Yang Xijun

Realization of matrix electric power conversion with practicality

A realization of three phase to three phase matrix electric power converter (33MC) with practicality is depicted, which is characteristic of modular configuration, simple and safe semi-natural semi-forced two-step commutation strategy, general over-current protection circuit, flexible generalized switching functions, combined bilateral power switches, and so on. A new approach to manufacturing-oriented 33MC comes forth, which is composed of 3 modular three phase to single phase non-square matrix electric power converters (31MC).

Power switch driving techniques in single-phase dual-parallel interleaved boost PFC

Three driving techniques are analyzed in single-phase dual-parallel interleaved boost PFC (DPIB-PFC) control circuit, which are synchronized driving, phase-shifted driving and frequency-divided driving. And two kinds of boost inductors are also discussed, which are separated inductor and coupled inductor. Many simulations and experiments are also carried out based on different driving techniques and boost inductors, when dedicated controller L4981A/L4981B, pulse width modulator SG3525A and a logic circuit are employed respectively. It proves by results that the three driving techniques are feasible in principle, especially phase-shifted driving, because they can bring about not only better PFC effects but also low cost.

Study on generalized switch functions for motor drive inverter

Based on the single-to-single phase matrix conversion technique, switch functions for a single-to-three phase matrix power converter are derived. Furthermore, the above idea is introduced into a conventional rectifier-inverter (RI), and so-called generalized switch functions are proposed. Such switch functions are characteristic of the follow-up of DC-link voltage variation and frequency drift, bringing about size-reductions in DC-link electrolytic capacitor and improved mains side power factor. In particular, when a valley-fill-filter substitutes for the electrolytic capacitor, the mains side power factor is much higher. Additionally, all the other switch functions, such as saddle wave PWM and flat-roofed wave PWM can also be deduced according to the same rule. Another point to be noticed is that such switch functions is identical in essence with those deduced from three-to-three phase matrix conversion. In the paper, all the above are discussed in theory and proved by simulation results, which is helpful to seek after generality among AC converters.

Analysis of capacitive parasitism in PWM inverter-fed motor

The effects of parasitic capacitance in induction motor system are unnoticed when it is fed from the AC line, but they are obvious when supplied directly from a PWM inverter. Consequently, many parasitic problems occur, such as motor-to-earth leakage current, bearing current, incoming line current distortion and uneven distribution of electrical stresses along the winding. On the basis of the uniform transmission line principle, a complete equivalent circuit of the PWM inverter-fed motor system is presented, based on which all the capacitive parasitic problems mentioned above are analyzed and simulated by means of PSPICE. All the results are consistent with the existing ones.