The Control Strategy Of Micro-grid And Distribution Grid With Micro-grid Fault Recovery Strategy Research

Faced with the energy crisis, environmental pollution gradually becoming serious oftraditional power system, Countries have put forward the development strategy of smart grid.Distributed generation has becoming one of the important directions of development of smartgrid because of its characteristics such as clean, renewable and so on. But the randomness andintermittence of distributed generation had become the important obstacle of restricting itsdevelopment. Therefore, the micro-grid technology was born. As a small independentcontrollable electric power grid, micro-grid can remedy the intermittence and instability of thedistributed generation, and it is a good way to ensure continuous power supply of the gridload. With the constant improvement of micro-grid technology development, the micro-gridand the distribution network can be the spare to each other, but the access of micro networkwill also bring great influence on the distribution grid, Such as the switch between islandingand grid connected mode, the positive and negative effect of the accessing and so on.In this paper, combining with the cooperation projects named Tianjin electric powercompany intelligent distribution grid fault recovery strategy, multi-loop feedback control ofmicro inverter control strategy was put forward based on the analysis of micro-grid controlstrategy and operation mode. The voltage and current loop were used in the controller. Outerloop uses the sagging power controller. Through the theoretical analysis of the controller weknow that, the output impedance of the inverter has relationship with the filter and the PIcontroller parameters. The inverter’s output impedance shows inductance characteristic under50Hz. And the sagging power controller was used in the low voltage micro grid which wassuitable for the high pressure system. The simulation results show that the micro-grid’s outputcan be adjusted flexibly to monitor the changes of loads after the islanding operation to ensurethe continuous power supply, the mode switch smooth and the inverter output is good enough.Micro-grid output can be adjusted according to the load situation according to themicro-grid controller. Combined with Tianjin electric power company’s project, themathematical model of distribution grid fault recovery was created which consideredmicro-grid’s accessing, and the distribution grid fault recovery strategy was proposed basedon the heuristic rules and genetic algorithm. The flow chart of specific recovery strategy wasgiven. We take the IEEE three feeder systems as an example, to study the effect of micro-gridof distribution grid fault. Grids were joined in some nodes and to be analyzed. Compared withexcluding micro-grid fault recovery, results show that, the fault recovery can not only restoremore load but high fitness value which containing micro-grid.