| Since the reform and opening up the rapid growth of economy in our country, promoted electricity demand rapid growth and the continuous expansion of grid. But the disadvantages of large power system is becoming more and more apparent, the construction cost is high, operation is difficult, and difficult to satisfy the increasingly safe and reliable and diversified demands of users for electricity. Especially in recent years, large area blackout accidents happened in the world of catastrophic consequences also fully exposed the vulnerability of the existing grid structures.Distributed power generation system is compared with the single and centralized traditional power supply system, the power generation units are independent, can control by itsself, don’t occur a massive power outage, have higher safety and reliability; Distributed generation can make up for a lack of security on the stability of interconnected power grid, may continue power supply when the unexpected disaster; Distributed power positions are flexible and dispersion, suitable for remote areas and power supply of the small and medium-sized cities, can greatly reduce the pollution of the environment; Transmission and distribution losses of distributed generations are low, greatly reduces the transmission and distribution cost and installation cost. Although compared with the large power grid, distributed generation has so many advantages, but also a large number of distributed power’s access bring many problems for grid protection and real time scheduling and power grid reliability and so on, so in order to give full play to the advantages of distributed generation and can reduce the impact and influence of distributed power for grid, currenttly combined distributed power supply and loads to construct microgrid (Microgrid) is a better way to solve these problems.Based on fully understanding the microgrid structures and the power grid structure and the related power electronics equipments of performances and reliabilities, with simulation methods mainly,this paper completed various micro energy resources’s modeling and simulation, grid-connection and island operation control.Main works include:(1) Introduced the background of microgrid, domestic and foreign research present situation and key technology.(2) Constructed the general model of photovoltaic cells, analyzed photovoltaic battery output characteristic, and realized the maximum power point tracking of photovoltaic cells based on the Boost converter using the incremental conductance method, compared the advantages and disadvantages of mountain climbing method and incremental conductance method, selected the increment conductance method to achieve photovoltaic cell’s maximum power point tracking; Introduced the basic principle of doubly-fed wind generator and vector control coordinate transformation relations, constructed no-load model of doubly-fed wind turbine with S function.(3)Introduced the principle of the DC/DC converter, then analyzed the design method of LC filter, dq transformation technology and the grid control theory, finally constructed a single-phase grid-connection for the DC source equivalent model to verify grid control theory.(4)Designed the grid-connection control strategies of photovoltaic cell and doubly-fed wind generator and constructed simulation model in MATLAB/Simulink, verified the correctness of the designed control schemes,and completed maximum wind power tracking control after the grid-connection with load.(5) Studied DER’ control method of microgrid island operation—V/f control and Droop control, constructed microgrid island operation simulation model in different operating mode,verified the validity of the designed control strategy. |
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