Design and Development of Micro Compensators with a Composite Strategy for Improved Power Quality in Secondary Distribution Systems

Abstract

Utilities are keen to extend their monitoring and accountability beyond secondary newlinedistribution without harming end customers. Recent standards recommend using newlinedistributed energy resources (DER) inverters in the volt-var mode for reactive power newlinecompensation. However, the advanced functionalities of DER inverters are not currently newlineused for lack of adequate monitoring/control at the 400 V level. Although newlinethe desirability of such a device is universally accepted, equipment cost is still an newlineimpediment to usage. A possible solution is to substantiate the cost of such a device newlinewith additional functionalities like power quality improvement. newlineShunt-connected devices were successfully employed to individually compensate for newlinea variety of power quality problems in the past. The capability of similar devices to newlinesimultaneously compensate for more than one power quality problem is also investigated newlinein the literature. It was experimentally verified that, for a STATCOM rated at newline25% of the effective load kVA, the voltage sag at PCC, at the end of the distribution newlineline, could be reduced by 39%. This thesis focus on voltage compensation at the newlinebeginning of the distribution line. The intended point of common coupling of such newlinea device is the secondary of a 11/0.415kV Dyn11 transformer. The rating of such newlinea device is slightly higher than the PFC capacitor rating (9 kVAr) for a 25 kVA newlinetransformer which constitutes 70% of the installation. newlineThis thesis proposes a micro compensator that is installed and maintained by an newlineelectric utility for monitoring and improving power quality in low voltage secondary newlinedistribution systems. Envisaged as a shunt-connected current-controlled voltage newlinesource inverter at 400 V level, a micro compensator performs reactive and harmonic newlinecompensation during peak periods. Hence the power factor and the power quality newlineat the point of common coupling are improved.During off-peak periods, a micro newlinecompensator provides dynamic reactive current support to compensate for voltage newlinesag or voltage swell.