Research On Three-Phase PWM Rectifier And Control Strategy

In order to govern high-power electronic devices harmonic, the three-phasePWM rectifier, with high power grade, high power factor, low input currentharmonics and power transmission reversible, becomes an important object to bestudied and applied.But the three-phase PWM rectifier is a strongly nonlinear, time-varying uncertainsystem, and the traditional linear control method is difficult to achieve the idealcontrol effect, with poor dynamic performance and parameter design complexity.Sliding mode control (SMC), which can effectively solve the control problem ofthree-phase PWM rectifier with good dynamic performance and robustness, is a kindof special nonlinear discrete control. By a large number of research andexperimentation, the sliding mode control has been successfully applied to the controlof the single-phase, three-phase PWM rectifier. On research literature, in most of thethree-phase PWM rectifier based on sliding mode control, voltage control loop isdesigned with sliding mode controller, but current control loop is still designed withtraditional controller. However, in the latter, the difficulty of the parameters oftraditional controller to be designed, and the modulation of the output signal by spacevector pulse width modulation technology to produce PWM control signal, make thedesign of the whole system become more complicated. At the same time, the PWMrectifier’s overall dynamic performance and robustness are affected by theintroduction of traditional control, too. In order to improve the performance of thePWM rectifier and simplify the system design further, this paper presents doublesliding mode control strategy, whose voltage control loop and current control loop areboth adopt sliding mode control method. The main research content of this paper is asfollows:First, introduce the circuit structure and control principle of PWM rectifierbriefly. In this basic, the three-phase voltage source rectifier (VSR) operation indifferent switch modes is analyzed. Then, set up the general mathematical model and dq mathematical model of three-phase VSR by the switch function and the coordinatetransformation. The sliding mode variable structure control theory and the controllerdesign are briefly introduced. Also, the fundamental problem of the sliding modevariable structure control is put forward. According to the established mathematicalmodel and the sliding mode control theory, the voltage control loop and the currentcontrol loop with sliding mode controller is designed in detail. At last, the slidingmode control algorithm is improved, so as to reduce the switch loss and weaken"chattering" to facilitate the implementation of the system.Secondly, use the simulation platform to build simulation system models for thethree control strategies, which are traditional PI control strategy, sliding mode controlcombined with traditional PI control strategy, and sliding mode control strategy. Bysimulation compare and results analysis, the feasibility and superiority of the controlmethod put forward by this paper is verified. At the same time, the simulation systemwith the improved algorithm is built and the simulation results between the improvedalgorithm and not are compared.Finally, the three-phase voltage source PWM rectifier hardware and software aredesigned. In hardware design, this paper specifically introduces the design of maincircuit topology structure and the important parameters; the auxiliary power circuit;the sampling circuit; the drive circuit and so on. In software design, this paper brieflyintroduces the design of main program; capture interrupt program; A/D samplinginterrupt program; algorithm program, etc.