Detecting with PMUs the onset of voltage instability caused by a large disturbance

Abstract

Abstract-This paper deals with long-term voltage instability triggered by the outage of transmission or generation equipments. It is shown how the onset of voltage instability could be detected in real-time from post-disturbance bus voltages provided by Phasor Measurement Units (PMUs), assuming observability of the whole region prone to voltage instability. An extended set of equilibrium equations is fitted to the measurements and the change in sign of sensitivities is monitored. The latter are easily computed even for a large system. The important effects of overexcitation limiters and load tap changers are taken into account. The approach is illustrated on a 52-bus 20-machine system, where PMU outputs are simulated from detailed time simulation.

Wide-Area Detection of Voltage Instability From Synchronized Phasor Measurements. Part I: Principle

“…(21) are obtained by setting the left hand side of (19) to zero. In practice, however, the reduced model detailed hereafter, extensively used in Quasi Steady-State (QSS) simulation [7], [23], offers a good compromise between simplicity and accuracy.…”

“…Most of them rely on Thévenin impedance matching condition [11], [12] or its extensions [13], [14], [15]. As long as the various buses are checked independently of each other, these methods accommodate the time skew of SCADA data and no time synchronization is needed; 2) methods requiring the observability of the whole region prone to voltage instability [16], [17], [18], [19]. They offer the potential advantages of wide-area monitoring.…”

Local vs. wide-area undervoltage load shedding in the presence of induction motor loads

“…The proposed scheme has been tested on a variant of the Nordic32 test system, already used in [12], [13]. The system Since voltage problems are experienced in the "Central" region, the latter has been provided with five load shedding controllers, as detailed in Table I.…”

Tracking the maximum power transfer and loadability limit from sensitivities-based impedance matching

“…PMU-based voltage stability monitoring approaches can be classified into two broad categories: (i) those requiring observability of the whole region prone to voltage instability; (ii) methods based on local measurements, which can be implemented in a distributed manner [3]. Some examples of methods within the first category are those presented in [4][5][6][7]. In [4] and [5], an extended set of equilibrium equations are fitted to the available system state; then, an efficient sensitivity analysis is performed.…”

“…Some examples of methods within the first category are those presented in [4][5][6][7]. In [4] and [5], an extended set of equilibrium equations are fitted to the available system state; then, an efficient sensitivity analysis is performed. The sensitivities of the total reactive power generation respect to individual loads [4], calculated from the fitted model, are used for voltage instability estimation.…”