针对并网点电压不平衡且同时含有5次、7次等电力谐波的弱电网运行环境,建立了双馈感应发电机(DFIG)的完整数学模型,评估了负序和谐波电压成分对DFIG电磁转矩以及定子输出有功、无功功率的负面影响,进而提出了一种转矩波动抑制策略.给出了相应的转子电流指令算法,并设计了比例-积分双频谐振(PI-DFR)电流控制器,其可在无需转子电流相序分解的前提下实现对基波正序、负序及谐波分量的有效、快速调节.实验结果表明,所提出的控制方案能够明显抑制恶劣电网条件下DFIG的电磁转矩波动,从而提高风电机组在电网故障时的不脱网运行能力.%An integral mathematical model of doubly-fed induction generator (DFIG) based wind turbine is developed under weak network conditions with voltage unbalance and distortion of fifth-order and seventh-order harmonics, where the influences of the negative sequence and harmonic components on the electromagnetic torque and stator active and reactive powers are modelled in details. An approach to suppress torque oscillations is then proposed, with a novel proportion integral-double frequency resonance (PI-DFR) current controller being designed and the rotor current references being re-arranged. It can effectively and quickly regulate both the positive/negative sequence and harmonic components, without the need of sequence decomposition of the rotor currents. Experiment results indicate that the proposed control can significantly suppress the torque oscillations and improve the power quality, and thus enhance the ride-through capability and operation reliability of DFIG-based wind turbine under adverse grid conditions.rnThe work is supported by National Natural Science Foundation of China (No. 50907057) and Scholarship Award for Excellent Doctoral Student Granted by Ministry of Education.
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