LCL并网逆变器的单逆变器侧电流控制性能分析

对LCL滤波并网逆变器来说,单逆变器侧电流闭环控制实现较为方便,但是控制延迟导致系统仍存在欠阻尼谐振甚至不稳定。无源阻尼方法虽可实现优良的电流控制性能,但会导致额外的功率损耗;附加数字滤波器的有源阻尼方法具有改善系统稳定性的能力,但是数字滤波器在非谐振频率处的幅值以及相位特性影响控制性能。以无源阻尼方法下系统性能为基准,对比了已有的逆变器侧电流闭环控制有不同的谐振频率同控制频率的比值条件下的性能,结果表明在一拍采样与计算延迟下,已有的单逆变器侧电流闭环控制难以兼顾系统稳定性、动态特性以及鲁棒性,附加数字滤波器的有源阻尼方法具有较大的局限性。

Investigations of Single Inverter-side Current Feedback Control for Grid-connected LCL-filtered Inverters

For grid-connected LCL-filtered inverter, the current control with single inverter-side current feedback is easy to be implemented. However, the digital control delay usually causes instability. The passive damping method is capable of satisfactory current control performance, but leads to extra power loss. The active damping method based on the use of a digital filter can improve the system stability, but the control performance is affected as long as the digital filter is not an ideal term that only works at the resonance frequency. In this study, taking the performance with passive damping method as a benchmark, performances with different filter-based active damping methods are compared in the case of different ratios of resonance frequency to control frequency. With a one-sample computation delay, the filter-based active damping methods with only inverter-side current feedback are all difficult to guarantee a satisfactory performance of stability, dynamic and robustness. Thus, the filter-based active damping methods have limitations in practical applications.