弱电网下LCL型逆变器自适应控制策略

Adaptive Control Strategy of LCL Filtered Inverter Under Weak Power Grid

LCL滤波器能强有力地衰减开关切换引起的谐波,被广泛应用于并网逆变系统中。然而,LCL滤波器存在谐振抑制问题,电容电流反馈等有源阻尼不失为行之有效的方法。但引入电网阻抗的弱电网工况会严重影响LCL型并网逆变器的控制性能。文中提出一种基于并网电流有源阻尼的LCL型并网逆变器自适应控制方法,采用即时触发型阻抗测量方法在线检测电网阻抗,实时修正电流控制器与有源阻尼控制器的控制参数,实现逆变器在弱电网下的自适应控制,使得系统在电网阻抗大范围变化下稳定运行。方案无需增加额外的传感器,降低了设备成本。论文最后通过实验验证了并网逆变器自适应控制策略的有效性。

LCL filter has been widely used in the grid-connected inverter due to the higher attenuation of the switching frequency harmonics. However,the resonance of the LCL filter is a severe problem to be solved,the capacitor-current-feedback active damping is considered as the effective method. But the control performance of grid-connected inverter will be affected by the weak power grid with impedance. In this paper,an adaptive control scheme of LCL filter-based grid-connected inverter based on grid-current-feedback active damping was proposed. The grid impedance on line by using immediately triggered impedance measurement method is detected, the constantly control parameters of the current controller and the active damping controller are updated, and the adaptive control strategy of the grid-connected inverter under weak power grid is formed. So the system can be stably operated under the wide variation of the grid impedance. In addition,it does not need to add any extra sensor in this scheme,the device cost will be reduced. Finally,a prototype was built and the effectiveness of the proposed adaptive control strategy of the grid-connected inverter was validated by experimental results.