Parallel operation of modular power factor correction circuits

The parallel operation of modular power factor correction circuits is illustrated. The modular units using boost converters are operated at a constant frequency with variable duty-ratio. Flexible load demand is met by changing the number of operating modules under the maximum current limit. The operating modules have the same frequency and duty-ratio, but are equally phase-shifted to each other by a fraction of the switching period to reduce the ripple content and to increase the ripple frequency of the input current. With this phase-shifted control strategy, balanced current sharing among modules can be achieved by operating the boost converters at discontinuous current mode, without the need of extra current control circuit. A prototype circuit consisting of 15 modular units, which supply the attempted power rating of 3.75 kVA was implemented to verified the theoretical prediction.