This paper investigates the use of reactive power reserves (RPR) as an indicator to estimate voltage stability margin (VSM) in an online environment. The methodology relies upon the relationship between system-wide RPRs and VSM. Statistical multilinear regression models (MLRM) are utilized in order to express how variations in RPRs can be transformed into direct information about VSM. Data regarding RPRs and system VSM are obtained through an offline voltage stability assessment (VSA) and stored in a database for further MLRM development. Different load increase directions and a comprehensive list of contingencies are considered to account for uncertainty present in real-time operations. Once properly designed and validated, the MLRMs are ready to be used in the online environment. The methodology is tested on the IEEE 30-bus system and a real size test system containing 1648 buses. Preliminary results show that MLRMs can be successfully employed in online VSM estimation.

This study proposes a man-in-loop control method to boost reactive power reserves (RPRs) while maintaining a minimum amount of voltage stability margin (VSM) bus voltage limits. The objective is to determine the most effective control actions in order to reestablish critical RPRs across the system. Initially, the concept of reactive power reserve sensitivity with respect to control actions is introduced. In the sequel, a control approach based on convex quadratic optimization is used to find the minimal amount of control necessary to increase RPRs above their pre-specified (offline) levels. Voltage stability margin constraints are incorporated using a linear approximation of critical RPRs.Simulation results show that system operators can optimally determine the right amount and location of control actions in order to restore critical RPRs and enhance VSM by using reactive power reserve sensitivities. Moreover, the optimization problem size can be made small if only the most effective control actions are selected, a desirable advantage for real time implementations of man-in-loop control.Index Terms-Emergency control, reactive power reserves, reactive power reserve sensitivity, voltage collapse, voltage stability control.

No abstract

Leading into this study, WWSIS-3 delved into the dynamic performance of the grid in the fractions of a second to 1 min following a large disturbance (e.g., loss of a large power plant or a major transmission line), which is critical to system reliability. In particular, that study examined the large-scale transient stability and frequency response of the Western Interconnection with high penetrations of wind and solar, and it identified means to mitigate any adverse performance impacts via transmission reinforcements, storage, advanced control capabilities, or other alternatives (Miller et al. 2014a, Miller et al. 2014b). Key findings included: • With good system planning, sound engineering practices, and commercially available technologies, the Western Interconnection can withstand the crucial first minute after grid disturbances with high penetrations of wind and solar. • Local stability, voltage, and thermal problems can be addressed with traditional transmission system reinforcements (e.g., transformers, shunt capacitors, local lines).

No abstract