中文摘要：

针对现有的基于直流母线电压信号的传统控制方法在不同的工作模式运行时存在电压控制偏差的问题，首先对现有的分层控制策略进行了改进，通过潮流计算确定了本地控制器参数，并以负荷端电压为控制目标，实现了将不同模式下的负荷端电压均控制在相同的参考值上；然后，利用仿真软件搭建了四端环形直流微电网及其控制算法的模型，并对不同模式间的切换进行了仿真分析，仿真分析结果验证了该策略的可行性和有效性。

英文摘要：

In order to solve the problem of deviation of voltage control of traditional control method based on dc bus voltage signal which is used under different working models, the now used hierarchical control strategy is improved, and the local parameters of controller are derived by tide calculation and the load voltage is controlled on the same value in different mode while it is looked as the control target. By using simulation software, a four terminal ring dc microgrid and its control algorithm is set up, and the switch process between different modes is simulated. The simulation results verfiry the feasibility and effectiveness of the proposed method.