Algorithm for voltage stability control in a power system network with integrated microgrid

Abstract

The electrical power system is a real-time energy supply system designed to generate, transport, and supply power to the load. As a rule, the electrical power system is planned to operate in stable conditions and correct loading conditions. However, these design expectations can be strained due to disturbance. Because of either the environmental concern or depletion of traditional energy source fossil fuels. The option of renewable energy has gained interest for its integration into the power system. The availability of solar has established potential demand for the rapid growth of solar photovoltaic (PV) energy connection to existing power grids at transmission and distribution levels. The integration of a microgrid photovoltaic system into the main utility is likely to bring some technical problems that request the upgrade of the power system to a smarter energy supply system that handles the dynamic characteristic of the power system in various operating states. One of those challenges can be described as voltage stability. The impacts of connecting a photovoltaic system to existing grids were considered with emphasis on the IEEE 9 bus transmission network. The existing grid is subject to dynamic load disturbance with a corresponding increase of 35% in power consumption. The dynamic increase of power in a stage of 5% for every 2 seconds of the real-time simulation produces a disturbance that leads to voltage instability in the power system. Developing a Real-time Digital Simulator Computer-Aided Design (RSCAD) model of the power network case study, this thesis aims to study the real challenges of integration of PV microgrid into the power system network considering the disturbance. The implementation of an algorithm, which considers the dynamic behaviour of the power system, was materialised by the modelling of a controller that monitors both the PV plant and the power system behaviours in an effort of restoring the voltage stability when the system generator failed. When the voltage collapse beyond the stability index of 0.95 p.u due to increased power consumption of the load, the controller shall generate a signal command to the inverter to allow a dynamic flow of power from the PV to the power system. Hence, the thesis contributes to the analysis of the stability of voltage in the electrical grid system with an integrated microgrid, by providing valuable algorithms for voltage stability control of the power system's electrical network with the integrated photovoltaic system in the RTDS environment.