LCL型并网逆变器的网压滤波前馈控制策略

LCL型并网逆变器的网压比例前馈策略因其实现方式简单、谐波抗扰能力良好而受到广泛应用,但是该策略在弱电网下的适应性较差,并网逆变器的前馈通道与电网阻抗产生交互影响,使得系统稳定性随着电网阻抗的增大而显著下降,恶化了入网电流质量。以改善网压比例前馈策略的适应性为目标,提出了一种基于多二阶滤波器的网压前馈控制策略,即在前馈通路上引入多个二阶滤波器,实现电网电压的选择性反馈。详细分析了该策略的输出阻抗特性以及谐波扰动的抑制情况,分析结果表明,该策略不仅可实现电网背景谐波的抑制,而且又不削弱系统在弱电网下的稳定性,从而提高了并网逆变器对弱电网的适应性。最后,仿真结果验证了该策略的有效性。

Grid Voltage Filtering Feedforward Control Strategy for LCL-type Grid-connected Inverters

Due to simple realization and good harmonic disturbance immunity,grid voltage proportional feedforward strategy of LCL-type grid-connected inverters has been widely applied,but this strategy has poor adaptability in the weak grid,the feedforward channel of grid-connected inverters interact with the grid impedance,which makes the stability of system decrease significantly with the increase of grid impedance,worsens quality of the injected grid current.Aiming at improving the adaptability of grid voltage proportional feedforward strategy,and putting forward a grid voltage feedforward control strategy based on multiple second-order filters,multiple secondorder filters were introduced in the feedforward path to achieve selective feedback of grid voltage,then characteristics of output impedance and suppression of harmonic disturbance were analyzed in detail.The results of analysis show that this strategy can not only suppress the background harmonics,but also don't weaken the stability of system in weak grid,so as to improve the adaptability of grid-connected inverters in the weak grid.Finally,the results of simulation verifies the effectiveness of this strategy.