Research On The Soft-Switching Three-phase PWM Converter Technique

With the widespread and in-depth application of power electronics rectifier devices, especially toward to high frequency and high power fields, it brings many negative effects such as harmonic pollution, loss of reactive power, electromagnetic interference (EMI), therefore it is necessary to renovate the conventional diode and thyristor rectifiers. Comparing with installing harmonic compensator and var compensator to centralize solving the problems of harmonic pollution and loss of reactive power, the soft-switching PWM converter technique is more suit for decentralized consumer to harness power supply (including harmonic pollution, loss of reactive power and EMI), it also has a more promising application for development and utilization of new energy resources, and is considered as a more active technique for energy-saving. The soft-switching PWM converter technique is one of most concerned objects in the field of power electronics and motor drive.Research on soft-switching PWM converter technique mainly concentrates on topology of main circuit, mathematic model building, system performance, control strategy and etc. This paper mainly study the soft-switching PWM converter technique, and search for the novel soft-switching converter and its control strategy.On the foundation of summarization for the topologies of three-phase PWM converter and their control strategy, a novel topology for three-phase resonant DC link (RDCL) converter is present, its operating principle is analyzed in details and its mathematical model is built, its operating modes, equivalent circuit and working conditions for the resonance are described.A phasor adjusting method for realizing unity power factor is proposed, and it is applied in variable power factor for converter control. By building the low frequency model of the system, in the rectifying mode and regenerating mode, the dynamic adjusting procedure of realization for unity power factor, absorbing or regenerating capacitive reactive power, inductive reactive power from or to power grid are investigated. The relations among the control angle a, the controlled power factor angle (?) , the maximum load, the maximum regenerating power and modulation index M, load, inductance are analyzed. The operating area of converter is investigated.To improve the dynamitic feature of system, a current feedforward control strategy for rectifying mode is proposed, its operating principle is analyzed and...