Research On Decoupling Control Of Single-Phase PWM Rectifier Based On Complex Vector Regulator

The PWM rectifier can achieve the same phase of voltage and current on the ac side,and can achieve constant voltage on the dc side,so it has been widely used in the field of railway traction,static reactive power compensation,electric vehicles,new energy power generation and other fields.In medium and high power applications,the energy loss of the rectifier is mainly composed of the switching loss of the device.In order to improve the output power of the PWM rectifier,the switching frequency must be reduced,which puts forward higher requirements for the control algorithm of the PWM rectifier.Therefore,it is of great theoretical significance and practical value to improve the control performance of PWM rectifier under high power and low switching frequency.First of all,this paper takes the single-phase PWM rectifier as the research object,and introduces the working principle of the single-phase PWM rectifier.On this basis,it is modeled and analyzed in dq coordinate system.Aiming at the cross coupling of dq axis current component,the complex vector modeling method is introduced to systematically analyze the coupling problem of rectifier.The two modeling methods are compared and analyzed,and the control block diagrams are given respectively.Secondly,the influence of the delay link on the rectifier control is analyzed,the complex vector modeling considering the delay link is carried out for the single-phase PWM rectifier,the coupling function of the system is established,and the influence of different switching frequencies on the rectifier is analyzed.In addition,the steady-state analysis of the traditional decoupling control method is carried out.Aiming at the serious dynamic coupling of the traditional decoupling control method at low switching frequency,a decoupling control method based on the complex vector regulator is presented,which eliminates the crosscoupling of the system with the principle of zero-pole cancellation and greatly improves the dynamic decoupling capability of the PWM rectifier.Then,the delay compensation of the current loop of the PWM rectifier is carried out for the coupling problem between the axes of the system caused by the delay of the digital control system with regular sampling at low switching frequency.The working principle of the Simth predictor is introduced,the rectifier delay compensation model based on the Simth predictor is established,the simulation model of the compensation algorithm is built,and the simulation results are deeply analyzed.In addition,the current predictive control is used to compensate the delay link,a delay compensation algorithm model based on sampling predictive control is established,the coupling effect of the inductance mismatch on the system is analyzed.the online identification of the inductance parameters is studied,and the influence of the delay link on the identification of the inductance parameters is reduced through the phase angle compensation,which indirectly solves the problem of cross-coupling of the dq axis current and improves the control performance of the rectifier at low switching frequency.Finally,the design of the low-power experimental platform based on DSP28335 is completed,the selection of ac inductors,supporting capacitors and other devices is carried out,and the design of sampling circuit and driving circuit is completed on the control circuit.The relevant algorithms are written by using CCS software,and the above algorithms are experimentally verified through the low-power experimental platform.