基于滤波电容电流补偿的并网逆变器控制

Control of Grid-connected Inverter based on Filter Capacitor Current Compensation

在并网逆变器中,LC滤波器因容易控制和具有良好的高频衰减特性而应用广泛。分析了输出滤波电容对采用LC滤波的并网逆变器并网电流幅值、相位和低次谐波的影响,提出一种采用滤波电容电流补偿和电网电压前馈的数字PI控制策略,给出了离散时间域下控制器参数的设计方法,并从电网谐波阻抗角度分析了控制器抑制电网电压扰动的能力。理论分析和实验证明,该方案能有效降低并网电流的谐波畸变率(THD),提高并网逆变器输出电能质量。

The LC filter is widely applied in the grid-connected inverter as it is easy to control and has preferable high frequency attenuation characteristic.The effect of output filter capacitor on magnitude, phase and low-order harmonics of grid current in grid-connected inverter with LC filter is analyzed.A digital PI control strategy with filter capacitor current compensation and grid voltage feed-forward is proposed and the design method of controller in the discrete time domain is given.Then the grid voltage disturbance rejection capability of the controller is analyzed in the perspective of harmonics impedance.Theoretical analysis and experimental results verify that the proposed control strategy can improve the THD of grid-connected current, as well as output power quality of the inverter system effectively.