Fuzzy Logic-Based Unified Power Quality Controller for Enhancement of Power System Stability

The paper deals with a Unified Power Quality Conditioner (UPQC), which aims at the integration of series and shunt active power filters for enhancement of power system stability. The proposed UPQC consists of two independent active filters, each with its own dc link, a device known as "OPEN UPQC". Power system stability investigated includes fast recovery of grid voltage after voltage sags, voltage swells, ground faults, and frequency oscillations. Two controllers are proposed for operating the OUPFC, namely a PI controller and fuzzy logic controller FLC. The fault ride through (FRT) ability of the FLC-based OUPQC is investigated and compared with the FRT of a PI-based UPQC. The comparison for each type of faults considered included time taken for fault recovery, harmonic level in waveforms, active and reactive power consumption, and system power factor. Switching the positions of the shunt and series devices is investigated to conclude the optimum connection status.