弱电网下基于加权系数的电网电压前馈控制策略

在含有电网电压背景谐波以及电网阻抗变化情况下,并网逆变器的控制性能会受到影响。直接电网电压比例前馈因其实现方便且可有效抑制电网背景谐波而获得广泛关注,但其在高电网阻抗的弱电网情况下会降低电流控制的相位裕度,影响并网稳定性。基于加权系数的电网电压前馈控制策略存在基波增益下降的问题,但是能够大幅提高并网逆变器的稳定性。首先,对并网逆变器进行数学建模,并结合阻抗稳定性判据全面对比分析了弱电网下基于加权系数的电网电压前馈控制策略和传统直接电网电压前馈控制策略的动、稳态性能,得出了前者在弱电网下具有更好的电网适应性;其次,给出了调整系统闭环增益的方式来提高并网逆变器基波跟踪性能的理论分析;最后,结合Matlab/Simulink仿真和实验,进一步验证了弱电网下基于加权系数的电网电压前馈控制策略的有效性。

Grid Voltage Feedforward Control Strategy Based on Weighting Coefficient in Weak Grid

Control performance of grid-connected inverter are affected by the grid voltage background harmonics and variable grid impedance. Due to its ease of implement ation and effective suppression of background harmonics, the direct voltage proportional feedforward received wide attention. However, this control strategy will reduce the phase margin of the current control and effect grid stability in weak grid. The grid voltage feedforward control strategy based on the weighted coefficient can significantly improve the stability of grid connected inverters despite the reduction of the fundamental wave gain. Firstly, combined with the impedance stability criterion, to analyse and compare the dynamic and static performance of the grid voltage feedforward control strategy based on weighting coefficient and the traditional direct voltage feedforward control strategy. It is concluded that the proposed strategy has better adaptability to the grid in weak grid. Secondly, the theoretical analysis of improving the fundamental tracking performance of grid connected inverters is given by adjusting the closed-loop gain of the system. Finally, Matlab/Simulink simulation and experiments are carried out to further verify the effectiveness of the grid voltage feed-forward control strategy based on the weighted coefficient in the weak grid.