Study On Modeling And Simulation For Distributed Generation System Based On Gas Turbin/Fuel Cell Combined Generation

Distributed generation (DG) is a small scale power generation system near consumer side for satisfying some special needs. Now common DG types can utilize multiple energy resources, make for environmental protection, and further improve the energy efficiency through combined heat and power mode and combined cooling, heat and power mode because of short distance between distributed generators and consumers and low transmission loss. Therefore, DG is regarded as a very promising generation technology from the viewpoint of energy-conservation and environment-protection. The research on DG has been started much later than conventional generation technologies, so it is necessary to further the research on DG models, DG control laws and potential impacts of grid connected DG on power system.DG includes extensive energy utilization modes, but there are several problems when applying one single mode, such as low energy efficiency, large random output fluctuation, and control difficulty. So it becomes the research focus to explore effective combinations of different DG energy utilization modes. Fuel Cell/Micro Gas Turbine (MGT/FC) hybrid generation system is efficient, beneficial to environmental protection and low in generation cost, so it will be one of the main DG modes. With further development and utilization of natural gas, it is certain that MGT/FC hybrid generation system will be widely applied in our country.Based on the aforementioned consideration, this paper selects the model of MGT/FC hybrid generation system and its impacts on power system as study objects. At first the latest progress in the two aspects is summarized, and then the statement emphasis is put on the author's research results in the same aspects. The main contents include the follows.(1) Combined with mechanism models and parameter identification data of thermodynamic and pneumatic processes, a detailed modularized simulation model is built to reflect main dynamic characteristics and control relations of Micro gas turbine. Research on modeling and relevant model simplification of the integration of permanent magnet generator and rectifier is carried out, external characteristic equations of permanent magnet generator with unidirectional rectifier are derived, and a mechatronics simulation model is built.(2) Electrochemical model of Solid Oxide Fuel Cell (SOFC) is analyzed and based on it mathematical models of three levels respectively corresponding to SOFC electrode, fuel cell and stack system are built. Then the third mathematical model is simplified for being applied to power system simulation and analysis.(3) Two modes of MGT/FC hybrid generation system respectively based on bottoming and topping cycle are reviewed and relevant simulation models are built.(4) Integrated control system of voltage source inverter operating as grid-connected interface is designed, which adopts current Sine pulse width modulation (PWM) regulation and can realize and well maintain constant power operation characteristics.(5) The whole simulation model of MGT/FC hybrid generation system is developed in PS ASP by its user defined (UD) modeling function and dynamic and steady simulation are performed. Dynamic response relations of simulation are basically consistent with measurement results and therefore the reliability and validity of the model is verified.(6) Cases of power system with the integration of MGT/FC hybrid generation are simulated and impacts of the latter on the former in several aspects are analyzed.