As renewable energy sources increasingly displace synchronous generators, bulk power systems face unprecedented voltage stability challenges during and after faults. Inverter-based resources (IBRs) such as solar and wind generators respond to disturbances differently than traditional synchronous machines, creating voltage dynamics that conventional metrics fail to capture.
The industry has long relied on short-circuit capacity (SCC) as a screening tool for grid strength. However, SCC provides only a coarse assessment. A bus with adequate SCC may still experience dangerous voltage dips, sluggish recovery, or transient overvoltages that violate operating standards—especially when dynamic loads, converter control interactions, or protection schemes compound the problem.
Researchers have introduced STVPI (Short-Term Voltage Performance Index), an electromagnetic-transient (EMT) based framework that measures voltage quality against user-defined performance criteria. The approach analyzes voltage waveforms at half-cycle resolution, comparing actual post-disturbance behavior to an ideal reference using statistical divergence methods. Two directional indices—STVPI+ for overvoltage and STVPI− for undervoltage—combine into a normalized severity score.
The metric scales from bus-level assessment (BSTVPI) to entire event analysis (ESTVPI), enabling simultaneous identification of weak buses and critical fault scenarios. Validation on the IEEE 9-bus and 39-bus test systems with IBR integration demonstrates the framework's capability to reveal voltage stability risks that conventional metrics overlook.
This advancement addresses a critical gap in grid planning and operation. As system operators integrate higher shares of inverters, STVPI provides a rigorous, criteria-aware tool for assessing dynamic voltage performance. The framework supports engineers in identifying where grid-strengthening investments—such as synchronous condensers, FACTS devices, or enhanced control schemes—are most needed to maintain reliability and ride-through capability in renewable-dominated power systems.
