Research The Grid-connected/islanded Control Strategy Of Microgrid Inverter

With the deepening of the global understanding of the energy crisis and environmental protection issues,the development and application of new energy has become the mainstream of research,and the development and application of new energy based microgrid systems based on power electronics devices have received increasing attention.This article takes the microgrid inverter as the research object,and studies the grid-connected/islanded control strategy of the microgrid inverter.The main contents are as follows:First,the background and significance of the microgrid are described,the main types,operation methods and control modes of the microgrid are introduced,and the research status of microgrid inverter on/off-grid control strategies is analyzed.Then,the main structure and system composition of the microgrid inverter are analyzed,and its various components are explained to a certain extent.Then the microgrid control strategies are analyzed and compared to their respective characteristics,and the applicable microgrid operation modes are summarized.Secondly,the grid connection control method of microgrid inverter is studied.A PQ control strategy for non phase-locked loop based on Hilbert transform is proposed.In microgrid inverter,the preset synchronous rotation frequency is used to mutually convert the positive and negative deviations of the specified frequency,and then the amplitude and phase of Hilbert Transformation and certain mathematical operations,this method can eliminate the positive-sequence harmonic components,basic negative-sequence components and negative-sequence harmonic components in the grid voltage,and extract the grid voltage synchronization signal to improve the performance of PQ control.Furthermore,the seamless switching and parallel switching technologies of microgrid inverters are studied.Firstly,a microgrid inverter control method based on virtual impedance and virtual synchronous generator was researched,which solved the problems of active and reactive coupling and generator voltage drop of virtual synchronous generator control.Based on this,an improved virtual synchronization Generator-controlled microgrid inverter seamless switching and parallel switching technology.This method uses VF control and improved virtual synchronous generator control as the basic control algorithm.It can effectively control the microgrid when it is connected to the grid,off-grid and on/of-grid.Finally,a low-power experimental platform for a microgrid inverter system is set up.The seamless switching and parallel switching technologies of microgrid inverters are experimentally verified,which proves the effectiveness and feasibility of the proposed control method.