Application of HVDC transmission within Nigerian transmission system: technical and economic evaluation

High Voltage Direct Current (HVDC) technology has recently emerged as a significant option in current power networks to address power transmission challenges. Therefore, this research project examines the potential impact of HVDC technology on the Nigerian transmission system. Based on the information provided by the Nigerian Electricity System Operator (NESO), a model of the 330 kV transmission network in Nigeria was created using DIgSILENT PowerFactory. Summer and winter load flow scenarios were examined to enhance the model's precision and consistency. The system performance was evaluated through stability and reliability studies, which helped identify suitable locations for HVDC links. The load point indices (LPIs) and system indices were used for the reliability evaluation, while the PV and QV analyses were used for the stability evaluation. An HVDC model was created and connected to the transmission network at two locations identified by the studies, Gombe and Yola buses. A comparison was conducted using two separate HVDC connections (Case 1: Azura-Gombe and Case 2: Azura-Yola) to identify the critical impact of HVDC on the system reliability and stability. The reliability and stability simulation showed that HVDC technology significantly boosts the reliability and stability of the transmission network and reduces energy losses. However, adding an HVDC link between Azura and Yola, Case 2, significantly improved overall performance, as evidenced by improving the system and load point indices and a better voltage profile and reactive power margin. The system indices, SAIDI improved by 0.07 h/yr, SAIFI by 0.19 interruption/yr, and ASAI enhanced by 0.11%, while the LPIs improved effectively by zeroing the Load Point Interruption Frequency (LPIF) and Load Point Interruption Time (LPIT). During the stability analysis, the loadability increased by 119% while the critical point improved by 0.061 pu/ -394 MVAR. Economically, the cost incurred in Case 1 is 79.17% lower than the base case even though new equipment (HVDC) is installed; this also applies to Case 2, which is 85% lower than the base case. Integrating HVDC technology could improve financial gain, considering improved energy supply, increased production, and general economic growth. This research has contributed significantly to revealed improvements in system and load indices, increased loadability, increased stability, and boosted financial gain with the HVDC connected.