| In the situation of growing energy shortage and environmental pollution, seeking green and renewable energy is becoming more and more important. Fuel cell power generation technology with its wide fuel sources, no pollution, high efficiency and not affected by the environment etc advantages, it has received widespread attention from experts and scholars around the world, especially the high gain DC- DC converter and grid inverter technology in the process of energy transmission. In order to satisfy high power Fuel cell power generation system's requirements which with the lower level numerical and the wider fluctuation range output voltage,the former grade DC- DC converter must have the ability of dealing with high voltage gain and high input current, meanwhile providing stable DC voltage for after grade inverter. The after grade inverter can be divided into single phase inverter and three phase bridge inverter, and the persistent control strategy often used constant voltage constant frequency(V/F) control, constant power(P/Q) control, droop control and so on,however the above control strategies have certain using restrictions and scope, furthermore the control accuracy is not high ect. On the base of above, the paper mainly researched the former grid high gain DC/DC converter topologies, control technology and later grade inverter control strategies. The main contents as follows:(1) Studied a combined high gain DC converter based on average voltage control and average current control algorithm, which not only has higher voltage gain, proper duty ratio,quicker PWM modulation response, smaller ripple, much lower switch tube voltage and current stress ect. Analyzed the topology's working principle, steady state performance in detail, furthermore established and analyzed the small signal model, which provides certain theoretical basis for the control circuit's designing and the parameters' selection, meanwhile through the simulation and experiment verified the feasibility and correctness of the high gain DC-DC converter's topology and control strategy in this paper.(2) Studied a kind of micro-grid inverter overall control strategy based on virtual synchronous generator algorithm, firstly selected the virtual synchronous generator algorithm as the control strategy the outer ring, designed virtual synchronous generator ontology algorithm, virtual prime mover adjustment and excitation current adjustment model respectively, meanwhile select the voltage current double loop control strategy as the inner ring, not only made the inverter with good droop characteristic of output voltage amplitude and reactive power as well as frequency and active power, but also tracked the changing load quickly, to improve the stability and reliability of the system. In addition, the paper improved the virtual prime mover control module,which can achieve frequency real-time control of nodifference, improved the control and response speed of frequency. The theoretical analysis and simulation results show that the studied inverter control strategy not only applied to one single inverter operation, but also suitable for the two inverters parallel operation.(3) Established the cascading fuel cell power supply system structure which is composed by the former DC converter and later grade inverter and it adopt two-level structure independent control strategy, achieved the purpose of transforming the fule cell chemical energy to AC electrical energy of load or big power grid required. Finally constructed the simulation model,validate the feasibility and correctness of the theoretical analysis. |
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