Study On The Power Control Of Distributed Generations In Microgrids

Distributed Generation (DG) refers to those small scale power generation devices which is scattered at the user site. It has various realization forms including microturbine, photovoltaic, wind power and other forms of power generation. It is one of the most important ways to solve energy and environmental problems. However, most DG have the problem of randomness and uncontrollable energy source, which would give rise to interference of energy balance in traditional power grid and affecting the stability of the power grid. For the safety and effective utilization of DG, a new type of small power system which is composed of DG and load, called Microgrid came into being. It can either operate in island mode or in paralleled mode. Microgrids not only contain DG using inverters for paralleled operation but also contain traditional power generation in form of synchronous machine. Electronic converters especially inverters is the key technology for using renewable energy.This Paper compares the difference of structure and control characteristics between traditional generation and DG, and then on the basis of experience further study the control strategy of grid-connected inverter waveforms and control strategy of power output; further discussion the stability of inverter controlled by droop strategy; and use simulation software to verify the correctness of theoretical analysis. Finally, for a specific Microgrid which contains two DG and one energy storage device, proposed centralized control strategy for Microgrid based on network control system. The main text is as follows:(1) Take microturbine generating system as the example, paper has established the DG control model and has carried on the comparison of DG model and the tradition synchronous generator in the field of working principle and the control characteristic.(2) Studied the single phase AC inverter voltage waveform control strategy as well as has designed the single-phase potential source output decoupling control plan, and has compared proposed decoupling plan with the traditional approximate decoupling plan in the simulation.(3) Studied the three-phase AC inverter voltage waveform control strategy as well as further discussed the three-phase potential source output decoupling control plan, and has compared two kind of different decoupling plans in the simulation.(4) Study the stability problem based on the droop method of DG, explore the impact of the drooping characteristic parameters on the stability of the output power control of DG in different capacity.(5) Research a kind of Microgrid which includes two DGs based on power decoupling control and one energy storage device based on droop characteristic control. In considering the communication network with longer sample period and communication delay case, suggest a centralized power control scheme based on predictive control.