基于无源阻尼的直流微电网稳定性分析

Stability Analysis of DC Microgrid Based on the Passive Damping Method

多变换器与负载交互所引起的稳定性问题已成为直流微电网领域的一个研究热点,但目前稳定性研究大多集中在单一控制的直流微电网,缺乏普适性。针对母线电压分层控制下的直流微电网稳定性问题,建立了各接口变换器在不同控制下的小信号模型和直流微电网等效阻抗模型,并利用阻抗比判据判定直流微电网3种模式的小信号稳定性,将稳定性最差的模式作为直流微电网系统稳定性的判定指标。采用无源阻尼法,通过增加阻尼电阻改善了负载阻抗特性,使直流微电网的稳定性得到提高并得出滤波参数对稳定性的影响规律。研究结果表明:模式2下直流微电网稳定性最差,在添加了12?阻尼电阻后,幅值裕量增加了12.7 d B,相角裕量增加了11.5°。因此无源阻尼可改善负载阻抗特性,从而提高直流微电网稳定性。

The system stability issues arising from dynamical interactions between the components and various loads have become a hot topic. However, the current stability researches mostly focus on the DC microgrid under the single control, which lacks universality. Aiming at the stability issues in the DC microgrid based on the bus voltage hierarchical control strategy, we established small-signal models of interface converters with different control modes and the equivalent impedance model of the DC microgrid. Based on the impedance ratio criterion, the stability of the microgrid in three modes was judged and the worst model was obtained as the stability baseline of DC microgrid. The method of passive damping of adding the damping resistance was used to improve load impedance characteristics, which led to the improvement of the stability. And then the influences of filter parameters on the stability were discussed. The simulation results show that DC microgrid stability is the worst under mode 2, and amplitude margin increases by 12.7 d B, phase margin increases by 11.5° after adding 12 ？ damping resistor. Therefore, with the method of passive damping, the load impedance characteristics can be improved, so as to improve the stability of DC microgrid.