Voltage Collapse Point Research Articles

Predicting steady-state instability

The ability to know how much load can be met and how much power can be sold while maintaining a safe distance from the point of voltage collapse and steady-state instability is of great concern both in the real-time dispatch and during the operations planning and scheduling activities of power systems. This is particularly true in an increasingly deregulated electric utility industry where power systems are, and will be, dispatched within smaller voltage and steady-state stability margins than in the past. The authors describe a new application of REI-Dimo techniques which targets power system operation close to the maximum power transfer capability while maintaining a safe distance from critical states.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

Prediction of voltage collapse in an integrated AC-DC network using the singular-value decomposition concept

Abstract A power system under heavy loading conditions may face the problem of voltage instability followed by voltage collapse. The minimum singular value of the AC power flow Jacobian has been popularly used as a static voltage stability index showing the distance between the steady-state operating point and the point of voltage collapse. In this paper, the concept of minimum singular value and condition number of the load flow Jacobian has been extended to study the voltage instability of a combined AC-DC system. The proposed method has been applied to determine the voltage collapse point in four sample AC-DC systems, three of them derived from the IEEE 14-bus system and the fourth a practical 156-bus Indian system. The model includes a switching scheme to check the converter control parameter limit violations. The effect of load changes at a single bus as well as at all the buses simultaneously on voltage collapse has also been studied.

Point of collapse and continuation methods for large AC/DC systems

The implementation of both point of collapse (PoC) methods and continuation methods for the computation of voltage collapse points (saddle-node bifurcations) in large AC/DC power systems is described. The performance of these methods is compared for real systems of up to 2158 buses. Computational details of the implementation of the PoC and continuation methods are detailed, and the unique problems encountered due to the presence of high-voltage direct-current (HVDC) transmission, area interchange power control, regulating transformers, and voltage and reactive power limits are discussed. The characteristics of a robust PoC power flow program are presented, and its application to detection and solution of voltage stability problems is demonstrated. >

Direct calculation of voltage-stability limit of electric power systems

On-line monitoring of voltage-stability conditions is a new requirement for the energy management systems of the electric power industry. Preferred by the utility engineers and dispatchers is an index which represents explicitly the margins to a voltage-stability limit (collapse point) expressed in a physical unit ordinarily used. For example, such indices are the system load and voltage-voltage-stability-margins (SVVSM) between the present operating point and a voltage collapse point. However, long computer time is required to calculate accurately the voltage collapse point by the conventional method because many multiple load-flow solutions are required. This paper presents a new algorithm to calculate directly, exactly, and rapidly the voltage-stability limit. The algorithm uses the load-flow equations and the explicit expressions of the voltage collapse root conditions are expressed as dR/dV = 0, where R is active or reactive power node injection, and modifying the conventional N-R load-flow program, and is not affected numerically by singular Jacobians. The proposed algorithm is verified through calculating the voltage stability limit of a 176-node power system.

電力系統の電圧安定限界の直接解法

On-line monitoring of voltage-stability conditions is a new requirement for the energy management systems of the electric power industry. Preferred by the utility engineers and dispatchers is an index which represents explicitly the margins to a voltage-stability limit (collapse point) expressed in a physical unit ordinarily used. For example, such indices are the system load and voltage-voltage-stability-margins (SVVSM) between the present operating point and a voltage collapse point. However, long computer time is required to calculate accurately the voltage collapse point by the conventional method because many multiple load-flow solutions are required. This paper presents a new algorithm to calculate directly, exactly, and rapidly the voltage-stability limit. The algorithm uses the load-flow equations and the explicit expressions of the voltage collapse root conditions are expressed as dR/dV = 0, where R is active or reactive power node injection, and modifying the conventional N-R load-flow program, and is not affected numerically by singular Jacobians. The proposed algorithm is verified through calculating the voltage stability limit of a 176-node power system.