直驱风电机组低电压穿越改进控制方法仿真研究

Simulation of Improved Control Method for Low Voltage Ride-Through of Directly Driven Wind Turbines

采用改进的瞬时对称分量法对电网电压瞬时值进行对称分量分解,提出了电网电压不对称跌落时D-PMSG的低电压穿越控制策略,按照电网电压正序分量和额定电压的比值减小发电机功率,并在解耦控制中分别控制正序和负序分量,正序通道完成能量的传输,负序通道产生和电网负序电压相等的负序电压,从而保证网侧逆变器电流中无负序分量,避免了逆变器非全相过负荷,充分利用其容量。仿真结果研究表明,提出的改进控制策略实现了不对称故障下的低电压穿越,并且保持了逆变器三相电流对称。

An improved instantaneous symmetrical components method is used to detect the positive sequence, negative sequence and zero sequence components of the grid voltage. The power of PMSG is reduced according to the ratio of grid positive sequence and rated voltage during symmetrical and asymmetrieal voltage dips. The positive and negative sequence components are controlled through respective channels. The power is transmitted in positive sequence channel while negative sequence voltage, which is equal to the grid negative sequence vohage, produced in the negative sequence channel. In this way, the inverter current does not contain negative sequence component, and overload in a certain phase of GSI I is avoided . The simulation results suggest that the improvement strategies help realize the LVRT function, and ensure the 3 phase current symmetry of the converter.