Combined detailed and quasi steady-state time simulations for large-disturbance analysis

in International Journal of Electrical Power & Energy Systems (2006), 28(9), 634-642

This paper deals with the simulation of long-term responses of power systems to large disturbances in the presence of discrete events. After outlining the power system model under the quasi steady-state ... [more ▼]

This paper deals with the simulation of long-term responses of power systems to large disturbances in the presence of discrete events. After outlining the power system model under the quasi steady-state (QSS) approximation, a method combining detailed and QSS time simulations is presented, the former being used for accuracy and the latter for efficiency reasons. Detailed time simulation is used to analyze the short-term period following a large disturbance and identify the discrete controls triggered. Next, QSS simulation is used to simulate the same time interval with the discrete controls imposed as external events, before letting the system evolve as usual in the long-term. This simple method has been successfully tested on the Hydro-Quebec system. (C) 2006 Elsevier Ltd. All rights reserved. [less ▲]

Quasi steady-state models for long-term voltage and frequency dynamics simulation

(2005, June)

The Quasi Steady-State (QSS) approximation of long-term dynamics relies on time-scale decomposition and consists of replacing faster phenomena by their equilibrium conditions, in order to reduce the ... [more ▼]

The Quasi Steady-State (QSS) approximation of long-term dynamics relies on time-scale decomposition and consists of replacing faster phenomena by their equilibrium conditions, in order to reduce the complexity of the whole model and increase the computation efficiency of time simulations. This paper describes the extension of a QSS model extensively used in long-term voltage stability studies, to readily incorporate the frequency dynamics that takes place over the same time scale. This extended QSS model relies on a common-frequency assumption. Its advantages, limitations and possible improvements are discussed through simulation results on the Hydro-Québec system, where it has been compared to full time scale simulations. Disturbances with an impact on either frequency or voltages are considered and the coupling between these two aspects of long-term dynamics is briefly discussed. [less ▲]

Design of an undervoltage load shedding scheme for the Hydro-Québec system

(2003, July)

This paper deals with the control logic of an undervoltage, closed-loop load shedding scheme aimed at protecting the Hydro-Quebec system against long-term voltage instability. This scheme relies on a set ... [more ▼]

This paper deals with the control logic of an undervoltage, closed-loop load shedding scheme aimed at protecting the Hydro-Quebec system against long-term voltage instability. This scheme relies on a set of "if-then" rules whose parameters are determined through combinatorial optimisation, relying on the system dynamic response over a set of scenarios. Preliminary results of the above optimisation technique are given, besides a brief description of the foreseen implementation. [less ▲]

A Time-Scale Decomposition-Based Simulation Tool for Voltage Stability Analysis

in Proceedings of the IEEE Porto Power Tech Conference (2001, September)

This paper proposes a time domain simulation tool combining Full Time Scale (FTS) simulation in the short-term period following a contingency and Quasi Steady-State (QSS) approximation for the long-term ... [more ▼]

This paper proposes a time domain simulation tool combining Full Time Scale (FTS) simulation in the short-term period following a contingency and Quasi Steady-State (QSS) approximation for the long-term phase. A criterion is devised to automatically switch from FTS to QSS simulation as soon as sufficient damping of short-term dynamics is reached. Various comparisons with FTS simulations have been performed on the Hydro-Qn6bec system. The proposed method is shown to combine accuracy of FTS with computational efficiency of QSS. Sensitivity of simulations to load model and the need for updating the whole model with frequency variations are also discussed. [less ▲]

Combinatorial optimization approaches to the design of load shedding schemes against voltage instability

(2000, October)

This paper proposes a methodology for the design of automatic load shedding against long-term voltage instability. In a first step, a set of training scenarios is set up, corresponding to various ... [more ▼]

This paper proposes a methodology for the design of automatic load shedding against long-term voltage instability. In a first step, a set of training scenarios is set up, corresponding to various operating conditions and disturbances. Each scenario is analyzed to determine the minimal load shedding which stabilizes the system, with due consideration for the shedding location and delay. In a second step, the parameters of a closed-loop undervoltage load shedding scheme are determined so as to: (i) approach as closely as possible the optimal sheddings computed in the first step, over the whole set of scenarios; (ii) stabilize the system in all the unstable scenarios and (iii) shed no load in the stable ones. The corresponding optimization problem is solved using three methods : genetic algorithms, branch and bound approach and the so-called “sequential design”. A detailed example is given on the Hydro-Qu´ebec system in which load shedding is presently planned. [less ▲]

Design of Load Shedding Schemes against Voltage Instability

(2000, January 27)

This paper proposes a methodology for the design of automatic load shedding against long-term voltage instability. In a first step, a set of training scenarios is set up, corresponding to various ... [more ▼]

This paper proposes a methodology for the design of automatic load shedding against long-term voltage instability. In a first step, a set of training scenarios is set up, corresponding to various operating conditions and disturbances. Each scenario is analyzed to determine the minimal load shedding which stabilizes the system, with due consideration for the shedding location and delay. In a second step, the parameters of a closed-loop undervoltage load shedding scheme are determined so as to: (i) approach as closely as possible the optimal sheddings computed in the first step, over the whole set of scenarios; (ii) stabilize the system in all the unstable scenarios and (iii) shed no load in the stable ones. The corresponding optimization problem is solved using a (micro-)Genetic Algorithm. A detailed example is given on the Hydro-Quebec system in which load shedding is presently planned. [less ▲]