Research On Improving Power Quality Of Microgrid Based On Energy Storage

The power system is the basic guarantee for maintaining social life and production,as the scale of the power system continues to expand,distributed power generation technology based on renewable energy has received more and more attention,in order to solve the adverse effects caused by many distributed power sources connected to the power distribution network,the concept of microgrid came into being.Compared with the traditional distribution network,the operation mode of the microgrid is flexible and includes a variety of distributed power sources,it has complex dynamic operation characteristics.In order to ensure the efficient and reliable operation of the microgrid and meet the power quality requirements of various users in industry and enterprises,microgrid power quality control technology has become one of the key technologies of the microgrid.The rapid development of energy storage technology has opened up new ideas for improving the power quality of microgrids.It is of great significance to compensate for various types of power quality with energy storage devices in microgrid.This paper studies the generation mechanism of microgrid power quality,based on this,proposed the improvement method with the help of energy storage systems.The main work is as follows:Aiming at the composition and operation characteristics of microgrid,the system level and micro power level control strategies of microgrid are analyzed,and the island and grid equivalent circuit model of microgrid is established.On this basis,the paper studies the reason for the microgrid transient power quality,and studies the production mechanism of the interaction between the power quality of the microgrid and the distribution network.In order to improve the transient power quality that occurs when the microgrid operation mode is switched,according to the operating characteristics of the microgrid and the working principle of the energy storage converter,researched the droop control single mode switching strategy,proposed a droop control strategy with improved power outer loop.The gradual approximation is used to reduce the voltage and frequency errors during the grid connection process,so that the voltage and frequency of the microgrid before the grid connection are constantly trending towards the voltage and frequency of the distribution network,and realized the smooth switching of the microgrid operation mode.In order to solve the influence of the power quality interaction between the microgrid and the distribution network,the paper proposed a power quality controller based on energy storage.Research the control strategies of each part of the power quality controller,and according to the connection method proposed coordinated control strategy for the energy storage system,through coordinated control between the super capacitor,micro power supplies and loads to maintain the stability of the voltage level and power balance of the point of common connection.In order to verify the improvement effect of the microgrid power quality controller on power quality,a corresponding simulation model was built under the Matlab/Simulink environment,and simulation studies were conducted from the aspects of voltage quality on the distribution network side and current quality on the microgrid side.The simulation results show that: the microgrid power quality controller based on energy storage power can effectively improve the power quality interaction problem between microgrid and distribution network.