低压微网中的单相电压独立下垂控制策略

Single-Phase Voltage Independent Droop Control Strategy in Low-Voltage Microgrid

三相四线制低压微网中,由于接入大量单相负荷,常引起三相不平衡情况。而传统控制方法在三相不平衡情况下不能有效控制低压微网在孤岛运行时的电压和频率稳定。针对三相四线制低压微网特点,设计了单相电压独立控制的下垂控制方法。论文首先在考虑低压微网的阻抗特性主要呈阻性的情况下,采用了改进的下垂控制方法,并设计了单相电压独立控制,使控制系统能够运行在三相不平衡负荷下;然后设计两级控制对低压微网孤岛运行时的频率和电压进行控制,并对误差量进行修正;最后根据设计的控制策略进行系统仿真分析验证方法有效性。在PSCAD平台上通过对搭建的小型低压微网算例仿真,验证了基于改进下垂控制的单相独立控制方法的有效性以及能够实现低压微网孤岛运行时电压频率稳定的要求,所设计的方法能够达到在三相不平衡情况下的控制目标。

In the three-phase four-wire low-voltage microgrid, the large amount of single -phase load will always cause three-phase imbalance .In such situation , the traditional control method will not keep the voltage and frequen-cy stable effectively when operating in low -voltage microgrid in the island mode .According to the characteristics of the three-phase four-wire low-voltage microgrid , a single-phase independent control has been proposed based on the droop control.Firstly, considering the impedance characteristic of the low voltage microgird mainly appears as re-sistance , the improved droop control method is adopted , and a single-phase independent control strategy has been designed to ensure the normal operation of the control system under the unbalanced loads .Then a two-level control strategy has been proposed to control the voltage and frequency in the microgrid during the island mode .Finally, a simulation analysis based on the proposed method is used to prove the effectiveness .A microgrid is set up on PSCAD , and the effectiveness of the single -phase control strategy will be verified based on the improved droop control .The proposed method can also meet the requirement of the voltage and frequency stability in the island mode .At the same time, the control method proposed in this paper can achieve the control objective under the condition of unbalanced three-phase .