Quantifying the Severity of Short-term Instability Voltage Deviations

Abstract

As power systems evolve from synchronous to inverter-based generation, voltage stability plays an increasingly important role. Voltage perturbations become faster and highly variable, and as such attract the research interest in the field of short-term instability monitoring and evaluation. The digitalization of the power systems provides a higher degree of observability by making use of synchrophasor measurements. The next step of utilizing such measurements by tailoring and applying innovative analytical and data-driven solutions is, however, still at the early development stage. In this paper, a novel approach that utilizes rapid post-fault voltage deviations for short-term instability quantification is investigated. The findings indicate that the approach is intuitive and effective. Finally, the paper discusses future research directions, enabled by the presented methodology, that deal with grid resilience challenges. Particularly, those related to postdisturbance system strength evaluation, as well as the real-time short-term instability evaluation and prediction, are addressed.

Beyond SCR in Weak Grids: Analytical Evaluation of Voltage Stability and Excess System Strength

“…A singular Jacobian matrix indicates a system voltage instability condition. The stability boundary is therefore found by solving the det(𝑱) = 0 expression, and is shown in (11).…”

“…This is lower than the angle stability limitation of 90° implied by the active power computed by (6). We, therefore, extend this approach further by incorporating the voltage stability boundary (11) into the power transfer (6) equation:…”

“…For transferring 𝑃 = 𝑃 𝑚𝑎𝑥 in (13), the reactive power required to maintain the voltage can be computed by combining (6) and (11), as shown in (14):…”

“…This paper focuses on steady-state characteristics. The dynamic performance is discussed in [8][9][10][11]. Other aspects of low system strength, such as protection misoperation [12,13] and power quality deterioration [6], fall beyond the scope of this paper.…”

System Strength: Classification, Evaluation Methods, and Emerging Challenges in IBR-dominated Grids

“…Furthermore, the potential for IBRs' interactions with each other and other controllers in the grid increases as system strength drops [6], and IBRs maloperation and disconnection become more likely [7]. The challenges are emphasized for short-term stability, as the displacement of SGs leads to faster and larger voltage deviations [8][9]. Furthermore, low system strength introduces protection maloperation risks, as fault currents are lower and with very different characteristics [10,11].…”