Research On Digital Control Technology Of Three-phase Inverter Based On SVPWM

Inverters,as core devices to realize electric energy conversion,play important role in various fields.With the development of microelectronic technology and modern control theory,inverters are developing in the direction of full digitization and intelligence.The reasonable selection and design of PWM and digital control strategies can directly affect the overall performance of the inverter system.This article taking a three-phase three-wire inverter as the research object,to realize the full digital control of the inverter,the paper mainly does the following work:First of all,by comparing and analyzing the current existing PWM control technology,SVPWM control technology is selected as the pulse control technology of the three-phase inverter.The basic principle of SVPWM control technology is analyzed,and the steps to realize the control algorithm are given.To facilitate the realization of digital design,the S-function is used to build a SVPWM simulation model in MATLAB according to its principle,and the flow block diagram of its implementation on DSP is also given.Secondly,the mathematical model of three-phase three-wire inverter is established and analyzed in three different coordinate systems.After comparative analysis,the fundamental voltage of the three-phase inverter output is converted into a DC quantity in dq rotating coordinate system,which can be realized by a PI controller without static errors and has good dynamic characteristics.Using the feedforward decoupling control strategy,the problem of coupling of state variables on the d and q coordinate axes is solved,so that the controller can be designed for the d and q axes respectively.Taking the d-axis as an example,the instantaneous voltage PI control strategy is selected to control the inverter output voltage.A digital PI controller is designed by continuous domain and direct discretization,respectively,and the range of PI control parameters that can make the system stable is obtained.Then,the main hardware circuit and software programming of the digital inverter system are discussed.The hardware system of three-phase inverter based on DSP and CPLD is designed,and the hardware circuit design diagrams of power circuit,filter circuit,sampling conditioning circuit and protection circuit are given.The main functions of the two control chips in the system are introduced,and the flow chart of the main program and interrupt program for digital control are given.Finally,the digital PI control algorithm and SVPWM control technology analyzed above are verified by building a designed experimental platform.The experimental results show that the three-phase inverter system based on digital PI control has good dynamic and steady-state characteristics.The feasibility of the designed inverter control strategy is verified.