提高LCL型并网逆变器阻抗重塑控制鲁棒性的延时补偿方法

阻抗重塑方法通过增大LCL型并网逆变器的输出阻抗,提高逆变器对电网谐波电压的抗扰能力。但阻抗重塑控制通常采用数字控制方法,存在控制延时,降低了逆变器的稳定性,并在高于1/6采样频率(f_s/6)的频率段减小了逆变器输出阻抗的模值。为此,提出一种LCL型并网逆变器的状态预估延时补偿方法,通过补偿延时环节产生的相位滞后,优化了虚拟阻抗函数。该方法显著增大了逆变器输出阻抗的模值,提高了阻抗重塑控制的鲁棒性,使逆变器在电网含有谐波电压时满足并网电流的谐波标准。以三相LCL型并网逆变器为例进行实验,验证了控制策略的有效性。

A Delay Compensation Method of the Grid-Connected Inverter with LCL Filter to Improve Robustness of the Impedance Shaping Control

The impedance shaping control is capable to increase output impendence of the grid-connected inverter with LCL Filter, enhancing the harmonic-rejection-ability against the grid-voltage distortions. However, digital control method is applied with a control delay, which decreases the stability of the inverter as well as the output impedance at the frequencies above 1/6 of the sampling frequency (fs/6). In this paper, a discrete state predicting method for LCL filter is proposed to modify the virtual impedance by compensating the phase lag in control loop. The proposed strategy can effectively increase the output impedance to improve robustness of the impedance shaping control, and exhibit strong rejection ability of grid-voltage harmonics. Experimental results with a LCL-type three-phase grid-connected inverter verify the validity of the proposed strategy.