it can have an bad effect on the application of wind power. In order to adjust active power balance, add energy-storing device in the wind power generator system. Different from the traditional way,the paper makes energy-storing device combine with the excitation system in the rotor side of the double-fed wind power generation. The energy-storing device combines with DC bus through charging and discharging circuit. Based on the stability of DC bus voltage, the paper research the control strategy of low-frequency inverter on SVPWM.Based on the requirements of doubly-fed wind power generation system to the AC excitation power, the paper designs the topology of AC excitation system and research on the mathematical model of the network side and rotor side inverter. According to the the role of grid side converter, the voltage and current double closed-loop control strategy is designed, in which the space voltage vector control technology is used. According to the role of rotor-side converter in AC excitation system, the control strategy of excitation system, which can adjust output voltage’s amplitude and frequency separately. The simulation results indicate that the grid-side converter outputs a stable DC voltage based on the power factor of 1 and the rotor side converter can output a kind of AC excitation current, which can change its amplitude and frequency arbitrarily. What’s more, used the double closed-loop control strategy of voltage and current, the DFIG achieves a stable frequency while the speed is changing. In order to realize flexible grid-connection, the paper researches a strategy, which is based on the parameters of grid-side voltage and then adjust the parameter of amplitude frequency and phase. In the process of the grid-connection, it makes the pulse current in a reasonable range.According to the operation characteristics of doubly-fed wind power generator, a flexible grid-connection strategy, which adjusts the rotor-excitation current’s amplitude,frequency and phase on basis of the grid voltage, is studied, in use of and network control strategy. The impact of current is controlled in a reasonable range during grid-connection, and ultimately a flexible grid-connection of double-fed wind power generator is achieved.