Study On The Connection Of A Micro-distributed Generation With The Grid

For the traditional growing shortage of fossil fuels, distributed energy resources as a new type of energy is increasingly attached importance by many counties in the world. Even with the economic crisis in United States, Obama also put a large number of government investment in the research of distributed energy technologies. China will vigorously develop the distributed energy included in the national "Eleventh Five-Year" development plan. Distributed energy resources mostly includes fuel cell generation system, solar energy battery generation system, wind energy generation system and biomass energy generation system. Especially large-scale wind power applications is increasing. Because there are many power electronic devices, such as wind power and by the impact of objective factors, the impact of the parallel is received increasing attention.This paper first described the concept of distributed energy, and the characteristics and the impact of parallel. And then it analyzes a variety of energy and network problems, focusing on photovoltaic solar energy and wind power and network issues, and the connection operation of small islanded micros-grid network is studied for the distributed generation (DG) units with small energy source, such as synchronous machines driven by combustion engines. Based on the four-order basic equation of the synchronous machine, using PI control, the frequency and phase difference are fed back to the excitation voltage to change the frequency and phase between the micro-distributed generation and the infinite grid. If the active power of DG can not be adjusted to increase the frequency of the islanded micro-grid without curtailing the load and interrupting power supply, the proposed method can be used to reduce the DG's voltage and the load power, on the other way, it can adjust the DG's frequency and phase angle, which is the main advantages of the proposed method. The simulations by the S function in the MATLAB show that choosing PI parameters, frequency and phase between the synchronous generator and the infinite grid will be the same while the output of the generator governor is kept unchanged. Results validate the feasibility of the method.