直驱风机三相短路电流特性分析
Three？？Phase Fault Current Characteristics of Permanent Magnet Synchronous Generator

为了深入分析直驱风机的故障特征,提出了直驱风机的网侧变流器简化模型和含卸荷电路的控制器外特性模型。网侧变流器是一个控制作用下的电能平衡系统,主要研究元件的功能和外特性,忽略网侧变流器的复杂结构,解析直驱风机的短路电流,实际是分析风机端电压跌落作用下的三相电流响应规律。与详细模型进行对比验证,结果表明:当卸荷电路不投入时,直驱风机短路电流稳态值与其输出功率和电压跌落程度有关,除含有工频分量外还有与控制参数相关的衰减频率分量,短路电流呈现先逐渐增大后再减小到稳态值的趋势,随着电压跌落程度的加深,短路电流最大值增加且达到最大值的时间也增加,暂态衰减过程延长;当卸荷电路投入时,短路电流为变流器输出电流的上限。提出的方法有效表征了直驱风机故障特性,对分析逆变型分布式电源的故障特征及其继电保护相关问题具有借鉴意义。
To analyze the permanent magnet synchronous generator (PMSG) fault characteristics, a simplified model of grid？？side converter and external characteristics model of controller with chopper are proposed. Grid？？side converter is an electric energy balance system under controlling action, its complex structure is ignored and the function and external characteristics are retained only. To reveal the PMSG short？？circuit current is to analyze the three？？phase current response under the action of turbine terminal voltage sag. A comparison with detailed model indicates that when chopper circuit does not operate, the value of PMSG current is determined by its output power and the degree of voltage sag; besides 50 Hz component, there are components whose frequencies are related to the control parameters; the fault current firstly increases gradually and then decreases to a steady value; with the increasing voltage sag degree, the maximum fault current gets greater and the corresponding period and transient decay time become longer; when chopper circuit operates, the fault current is just the maximum converter current