Research On Control Algorithms Of Voltage Source Inverter

Voltage Source Inverter(VSI)is widely used in the fields of uninterrupted power supply,new energy generation,and new energy vehicles,and has become an indispensable key equipment for modern industry and residents.In order to effectively improve the performance of the inverter,a reasonable control strategy is one of the key technologies in the inverter system design.However,the inverter is a kind of time-varying and coupled program control system.The conventional Proportional Integral(PI)rule cannot theoretically achieve static error tracking for this kind of system,which requires other control methods for effective control.Therefore,this dissertation studies the decoupling control methods in the dq coordinate system and model predictive control methods with VSI as the object.The main contents are as follows:Firstly,a discrete three-phase VSI system model under Y-load is established,and the discrete model is transformed into a continuous model using a switch averaging operator.The dq coordinate transformation is used to convert the ABC model of the inverter into a two-phase dq model.At the same time,the linearization is performed at the steady-state operating point,and its dynamic dq model is further obtained.Using the decoupling principle,a three-phase VSI mathematical model with no coupling term is obtained.On this basis,the open-loop transfer function of the inverter is deduced,which lays a theoretical foundation for the study of subsequent control strategies.Secondly,the basic principles of Sinusoidal Pulse Width Modulation(SPWM)and Space Vector Pulse Width Modulation(SVPWM)are discussed in detail.The advantages and disadvantages of unipolar SPWM,bipolar SPWM and SVPWM modulation are analyzed.Finally,the differences and connections between the two were discussed and verified by simulation and experiment.Again,based on the established open-loop transfer function,a voltage-current dual-loop PI controller is designed.Using the pole-zero configuration principle,the control parameters of the controller are obtained,and the control parameters are optimized by using the Bode diagram.With the microprocessor DSP TMS320F28335 as the core,a 750 Wthree-phase VSI system was built.The experiment verifies the rationality and correctness of the control algorithm.Finally,on the basis of the single-phase VSI discrete model,Finite-Control Set Model-Predictive Control(FCS-MPC)and Continuous-Control Set Model-Predictive Control(CCS-MPC)are performed study.The choice of the minimum cost function is discussed.Aiming at the deficiencies of traditional model predictive control,an improved MPC control method is presented.Based on the traditional MPC control method,the Integral and Proportional-Integral compensation terms are added respectively.Through the proportional adjustment,the transient characteristics of the system output are improved,the integral function is used to increase the steady-state performance of the system output,and reduce the steady-state error of the output voltage.Based on the established 250 W single-phase VSI system,algorithm verification was performed.