微电网系统中平滑切换的研究

Study on smooth transition in micro-grid system

微电网除自治与并网稳态模式外,还存在两种模式间的过渡过程。为了确保本地敏感负载供电不受影响,必须实现两种模式间的平滑切换。文章通过PSIM仿真,对微电网平滑切换的控制算法进行分析与验证。微电网工作在并网模式时,逆变器采用PI调节器与重复控制相结合的控制方法,当电网出现故障时,微电网切换到自治运行模式。自治运行模式下采用电压电流双闭环控制,当电网恢复正常,切换到并网运行模式。在实际应用过程中,该算法能够实现自治和并网两种模式之间的平滑切换,控制效果良好。

The micro-grid system has two stable operation mode, autonomous mode and grid-connect- ed mode, and also a transition process between them. The transition process is not easily the start-stop of micro-sources. It is necessary to achieve a smooth transition process of the two double to ensure no impact on power supply of local sensitive load. This paper analyzes and verifies the proposed control strategy by PSIM simulation. While the grid is normal, the micro-grid operates in grid-connected mode. The mixed control stragegy of PI regulator and repetitive control improves the quantity of grid-connect- ed current, While the grid is abnormal, static transfer switch （STS） opens and the micro-grid transfers to autonomous mode. In autonomous mode it applies double closed loop, voltage outer loop and current in- ner loop. Once detecting the grid to resume normal, it adjusts the amplitude, frequency and phase of the inverter output voltage to consistent with the grid. Then STS closes and the micro-grid transfers to grid- connected mode. The control straegy is applied in the dual-mode PV experimental platform. It achieves smooth transition of the two double and the control effect is good.