| With the rapid development of new energy and Microgrid technology,in order to improve the flexibility of Microgrid effectively and its management and control ability for distributed power generation,and to support the operation of Energy Internet,the way of using PET to connect Microgrid to power grid has been concerned and studied widely.PET has a multi port structure and the converter of each port is flexible and controllable,and it can realize the functions of electrical isolation,voltage level transformation and energy transfer,so it can meet the access requirements of various forms of load,power supply and energy storage equipment in the future AC/DC hybrid distribution network.It is critical to control the PET,which is the key part of the Microgrid connected to the main network.At present,PET control technology has been extensively studied,but due to the lack of an effective mechanism of integration with the power grid in the traditional control strategy,the microgrid can not participate in the operation and control of the main power grid.Therefore,in order to solve the above problems,this paper studies a scheme of cascaded H-type PET controlled by virtual synchronous machine.This scheme can not only adjust the voltage and frequency of microgrid,but also support the voltage and frequency stability of power system.Firstly,based on the analysis of the micro grid connected to the main grid,the control strategy of virtual synchronous machine is proposed,meanwhile this paper introduces the research status of PET at home and abroad,and makes a comparative analysis of PET topology based on MMC and PET topology based on cascaded H-bridge.The results show that the PET topology based on cascaded H-bridge is the most widely used and the control technology is more mature.Therefore,this paper takes the cascaded H-bridge PET topology as the research object,aiming at the application of the micro grid interconnecting with main grid system based on the cascaded H-bridge PET interface,based on the analysis of the advantages and disadvantages of the traditional PET control scheme,a cascade H-bridge PET scheme controlled by synchronverter virtual synchronous machine technology is studied.Secondly,the working principle of each module of pet topology is analyzed and its working mode is analyzed.On this basis,the control strategies of each module are analyzed and designed.According to the control requirements of PET input stage and output stage,this paper analyzes the operation mechanism of virtual synchronous machine,and puts forward corresponding control strategies of virtual synchronous machine.At the same time,in order to control the DC side voltage of the input stage,the voltage sharing control technology is introduced.Through the analysis of the transmission characteristics of the isolation stage,the traditional input voltage sharing control strategy is adopted.Finally,taking the operation system of microgrid connected to the main grid based on PET as an example,the parameters of PET main circuit and control circuit are designed.Then based on MATLAB/Simulink simulation environment,the steady state characteristics of the system in the stable state and dynamic conditions of the main network are verified,the feasibility and effectiveness of the cascaded H-bridge PET system based on the virtual synchronous machine control are proved,the control objectives are realized,and the correctness of the theoretical analysis and simulation results is further verified,and the correctness of theoretical analysis and simulation results is verified by setting up RT-LAB semi-physical experimental simulation platform. |
PDF Full Text Request