Monitoring And Assessment Of Power Quality For Renewable Distributed Generation In Vector Distribution Network

Abstract

Power quality problems are raising concerns to authorities, utilities as well as customers in the past decades. This is mainly due to the following two reasons: the awareness of impact of grid supply on the power quality sensitive electrical appliances, and the decreasing amount and severity of the power reliability issues in contrast. The modern electronic equipment which electrically modelled as a non-linear devices, not only respond better than traditional resistive devices, but also generates power quality issues to the distribution network. Thanks to the modern protection and control technologies, the security of power supply has been maintained and for most of the time for almost all load regions, the amount of outages and black-outs has been greatly reduced. Thus customer attention has shifted more from availability of supply towards the quality of power supplied. In New Zealand, various researches have been done on the non-linear devices, which include one funded by the government that provides guideline to the devices imported and used in the country. Distribution companies as an important part of New Zealand's power network are facing challenges to their main objectives: maintain secure and quality of supply to their customers. One of the challenges being the quality power supplied to customers while accommodating more non-linear devices. These non-linear devices include but not limited to the electronic appliances, new inverter controlled distributed generation devices, and the future trend, electric vehicles. As the largest distribution company in New Zealand, Vector is planning and monitoring the trend and potential impact of small scale renewable distributed generation to its network. Trials and studies have been conducted for the inverter controlled distributed generation devices. Trials of installing micro wind turbine and solar PV panels have been applied across Vector's network in Auckland and Wellington region (previously owned by Vector). Three stages power quality studies have been conducted for a couple of sample micro wind turbines and a solar PV panel in Auckland. The three stages of the study are sampling of the distributed generation device, normalised and justification of the result, and the application of distribution generation models in the network model for impact study. In the sampling stage, Dranetz power quality meters were used for measuring and recording voltage and current outputs from distributed generation devices. In the normalisation and justification stage, records over months were summarised and inverter models are built in software ATP-Draw for comparison. In the modelling application stage, models are created and applied in Vector's DIgSILENT PowerFactory version 14 model. Some preliminary studies were also done for possible solutions for electric vehicles.