Research On Modulation And Control Strategy Of Three-Phase Current Source PWM Rectifier

Pulse width modulation(PWM)converter can be divided into voltage source PWM rectifier and current source PWM rectifier according to its DC side energy storage form when it operates in rectifier mode.Because of its simple structure,step-down output and direct start-up,CSR has great application prospects in data center power supply,electric vehicle charging,aviation power supply,motor drive and other fields.With the development of magnetic material technology and new semiconductor devices,the efficiency and power density of CSR will be further improved,which will have a broader development space.Taking three-phase current source PWM rectifier as the main research object,this paper studies its space vector pulse width modulation(SVPWM),control strategy and parameter design.In this paper,according to the characteristics of CSR DC side power supply,the topological structure and working mode of CSR are analyzed with ternary logic switching function,and the SVPWM modulation principle of CSR is introduced.According to the working principle of CSR,an equivalent CSR analysis model is proposed,the evolution relationship between CSR and buck DC chopper circuit is described,and the expression of DC side current ripple peak value is derived;Combined with Kirchhoff’s law of voltage and current,the mathematical models of CSR in different coordinate systems are established.Secondly,the paper focuses on the analysis of the SVPWM modulation strategy of CSR.On the basis of the traditional SVPWM modulation implementation process,based on the twelve sector SVPWM implementation mechanism,the paper analyzes the commutation process and switching loss of CSR switches.Then,according to the multi degree of freedom of SVPWM modulation,the paper compares different modulation strategies,and focuses on the influence of modulation strategy on the input and output characteristics of the system;Finally,an optimized sector space vector modulation strategy is proposed to improve the current ripple of CSR DC side.When the DC side of CSR is connected with capacitive load,the existence of LC filter and DC side capacitor makes the control system more difficult.Therefore,this paper proposes a multi loop control strategy for CSR DC voltage control.Firstly,the suppression ability of different passive damping methods to the grid side LC resonance is analyzed,and the capacitor voltage feedback active damping method is used to suppress the grid side LC resonance.Secondly,the voltage oriented multi loop control large signal model is established in the d-q coordinate system,and the active and reactive power of the system are controlled independently by the d-axis and q-axis components of the grid side current.Based on the active damping control of AC side,DC side voltage control with delay and DC side current control,the controller parameters are designed with the aid of MATLAB / SISO design tools.Finally,a capacitor current compensation method of grid side filter is proposed based on phasor method to construct a capacitor voltage feed-forward channel and realize power factor correction under indirect current control strategy.This paper verifies the modulation and control strategy proposed in this paper by Matlab/simulink,Modelsim and other software and the construction of a three-phase current source PWM rectifier experimental prototype.The simulation and experimental results show that the modulation strategy proposed in this paper can reduce the peak current ripple at the DC side;the control strategy makes the system have good steady and dynamic performance,among which the voltage and current at the network side keep the same phase,improve the harmonic current and output voltage stability.