Generation Rescheduling Based on Energy Margin Sensitivity for Transient Stability Enhancement

Abstract

-This paper presents a generation rescheduling method for the enhancement of transient stability in power systems. The priority and the candidate generators for rescheduling are calculated by using the energy margin sensitivity. The generation rescheduling formulates the Lagrangian function with the fuel cost and emission such as x NO and x SO from power plants. The generation rescheduling searches for the solution that minimizes the Lagrangian function by using the Newton's approach. While the Pareto optimum in the fuel cost and emission minimization has a drawback of finding a number of non-dominated solutions, the proposed approach can explore the non-inferior solutions of the multiobjective optimization problem more efficiently. The method proposed is applied to a 4-machine 6-bus system to demonstrate its effectiveness.

Risk-Based Active Power Redispatch Optimization

“…Several interesting approaches to extending the SC UC/ED and SC OPF with constraints based on transient stability assessment (TSA) may be found in the literature, however, they differ with respect to many criteria. First of all the way of incorporating rotor dynamics into the linear optimization problem spans from using trapezoidal rule [2,3] or Taylor series expansion [4] (to convert differential equations into algebraic ones) to involving direct (or direct-temporal) TSA methods like single-machine equivalent (SIME) [3,[5][6][7] or the transient energy function (TEF) [8][9][10][11]. These methods are used to rank the synchronous machines by their stability margin (or its sensitivity to generation changes) with respect to a considered set of contingencies, however, the critical clearing time (CCT) was used for ranking as well [12].…”

“…These methods are used to rank the synchronous machines by their stability margin (or its sensitivity to generation changes) with respect to a considered set of contingencies, however, the critical clearing time (CCT) was used for ranking as well [12]. Secondly, the procedure of finding the amount of power to be shifted from the least stable generators could be based on the identified energy margins, inertia constants [11], values of the rotor speed at the fault clearing time [9] or the power angle trajectory sensitivity [13][14][15]. In most cases, the power shifting was performed in small steps within an iterative procedure.…”

“…The general scheme of the redispatch optimization proposed in this paper is shown in Figure 1. Its basic concept is similar to those described above [2][3][4][5][6][7][8][9][10][11][12][13][14][15], but there are three major differences. First of all, going beyond TSA towards a more comprehensive dynamic security assessment is considered here, where not only transient rotor angle but also frequency and voltage instabilities may be tackled-by applying proper dynamic models [7].…”

“…In between the dynamic risk assessment and the remedial actions design, this risk values R are used to verify the stopping criterion and assess whether remedial actions are necessary. In the first approach, a threshold-based stopping criterion similar to the ones described in the literature [2][3][4][5][6][7][8][9][10][11][12][13][14][15] was used and its aim was to allow stabilizing the system against credible contingencies. It was defined by the following inequality (2):…”

“…However, we decompose it to every synchronous generator and identify the critical (the least stable ones) and non-critical machines (CMs and NMs, respectively). Similar identification is used in many approaches listed in Section 1, including those utilizing SIME [3,[5][6][7] or TEF [10,11] methods. It serves the purpose of conducting the redispatch by shifting the active power from CMs to NMs.…”