Research And Implementation Of Three-phase PWM Rectifier Based On Sliding Mode Control

With the introduction of China’s "dual carbon" strategy,higher requirements have been placed on the green development of energy.Especially in the process of coal production,the variable frequency control system as a key equipment has been widely concerned by scholars.In the variable frequency control system,the rectifier mostly adopts diode uncontrolled rectifier,which has a low power factor and cannot achieve four-quadrant operation,resulting in energy waste.This thesis takes the three-phase voltage source PWM rectifier as the research object,and studies the problems of start-up inrush current,poor dynamic performance and robustness existing in the traditional PI control strategy.This thesis introduces the research status of PWM rectifier,start-up inrush current and robustness in detail,analysis the working principle of PWM rectifier,and deduce the mathematical model of three-phase voltage source PWM rectifier.Then,the design of double closed-loop control strategy and PI controller is introduced in detail.The problem of start-up inrush current is deeply studied,its generation mechanism is analyzed in detail,and its influencing factors are deduced.Then,two suppression methods are introduced:ramp up curve method and start-up inrush current suppressor.Finally,the effectiveness of the suppression method is verified by MATLAB simulation.The traditional PI control strategy is simple to implement and has good steady-state performance.However,when the system is disturbed,it’s likely to cause instability of DC side voltage and poor dynamic performance.Aiming at this problem,the sliding mode control(SMC)strategy is introduced in this thesis.In order to improve the performance of phaselocked loop when the power grid is unbalanced,the dual second order generalized integrator phase-locked loop(DSOGI-PLL)is mainly studied.And the space vector pulse width modulation(SVPWM)technology and its implementation method are discussed.In order to solve the contradiction between the robustness and chattering in the SMC strategy,the extended state observer(ESO)is introduced into the voltage loop,and the approach law is used to redesign the voltage loop.Finally,the simulation results shows that the SMC strategy based on ESO not only improves the robustness of system,but also reduces the chattering.Based on the above theoretical analysis,TMS320F28335 is selected as the main control chip,the hardware circuit and software program of the three-phase voltage source PWM rectifier are designed,and the experimental platform is built to verify the correctness and feasibility of the theoretical research.