Investigation of Power Flow Tracing Strategy Using an Index in a Transmission System with Solar PV for Congestion Management

Voltage stability indices (VSI) have been developed to solve for uncertainty and irregularities that occur beyond the boundary of a standard operating limit of the power system. Maintaining voltage at each bus are crucial to avoid blackouts which are mainly due to insufficient reactive powers especially when demand is high. Integration of distributed generation (DG) into the system can help improve the performance level, especially during congestion and heavy loading. This paper demonstrates the performance of LQP _L T in tracing the weak buses present in IEEE 14 bus system. Besides that, to test for the validity and reliability of the index, other VSIs are used, namely FVSI, NLSI and VLSI for performance comparison. MATPOWER cases were utilized for load flow analysis while simulations for the LQP _L T algorithm is done in MATLAB. Solar photovoltaic (PV) integration in IEEE 14 bus system is done considering for both base case and heavily loaded scenarios. Upon performance comparison of the indices, LQP _L T identified weak bus was verified using exact loss formula. This method is an approximation analysis that is used to determine the most suitable location for solar PV positioning and sizing. Both LQP _L T and exact loss method have a consistent outcome in identifying the weak bus. Solar PV sizing was further computed using the same exact loss formula and placed at the identified weak bus. The result obtained from the study shows that the LQP _L T index is robust and efficient to analyze the power flow present in the transmission system. The list of weak buses is arranged in descending order from highest to lowest index amount. Last but not least, PV placement with appropriate sizing at the identified weak bus greatly improved the overall system stability and losses.