Research And Development Of Dual-PWM Converter System Controlled By Single DSP

Since ac drives have been applied into many fields of human being, a great deal of electric energy has been saved, and the remarkable technical economy benefit has been achieved. However, these drives, specially large-capacity, have some problems worthwhile to be studied presently, such as, high harmonic pollution generated by uncontrollable or phase-controlled rectifier in system, the electrolytic capacitor in dc-link hampering system integration, energy dissipation as a result of rapid brake of large inertia drive. Dual PWM converter with its simple structure, easy control, two-way flow of energy, green Power electronics technology is becoming a hot research issue, which represents the development direction of the drive. In this dissertation, in order to limit the harmonic pollution, achieve unit input power factor, realize energy can flow between power grid and motor, and improve the system reliability, the PWM Rectifier-Inverter Drive system is studied. Some key technologies, including system modeling, digital control, hardware development and parameter design etc., are researched in detail.The present status about control techniques of ac drives and PWM rectifiers, relative design method of the control and the dual-PWM control system are summarized roundly, after a large of domestic and overseas literatures’reading work. From the main circuit topology of three-phase system, the working principle of the system is analyzed. The dual-PWM system mathematical model in three-phase stationary reference frame and the concept of space vector is introduced. Then the model on the two-phase stationary reference frame and two-phase rotating coordinate frame are derived through the transformation of the coordinates. Then it explains the basic theory of the vector control and the algorithm of flux oriented control, these are the theoretical bases of this dissertation.The dual-PWM control system design is studied in the paper. Their inner loops are similar while double close-loop control structure is used in both PWM rectifier and ac drive. A uniform control structure of inner loop is built on the base of feedforward compensation decoupling method. Then the voltage control loop and the speed control loop of the control system are designed. Then the principle of SVPWM algorithm is presented. The result of the simulation in the Simulink verifies the validity of this algorithm.The rectifier, inverter and the dual-PWM integration control are simulated in the MATLAB/Simulink, The result of the simulation proves the control system has a very quick dynamic response and high steady state accuracy. Then the influence in dynamic response performance is analysed by the compensation decoupling error.At last, In order to get fine current tracking, voltage tracking, harmonic restraint and disturbance rejection, the AC inductance and DC capacitance of there-phase dual-PWM system are designed optimally. A TMS320F28335-based experimental platform of three-phase dual-PWM control system is presented and relative headware circuit are designed.