Akhtar Kalam

Simple and efficient method for load flow solution of radial distribution networks

The paper presents a simple and efficient method for solving radial distribution networks. The proposed method involves only the evaluation of a simple algebraic expression of voltage magnitudes and no trigonometric functions as opposed to the standard load flow case. Thus, computationally the proposed method is very efficient and it requires less computer memory. The proposed method can easily handle different types of load characteristics. Several Indian rural distribution networks have been successfully solved by using the proposed method.

A practical approach to accurate fault location on extra high voltage teed feeders

The basis of an alternative approach for accurately locating faults on teed feeders is described. The technique developed uses fault voltages and currents at all three ends. The method is virtually independent of fault resistance and largely insensitive to variations in source impedance, teed and line configurations, including line untransposition. The basic theory of the technique is presented. It is extensively tested using simulated primary system voltage and current waveforms, which include the transducer/hardware errors encountered in practice. The performance clearly shows a high degree of accuracy. >

The Real-Time Publisher/Subscriber Communication Model for Distributed Substation Systems

In the past decade, new communication schemes have been designed and retrofitted into substations by utilities to integrate data from relays and intelligent electronic devices (IEDs) and capitalize on the protection, control, metering, fault recording and communication functions available in digital devices. The introduction of IEC 61850 has made it possible and justifiable to integrate station IEDs on a high-speed peer-to-peer communication network (Ethernet) through standardization. However, more advances are needed in order to establish an open and standard working environment allowing for more functions to be developed. In this paper, the authors propose a real-time publisher/subscriber communication model as a means of satisfying the unique behavior and communications needs of the IEC 61850 protocol. The authors provide a detailed design and implementation detail of this model along with interesting performance results. The target audience for this paper includes power system protection and automation engineers and technicians as well as research personnel who have at least a basic understanding of the IEC 61850 international standard and other technology mechanisms addressed in this paper.

The Application-View Model of the International Standard IEC 61850

The introduction of IEC 61850 as the de facto SA standard for the communication between devices in a substation and the related system requirements has made it possible and justifiable to integrate station Intelligent Electronic Devices (IEDs) on a high-speed peer-to-peer communication network (Ethernet) through standardization. IEC 61850 presents a set of standard object-oriented (OO) data models to describe the processes to be implemented and controlled in a substation and a set of service models for the interactions between devices in a substation and the transfer of all sorts of IED data. IEC 61850 proposes the concept of standardizing IED data using data objects referred to as logical nodes. This makes it possible to achieve the ldquoplug and playrdquo capability so that information and commands can be shared on a single network independent from any implementation. In this paper, the authors describe the standards application-view model and present the use of OO methodology and techniques for the implementation of the Logical Node (LN) application-view data model of the standard. The target audience for this paper includes power system protection and automation engineers and technicians as well as research personnel who have at least a basic understanding of the IEC 61850 international standard and other technology mechanisms addressed in this paper.

Object Modeling of Data and DataSets in the International Standard IEC 61850

In the past decade, new communication schemes have been designed and retrofitted into substations by utilities to integrate data from relays and intelligent electronic devices (IEDs). The idea of standardizing the language of communication between IEDs has evolved as the key for the advancement of connectivity and interoperability within a SA system. The most important outcome of this standardization process has been the IEC 61850 standard. IEC 61850 is an abstract application layer protocol aimed at providing interoperability between a variety of substation and feeder devices by describing how devices are to communicate in a substation as well as the related system requirements. In this paper, the authors describe the standards application-view model and present the use of OO methodology and techniques for the modelling and implementation of the data and dataset application-view object models of the standard. The target audience for this paper includes anyone interested in getting an overview of the IEC 61850 international standard, and understanding how the object-oriented models proposed in the standard standardize the data found in IEDs and the communication of this date between substation devices.

An indirect adaptive fuzzy-logic power system stabiliser

Abstract An indirect adaptive fuzzy power system stabiliser (AFPSS) is developed using the concept of fuzzy basis functions. The power system is modelled using differential equations with nonlinear parameters which are functions of the state of the system. These nonlinear functions may not be known, however, some linguistic information is available about them. Utilising this information, fuzzy logic systems are designed to model the system behaviour. The control law is obtained using the uncertainty principle. Based on the Lyapunovs synthesis method, adaptation rules are developed to make the controller adaptive to changes in operating conditions of the power system. The simulation studies are carried out for an industrial cogenerator and utilise a one-machine infinite-bus model. Nonlinear simulations reveal that the performance of AFPSS is better than the performance of a conventional (linear) power system stabiliser for a wide range of operating conditions.

Genetic algorithm-based system identification of active magnetic bearing system: A frequency-domain approach

The main focus of this paper is on system identification of an active magnetic bearing system (AMB) using genetic algorithm (GA) for optimal controller design purpose. In the first step, an analytical model of the system is derived using principle of physics and taking into account both the rigid body and bending body modes of the system. In the next step, as AMB system is inherently open-loop unstable, a closed-loop system identification approach is adopted. The actual frequency response data are collected under closed-loop condition. As it is expected from the analytical model, the system has two dominant resonant frequencies which have to be accurately identified. To fit the frequency response of the system into a desired order transfer function, weight vectors are used to emphasise the resonant frequencies. Subsequently, GA is employed to search the optimal values of the required weight vectors and their corresponding scaling factors automatically in order to best fit the measured data. For verification of the proposed method, the model obtained from GA is compared with some well-known methods such as prediction error method (PEM) and subspace state space system identification (N4SID) method. Eventually, a PID controller and two notch filters are designed based on the obtained model and implemented on the actual system and the performance of the designed controller is compared with the on-board analogue controller.

PID-type fuzzy logic controller for active magnetic bearing system

This paper describes the design of a PID-type Fuzzy Logic Controller (PID-FLC) and its application on the stabilization of an Active Magnetic Bearing System (AMB). The proposed PID-FLC is obtained by combining a PD-type Fuzzy Logic Controller (PD-FLC) and a Pi-type Fuzzy Logic Controller (PI-FLC). A multi-objective Genetic Algorithm (MOGA) is used to determine the scaling factors of the inputs and outputs of the PID-FLC. The designed controller is then coded in C and implemented in real-time on a Digital Signal Processor (DSP) card. The results from the PID-FLC are compared with those of a conventional lead-lag type controller and the systems on-board analogue controller. Designing controllers based on classical methods could become tedious, especially for systems with high order model. In contrast, PID-FLC controller design requires only the tuning of some scaling factors in the control loop and hence is much simpler than classical design methods. The experimental results have also verified the enhanced performance and robustness of the system under the proposed PID-FLC control in the presence of disturbance.

Comparison of fuzzy logic based and rule based power system stabilizer

The results of applying a fuzzy-logic-based and a rule-based power system stabilizer for a synchronous machine are compared. To achieve good damping characteristics over a wide range of operating conditions, speed deviation and acceleration of a synchronous machine are chosen as the input signal to the stabilizers. The stabilizing signal is determined from certain rules for a rule-based power system stabilizer. For the fuzzy-logic-based power system stabilizer, the supplementary stabilizing signal is determined according to a fuzzy membership function depending on the speed and acceleration states of the generator. Simulation shows that the fuzzy-logic-based power system stabilizer is superior to the rule-based stabilizer due to its lower computational burden and robust performance.<<ETX>>

A fuzzy logic controller applied to power system stabilizer for a synchronous machine power system

A fuzzy logic controller has been applied to a power system stabilizer for a synchronous machine infinite bus power system. Speed deviation ( Delta omega ) and acceleration (d omega /dt) of the synchronous machine are chosen as the input signals to the fuzzy controller in order to achieve good dynamic performance over a wide range of operating conditions. The use of two look-up tables instead of one results in good system dynamic performance. Simulation results show that the proposed fuzzy logic power system stabilizer provides good dynamic performance over a wide range of operating conditions subject to different disturbances.<<ETX>>