Research And Design Of The PWM Rectifier In A Dual PWM Converter System Based On A Single DSP Control

Power electronics technology is the most active areas in the modern electrical technology. At the same time, with the development of power electronic devices and high-performance control chips, technology of modern AC motor variable frequency control, has been widely used in various fields in the industrial control. However, there are many problems of the universal rectifiers which needed to be resolved, such as a large current harmonic pollution causing by uncontrollable or phase-controlled rectifiers, huge size of DC capacitor, easy damage, irreversible energy and excessive voltage fluctuations in the load disturbance. Therefore, in my graduate paper will take dual PWM inverter as object of study. Some key technologies, including system modeling, control strategy, hardware development and parameter design etc., are discussed in detail to improve the performance of the inverter.In this paper, mathematical models of three-phase voltage source PWM rectifier are established respectively in the stationary coordinate and synchronous rotating coordinate based on the topology of the main circuit. The principle of space vector PWM technique is analyzed, which is easily to be implemented in a digital chip. This method can not only avoid trigonometric functions computing, but increase the computing speed and accuracy.Obtaining accurate grid phase angle is one of the core technologies of PWM Rectifier, so in this paper adopts a scheme of single synchronous reference frame software phase locked loop (PLL). The PLL can accurately and quickly get the grid phase angle in the case of grid system balance. This thesis has also designed an internal current control loop and the external voltage control schemes based on the system model analysis and current feed forward decoupling control principle.The research of integrated control strategy of dual PWM inverter, dual-closed loop PI control can hardly let PWM rectifier obtain good dynamic performance under load variation, because of its inherent demerit in control structure and the lag of PI regulation. In order to improve the anti-interference capability, a dynamically load current feedback control strategy was designed. In Simulink environment, a two-level PWM rectifier control system is built and the simulation results were analyzed deeply.At last, the AC inductance and DC capacitance of there-phase dual-PWM inverter control system are designed optimally. A TMS320F28335-based experimental platform of three-phase dual-PWM control system is presented and relative hardware circuits are designed.