电压型级联系统中减小源变换器输出阻抗的有源阻尼控制方法

An Active Damping Method to Reduce Output Impedance of Converters in Voltage Source Cascaded System

在级联系统中,源变换器和负载变换器之间阻抗的相互作用可能会影响系统的稳定性。许多文献分析了不同控制方法、电路参数等因素对变换器阻抗特性的影响,并针对优化变换器的阻抗设计提出了多种无源阻尼或者控制的方法,从而提高变换器的稳定裕度,以保证变换器构成的级联系统维持稳定。本文基于变换器的小信号模型,提出了一种实现虚拟电阻的有源阻尼控制方法,以降低变换器的输出阻抗,优化其阻尼特性。该方法通过采样变换器输出电压中的交流分量,经过有源阻尼控制器作用后叠加至调制波以产生控制信号,从而实现在变换器小信号模型的输出端连接虚拟电阻的效果,达到降低输出阻抗的目的。由于虚拟电阻仅存在于小信号模型中,所以变换器的稳态工作点不受影响。通过仿真和实验验证了该方法的正确性。

In a cascaded power system, the system stability can be affected by the impedance interaction of the source converter and the load converter. Many literatures analyzed the effects on the impedance characteristics of the converter from different control methods and circuit parameters.Besides, different passive damping methods and control methods to improve the impedance characteristics of the converter are proposed to ensure the cascaded system stable. On the basis of the small signal model, an active damping method to emulate a virtual resistor, which is connected in parallel with the output of the converter 's small signal model, is presented in this paper. By this means, the output impedance of the converter can be decreased and the damping characteristics can be improved. The AC component of the output voltage needs to be sampled by the active damping controller so the steady-state operating point is not affected. Therefore, the effects caused by the impedance interaction between the source converter and load converter can be weakened. The effectiveness of this method is verified by the simulation and experiment results.