多目标约束下逆变器阻抗的电流矫正方法

弱电网下锁相环与电网阻抗间的耦合会造成系统不稳定.含前置低通滤波器锁相环的并网逆变器虽能改善并网系统稳定性,但存在并网电流相位滞后问题.本文通过将滤波器从锁相环支路“拆分”,提出了一种电流二阶校正的阻抗重塑法,以基波电流控制性能、相角裕度、低频幅值为约束建立了多目标约束函数,单独优化设计了二阶校正环节参数,提高了并网逆变器的弱网稳定性,实现弱电网下的单位功率因数并网.最后在StarSim实验平台验证了所提控制方法的有效性.

Current correction method for grid-connected inverter impedance under multi-objective constraints

Under a weak grid, the system instability can be jeopardized by the interaction between the phase-locked loop and the grid impedance with increasing impedance. Although the stability of grid-connected system can be improved by a phase-locked loop with a serial low-pass filter (LPF), it leads to a lag phase of injected grid current. Based on the equivalent transformation and frequency division optimization, an impedance reshaping method with second-order correction of the current is proposed. Then a multi-objective constraint function is established with the constraints of base-wave current control performance, phase angle margin, and low-frequency amplitude. And the parameters of the second-order correction link are optimally designed by this function. The method improves the weak grid stability of the grid-connected inverter and realizes the grid connection with unit power factor under the weak grid. Finally, the effectiveness of the proposed control method was verified on the StarSim experimental platform.