Effects of using DC-side average current-mode control on a three-phase converter with an input filter and distorted supply

The use of DC-side current sensing and proportional plus integral average current-mode control is analyzed and shown to have several beneficial effects when applied to a three-phase, step-down, AC-DC, unity-power-factor converter. Conventionally, a large DC-side inductor was used with the considered converter, in order to reduce the propagation of harmonic currents due to non-sinusoidal supply voltages that result in the input currents being non-sinusoidal. A single DC-side current sensor, when used with an EPROM sinusoidal look-up table PWM modulation method, is shown to have a number of benefits including; reduction of the harmonic currents when a finite-value DC-side inductor is used, hence giving near-sinusoidal input currents and damping of the DC-side LC filter. Two other benefits are mentioned. The current-control loop is designed and the often ignored effect of the input filter on system stability is discussed. Two SIMULINK^TM simulation models are developed and compared with each other.