Research On Cooperative Control Of Hybrid Ac/dc Micro-grid And Response Strategy Of Active Load

In recent years, micro-grid system has brought modern electric power systems research into a new era because of its advantages, it promotes the development of power system greatly by integrating the advantages of a variety of micro-sources. Comparing with traditional AC or DC micro-grid, a hybrid AC/DC micro-grid has flexible structure and high energy efficiency but complex control. This paper researched on the control strategy of hybrid AC/DC micro-grid in different operating status to ensure the stable operation in small perturbations. In order to reduce abandoning wind and sun, improve the utilization efficiency and realize load shifting, this paper researched on the active load response by swarm intelligence algorithm.Firstly, this paper established the mathematical model of typical micro sources, including photovoltaic(PV), wind turbine and battery(BA). For PV, this paper used the established model analyzing the output characteristic in different environments, realized the maximum power point tracking by disturbance observer method in DC/DC converter to ensure maximum utilization of light energy. For wind turbine, this paper analyzed the mathematical model of each module and the simulation result proved the mathematical model was effective which laid a foundation for participation in frequency regulation of wind turbine. For BA, this paper analyzed the working principle of the bidirectional DC/DC converter and the simulation result proved the model can effectively keep the stable of the DC bus voltage.Secondly, according to the structure and operational characteristics of hybrid AC/DC micro-grid, this paper proposed a coordinated control strategy. In grid-connected mode, PV and wind turbine work in maximum output power to take full use of renewable energy, micro-grid management system adjusted the exchange power by changing the output power of micro gas turbine and the battery only adjusted the DC bus voltage. In island mode, the PV still worked in maximum output power, the battery, wind turbine and gas turbine cooperatively adjusted the system to keep the stable of frequency and voltage. The simulation result proved the proposed cooperative control strategy was effectively on controlling exchange power, restricting frequency fluctuation and keeping DC Voltage stable.Finally,as the renewable energy has large fluctuations, the daily load curve and renewable energy output curve doesn’t match, the output curve of gas turbine has large peak and valley difference after adjusting and the system has low efficiency, this paper proposed an active load response strategy with price incentive policy. The strategy used ant colony algorithm and made minimum electricity costs as the target function to arrange the power task. By contrast verification, the result proved the ant colony this paper used could quickly and efficiently realize active load response, efficiently reduce the output peak and valley difference of gas turbine and improve the comprehensive utilization efficiency of the system.This Project was funded by the National Natural Science Foundation of China(NSFC). Project name: The Basic Theory and Key Technology of Environment Friendly Integration between Smart Grid and Electric Vehicle(51361130153).