Voltage Stability Point Of View Research Articles

A novel placement strategy for facts controllers

In this paper, a new method called the extended voltage phasors approach (EVPA) is proposed for placement of FACTS controllers in power systems. While the voltage phasors approach (VPA) identifies only the critical paths from the voltage stability viewpoint, the proposed method additionally locates the critical buses/line segments. The results of EVPA are compared with the well-established line flow index (LFI) method for nine-bus, 39-bus, and 68-bus systems. It is shown that the EVPA provides accurate indication for the placement of FACTS controllers.

A Novel Placement Strategy for FACTS Controllers

In this paper, a new method called the extended voltage phasors approach (EVPA) is proposed for placement of FACTS controllers in power systems. While the voltage phasors approach (VPA) identifies only the critical paths from the voltage stability viewpoint, the proposed method additionally locates the critical buses/line segments. The results of EVPA are compared with the well-established line flow index (LFI) method for nine-bus, 39-bus, and 68-bus systems. It is shown that the EVPA provides accurate indication for the placement of FACTS controllers.

Design of robust coordinated SVC supplementary controllers

Abstract A method for designing coordinated H ∞ SVC supplementary controllers is presented to improve the damping of interarea oscillations. A distributed controllers are designed considering overvoltage problem, which is thought to be a critical issue for SVC to design a supplementary damping controller. The proposed method contains a method to obtain dynamic equivalents of a power system model through an uncertainty minimization procedure. This method is aimed for realizing a tight design for distributed controllers so that a better performance of the total system can be gained. In addition, an uncertainty minimization process is used to regulate indirectly the controller's output so that the overvoltage problem is treated in the design step. The locations of SVCs are determined from the voltage stability point of view using bus participation factor. An effective input to damp oscillations is selected based on residue concept. The effectiveness of the proposed control design is demonstrated through nonlinear numerical simulations in five machine eight bus system under several critical operating conditions.

Series capacitors combined with static VAR compensators for enhancement of steady-state voltage stabilities

Use of series capacitors (SC) alone or in combination with static VAR compensators (SVC) for enhancement of steady state voltage stability are illustrated. The appropriate compensation percentage is obtained from the steady-state voltage stability point of view. The influence of a combination of SC and SVC on ratings and performance are studied. Limitations of the use of series capacitors alone are examined.

Identifying electrically weak and strong segments of a power system from a voltage stability viewpoint

Voltage instability leading to collapse appears to be due to the inability of networks to meet a demand for reactive power at certain critical (or weak) buses. Practical control algorithms to prevent voltage collapse should identify the critical buses in the network and maintain control on voltages at these buses in particular. Two methods are proposed for identifying the weak buses and segments in power transmission networks. Both methods employ a technique presented earlier for determining the static voltage stability limit in multimachine power systems. The first method is based on the relative change in the bus voltages going from an initial operating state to the voltage stability limit. The second method is based on the sensitivity parameters computed at the voltage stability limit.

A probabilistic approach to the voltage stability analysis of interconnected power systems

Abstract In planning a power system it is always necessary to assess whether a voltage collapse occurs during a prefixed system operating condition. However, present approaches to the analysis of voltage instability phenomena in interconnected power systems are deterministic and, consequently, they cannot take into account the unavoidable uncertainties associated with the bus load forecast. This is indeed an important limitation. In this case the application of probabilistic techniques is the most feasible alternative. On the basis of this observation, in this paper a probabilistic approach to the voltage stability analysis of interconnected power systems is presented; it treats loads as random uncorrelated variables with normal distributions. The method proves suitable for determining systematically, for each expected system operating condition, the statistics of all the node voltages which are critical from the voltage stability viewpoint. The capability and usefulness of the suggested approach are illustrated by carrying out simulation studies on a sample power system.