中文摘要：

分析了电网电压不平衡时系统机侧与网侧变流器的运行工况及控制方式，提出一种在两相静止坐标系下采用准比例谐振（PR）控制器来控制交流电流以达到控制有功功率恒定的网侧变流器控制策略。该控制策略以控制直流母线稳定为控制目标．在两相静止坐标系下采用准PR控制器避免了反复的坐标变换而导致的延时问题。在电网电压发生不对称故障时能保持直流母线电压的稳定无波动，从而不干扰机侧的稳定控制，使整个系统的安全性和稳定性得到提升。搭建了小值不平衡的仿真模型和一套笼型异步风电系统在大值不平衡电网电压下的实验验证系统。仿真和实验结果验证了所提策略的可行性和有效性。

英文摘要：

The operating conditions of machine-side and network-side converters under unbalanced grid voltage and the control of them are analyzed, and an control strategy for achieving AC tracking control using quasi proportional resonant（PR） controller in a two-phase stationary coordinate system is proposed to control the active power constant. This control strategy aiming at controlling the DC bus stability, using quasi-PR controller in a two-phase stationary co- ordinate system can avoid delay problem which caused by the repeated coordinate transformation.When the grid volt- age occurs a sudden fallen breakdown, it can maintain a stable DC bus voltage, so as not to interfere with the ma- chine side stability control, so that the security of the whole system is improved.Simulation model of small value un- balance and a squirrel-cage asynchronous wind power system under large values unbalanced experimental verification systems are built.Simulation and experimental results verify the feasibility and advantages of this strategy.