Sejid Tešnjak

A component-based power system model-driven architecture

This letter describes an approach of applying the model-driven development in power systems. A component-based model-driven architecture, that gives full flexibility of the automation in source code generation, is introduced. A design pattern to code generation is described.

Undervoltage load shedding using global voltage collapse index

Increasingly higher demand in power created problems in power system operation since the growth of the transmission system is restricted. System often function close to their stability limits and sometimes loads need to be shed in order to prevent system from collapsing. In this paper one undervoltage load shedding (UVLS) method to prevent voltage collapse is presented. This method is based on a global index, which indicates voltage collapse proximity and voltage magnitudes on critical buses. Global index for voltage collapse proximity determination is calculated based on power flow Jacobian matrix operations. Considering that on the voltage stability limit Jacobian matrix becomes singular, it cannot be inverted. Therefore method involving eigenvalue calculation is used here. IEEE 14 bus system was used as a numerical example, which showed how loads and system in general can be saved from voltage collapse using UVLS.

An overview of ancillary services in an open market environment

The worldwide restructuring of the electrical energy industry is followed by processes like deregulation, liberalization and commercialization. These changes introduce new paradigms such as competition in generation and the concept of electricity supply as a commodity market and creates a new set of transactions among utilities and new agents and end users. An important aspect is the role of competitive markets stressed by the new regulation in procurement and remuneration of ancillary services. These services are required to provide stability and security of supply. Ancillary services have a variety of terms used through the world to name them (e.g. system services, support services) and it is not easy to define or classify them. The objective of this paper is to give a possible classification scheme for ancillary services to allow an easier identification of the roles of suppliers and buyers. Also, means by which the costs of various services can be measured, quantified and allocated are discussed and one method for cost allocation is proposed.

Power flow regulation by use of UPFC's injection model

The main purpose of this paper is to investigate the power flow regulating capabilities of an UPFCs injection model by using all three UPFCs control parameters simultaneously. The control system of the model is developed and its contributions to power flow regulation are explored on a multi-machine test system. The analysis is carried out from dynamic aspect utilising time-domain simulations. With the UPFC being embedded in the system, the analysis is concentrated on a transmission system compensation issues. It is shown that the model can fulfil functions of reactive shunt compensation, series compensation and phase shifting meeting multiple control objectives by applying boosting transformer injected voltage and exciting transformer reactive current.

A general-purpose symbolically assisted numeric computation environment as a support in power engineering education

This paper describes and illustrates a Windows-based, general-purpose, symbolically assisted numeric computation environment within power engineering education applications. The examples considered include fundamental problems derived from three areas: power system analysis and optimization, electric machinery, and feedback control systems.

An object-oriented graphical package for power system simulation and analysis

Object-oriented programming is a major trend in computer software because it increases flexibility of large-scale software systems. This paper presents an intuitive windows-based package for the power system analysis. The advantages of the object-oriented approach are demonstrated with an implementation of the graphical part of the package. To achieve usage flexibility the package is designed to have the following features: a graphical editor to visually edit the power system diagram, results processing and exporting and graphic presentations. The application programs in this package include the power flow calculation, the continuation power flow calculation, the available transfer capability calculation, and sensitivity analysis. This package may be useful for educational and training purposes.

Neural network frequency control for thermal power systems

A neural network control scheme for thermal power system is described. No off-line training is required for the proposed neural network controller. The online tuning algorithm is provided. The stability of the controller is proven. The performance of the controller is illustrated via simulation.

A mathematical model for studying power system frequency changes

Mathematical model for studying electric power system (EPS) frequency changes is developed. The model gives user an estimation of the weighted average frequency of the entire electric power system during time range of primary control. In paper are presented effects of changing some model parameters on system frequency behavior.

Example of undervoltage load shedding implementation

After deregulation of power systems, large problems with voltage stability incurred due to the large transits of power transmitted to large distances. Systems are very stressed and often work on their limits. Therefore, single contingency is sometimes enough to cause system collapsing. One of the most economic methods to prevent larger scale voltage collapse is undervoltage load shedding (UVLS). In this article, implementation of UVLS scheme is tested in New England Test System and then modeled in part of Croatian power system. Simulation of system behavior is presented as well.

Impact of the Competitive Environment on the Generating Units Maintenance

Maintenance of the power generating facilities in due time is essential for economical and reliable operation of the power system. Economical aspects, which bring revenue, and technical aspects, which keep the power system above the desired level of reliability, have to be confronted and the cheapest solution, which complies with the strict technical limitations, has to be obtained. This paper addresses the problem of obtaining the optimal maintenance schedule for generating units. For this purpose, this paper discusses the mathematical programming method - Benders decomposition. After the brief description, an application of the Benders decomposition on the three Croatian hydroelectric power plants in a row on the River Drava is carried out.