Passivity-based control technique for UPS inverters

This paper presents the design of a passivity-based control for an inverter used in uninterrupt power supplies (UPS). The design of the passivity-based control considers an auxiliar system which describes the desired behavior of the inverter and the global asymptotic stability is proved. Several important requirements such as a sinusoidal output voltage, low total harmonic distortion (THD) and a fast transient response are accomplished with this control scheme. To show the performance of this nonlinear control two experimental applications are used, an UPS with three-phase output of 33kVA and an UPS with two parallel inverters of 1kVA each one with an unbalanced nonlinear load. The experimental results show that the passivity-based control has a better performance than a PI control and together with its simple implementation, they are the main contributions of this work. The implementation is analogical and was built with low-cost hardware. The performance shown in the experimental results is evaluated in real conditions.