AC/DC/AC PWM converter with minimum energy storage in the DC link

The family of quasi-direct power converters, i.e. forced-commutated AC/DC/AC power converters including small energy storage devices in the DC link, is introduced. In particular, the case of a three-phase to three-phase quasi-direct converter is considered. Since energy storage minimization calls for instantaneous input/output power balance, a proper control strategy is needed. A simple and effective control technique suitable for this purpose, which also provides high power factor and small distortion of the supply currents, is described. The general properties of quasi-direct power converters are discussed, design criteria of both power and control sections are given, and experimental results of a 2 kVA prototype are reported