Research On SVPWM Modulation And Control Techniques Of Three Phase Current Source PWM Rectifiers

The PWM rectifier can be classified into voltage source PWM rectifier(VSR)and current source PWM rectifier(CSR).Compared with three phase VSR,three phase CSR can provide a wider output voltage range and allow for current limit in case of output short circuit and start up directly without pre-charging circuit,which mean more efficient and reliable.Three phase CSR has been applied in data and communication centers,aerospace power supplies,superconducting magnetic energy storage systems and other fields.With the development of superconducting coils and new power devices,the efficiency and power density of three phase CSR can be further improved,which will bring more extensive application prospects.In this paper,the SVPWM modulation strategies and control technologies of three phase current source PWM rectifier are researched.The topology and operation principles of three phase CSR are analyzed firstly,and then the model and equivalent circuit are established based on three phase static coordinate system.By converting into two phase rotating coordinate system,the static characteristics of three phase CSR including output voltage gain,reactive and active power and power factor are analyzed.This paper focuses on the SVPWM modulation strategies and control technologies of three phase CSR.The three phase CSR trilogic SPWM signal can be generated by linear combination of three phase VSR bilogic SPWM signal.Based on the operation mode analysis,the principle of SVPWM modulation is studied,and the duty cycle of current space vector in every sector is derived.SVPWM modulation has different current space vector action sequences,which correspond to different switchover sequences of operation modes.By comparing the switching losses,input capacitor voltage ripple and output inductor current ripple of different current space vector action sequences,the twelve-segment five-segment SVPWM modulation strategy can realize the minimum switching losses and optimal ripple characteristics.Compensation parameters for indirect current control loop are designed.Under unbalanced mains condition,the second harmonic of the DC side voltage can be eliminated by shifting the mains voltage to select the positive and negative sequence components of the switching function.Based on analytical relationships,the stresses of power devices and design criteria of input and output filter are derived in detail,which guides the device selection and parameter design.The conduction losses and switching losses of power device and passive components losses including the output LC filter and the input filter inductor are calculated in detail.By forming loss calculation method,the study provides theoretical guidance for engineering design.Finally,by constructing a 1kW hardware prototype,the effect of control strategy for mains unbalanced condition on DC side voltage and mains current harmonic suppression is verified.Analyzed by the power factor(PF),total harmonic distortion of current(THDI)and efficiency curve under different loads,the excellent performances of three phase current source rectifier based on twelve-sector five-segment SVPWM are verified,including high PF,low THDI and high efficiency.