Investigation on the location and sizing for solar PV using LQ_LT index and exact loss formula for heavily loaded transmission systems

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Mohamad Razin Naim Mohd Alias, Mr.
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Voltage stability indices (VSI) are indicators that have been developed to identify weak buses in the power system. Maintaining voltage within safe operating limits at each bus is crucial to avoid voltage collapse. Integrating renewable distributed generation (DG) into the system can help maintain the voltage within the security limits during congestion and heavy loading. The first objective is to investigate the performance of reactive power tracing capable index, named LQP_LT in identifying the weak load buses that are present in IEEE 14 bus and IEEE 30 bus systems. All the simulations were carried out using MATLAB via MATPOWER optimal power flow. The LQP_LT index incorporates proportional sharing methods to identify the weak load buses and generates a priority ranking list. The identification of weak buses was done by creating a contingency scenario whereby simulations carried out on heavily loaded buses. The performance of the LQP_LT index was validated by comparing the ranking results obtained with other established voltage stability indices, namely, FVSI, NLSI and VSLI. In addition, the weak load buses identified via LQP_LT were also compared with the exact loss formula. The second objective is to determine the sizing for solar PV placement using exact loss formula. In the literature, the exact loss formula is also capable to determine the location and sizing for solar PV. Results obtained highlight that both LQP_LT and the exact loss method have consistent data regarding on bus allocated for PV installation results for the solar PV placements. Moreover, the utilization of solar PV has significantly improved the overall system voltage stability. In the IEEE 14 bus system, voltage per unit for bus 14 is enhanced by 0.74% at a loading factor of 1.90. In the IEEE 30 bus system, bus 8 voltage level was improved by 11.17 % at a loading factor of 1.60. Solar PV also helps in reducing the transmission losses available at the critical branch. For instance, the percentage of reactive loss lessened in branch 14 (bus 7 and bus 8) in the IEEE 14 bus system at maximum loading is 15.7%. On the other hand, for the IEEE 30 bus system, branch 2 (bus 1 and bus 3) at maximum loading (load factor 1.60) had its reactive losses reduced by 43.83% with the assistance of solar PV.
LQ_LT index and exact loss formula