低压微网中基于单相电压独立控制的下垂控制

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。

A Droop Control Strategy based on Single-phase Independent Control in Low-voltage Microgrid

In the three-phase four-wire low-voltage microgrid, three-phase imbalance usually happens because of a large number of single-phase loads. In this situation, the traditional control method cannot effectively control the voltage and frequency stability when the low-voltage microgrid operates in the island mode. According to the characteristics of the three-phase four-wire low-voltage microgrid, this paper designs a single-phase independent control based on the droop control. This paper firstly uses the improved droop control considering that the impedance characteristic of the low voltage microgird is mainly resistance, and also designs single-phase independent control to ensure the control system have the ability to run under the unbalanced loads. Then this paper designs a two-level control strategy to control the voltage and frequency in the microgrid during the island operation. Finally, a simulation analysis based on the proposed method is used to prove the effectiveness. A microgrid is set up on PSCAD, and verifies the effectiveness of the single-phase control strategy based on the improved droop control. The proposed method can also realize the requirement of the voltage and frequency stability during the island operation. At the same time, the control method proposed in this paper can achieve the control objective under the condition of unbalanced three-phase.