Research On Optimization Control Methods For Burst Mode And Input Current Of Three-phase VIENNA Rectifier

With the continuous improvement of science and technology,people’s demand for power quality is increasing.As well,the application of high-power three-phase PWM rectifiers is more and more extensive.The three-phase VIENNA rectifier has the advantages of high efficiency,high power density,low switch voltage stress and low current THD,which leads itself to be a hotspot in the field of power electronics.Firstly,this paper analyzes the topology structure and operating modes of VIENNA rectifier.Mathematical model is established in dq coordinates using averaging method.On this basis,the double closed-loop control strategy of voltage outer loop and current inner loop is adopted.The outer loop is used to stabilize the output voltage,and the inner loop is used to achieve unit power factor and reduce current THD.Both loops are controlled by PI.The design process of PI parameters is given in detail in this paper.Next,this paper compares the effects of SVPWM and SPWM with three components on the performance of VIENNA.Through the calculation of the inductor voltage,the distribution of the high-order harmonics of the inductor current using different modulation methods is obtained in a grid cycle.The results show that under the SVPWM modulation,the VIENNA circuit has less high-order current harmonics,which may lead to a lower total THD.However,SPWM with three components has a better ability of midpoint adjustment.With the consideration of higher power density,this paper chooses SPWM with three components as the modulation method.VIENNA rectifier has a problem that the voltage is uncontrollable under light load.This paper introduces a traditional burst-mode strategy using output voltage hysteresis control,which can achieve voltage stability under light load.Then,in order to reduce the output voltage ripple in the traditional mode,two improved burst-mode strategies are proposed in this paper,which use the voltage loop output and the d-axis duty ratio as burst-mode judgment conditions.The simulation and experiment results show that the two improved strategies can greatly reduce the output voltage ripple of VIENNA rectifier under light load.Finally,this paper optimizes the input current of VIENNA rectifier.The effects of inductor voltage,DCM mode and switchs’ junction capacitance on current zero-crossing distortion are analyzed.The distortion range caused by different load conditions is calculated,and a zero-crossing optimization strategy whose compensation range can be adjusted is proposed.The strategy can make a significant change in the input current.In addition,the driving delay introduces a large number of low-order harmonics in the input current.a driving delay compensation strategy is proposed to reduce the current THD.In this paper,the above two current optimization strategies are combined,and the effectiveness of the proposed strategies is verified by simulation and experiment.