Microgrid Modeling And Simulation Of Its Operation And Control

Energy is the driving force for social and economic development. It is the lifeline of human existence and reproduction. The gradual depletion of conventional fossil fuels, so that the energy crisis has been gradually approaching. China energy industry in the21st century will be new industrial transformation type, therefore, reasonable adjustment of energy structure, vigorously develop of renewable energy and other new energy, diversification of clean energy development is the only way for social sustainable development in our country. In this context the distributed power was vigorously developed. But distributed power has the disadvantages of high access costs, difficult control etc. Also the distributed power supply must be immediately out of operation when the large grid is not in normal operation and this greatly limits the utilization efficiency of distributed power supply. The microgrid arises at the historic moment. Microgrid is a new network structure and is composed of micro power, load, energy storage system and control device. The source of microgrid is usually distributed source including micro gas turbine, fuel cell, photovoltaic cells, wind turbine and super capacitor. They are connected on the user side and they have the characteristics of low cost, low voltage and low pollution. Development and extension of microgrid can promote mass access of distributed power supply and renewable energy. It is a kind of effective way to realize active power distribution network and let the traditional power grid to make the transition to the smart grid. In this paper, the modeling, operation and control of the micro power grid are analyzed in the backdrop of the microgrid. And the simulation model is established for validation.First, the microgrid is modeled. Micro grid consists of a variety of distributed power supply, so that modeling is especially important for distributed power supply. Focus on the analysis of the doubly fed wind power generator (DFIG) that is the most widely used now. Starting from the basic principle and structure, its mathematical model of wind turbine, wind speed model, variable pitch control model and doubly fed generator model were established. Based on the mathematical model, a simulation model of the doubly fed wind power generation system was build in the PSCAD. The working principle, power genaration characteristics and mathmatical model of micro gas turbine, fuel cells and photovoltaic cells were analyzed. Their model was also build in PACAD. The common storage devices—super capacitor modeled and analyzed. Study on super capacitor is very necessary because energy storage can provide short power supply, improve power quality and potimeze the micro power operation.Then on the basis of modeling, the control strategy of microgrid was introduced. And the control strategies of micro power and energy storage device are analyzed, including P/Q control mode, Droop cotrol mode and U/f control mode. Several kinds of micro overall control strategy is presented. The master-slave control strategy was selected to be the over control strategy. A specific micro power control mode was established, especially the super capacitor that is master control unit. Super capacitor controller is designed.Finally, according to the mathematical model and control model that has been established, the simulation model was created in the power system simulation PSCAD. The operation and control, frequency stability and voltage stability of the microgrid were analyzed in PSCAD. The results shows that this model is effective.