增强并网逆变器对弱电网适应能力的控制策略

弱电网中,并网逆变器与感性电网阻抗之间产生交互耦合从而引发谐振现象,采用电压比例前馈控制虽然可以抑制谐振,但其额外引入的正反馈回路也会降低并网逆变器的相角裕度。针对这种局限性,建立LCL逆变器并联系统的数学模型及诺顿等效电路,再利用阻抗法分析电压前馈控制对系统稳定性的影响,并提出了一种新型的基于相位超前补偿的电压前馈控制策略,既保留了传统电压前馈控制的优点,又增大了并网逆变器输出阻抗的相角裕度,使系统对电网阻抗具有较强的鲁棒性。最后,通过仿真验证了新型控制策略的可行性。

A Control Strategy for Improving the Adaptability of Grid-connected Inverter to Weak Power Grid

In a weak grid,the resonance phenomenon is caused by the interaction coupling between the gridconnected inverter and the inductive grid impedance.Although voltage proportional feedforward control can be used to suppress resonance,the additional positive feedback loop introduced will also reduce the phase angle margin of the grid-connected inverter.For these problems,a mathematical model and Norton equivalent circuit of LCL inverter parallel system were established,and the influence of voltage feedforward control on the stability margin of the system was analyzed by impedance method.Aiming at the limitations of traditional voltage feedforward control,a new voltage feedforward control strategy based on advanced phase compensation was proposed,which not only retains the advantages of voltage feedforward control,but also increases the phase angle margin of the output impedance of the grid-connected inverter,and improves the adaptability of grid-connected inverters to weak grids.Finally,the feasibility of the new control strategy was verified by simulation.