PQ Improvement of Four Wire Distribution Grid Based Dual Stage Solar PV Array Integrated UPQC

This work presents a system that combines a dual stage solar photovoltaic (SPV) array with a unified power quality conditioner (UPQC) to enhance power quality (PQ) of a four-wire distribution grid. Four wire UPQC-SPV arrangement is controlled to solve PQ issues like neutral current, balanced and unbalanced voltages sag, swell, harmonics, reactive power, etc. A four-wire UPQC is a combination of two voltage source inverters with four legs coupled back-to-back at shared DC-link. Presented four-wire UPQC-SPV system is simulated for several conditions, including load imbalance, unbalanced grid voltages sag, swell, and harmonics, fluctuating solar insolation in a real time simulation OPAL-RT and verified in hardware implementation. Effectiveness of presented system is compared with other control techniques. Total harmonic distortions (THDs) of load side voltages and grid side currents are in the limit of the IEEE 1159 and the IEEE 519-2022 standards' permitted limits.