Lyapunov Based Controller for 3φ VSI Stage of a UPS and a Distributed Generation Units

In this paper, a Lyapunov based voltage controller (LBVC) for the voltage source inverter (VSI) stage of a 30 UPS and a distributed generation (DG) unit has been investigated. The modeling and analysis have been carried out in the synchronous reference frame. It is shown that, theoretically, a 30 VSI controlled using LBVC behaves as an ideal controlled voltage source with unity voltage gain and zero output impedance. Moreover, the d and q axis voltage relations are found to be completely decoupled. LBVC is shown to achieve a better transient response, better disturbance rejection and lower voltage harmonics as compared to conventional multi-loop PI-based voltage controller (PIBVC). In addition, LBVC controlled VSIs, when used as DGs in an islanded microgrid, provide marginally better reactive power sharing as compared to PIBVC controlled VSIs. Finally, the LBVC has been implemented on a laboratory scale inverter feeding a 500W load.