AC power line conditioner based on switch-clamped scheme

This paper introduces a novel AC line conditioner with high input power factor and clean AC output voltages for isolating the linear or nonlinear loads. A four-wire AC/DC rectifier with switch-clamped topology is adopted to draw the balanced sinusoidal line currents from the AC supply system. The hysteresis comparators are used in the inner control loop to track the line current commands with unity power factor. The DC bus voltage controller is adopted in the outer control loop to regulate the DC-link voltage. A voltage compensator is used to reduce the voltage unbalance between the two DC side capacitor voltages. A four-wire three-leg inverter with switch-clamped topology is adopted in the system to provide clean AC output voltages to the critical or sensitive loads. The carrier-based current control scheme is adopted to generate the stable output voltages. There are three voltage levels generated on the phase to neutral voltage of the proposed system. Based on the proposed control scheme, the sinusoidal line currents with nearly unity power factor can be drawn from the AC supply system, and the balanced AC voltages can be provided to the output load. Experimental results show the validity and effectiveness of the proposed control strategy.