Uninterrupted Power Quality (UPQ) is an innovative concept, combining the functionalities of an active harmonic filter and a UPS into a single robust solution. UPQ protects mission critical processes from supply interruptions and voltage sags while maintaining supply voltage quality by compensating harmonic currents and the reactive power fluctuations of non-linear loads. UPQ has two operation modes. In secured supply conditions, it operates in power quality mode, performing active filtering of harmonic distortions as well as load balancing and flicker mitigation. When it detects a voltage sag or power outage in the supply network, it shifts to power protection mode to protect against critical loads. UPQ is available from low up to medium voltage level