微电网系统母线电压和频率无静差控制策略研究

Research of non-steady state error control strategy of bus voltage and frequency in micro-grid system

当外电网发生故障时,微电网系统与外电网断开,运行在孤岛模式。此时,由于微电网系统失去了外电网的支撑,微电网系统交流母线电压和频率需要采用下垂控制。针对传统下垂控制导致电压和频率存在静差问题,分析控制参数对微电网系统逆变器输出阻抗的影响,并研究系统输出阻抗呈感性的方法。在此基础上,提出无通讯线时消除电压和频率静差问题的控制方法,并分析下垂系数对系统稳定性的影响。最后,通过仿真和实验对控制方法进行了验证,仿真结果表明采用下垂曲线平移的办法减小静差,有功-频率和无功-电压下垂曲线垂直上移,没有发生明显的波动,而且按照设定的下垂系数比例进行合理分配;负载从680 W突增至1 050 W,再从1 050 W突减至680 W,两台逆变器输出电流迅速满足负载突变的要求,而且负载突变对母线电压影响较小。结果表明本文控制方法的正确性和可行性,研究结果将对微电网的稳定运行提供一定的理论及实验指导。

When the micro-grid system is running in islanding mode, it＇ s disconnected from external pow- er because of the grid failure. In this case, the AC bus voltage and frequency of micro-grid system need to use droop control due to the loss of support from the grid. As the steady state error problems of voltage and frequency problems exist in the traditional droop control, the influence of the control parameters of the mi- cro-grid system inverter output impedance was analyzed, and the method of the system~ output impedance for inductive was studied. Based on the above studies, a control method to eliminate voltage and frequency steady state error problem without communication line was put forward, and the impact on system stability by droop factor was analyzed. Finally, simulations and experiments control method was validated. The sim- ulation results show drooping curve translational approach reduces the static error, active-frequency and reactive-voltage sag vertical curve shift, significant fluctuations do not occur, and in accordance with the proportion set droop coefficient reasonable allocation;sudden load increases from 680 W to 1 050 W,and then suddenly reduced from 1 050 W to 680 W, and two inverter output current quickly meets the load re- quirements of mutation, and mutation on load bus voltageis is smaller. The results show the correctness and feasibility of the control method, and provide theoretical and experimental guidance for stable opera- tion of microgrids.