Research On The Smooth Switching Control Strategy Of Microgrid

In recent years,due to the aggravation of the energy crisis and the increase of the demand for electricity,the development of distributed generation using new energy generation technology is an inevitable trend of power structure reform.Because of the difficulty in controlling the power grid when single distributed generation is connected,every country in the world has widely put attention to the integration research and development of Distributed Generation(DG)microgrid into the main grid.The future development direction of power system is smart grid.Microgrid is an important part of smart grid.It can effectively solve problem that the new energy power generation system is not easy to control and avoid the possible widespread blackouts,offering great practical significances to all sectors of society.This paper firstly elaborates the development background and significance of microgrid,which indicates that the research and development of microgrid is an inevitable trend.To realize the stable operation of the microgrid and a wide range of input use,the smooth transition between the grid-connected mode and the islanding operation mode is very necessary.This paper described the overseas and domestic research status of smooth transition control is describedThen,according to the characteristics of microgrid in both grid-connected and the islanding operation modes,a control strategy is proposed to achieve smooth transition between these two modes.Under grid-connected mode,the distributed generations in the microgrid adopt PQ control,and the utility power grid provides the support of voltage and frequency to ensure the overall stability of the microgrid.When the utility power grid failed or active microgrid solution with the column,islanding detection device detects that and the microgrid runs to the islanding operation mode,the improved droop PQ-Droop control strategy is employed to the energy storage device,mainly to compensate the power shortage of the whole system,and at the same time support the voltage and frequency of the microgrid system.Considering under islanding operation mode,it may happen that the power required for the loads exceeds the output power of the distributed generations supply.Therefore,combine the control strategy with the removal of the load control.In other words,when the switching the microgrid operation mode,it is necessary to detect the supply and demand of power in the microgrid.According to the results of the detection,some load can be cutting to ensure the stability of the important load.Finally,modeling with the MATLAB/Simulink software packages,and simulating in different situations,such as constant light irradiance,changing light irradiance and exceed load power.Simulation results confirm that the proposed control strategy is effective.By controlling the distributed generation,the control strategy ensures the operation voltage and frequency under grid-connected mode,islanding mode and transitions between them.Furthermore,the stability of the output power is also achieved,effectively guarantee the normal work of the important loads within the microgrid.