Research on Modeling and Control Strategies of Pv and Microturbine Hybrid Microgrid
|Keywords||Photovoltaic Microturbine Modeling Control Strategy Time Series Method|
This thesis was supported by Natural Science Foundation of Chongqing (CSTC 2009BB6190) and independent research project of State Key Laboratory of Power Transmission Equipment & System Security and New Technology (2007DA105127092 08).With the worsening of energy crisis and environment pollution, microgrid technology has become a hot topic as a feasible solution. The microsource of photovoltaic becomes one of renewable energy sources with the greatest development potential because of abundance, wide distribution, cleanness and so on. Because the PV generation is obviously intermittent, the output power is greatly influenced by the variable weather. In order to improve the reliability of PV generation, the controllable microsource or distributed storage is added in with the PV generation to form hybrid microgrid. Among the controllable microsource, microturbine can supply hot and cold load at the same time. With the advantages of low emission, high efficiency and better fuel adaptability, microturbine has become the most promising distributed power in the combined cooling heating and power microgrid. Therefore, it has great significance to research the operating characteristics and control strategy of the hybrid microgrid composed of PV and microturbine. The main content is as follows:①PV generation and PV inverter principle is analyzed to study the operating characteristics and influence factor of PV generation. A user-designed PV array and maximum power point tracking control model are developed. A constant-current source electrical model can be driven by the current output signal of the PV array control, by which a real PV array equipment can be simulated. The incremental conductance method is used to achieve MPPT control. The PV generation system model is builded to verify the I-V and P-V characteristic curve of PV array. The influence of illumination and temperature change on the system transmission power is analyzed.②Based on the working principle and mathematical model of microturbine and its power electronic converter, according to the microgrid characteristics in grid and island state, an overall model of a microturbine generation system with double PWM converters is established. In order to maintain the DC voltage, rectifier uses a constant voltage control method. Based on V/F and PQ control strategies, the control algorithm of inverter is achieved in grid and island state. The operating characteristics of microturbine generation system with dynamic load is analyzed.③The dynamic model and operating characteristics of PV and microturbine generation system are analyzed,and the control strategy of PV and microturbine hybrid microgrid using the time series method with variable steps is researched. When the microgrid operates on the grid-connected mode,the controllable microturbine is used to smooth the photovoltaic power fluctuation and make the hybrid microsource becoming a scheduled power source. When the microgrid operates on the islanding mode,the storage battery which responses the rapidly changing power together with microturbine compensated the power difference between PV and load, and this can realize the stable operation of microgird. The time series method with variable steps is adopted to predict the power of PV and load according to their frequency characteristics, and the microturbine’s disadvantage of slow response is overcome. In order to improve the efficiency and lifespan of batteries, a modular control mode for battery management is proposed to guarantee the reliability of hybrid microgrid.④The PV and microturbine hybrid microgrid simulation model is established in PSCAD/EMTDC, the control algorithmic is achieved in Matlab. It verifies the validity of the proposed theory and method through hybrid simulation. The operating characteristics in three state contained grid-connection, islanding and mode switching are analyzed. The influence of variable step time series method on the power fluctuation of microgrid junctor is analyzed, and the status of the modular battery management is researched.