LCL滤波器有源阻尼控制机制研究

Research on Control Mechanism of Active Damping for LCL Filters

有源阻尼技术是实现LCL滤波器谐振峰值抑制的有效方法,目前已经有多种有源阻尼方案被提出。但已有文献对有源阻尼方案进行分析时均未涉及有源阻尼的机理问题,未给出各方案提出的依据。该文深入分析有源阻尼技术,指出有源阻尼实质上是对系统谐振峰值附近对应的输出频率成分的反馈控制,当该反馈为负反馈时可以实现较好的抑制效果,且反馈深度越深,谐振峰值抑制效果越好。在此基础上,不仅解释了现有基于逆变器侧电感电流、滤波电容电流及其电压反馈控制的有源阻尼技术的本质,还得到了基于包括滤波电容、逆变器侧电感以及网侧电感在内的有源阻尼反馈环节的设计要求,并推演了LCL滤波并网系统中可行的有源阻尼控制方案。实验结果验证了理论分析的正确性。

A technology named active damping is commonly adopted to eliminate the resonance peak of LCL filters. Many active damping strategies have been proposed in the literatures before. However, the control mechanism of active damping has not been involved yet, also the theoretical basis for the proposed strategies. In this paper, a thorough research on active damping has demonstrated that the essence of active damping is the feedback control at the frequencies where the resonance peak lies. Moreover, a better damping effect is obtained when the control is negative feedback, and the deeper the feedback the better the inhibition of the resonance peak. Based on this, the essence of the existing control strategies based on inverter-side inductor current, filter capacitor current and voltage was analyzed; the principles for the design of active damping control through filter capacitance, inverter-side inductance or even grid-side inductance were proposed, as well as the feasible active damping control strategies in systems with LCL filters. Experimental tests validate the analysis.