Practical control implementation for 100 kVA three-phase four-wire online voltage regulator

This paper presents high performance control algorithms for a 100 kVA three-phase four-wire online voltage regulator. The 100 kVA voltage regulator is composed of a PWM rectifier, a center-tapped DC bus, and an inverter. The rectifier connects with the grid through an LCL filter, providing power factor correction and DC-link voltage regulation. The inverter output power is fed forward to the rectifier side to generate an accurate instantaneous command for the current inner loop, thus achieving dynamic stiffness with step load. Moreover, the inherent drawback of DC capacitor voltage imbalance along with neutral available PWM rectifiers is eliminated by extracting and feeding back the DC component of inverter output. The inverter supplies a regulated sinusoidal voltage to either linear load or impulsive non-linear load. Load disturbance decoupling is incorporated at the inverter side to augment the state feedback control for better transient response and reduction of total harmonic distortion (THD) under non-linear load. Finally, a 100% power test procedure is presented for hardware design verification in laboratories with less power capacity. Experimental results are given to verify each employed control strategy, showing high stability, low THD and fast dynamic responses.