PWM control of three-phase series resonant DC link converters for UPS applications

This paper present a novel PWM control strategy that can be used for general 3 phase AC/AC series resonant DC link converters in uninterruptible power supplies (UPS) applications. The algorithm can achieve control over unity input power factor and provide low total harmonic distortions of input and output line currents. The control is performed in the DQ rotating reference frame and incorporates a modified space vector PWM strategy for determination of switching instants. A control algorithm has been derived to provide decoupling of the d and q-axis responses, allowing effective use of linear controllers to force the error signal to zero. Results from simulations and experimental studies show that a close to unity input power factor and total harmonic distortions as low as 1-2% can be achieved for both the input currents and output voltages.