基于虚拟直流机的直流微电网电压稳定控制策略

针对大量恒功率负荷接入直流微电网致使直流微电网失稳的问题，提出了一种基于虚拟直流机(VDCM)的直流微电网电压稳定控制策略。控制策略以储能双向DC/DC变流器为研究对象，基于直流电机原理，以电感电流为反馈量在传统下垂控制的基础上引入VDCM环节，增强系统阻尼，降低恒功率负荷对系统稳定性的影响。通过建立所提控制策略下的直流微电网小信号模型，利用阻抗匹配原则分析相关参数变化时系统的稳定性，并将其与传统的VDCM控制策略进行对比。最后，搭建仿真模型和硬件实验平台，验证所提控制策略的有效性。结果表明：所提控制策略使变流器具备了直流电机的惯量和阻尼特性，在提升系统稳定性的同时，也在一定程度上改善了系统动态响应性能，且其控制效果优于传统的VDCM控制策略。

Voltage stability control strategy of a DC microgrid based on a virtual DC machine

To solve the problem of DC microgrid instability caused by constant power load, a voltage stability control strategy based on a virtual DC machine (VDCM) is proposed. Taking the bidirectional DC/DC converter of energy storage as the research object, and based on the principle of a DC machine, the control strategy introduces a VDCM link on the basis of traditional droop control with the inductance current as the feedback quantity to increase the system damping and reduce the influence of constant power load on system stability. By establishing the small signal model of the DC microgrid with the proposed control strategy, the stability of the system when relevant parameters change is analyzed with the principle of impedance matching. Then the proposed control strategy is compared with the traditional VDCM control strategy. Finally, the simulation model and hardware experimental platform are built to verify the effectiveness of the proposed control strategy. The results show that the strategy makes the converter have the inertia and damping characteristics of a DC machine. This not only improves the stability of the system, but also improves the dynamic response performance to a certain extent. Its control effect is better than that the traditional VDCM control strategy.

This work is supported by the National Natural Science Foundation of China (No. 51977074).