Reactive power control functions for distributed PV sources

Abstract

The integration of distributed generation is one of the biggest changes facing the power industry, with greenhouse gas mitigation and the smart grid initiative. With result of the increasing penetration of grid-connected distributed generators, such as solar photovoltaic (PV) sources the system voltage regulation becomes challenging. Specifically, capacitor banks and step voltage regulators that normally boost voltage slightly may push utilization voltages either above or below the adopted ANSI voltage limits because of the variable nature of PV sources. This can adversely affect the expected reliability requirements for the utility and also decrease the life span of voltage-regulating equipment due to excessive operations. This thesis work studies the effects of large-scale penetration of distributed PV sources using several IEEE radial distribution test feeders. Based on the simulation results, tap-changer excessive operations, voltage fluctuations, and voltage rise in the feeders are identified, and the additional capacity of reactive power control of inverters to minimize the voltage fluctuations is analyzed. With the presence of a communication infrastructure, it is expected that distributed generators could be more efficiently operated, especially the inverters, which will be able to perform several grid support functions including voltage regulation and reactive power support. Therefore, this work also focuses on developing a power loss minimization technique while utilizing the additional benefits of dispatchable reactive power from a cluster of distributed resources. The proposed technique is tested using IEEE 13- and 34-node test feeders, and the results show that the proposed technique will minimize the real power loss in the radial distribution feeders.