Simulation of a single-phase UPS inverter under sliding mode control by DC line current measurement for feedback

It is common practice to measure the instantaneous load current for realizing current trajectory control for UPS Inverters. A recent paper describes an interesting sliding control mode scheme for 1-ph inverters with an LC filter in which the a.c. load current needs to be monitored. A modification to the scheme is presented in this paper which enables sliding mode control by monitoring the instantaneous D.C. line current and the load voltage. A simple observer can estimate the load current. The use of the observer helps in overcoming the problem of high voltage swings experienced by current sensors and errors due to common mode signals.