一种永磁直驱风力发电系统不对称电网故障下低电压穿越方法

摘要

In order to improve the low voltage ride through capability of permanent magnet synchronous generator (PMSG) wind turbine under asymmetric fault,an improved control method was proposed,which was based on storing the active power surplus in the turbine-generator mechanical system inertia.The formation mechanism of active power double frequency components under unbalanced grid voltage level was analyzed,and the influence of active power ripple on the electromagnetic torque of generator and on the voltage of DC bus was discussed.Fuzzy control was applied to suppress the influence on the electromagnetic torque of generator,and super capacitor was applied to suppress the influence on the voltage of DC bus.Simulation results showed that the control method could suppress the double frequency components of the generator electromagnetic torque and that of the DC bus voltage at the same time,verifying the control method.%为了提高永磁直驱风力发电系统在不对称电网故障下的低电压穿越(LVRT)能力,改进了现有基于发电机转子储能的LVRT策略.分析了电网电压不对称跌落时,有功功率2倍工频分量产生机理,讨论了功率波动对发电机电磁转矩和直流母线电压的影响.采用模糊控制抑制功率波动对发电机电磁转矩的影响,以及采用超级电容抑制功率波动对直流母线电压的影响.仿真表明,该控制策略可同时抑制电磁转矩和直流母线电压的2倍工频波动;仿真结果验证了该策略的有效性.