直驱式永磁同步风力发电机不对称故障下的改进控制

Improved control strategy of direct-driven permanent magnet synchronous generator for wind turbine under unbalanced grid faults

在分析直驱式永磁同步风力发电机(permanent magnet synchronous generator,PMSG)全功率变换器功率特性基础上,推导了直流侧电压、并网电抗器功率及网侧输出功率之间的关系,提出了不对称故障下系统的改进控制策略,以实现该型机组的低电压穿越。该控制策略基于电网侧变换器、电机侧变换器功率平衡协调控制思想,将电网跌落信息反馈给电机侧变换器,实现两个变换器的协调控制;同时,在直流侧电压维持在安全范围内的前提下,采用弱控制,以一定的直流侧电压波动为代价,达到消除网侧有功功率2倍频波动的目的。仿真研究结果表明,基于功率平衡协调控制的改进控制策略可较好的实现直驱式永磁同步风力发电机的不对称故障穿越。

An improved unbalanced grid fault ride-through control strategy is proposed to meet the low voltage ride through（LVRT） requirements based on the analysis of power characteristics of a full rated converter for direct-driven permanent magnet synchronous generator （PMSG）. According to the power characteristics,the relationship among dc-link capacitor voltage, power absorbed by interface reactors and grid-side power output is studied. The information of grid voltage drops is introduced into generator-side converter control to achieve coordinated control of grid-side converter and generator-side converter. The soft control strategy on dc-link capacitor voltage is adopted to suppress double-frequency active power ripple at the expense of a certain voltage fluctuations which is still within the safety range. The simulation results demonstrate that the proposed control strategy can enhance direct-driven PMSG^s unbalanced grid faults ride-through capability.