Use of Distributed Generation to Control Reactive Power at the Transmission Distribution Interface

There is an increasing interest in obtaining reactive power services for the transmission system from distributed energy resources. This involves coordination between the transmission and distribution companies, and the distributed generators. This paper presents a methodology to quantify the extent of reactive power provided by distributed generators to the reactive power seen at the transmission and distribution interface. Two case studies using computer load flow simulations are presented based on a real-world network. Results showed that when the distributed generators connected to the distribution network absorb reactive power there will be a multiplier of around 110% in the reactive power drawn from the transmission system. Similarly, if the distributed generators export reactive power the multiplier is around 90%. This study shows that there is a potential for providing reactive power support from distribution networks to the transmission system at the expense of additional active power losses in the distribution system.