Research On Control Strategy Of Dual-PWM Variable Frequency Speed Regulation

With the development of agriculture and industry, the motors have been widely used in every aspect of industrial production and people's daily life as uppermost power equipment. And the goal of controlling the speed regulating performance effectively is pursued by people in the field. At present, AC driving system has been the main direction of electric drive system because of its large capacity, high speed, good performance. The structure of voltage source non-controlled or phase-controlled rectifying circuit with fully-controlled inverting circuit is often applied in traditional AC electric drive system. But the structure is difficult to realize regeneration braking and four-quadrant operation, and causes harmonic pollution to power network. A new dual-PWM converter based on Pulse Width Modulation technique is proposed in this paper. It have the capability of bi-direction flowing of energy with high power factor and improving the performance of power system.Firstly, the operation principle of dual-PWM converter is analyzed and the working principle of rectifier is also represented. Based on the study direct power control (DPC) strategy of PWM rectifier, a new kind of switching table is proposed with good dynamic response. Virtual flux orientation is introduced on the base of DPC strategy, making the structure simplifier and cost lower. Field Oriented Control (FOC) technology of rotor flux orientation is applied in the control of inverter. Aiming at the shortage of traditional voltage-mode flux observer, a new observer is developed to gain mechanical features. And then, three-phase rectifier direct power control system with outer voltage loop and inner power loop is designed. Compared with traditional control systems with inner current loop, the new control system has several advantages, such as simple structure, high power factor and lower total harmonic distortion. The direct power control system of three phase PWM rectifier is also designed on the basis of DSP TMS320LF2407A. And the control program is programmed. Finally, the design is simulated in Matlab7.0/Simulink platform.The simulation results agree well with those of the experiments, and demonstrate the correctness of the analysis and the feasibility of the design.