Series and parallel operation of hysteresis current-controlled PWM rectifiers

Different strategies for series and parallel connections of hysteresis current-controlled PWM rectifier have been investigated by experiments, computer simulations, and analyses. Each rectifier unit delivers near-sinusoidal current waveforms at unity (or even leading) power factor. Of particular concern are the questions of: (i) system stability; (ii) the capability of the modular units to share voltage (series connection) and current (parallel connection) under steady-state and transient operation; and (iii) sensitivity of performance characteristics to component tolerances. Experiments were made on 1 kW bipolar transistor modular units. Two configurations, having independent local control (type A) and common switching control (type B), respectively, were studied. The study shows that type B is more economical than type A and appears to give a satisfactory performance. >