| Abstract: | Recently, the voltage-fed type PWM converters have been investigated for their ideal and inherent properties as a dc power source. However, the current control system generally used may be somewhat complicated due to dc voltage detection. We propose here a simple control system of the PWM converter using the power factor control in which dc voltage detection is not always needed. In this system, the dc voltage is given by the line voltage and the modulating index of the PWM converter. The principle of the PWM control system is shown at first. From the simplified circuit model and its phasor diagrams, some basic relations of the PWM converter system are obtained and some fundamental characteristics are shown. From these investigations, it is seen that the phase control region is restricted to a certain angle, which depends on the setting power factor, the modulating bypass index of the PWM and the load. Under the operating condition of unity power factor, it is given by ±π/4 for both the converting and inverting operations. The system can be operated over the all-control range of the modulating index by restricting the angle to this critical value for the angle over this control range. The ideal operating characteristics as a dc power source can be verified by some experimental results, including the operating waveforms of line current, the steady state characteristics and the transient response between both operations of the converter and inverter. In this system it is simple to construct the control circuit; it also has some inherent and excellent characteristics as a voltage fed type dc power source. This control system may be applicable to any types of PWM converter used today. |
