Research Of Key Technology On Operation Control Of Hybrid AC/DC Microgrid

Nowadays, the global energy excessive consumption and environmental problems are needed to be solved urgently. As a power generation and distribution system which takes the advantage of clean renewable energy, the microgrid has a broad prospect of application and development. The distributed generations of microgrid connect to the system by power electronic conversion devices, which improve the performance of flexibility under controlling. However, the converters comprise many sorts and the distributed generations have different output characteristic, which make it more difficult to keep the power balance and maintain the magnitude and frequency of voltage in the system. Depending on the effective operation control strategies such as master-slave control and equivalent control, the power flow can be controlled coordinately and the clean renewable energy can be made full use of in the microgrid.The hybrid AC/DC microgrid contains the advantages of AC microgrid and DC microgrid, simplifying the procedure of power conversion and reducing the energy loss brought by multistage power conversion. Meanwhile, the hybrid AC/DC microgrid can satisfy the power energy demand of AC load and DC load at the same time. Depending on MATLAB/Simulink simulation platform, the thesis sets up the simulation model of hybrid AC/DC microgrid and researchs the operation control strategies of Hybrid AC/DC microgrid. As a result, the power balance and stable operation are realized by master-slave control strategy in the system. The concrete work is as follows:Firstly, the control methods which include the PQ control, VF control and Droop control applying to the micro source are analyzed. In addition, the thesis analyzes the control methods which include master-slave control, equivalent control and multi-agent system applying to the microgrid.Secondly, the photovoltaic power generation unit is studied, furthermore, the equivalent simulation model of photovoltaic power generation in a changing external environment is established. The different methods of maximum power point tracking (MPPT) are simulated and compared, which include the traditional fixed step perturbation and observation method and improved variable step perturbation and observation method, verifying the advantage of improved perturbation and observation method. A bidirectional DC/DC battery energy storage unit is established, which plays an important stabilizing role for votage during the running process of microgrid. The control strategies of energy storage unit used in grid-connected operation and islanded operation respectively are designed and simulated.Thirdly, the thesis sets up the mathematical model of bidirectional converter that connects the AC bus and DC bus. The control strategies of bidirectional converter working on grid-connected operation and islanded operation respectively are designed and analyzed. The parameters of capacitor which is in the DC side of bidirectional converter and LC passive filter which is in the AC side of bidirectional converter are calculated. In addition, the transfer function and reasonable control parameters are obtained. The UQ control, PQ control and VF control are analyzed and made a detailed derivational process.Finally, the thesis builds a simulation platform for the whole hybrid AC/DC microgrid in MATLAB/Simulink. The typical operating conditions of the hybrid AC/DC microgrid are analyzed. The typical working conditions and switching process between different working conditions are simulated, as a consequence, the correctness and reliability of master-slave control strategy and micro source control strategies adopted in the thesis are verified. Furthermore, the dynamic process of operation control is analyzed in hybrid AC/DC microgrid.