针对并网点电压不平衡且同时含有5次、7次谐波电压的电网条件，文中利用串联网侧变换器和并联网侧变换器的协调控制以及正向同步旋转轴系下的比例积分-双频谐振(PI-DFR)控制器，提出了基于串联网侧变换器的双馈风电系统在不平衡且谐波畸变电网电压下的改进控制策略；在实现了定转子电流平衡无畸变、发电机输出功率和电磁转矩无波动的同时，亦消除了系统输出有功功率的2倍和6倍频波动。此外，还提出了考虑并联网侧变换器电流容量时参考电流指令在其电流最大值下的分配原则及分配后的参考电流指令。对一台2 MW基于串联网侧变换器的双馈风电系统在不平衡且谐波畸变电网电压下的仿真分析，验证了所提控制策略及并联网侧变换器参考电流指令分配原则的正确性。%In view of the grid condition that the voltage at the grid connection point is unbalanced and contains fifth-and seventh-order harmonics,this paper presents an improved control strategy for a doubly-fed wind power system with series grid-side converter (SGSC) by coordinated control of the SGSC and parallel grid-side converter (PGSC).A proportional-integral double frequency resonance(PI-DFR)controller in the positive synchronous rotating reference frame during network unbalance and fifth-and seventh-order harmonics distortion is investigated.With the proposed control strategy,the stator and rotor currents are balanced distortion free and the generator”s output power and electromagnetic torque pulsation free.While two-fold and six-fold frequency pulsations in the total active power output of the doubly-fed wind power system can be restrained.In addition,the allocation principles of the reference currents in the PGSC are studied when considering the current capacity of PGSC.Finally,simulation results of a 2 MW doubly-fed wind power system with SGSC under unbalanced and distorted grid voltage condition are used to verify the proposed control strategy and allocation principles of PGSC”s reference currents.
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