Voltage stability improvement and transmission loss minimization for a 6-bus Oman electrical system based on modal analysis and reactive power compensation

Abstract

Oman Electricity Transmission Company has a problem in voltage drop this year as shown in their contingency plan in 2019 due to an increase on load demand and a power loss in Oman grid system. This project proposed a method to analyse and develop a reactive power compensation technique to determine ideal reactive power compensation to reduce transmission loss and improve voltage profile. In the proposed method, as a single objective the amount of additional reactive power is first calculated for each load bus which totally around 120.51 MVAr, this power is then injected for each load bus (Nizwa, Birkat Al Mouse, Izki, Sumail). For multi-objectives, further analysis has been performed to select particular buses to inject the additional reactive power into and to understand the optimal placement of compensating equipment. The proposed model determines the specific number of minimum Eigen-values and related Eigen-vectors for a reduced Jacobian matrix (JR). The computed Eigen-values for the reduced Jacobian matrix was evaluated to check system stability. A voltage system is stable if all the Eigen-values obtained are positive. However, a zero Eigen-value indicates the system is drifting towards voltage instability. Additionally, the possible voltage breakdown condition of 6-bus electrical system is predictable, and was determined by discerning the participation factor for the lowest positive Eigen-values. Critically weak buses would have the lowest Eigen-values, providing the optimal position for the placement of the capacitor in the selected system to achieve a high voltage stability margin. The proposed method has been validated with the 6-Bus Oman Electric grid system and compared with both Particle Swarm Optimization and Genetic Algorithm method in order to select the more effective technique. In addition, the cost minimization has been studied by using PSO and found that there was a decrease in fuel consumption from 10.9 Omani Rial (OMR) to 9.0068 OMR per hour which represents a reduction by 17.4%.