LCL滤波的风力发电网侧变流器不同控制结构下的性能研究

Performance of grid-side converter under different current control structures in wind power generation with LCL filter

风力发电系统中LCL滤波器的电网侧电流反馈和变流器侧电流反馈都可用作电流闭环控制,但不同的电流反馈控制结构会对变流器产生不同的影响。分别在理想电网无阻尼电阻、非理想电网无阻尼电阻和理想电网有阻尼电阻3种情况下对风力发电网侧变流器进行了分析。建立了电网电压定向的同步旋转dq坐标系下的风力发电网侧变流器数学控制模型,其中PI控制器被用于补偿被控电流的误差。根据推导出的不同电流控制结构下的闭环传递函数,对其进行了根轨迹分析。通过分析及仿真发现变流器侧电流反馈控制结构相对于电网侧电流反馈控制结构控制算法较复杂,但是系统稳定性好,电网电流的谐波畸变率较低,而电网侧电流反馈控制结构尽管抗电网扰动性较强,但调节器参数受到很大限制,系统动态响应速度较慢,稳态精度较低。

In wind power generation system with LCL filter, both grid-side and converter-side current feedbacks can be used for closed-loop current control. However, grid-side converter shows different performance in different current control structures. Three cases are analyzed： ideal grid without filter damping, non-ideal grid without filter damping and ideal grid with filter damping. The mathematical model of grid-side converter with LCL filter in dq rotating coordinates for voltage oriented control is set up and its PI regulator is used to compensate current error. The transfer function of current loop is deduced for different control structures and its root locus is also analyzed. The theoretical analysis and simulative results show that, the converter- side current feedback control is more complex,with better system stability and lower total harmonic distortion of grid current, while the converter-side current feedback control is more robust, with bigger limitation of regulator parameter,lower dynamic response and lower static accuracy.