Research On Three-phase Current Type PWM Rectifier Based On Predictive Control

Current type PWM rectifier is an important part of PWM rectifier system and is widely used in power systems.Compared with traditional rectifiers,current-type PWM rectifiers have the characteristics of high power factor,low harmonic current content on the grid side,and two-way energy flow.With the development of new material technology,its shortcomings of low efficiency are gradually overcome,so three-phase CSR has attracted more and more attention from scholars.This paper mainly starts from two aspects of grid-side current harmonic suppression and power factor,and studies the control strategy of three-phase CSR.The main work and achievements of this paper are as follows:Firstly,the topology structure,mathematical model,working principle and commutation of three-phase CSR are introduced in detail,which provides a theoretical basis for the realization of three-phase CSR control strategy.During the commutation process,the stress of the switching device was analyzed in detail.Based on this,an absorption circuit was designed to suppress the overvoltage spikes of the switching device and ensure the safety of the experimental equipment.Secondly,the resonance problem of the three-phase CSR grid-side LC filter is analyzed,and it is pointed out that under the condition of the LC filter resonance,the harmonic content of the grid-side current will increase,so this paper proposes a traditional double closed loop based on capacitor voltage feedback.Active damping control strategy.This control strategy uses a combination of understanding coupling and active damping to suppress the influence of the coupling term and LC filter resonance on the system network measured current waveform.The outer loop uses DC-side current feedback.The method weakens the influence of the DC output-side fluctuations,and the design of the inner and outer loop controllers of the system is explained in detail in the article.Through simulation verification,this method can effectively track the system given,and the system has good dynamic response performance under a given mutation.Again,in order to further reduce the harmonic content of the grid-side current,this paper proposes a strategy for the inner loop using a predictive controller and the outer loop using a PI controller.In the specific implementation,the coupling of active and reactive current Compensation to achieve complete independence of active and reactive power.In the outer loop design process,the calculation delay and the control delay are compensated.This method reduces the pulsation rate of the DC output current,and has a stronger effect in suppressing current harmonics.It achieves high power factor and low harmonic content.Control objectives.Finally,build experimental equipment for verification.By designing the buffer circuit based on the analysis of the device stress in the commutation process in the previous chapter,and by experimentally verifying and analyzing the voltage waveforms across the IGBT and diode,it can be concluded that the buffer circuit can effectively suppress Voltage spikes.