弱电网下LCLCL型并联逆变器并网系统的电流优化控制

针对LCL型滤波器存在的缺陷,采用基于电容电流比例反馈的LCLCL型滤波器,在保留传统滤波器高频谐波衰减能力的前提下,实现了在系统开关频率处对谐波的陷波作用。建立了弱电网下两台并联逆变器并网系统的诺顿等效模型,分析了电网阻抗在逆变器与电网之间的耦合作用;考虑电网阻抗影响的电网电压前馈控制会引入一条额外的并网电流正反馈回路,降低系统的相位裕度;通过采用谐振前馈控制,可实现前馈控制与电流控制在基波频率的中高频段处解耦,提高系统的稳定性,优化并网电流的品质。最后通过Matlab/Simulink的仿真分析验证了所提策略的可行性和有效性。

Optimal control of grid-connected current in grid-connected system of LCLCL parallel inverter under weak grid

Aiming at the shortcoming of traditional LCL filter, this paper uses LCLCL type filter based on proportional feedback of capacitive current to realize the notch action of harmonic at switching frequency on the premise of retaining the high frequency harmonic attenuation ability of LCL filter. Secondly, the Norton equivalent model of two parallel inverter grid-connected systems under weak grid is established, and the coupling effect of grid impedance between inverter and grid is analyzed. An extra positive feedback loop of grid-connected current will be introduced into the feedforward control of power grid voltage considering the impedance of the power system, which can reduce the phase margin of the system. By using the resonant feedforward control, the feedforward control and grid-connected current control can be decoupled at the middle and high frequency of the fundamental frequency, the stability of the system can be improved and the quality of the grid-connected current can be optimized. Finally, the feasibility and effectiveness of the proposed strategy are verified by simulation analysis in MATLAB/Simulink.