A thesis submitted in partial fulfillment of the requirements for the degree of Master of Engineering

Thesis (M.Eng.) - Asian Institute of Technology, 1997

Voltage control problem in power systems is one of the most important aspects of modern power system operation and planning. Voltage is one of the basic parameters indicating the quality of supplied energy. Optimization of voltage and reactive power, together with economic load dispatch, ensures not only minimum cost but also reliable and secure operation of the system. The aim of the present study is to critically assess the voltage situation in Vietnam power system network and to find measures to solve its inherent voltage problem. Analysis of present voltage/reactive power controlling practices is carried with the help of load flow studies for different operating scenarios. Optimal Power Flow (OPF) has been utilized to exploit the available reactive power resources to overcome voltage problem. Problem of reactive power planning has been studied for situations before and after the application of Optimal Power Flow. Optimal Power Flow is used popularly by electric utilities around the world to ensure the optimal combination of existing voltage/reactive power controlling devices before considering the installation of new devices. This allows utilities to avoid considerable investment. It has been found that Optimal Power Flow can be utilized to decide the optimal settings of generators and transformer tappings in the daily operation of Vietnam power system. Although OPF could not solve the voltage problem in the network completely, it helps in reducing the transmission loss. Further measures, such as installation of new capacitors have been suggested to mitigate the voltage problem.