Cascaded multilevel inverter based active filter for power line conditioners using instantaneous real-power theory

This paper presents a three-phase, five-level cascaded multilevel voltage source inverter based active filter for power line conditioning to improve power quality in the distribution network. The active filter compensates both reactive power and harmonic currents drawn by non-linear loads; additionally it facilitates power factor corrections. The compensation process is based on concept of p-q theory. However, in the proposed approach only calculation of real-power (p) losses are conducted. This method is simple and different from conventional methods; it provides effective compensation for harmonics. The cascaded multilevel inverter switching signals are derived from the proposed triangular-sampling current controller that results in a good dynamic performance under both steady state and transient operations. The dc-bus capacitor voltage of the cascaded inverter is controlled and reduced ripple voltage using PI-controller. This proposed cascaded active power filter system is validated through extensive simulation under transient and steady state conditions with different non-linear loads.