Implementation of independent improved neutral current controller using four leg PV-VSI

Abstract

An independent improved neutral current controller is implemented in a three-phase (3p) four-wire (4w) low voltage (LV) distribution network with a four-leg voltage source inverter (VSI) and photovoltaic (PV) installations in this paper. The PV VSI is designed to control active power at unity power factor (p.f) with additional improvement in the neutral current controller using the load generated neutral current as a direct reference. As, inherently, most of the three-phase four-wire LV distribution networks exhibit voltage unbalance characteristics due to divergent load connection types such as single- and three-phase loads, the independent control over neutral current at the point of common coupling (PCC) becomes imperative especially for decentralized controllers. The improved performance of the neutral current controller both at customer's installation and at the distribution transformer (DT) terminal is investigated by implementing the designed PV-VSI with actual Australian (Energex) LV network model in PSCAD/EMTDC software environment. The performance of the designed four-leg VSI is compared with the traditional active neutral compensator with actual single phase customer loads. The results show that, with the proposed independent neutral current controller, improved neutral compensation can be achieved for unbalanced LV networks for whole day operations.