Control And Protect Of Fuel Cell Grid-connected Inverter

Nowadays, research on renewable energy and distributed power generation has drawn more and more attentions because of the lack of energy, pollution and disadvantage of centralized power supply. The control and grid-connected protection of inverter, an important part of distributed power system, becomes an international hotspot of research.A fuel cell grid-connected inverter, which can work in stand-alone or grid-connected mode, is proposed in this paper. It can work in stand-alone mode to supply the local load while in grid-connected mode to offer power to the grid.Firstly, this paper discusses the background of research on grid-connected inverter, including the introduction of distributed power generation, structure of grid-connected fuel cell system, standard of grid-connected by IEEE, etc, and gives comparison among many control methods of inverter output current, and analyzes control methods of instance voltage inner-loop and average voltage outer-loop and technology of digital phase lock in detail. Secondly, a current control method based on active or reactive current, with which the magnitude and phase can be controlled effectively, is proposed in this paper. Thirdly, this paper analyzes the model of islanding detection for fuel cell system, proposes islanding detection method based on output power variation which has been theory analyzed and emulated. Finally, this paper introduces the design for a 5kW fuel cell grid-connected inverter and gives experiment results of stand-alone, grid-connected and anti-islanding detection.