Dead Time Compensation Method In Three Phase PWM Rectifier Based On Deadbeat Control

PWM rectifier is widely used in active power filter,HVDC,renewable energy generation due to the advantages of running in unit power factor,the sinusoidal current of grid side,bidirectional energy transmission.The deadbeat control technique can realize the accurate tracking of a given current signal in a switching cycle,and can provide fast transient response,and reduce the current distortion and current ripple.And in order to prevent the bridge arm straight up and down the bridge,there must be the dead time protection,however the addition of the dead time will cause the bad influence of the low order harmonics and the current distortion,which is not conducive to the accurate tracking of the current of the three-phase PWM rectifier.Therefore,the dead time compensation is necessary.During this paper writing,first of all,based on the development of PWM rectifier,the classification of rectifier and the control method of voltage PWM rectifier are discussed.The mathematical model is used to demonstrate the transformation process of the rectifier from the three-phase stationary coordinate system to the two-phase stationary coordinate system and the synchronous rotating coordinate system.The space vector PWM(SVPWM)is applied to the rectification bridge drive control.The control system is the classic outer loop voltage and inner loop current control.In addition,the deadbeat control technique is applied in the inner loop,and the advantages of its application in the current loop control are explained.Secondly,this paper describes the causes and consequences of dead time to PWM rectifier:The additional time to protect the bridges of rectifier the increase of low order harmonics and distortion of current waveform.At the same time,this paper analyzes the principle of several kinds of dead time compensation methods and compares the simulation results,then concludes that the key of dead time compensation lies in the accurate judgment of the current polarity of the network.Because the existence of current zero clamp interference the polarity judgement,therefore,the accurate estimation of the current polarity is introduced according to the estimation of the current ripple.The simulation model is built by MATLAB,and the simulation results verify the feasibility of the method.Finally,according to the operating parameters of the three-phase voltage source PWM rectifier and the existing devices in the laboratory,the software program and hardware equipment are designed.The software,uses STM32F407ZG as the core control software is designed;As for hardware,mainly carries on the design of control circuit and main circuit,including sampling circuit,power supply circuit,an external reference protection circuit and calculation.And the superiority of deadbeat control of three-phase PWM rectifier and the feasibility and validity of the dead time compensation based on the ripple current to judge the current polarity are verified by the experiment of the experimental platform.