Real-Time Voltage Stability Assessment With a Novel Bus Index Considering Impact of Connection to Distribution Networks

Many real-world power systems operate near voltage stability limits due to rising power demands, limited generation sources, and delays in development projects. Therefore, conducting online voltage stability assessments of power systems is crucial to ensure stable system operation. Various indices have been proposed in recent years to assess voltage stability in this context. One of the main challenges of these indexes for implementation in real-world power systems is their formulation with two-bus and single-line systems and their generalization to multi-bus and multi-line systems, which makes them non-rigorous. In formulating the existing indexes that use the concept of voltage sensitivity to active power, the effect of the lines from which the bus receives active power can be seen separately in evaluating bus voltage stability. At the same time, for accurate evaluation, the set of lines and the received power of all lines should be considered together in formulating the index. To meet this challenge, a new real-time index for voltage stability assessment is introduced in this paper. Furthermore, the effect of distribution systems in voltage stability is investigated in this study using simultaneous modeling transmission and distribution systems. The test results of the proposed index on the power system of the 3-bus system and the IEEE 14, 30, and 118 bus systems show its superior performance compared to the existing index. Specifically, to increase the apparent power loading in the 118-bus system, the maximum error of the proposed index is 3.37%. Meanwhile, for index P and index L, the maximum error is 29.6% and 30.75%, respectively. Finally, the results show that modeling the distribution system in the 3 and 118 bus systems reduces the maximum active power loading by 35.21% and 59.27%, respectively.