交直流混合微电网互联变流器改进控制策略

互联变流器是交直流混合微电网的重要组成部分,需要承担交流微电网与直流微电网间的功率分配任务,需要具有良好的动态性能。针对孤岛模式下传统下垂控制的互联变流器存在惯性小、系统瞬态性能差的问题,提出了基于自适应下垂控制的互联变流器控制策略。在下垂系数中引入交流微电网频率的倍数与直流微电网电压差值的微分量,动态增加系统惯性,提高系统瞬态性能。在此基础上,为了避免互联变流器整流与逆变模式的频繁切换,提出滞回控制方法,提高了系统的稳定性。最后,Matlab/Simulink仿真结果表明,孤岛模式下自适应下垂控制方法能够有效增加系统的惯性,提高系统动态过程的稳定性。滞回控制方法可以有效减小死区加入导致的交直流两侧功率分配偏差。

Research on online operation method for protective relay of smart substation

As an important part of a hybrid AC/DC microgrid, the interlinking converter not only needs to allocate the power between the AC microgrid and the DC microgrid, but also needs good dynamic performance. In order to solve the problem that the interlinking converter based on the traditional droop control has small inertia and poor transient performance in the islanded mode, the interlinking converter control strategy based on adaptive droop control is proposed. By introducing the difference between the frequency of the AC microgrid and the voltage of the DC microgrid in the droop coefficient, the system inertia is dynamically increased and the system transient performance is improved. In order to avoid frequent switching of the interlinking converter rectification and the inverter mode, a hysteretic control method is proposed to improve system stability. Finally, the simulation results of Matlab/Simulink show that the adaptive droop control method in the islanded mode can effectively increase the inertia of the system and improve the stability of the dynamic process. The hysteresis control method can effectively reduce the power difference between the AC and DC sides caused by the dead zone addition.This work is supported by National Key Research and Development Program of China (No. 2017YFB0903100) and Science and Technology Project of State Grid Corporation of China (No. 521104170043).