Abstract
Power system stability is a major challenge in the secured operation of today’s interconnected power systems. Voltage stability as a branch of power system stability, is a major problem facing power systems in Ghana. The power system is subjected to major blackouts or collapses due to voltage instability. It is manifested by several distinguishing features: low system voltage profiles, heavy reactive line flows, inadequate reactive support, and heavily loaded power systems. Voltage stability depends on the ability of a power system to maintain acceptable voltage for system buses under normal conditions, and system disturbances. This paper evaluates the steady-state voltage stability of the power system through modelling and simulation using the Power System Simulator for Engineering power system analysis software and the results validated with MATPOWER. Load flow simulations using the Newton Raphson method under steady-state base load condition with and without contingencies were done. Simulation results revealed under normal, and contingency cases show the power system has voltage profile, that violates the voltage stability constraint of between 0.95 pu and 1.05 pu for normal system voltage, high transmission system losses and heavy congestion. The Flexible Alternative Current Transmission System (FACTS) devices was used to improve the power system stability. Three types of FACTS devices: SVC, STATCOM, and TCSC are selected and optimally placed in the power system to improve voltage stability. Generic algorithm as artificial intelligence-based method was used in MATLAB environment to optimally size and locate five (5) FACTS devices; one (1) STATCOM and four (4) SVC in the power system. The algorithm was found to be reliable as it yielded good results by the improvement in voltage stability and decreasing the transmission line active and reactive power losses significantly.
Highlights
The introduction of Ghana’s power sector reforms about a decade ago have seen the functions of power generation and transmission delegated to two companies namely: the Volta River Authority (VRA) and the Ghana Grid Company Limited (GRIDCo) respectively
The base case power system for the simulation is made up four areas: GRIDCo, CIE, CEB, and SONABEL, of which the interconnected network constitutes 199 buses, 268 transmission lines, 81 transformers, 52 generators, and 98 load centres
The PSSE weekday off-peak base case, and 330 line contingency simulation results were validated using MATPOWER and the validation indicates that, MATPOWER simulation results are within a deviation error of ±5%
Summary
The introduction of Ghana’s power sector reforms about a decade ago have seen the functions of power generation and transmission delegated to two companies namely: the Volta River Authority (VRA) and the Ghana Grid Company Limited (GRIDCo) respectively. The liberalisation and deregulation of the industry and the introduction of the grid code in line with the reforms poses a great challenge to utilities in the generation, transmission and distribution sectors. The current increase in electrical energy demand due to current modern lifestyles have made the world including Ghana to fully depend on power systems to propel industrial and economic growth. FACTS technology is essential in alleviating some of the difficulties by enabling utilities get reliable service from the transmission facilities and enhance the power system stability. With the relatively low investment compared with new transmission and generation facilities, FACTS technology allows for better utilisation of the existing transmission and generation facilities
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