弱电网下计及背景谐波的多并网逆变器阻抗重塑谐振抑制方法

弱电网下多逆变器并网系统的谐振问题一直广受关注，当计及背景谐波时，逆变器的电网电压前馈环节引入正反馈通路，将进一步恶化系统的电能质量。鉴于此，提出了一种弱电网下计及背景谐波的多并网逆变器阻抗重塑谐振抑制方法。通过对逆变器的控制环节进行导纳划分，建立基于三分解导纳的多逆变器并网等效模型，并利用模态分析法得到逆变器数量和电网侧阻抗变化时系统的谐振特性。计及电网电压前馈和电容电流反馈环节，对加权电流控制进行改进，并通过公共耦合点并联虚拟导纳对逆变器进行阻抗重塑，以实现对弱电网下系统谐振的抑制。仿真结果表明，所提方法既能极大地减小背景谐波对逆变器输出电流的影响，又能有效地抑制弱电网下多逆变器并网系统的谐振。

Resonance suppression method for multiple grid-connected inverters with impedance remodeling with background harmonics in a weak power grid

The resonance problem of multi-inverter grid-connected systems in weak grids has been widely discussed. When the background harmonics are taken into account, the grid voltage feed-forward link of the inverter introduces a positive feedback path, which will further deteriorate the power quality of the system. Thus a resonance suppression method for impedance reshaping of multi-grid-connected inverters with background harmonics accounted for in a weak grid is proposed. By dividing the control links of inverters into conductors, a triple-decomposition conductor-based equivalent model of the multi-inverter grid-connected system is established. The resonance characteristics of the system are obtained using the modal analysis method for the variation of the number of inverters and the grid-side impedance. Taking into account the grid voltage feed-forward and capacitor current feedback links, the weighted average current control is improved and impedance remodeling of the inverters is performed by connecting virtual conductors in parallel at the point of common coupling to achieve suppression of the system resonance in a weak grid. Simulation results show that the proposed method can both greatly reduce the influence of background harmonics on the inverter output current and effectively suppress the resonance of the multi-inverter grid-connected system in a weak grid.