The Research And Developent Of Grid Connected Fuel Cell Inverter

The fuel cells are viewed as the best clean and efficient generation technology due to their high energy conversion efficiency and environment friendliness. At present, the fuel cell usually connected to grid as distributed generation system, grid-connected inverter is the key component of the distributed generation system, the stability and reliability and efficiency of the inverter decide the performance of the distributed generation system.At present, scientists focu on the topology and control technology while do some research on the grid-connected inverter. The efficiency and stability of the system was decided by the inverter topology; grid-connected inverters usually use the close-loop control of current, control the current frequency and phase can follow the grid voltage. And the current distortion must limited in a certain range to reduce the impact of the grid harmonic, the inverter can supply the power to gird as unity power factor.The dissertation based on the BALLARD Nexa? proton exchange membrane fuel cell (PEMFC), finished a grid-connected inverter, it can work in independent power status and grid-connected status. This system can be divided into three parts, as DC/DC boost converter, DC/AC inverter and control system. By the natural output characteristics of PEMFC, the dissertation designed a push-pull forward converter which can applies to low-voltage and wide input situation. And give detailed instructions of this circuit topology and working principle. The latter stage of DC/AC uses the full-bridge inverter that drive by SPWM modulation, the dissertation used close-loop control of voltage while the inverter work in independent state, it can ensure reliable operation of the load; and used close-loop control of current while the inverter work in grid-connected state, that can put the electric energy generated by PEMFC back to grid in unit power factor. The dissertation used the passive islanding detection method which can applyed to low power grid-connected inverter, according to the grid voltage and frequency to determine whether the island happened, and trigger the island protection. At last, I finished the1kW grid-connected inverter prototype on the basis of theoretical analysis. Experiments show that, the inverter prototype works well, and it meets the design requirements, that verify the correctness of theoretical analysis, this topic proposed a solution for small and medium-power fuel cell distributed generations system.