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传统直接功率控制(DPC)所用开关表的输出控制矢量离散且固定,导致脉宽调制变换器的交流输入电流富含谐波,在交流输入电压波动和不对称的情况下更为明显,无法满足基于双馈异步发电机(DFIG)的变速恒频风电机组在故障下的不间断运行要求。在分析网侧变换器数学模型和DPC原理的基础上,提出了一种基于复开关表的DPC新策略。该策略可根据变换器的交流输入电压、瞬时功率等工作状态,提供细化的开关表以供选择,从而在保留传统DPC结构简单特点的同时,获得了高精度的控制效果。仿真和实验结果表明,该控制策略在电网发生对称性过电压、电压跌落和不对称性故障时,均能保持三相输入电流的平衡、稳定,用于DFIG风电机组交流励磁变频电源的控制中能提高电网故障下风电系统的穿越运行能力,并减少脉宽调制变换器产生的电力谐波污染。
The output control vector of the switching table used by the traditional direct power control (DPC) is discrete and fixed, resulting in that the AC input current of the pulse width modulation converter is rich in harmonics, which is more obvious when the AC input voltage fluctuates and is asymmetric, Uninterrupted operation of variable speed constant frequency wind turbines based on doubly fed induction generator (DFIG) under fault conditions. Based on the analysis of math model and DPC principle of grid-side converter, a new DPC strategy based on complex switch table is proposed. According to the AC input voltage, instantaneous power and other working states of the converter, this strategy can provide a detailed switch table to choose from, which can achieve high-precision control effect while retaining the simple features of the traditional DPC structure. The simulation and experimental results show that the proposed control strategy can balance and stabilize the three-phase input current in the event of symmetrical overvoltage, voltage sag and asymmetry faults in the grid. This control strategy can be used in the control of AC excitation variable frequency power supply of DFIG wind turbines Can improve the running ability of the wind power system under the grid fault and reduce the power harmonic pollution generated by the PWM converter.