Study On VIENNA Rectifier Compound Control Strategy Based On Improved SVPWM

In recent years,the electric vehicle and Internet industries have risen rapidly,and a safe and stable DC power supply system is the most powerful power supply guarantee in these fields.The VIENNA rectifier has a three-level structure.The full-control device in the three-level topology has relatively few applications and is simple to control.It is an excellent topology for the rectifier pre-stage with power factor correction.This article mainly analyzes and studies the control strategy and modulation strategy of the three-phase VIENNA rectifier,and puts forward a new idea to solve the problem.The main work is as follows:(1)Working principle and mathematical model analysis of three-phase voltage-type Vienna rectifier.First,according to the working process of the VIENNA rectifier topology analysis,establish the mathematical model of three-phase static coordinate system,through the mathematical model of rotating coordinate system is derived,and analysis the double closed loop control strategy and current loop feedforward decoupling control,and then the mathematical model of ac input current harmonic component is derived,6k+1 harmonics through coordinate transformation under the rotating coordinate system into 6k times ac component;Finally,the inductance and capacitance parameters in the main power circuit are calculated and selected.(2)The SVPWM modulation strategy of VIENNA rectifier in 60 degree coordinate system is proposed.First,the dissertation analyzes the equivalent two-level SVPWM modulation strategy of the VIENNA rectifier in the traditional αβ coordinate system.Aiming at the problems of the three-two-level conversion,the small sector judgment and the calculation of the action time and other irrational calculations,the algorithm is complicated,etc.The dissertation proposes the SVPWM modulation strategy of the VIENNA rectifier in a 60-degree coordinate system,transforms the target voltage vector into a 60-degree coordinate system,and directly establishes the coordinate axis on the sector boundary line,reducing the amount of calculation of irrational numbers,and is performing three-two Before the level conversion,the unitization process is performed,so that the coordinates of the basic vector are all integers,which simplifies the conversion process.(3)Study on control strategy of outer loop DC voltage and inner loop AC current.Current inner loop adopts the conventional Repetitive Control and Proportional integral Control and the Control strategy of parallel voltage outer loop adopts the traditional PI Control strategy of PI parameters according to the working characteristic of system design,based on the working characteristics of current inner loop,detailed description part repeated internal model Control strategy and the design of the compensator,to enhance the stability of the system and the steady state characteristics,as the internal model by using zero phase shift filter coefficient to carry on the design,and with constant of internal model coefficient is less than 1 are analyzed and compared,A repeated-control compensator is designed for the controlled object of the current loop,and the different orders of the lead link are compared and analyzed.(4)A current loop compound control strategy based on fast repetitive control strategy is proposed.The main harmonic content of the grid current is 6k±1.After coordinate transformation,it is the 6k AC component in the dq coordinate system.This paper proposes a compound control strategy that uses fast repetitive control and PI control in parallel in a two-way rotating coordinate system.,Where the fundamental component is a direct current under the rotating coordinate system after coordinate transformation,which is controlled by PI controller,and the main harmonic component 6k±1 is transformed into the 6k harmonic after coordinate transformation,for the 6k harmonic For internal model design,since the internal model part contains a fractional delay part,Lagrange interpolation polynomials are used for equivalent approximation,which reduces the cycle of rapid repetitive control operation and further reduces the amount of data storage to 1/6 of the original.(5)Simulation and experimental verification.Through simulation and experiment,the modulation strategy and compound control strategy are verified to prove the feasibility of the theory.Moreover,through simulation and experiment,the value range and optimization of each parameter in the compound control strategy are compared and studied to verify the correctness and feasibility of the controller parameter design method in this paper.