Research Of Voltage-type Rectifier Based On Sliding Mode Variable Structure

Three-phase PWM voltage-type rectifier has the capabilities of low current harmonic content,stable output DC voltage,rapid dynamic response speed,long-term stable run under single power factor and power feedback.Compared with the conventional uncontrollable rectifier and semi-controlled rectifier,it has obvious advantages which gets attraction of scholars from all walks of research.Through access to a large number of articles,the principle of model establishment of three-phase voltage-type rectifier and mutual conversion among three-phase still coordinate/two-phase still coordinate/two-phase synchronous rotation coordinate/60~o coordinate system have been determined.In this dissertation,sliding mode variable structure control strategy based on variable exponential law was presented and consequence that the improved variable exponential law has better capability,compared with conventional ones,to inhibit the dithering problem of sliding mode variable structure itself was verified.In this dissertation,voltage rectifier was designed by a closed-loop control strategy of voltage loop and current loop.The voltage loop adopts sliding mode variable structure strategy based on variable exponential law,fully utilizing the fast response of variable structure control to load mutation and strong robustness to system parameter perturbation.The current loop adopts variable structure strategy of state feedback linearization,fully utilizing differential geometry method to weaken the dependence on mathematical models,improve the dynamic and static performance and anti-jamming capability of the system.In this dissertation,the PWM modulation technology of three-phase voltage-type rectifier was given the conventional method and60~o coordinate system modulation method.It could be shown that this dissertation's method avoid a large number calculations of trigonometric functions and irrational number and reduce the cost of computer?In the end,Matlab was used to establish the model of three-phase voltage-type rectifier under non-linear control strategy.The accuracy of three-phase rectifier control circuit was verified by comparing performance among DC side output starts response,load fluctuation as the output changes,DC side outputs dynamic response as the input voltage or system parameter is disturbed and AC side input current harmonic content.Compared with conventional PI control on three-phase rectifier,the method used in this dissertation was found having obvious superiority on comprehensive performance.