Sliding Mode Control of Single-Phase UPS Inverters Using a Three-Level Hysteresis Switching Function

A new approach to the sliding mode control of single-phase UPS inverters is introduced in continuous-time. A three-level hysteresis switching function is used to directly control the inverter switches. The theoretical and predicted switching frequency expressions are given. The performance of the proposed control method has been tested through computer simulations using different loads (a load which draws a square-wave current, diode bridge rectifier load, and triac-controlled resistive load). Simulation results verify the correct operation of the proposed control approach. Also, the switching frequency prediction is seen to be quite accurate