Improving the Nigerian 330kV Power System Steady State Voltage Stability Using Static VAr Compensation and Genetic Algorithm Optimization
ABSTRACT
The Nigeria 330kV network has been presented in this research work. The network just like many power systems in the world suffer from voltage instability caused by the variation in the reactive power requirement of the systems’ components. This has a resulting effect on consumers’ loads designed to operate within a specific voltage range. The system voltage goes high when there is excessive injection of reactive power and goes low when there is excessive absorption of reactive power. Ten (10) generating station buses and twenty-two (22) transmission line buses totalling thirty-two (32) buses were considered. Load flow solution was performed on the buses using Newton-Raphson method. This was programmed in matlab and the voltage magnitudes of all the buses were determined. The steady state voltage stability was investigated and the problem buses were identified. These were bus 16 (Yola), bus 23 (Alaoji), bus 26 (Gombe) and bus 30 (Ugwuaji). The voltage magnitude of bus 16 (Yola), bus 26 (Gombe) and bus 30 (Ugwuaji) are higher than what is specified in the Operating Procedure of the National Control Centre while that of bus 23 (Alaoji) is lower than the statutory limit specified. The Static VAr Compensation scheme deployed did not allow a noticeable voltage drop or voltage increase beyond the statutory limit. The scheme was used in this research to supply reactive power to boost the power system voltage magnitude on any of the problem buses and absorb reactive power to reduce the voltage on any of the buses. The compensation scheme reduced the voltage magnitudes of bus 16 (Yola), bus 26 (Gombe) and bus 30 (Ugwuaji) from 1.137pu to 0.975pu, 1.131 to 0.986pu and 1.055pu to 0.987pu respectively. The reactive power compensation scheme was also applied to bus 23 (Alaoji) to increase its voltage magnitude from 0.832pu to 0.954pu. Other buses that were affected positively are bus 10 (Kaduna) from 1.049 pu to 1.000 pu, bus 13 (Kano) from 1.042 pu to 0.992 pu, bus 14 ( Jos) from 1.052 pu to 0.993 pu, bus 15 (Makurdi) 1.051pu to 0.992pu, bus 18 (Benin) from 1.026pu to 1.027pu, bus 19 (Onitsha) from 0.978 to 0.984, bus 22 (New Haven) from 0.975pu to 0.981pu. The transmission line active power losses in the network were also determined before and after the compensation were applied. These two values were compared to get the increase in transmission efficiency due to the compensation. The compensation brought about a 17.48 percent increase in efficiency. The Static VAr Compensation scheme in this research has been shown to be an efficient tool in maintaining short and long term voltage stability so as to reduce overall transmission losses in the Power System Network. In order to ensure a cost effective optimal load flow, Genetic Algorithm was employed to reduce the cost of electricity generation by the generating power stations. These allotted the generating stations with appropriate capacity to meet the load demand while reducing the cost. This further improved the voltage stability of the network.
