| This dissertation is focus on the power optimization problem of microgrid,the control methods and optimization strategies are investigated.Firstly,a smooth control and energy distribution strategy for the microgrid hybrid energy storage system is proposed to solve the control and energy distribution problems of microgrid during connected and off grid operation.Secondly,an improved droop control strategy of micro-source inverter based on variable virtual impedance is proposed to realize the smooth switching and stable operation of the microgrid in the process of connected and off grid operation.Finally,a method to build the hierarchical control system structure of microgrid and a method to solve the distributed constrained optimization problem are proposed to complete the construction of the power optimization model of microgrid and realize the distributed optimal control of microgrid.The main works and contributions are given as below:(1)Aiming at the problem of smooth control and energy distribution of the microgrid hybrid energy storage system,by analyzing the advantages and disadvantages of different combined structures of hybrid energy storage,a microgrid hybrid energy storage system model based on the coupling of supercapacitors and batteries in the DC-DC converter connection structure is established.The power distribution strategy of the hybrid energy storage system and the power feedforward control strategy based on time keeping are proposed to realize the smooth control and energy distribution of the hybrid energy storage in the microgrid.The simulation results show that compared with the traditional control strategy,this strategy can more effectively suppress the fluctuation of active power,not only can better play the advantages of supercapacitors and batteries,but also improve the safety of the system and the life of the battery,which satisfies the consideration of the sudden change of grid load to maintain system stability.(2)Aiming at the optimization control problem of micro-grid micro-source inverter,according to the analysis of the basic principle of micro-source inverter droop control,the influence of various types of line impedance on the output power balance of micro-source inverter and the stable operation of microgrid,the output model of the micro-source inverter is established.On the basis of the traditional droop control method,an improved droop control strategy of micro-source inverter based on variable virtual impedance is proposed.The simulation results show that compared with the traditional droop control,the improved strategy can effectively reduce the voltage deviation of the microgrid,achieve the average power distribution,and improve the operation stability and power quality of the microgrid.(3)Aiming at the optimal control problem of microgrid,a new hybrid layered control system structure based on multi-agent is proposed,and a power optimization model of microgrid with intermittent distributed power supply and hybrid energy storage is built,and a solution of distributed constrained optimization problem based on potential game theory is provided.The convergence proof of the control law verifies that the control strategy can improve the stability of connected grid and off grid switching and the reliability of system operation,and then realize the optimal control of the microgrid.(4)Aiming at the optimal scheduling problem of multiple microgrid during connected grid operation,the scheduling model of microgrid based on multi-agent regional combination is built,the improved droop control method is used to realize the optimal control of each unit in microgrid,the distributed constraint optimization problem solving method based on potential game theory is used to complete the global optimization of scheduling model,realize the optimization scheduling for microgrid of regional combination.The simulation results show that the optimal dispatching scheme adopted in this chapter has good adaptability and error correction ability,and can solve the new energy consumption problem while alleviating the transmission capacity limitation,and is suitable for solving complex system problems. |
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