Study On The Modeling Of Microgrid And Its Protection

Distributed Generator (DG) becomes an important supplement for power grid, when the global energy and environment problem is more and more pressing, and the disadvantages of the traditional one-way power grid is more and more obvious. Although the Distributed Generator is eco-friendly, high efficiency and has advantage in installation location of localization, what's more, it can reduce the transmission and distribution line loss, lower the operation cost, when be put in the network it will pose negative impact on the utility network because of its randomness, small capacity, small inertia and low overload ability.Microgrid is a new single controlled distribution network unit, which can be coordinated with the higher concentration of Distributed Generator supply and reduce the burden of grid control, take advantages of the Distributed Generator, so as to ensure the efficient use of Distributed Generator. As a power system, microgrid has its own characteristics compared to the traditional power system, has two different operating modes, the traditional protection method can't meet its requirements. So the protection method of microgrid is the key to obtain further development of microgrid.This paper made the modeling of distributed generators, such as photovoltaic cells, wind turbine, micro gas turbine and super capacitor in PSCAD/EMTDC, accoding to their mathematical model or the engineering model. Study the P/Q control and V/f control of the Distributed Generation invert, then put out the control strategies of the whole microgrid.Thid paper choose master slave control as the control strategy of the microgrid, and complete the model of microgrid included photovoltaic cells, wind turbine, micro gas turbine and super capacitor. The simulation experiment which included changing power output of micro source, running mode conversion and cutting load under islanding operation is done on the model. It verified the accuracy of the control strategy and the stability of the micro-grid during grid-connecting and islanding operation.At the last, the paper analysis the influence to the relay protection when Distributed Generator is applied to microgrid and the requirement of microgrid on protection through the theory. The basic principle of the current differential protection and inverse time current protection was expounded, and established the protection modules in the simulation software. Micro-grid feeder protection strategy was proposed under different operations, the simulation experiment was done to verify effectiveness correctly of the proposed protection module and protection strategy.