S. Aboreshaid

Probabilistic transient stability studies using the method of bisection [power systems]

In this paper, a method of bisection is introduced as a tool to considerably reduce the amount of computation time required in the stochastic evaluation of power system transient stability. This method proves to be very helpful in predicting the number of stability runs required to calculate the probabilistic transient stability indices for a given system location, a certain transmission line or for the overall power system. The developed method is examined utilizing a hypothetical test system and the effect of load forecast uncertainty is illustrated. The effect of modeling and employing high-speed simultaneous or adaptive reclosing is also presented and discussed.

Impact of unified power flow controllers on power system reliability

This paper examines the impact of a unified power flow controller (UPFC) on power system reliability. The UPFC is employed in the system to adjust the natural power sharing of two different parallel transmission lines and therefore enable the maximum transmission capacity to be utilized. The results of the investigations show a significant improvement in the system reliability by utilizing the UPFC. The improvement is measured using three reliability risk indices, namely, the loss of load expectation (LOLE), the loss of energy expectation (LOEE), and the system minutes (SM). The paper also presents a comparison between the effects of the UPFC and a thyristor controlled series capacitor on the system reliability.

Damping power system oscillations using a fuzzy logic based unified power flow controller

This paper presents a new control method based on fuzzy logic technique to control a unified power flow controller (UPFC) installed in a single-machine infinite-bus power system. The objective of the fuzzy logic based UPFC controller is to damp power system oscillations. Phillips-Herffron model of a single-machine power system equipped with a UPFC is used to model the system. The fuzzy logic based UPFC controller is designed by selecting appropriate controller parameters based on the knowledge of the power system performance. Simple fuzzy logic controller using mamdani-type inference system is used. The effectiveness of the new controller is demonstrated through time-domain simulation studies. The results of these studies show that the designed controller has an excellent capability in damping power system oscillations

Voltage stability considerations in composite power system reliability evaluation

This paper presents an approach which includes voltage stability considerations in the adequacy assessment of a composite power system. A fast technique for the probabilistic assessment of voltage stability is presented which can be used in conjunction with detailed contingency evaluation in a composite system adequacy assessment. Voltage stability is quantified using an indicator that can be easily included in the framework of an existing composite power system adequacy program. The effect on the adequacy indices (load point and system indices) of incorporating voltage stability constraints is illustrated by application to the IEEE-Reliability Test System.

Stochastic evaluation of voltage sag and unbalance in transmission systems

Voltage sags, also known as dips, are important to industrial reliability. This paper presents a Monte Carlo based approach to evaluate the maximum voltage sag magnitudes as well as the voltage unbalance in transmission systems. In this context, investigations have been conducted on a system model taking into consideration the uncertainty in several factors associated with the practical operation of a power system. MATLAB is used in the simulation studies.

Well-being analysis for HVDC transmission systems

This paper presents a technique to evaluate the degree of reliability well-being of HVDC transmission systems. The system well-being is categorized in terms of power system health and margin in addition to the conventional risk index. A hybrid approach is presented to determine the well-being indices for HVDC transmission systems. Two performance indices designated as the healthy performance index and the total system performance index are used to describe the load carrying capability and degree of power system well-being. The technique is illustrated by application to a simple hypothetical configuration and two practical HVDC power systems.

Probabilistic Evaluation of Transient Stability of a Wind Farm

This paper presents a probabilistic-based approach to evaluate transient stability of a wind farm. In this context, investigations have been conducted on a hypothetical system representing a typical wind farm taking into consideration the uncertainty of several factors associated with the practical operation of a power system. A risk index that reflects the likelihood that the wind farm encounters an instability problem is presented. The time domain simulations are obtained using the electromagnetic transient program (EMTP).

Unit commitment health analysis for interconnected systems

The concepts previously published for unit commitment and operating reserve assessment in an isolated power system using a system well-being framework are extended in this paper to evaluate unit commitment and spinning reserve requirements in interconnected power systems. The problem of interconnected power systems unit commitment is decomposed into two subproblems. Unit scheduling is first performed in each isolated power system in accordance with the specified operating criterion. This is then followed by interconnected power system evaluation. The analysis is further extended to determine the operating state probabilities for the overall interconnected power system. The paper illustrates how power system well-being is improved by interconnection with other power systems. The concepts contained in the paper are illustrated by application to two radially interconnected IEEE-RTS.

Composite system reliability evaluation incorporating an HVDC link and a static synchronous series compensator

This paper presents an approach to perform AC/DC system reliability analysis in a composite system where a hybrid compensating scheme is employed in the AC link to adjust the transmission infeed impedance and, therefore, increase the transmission system capacity. The hybrid scheme consists of a static synchronous series compensator (SSSC) and a fixed capacitor. Reliability models associated with a bipolar DC link and the hybrid compensating scheme are developed. A wide range of indices is calculated at both the load point and system levels using a contingency enumeration technique. The capabilities of the technique and the models presented in the paper are illustrated using a small but typical AC/DC system.

Stochastic evaluation of voltage sags in series capacitor compensated radial distribution systems

Voltage sags, also known as dips, are important to industrial reliability. This paper presents a Monte Carlo based approach to evaluate the maximum voltage sag magnitudes in series capacitor compensated radial distribution systems. In this context, investigations have been conducted on a sample distribution system model taking into consideration the uncertainty of several factors associated with the practical operation of a power system. The Power System Blockset of MATLAB is used in the simulation studies.