The Research On Self-healing Control Strategy For Microgrid In Intentional Islanded Operation Mode

With the change in energy structure and the super-high requirement of the power quality meeting the rapid development of the society, the concept of microgrid is proposed. The microgrid is one of the most important fields in the development of power industry since the 21st century. The activity of the microgrid can be fully demonstrated by means of the application technology of the islanding effect and the stability in the intentional islanded operation mode. In this case, the reliability of power supply is improved, which is of great significance.First of all, the concept of microgrid is introduced in this dissertation as well as the distributed generation, which is one part of the microgrid. And then, the two operation modes of microgrid are described, especially the intentional islanded operation mode. On this basis, the theme of this dissertation is put forward, that is, the research on control strategies of the microgrid in intentional islanded operation mode.Currently, there are two main types of control strategies of microgrid, that is, PQ inverter control(PQ) and voltage source inverter control(VSI). Both of the two methods are the local control strategies based on the local information by controlling the power electronic interface and can meet the requirement of the rapidity of operation. However, as the microgrid is small and weak, it will make the power system even worse and the control objectives may not be achieved by means of the local control strategies.In view of the shortages of the above local control strategies, a novel control strategy, the integrated self-healing control strategy, is proposed in this dissertation. The concept of self-healing grid is introduced into the microgrid, and the control framework is designed. Meanwhile, the control functions of the self-healing control strategy are illustrated in terms of preventive control, emergent control and restorative control. In addition, focusing on the emergent control, the PID closed-loop control is introduced. The self-healing emergent control strategy is formed by combining the PID closed-loop control with the above local control. In this event, the global control and the local control can be coordinated. This self-healing control strategy can not only retain the rapidity of operation, but also guarantee the stability of the microgrid in the case of the smallest loss of load. Finally, the effectiveness and superiority of the proposed control strategy are validated with PSCAD/EMTDC based simulation tests.