P. Kacejko

Optimal Control of Wind Power Generation

Power system control is a complex task, which is strongly related to the number and kind of generating units as well as to the applied technologies, such as conventional coal-fired power plants or wind and photovoltaic farms. Fast development of wind generation that is considered as unstable generation sets new strong requirements concerning remote control and data hubs cooperating with SCADA systems. Considering specific nature of the wind power generation, the authors analyze the problem of optimal control for wind power generation in farms located over a selected remotecontrolled part of the System Operator grid under advantageous wind conditions. This article presents an original stepwise method for tracing power flows that makes possible to eliminate current (power) overloading of power grid branches. Its core idea is to consider the discussed problem as an optimization task.

Overhead Transmission Line Sag Estimation Using a Simple Optomechanical System with Chirped Fiber Bragg Gratings. Part 1: Preliminary Measurements

A method of measuring the power line wire sag using optical sensors that are insensitive to high electromagnetic fields was proposed. The advantage of this technique is that it is a non-invasive measurement of power line wire elongation using a unique optomechanical system. The proposed method replaces the sag of the power line wire with an extension of the control sample and then an expansion of the attached chirped fiber Bragg grating. This paper presents the results of the first measurements made on real aluminum-conducting steel-reinforced wire, frequently used for power line construction. It has been shown that the proper selection of the CFBG (chirped fiber Bragg grating) transducer and the appropriate choice of optical parameters of such a sensor will allow for high sensitivity of the line wire elongation and sag while reducing the sensitivity to the temperature. It has been shown that with a simple optomechanical system, a non-invasive measurement of the power line wire sag that is insensitive to temperature changes and the influence of high electromagnetic fields can be achieved.

Optimal voltage control in distribution networks with dispersed generation

The article presents a new method for voltage control in medium voltage distribution networks with dispersed generation. A linear mathematical model of a distribution network has been proposed. The model makes possible to optimally select feeding voltage of a medium-voltage network as well as reactive power in dispersed power sources according to the actual load and active power generation.

Power system stability screening for long-term planning of transmission network development

Stability analyses of a power system are performed at short-term and mid-term planning of transmission network development. Increased load demands and market economics are pushing transmission networks closer and closer to their operational limits. Therefore it is necessary to perform even a simplified power system stability assessment also at long-term planning. The article shows that very simple criteria of angle stability and voltage stability based on short-circuit power can be used as screening filters for fast contingency selection. The suggested criteria have been verified for a real large-scale system.

Power system state estimation using wire temperature measurements for model accuracy enhancement

Power system state estimation is a process of real-time online modeling of an electric power system. The estimation is performed with the application of a static model of the system and actual measurements of electrical quantities that are encumbered with error. Usually, a model of the estimated system is also encumbered with uncertainty, especially power line resistances that depend on the temperature of conductors. Presently, a considerable development of technologies for dynamic power line rating can be observed. Typically, devices for dynamic line rating are installed directly on the conductors and measure basic electric parameters such as current and voltage as well as non-electric ones as surface temperature of conductors, their expansion, stress or the conductor sag angle relative to the plumb line. The objective of this article is to present a method for power system state estimation that uses temperature measurements of overhead line conductors as supplementary measurements that enhance quality of the model and thereby the estimation accuracy. Power system state estimation is presented together with a method for using temperature measurements of power line conductors for updating the static power system model in the state estimation process. Results obtained with the application of that method have been analyzed based on the estimation calculations performed for an example system with and without taking into account the conductor temperature measurements. The final part of the article includes conclusions and suggestions for the further research work.

Method of reducing the uniform of the daily graph of electrical load electric grids with renewable sources of energy

The paper contains the method of matching generation graph of photovoltaic electric stations and consumers. Characteristic feature of this method is the application of morphometric analysis for assessment of non-uniformity of the integrated graph of energy supply, optimal coefficients of current distribution, that enables by mean of refining the powers, transferring in accordance with the graph, to provide the decrease of electric energy losses in the grid and transport task, as the optimization tool.

Newton binomial in the generalized Cauchy problem as exemplified by electrical systems

Presented in the paper are direct and indirect correspondence rules between the set of real and complex coefficients of two interrelated linear differential equations of random order, each of them being able in an individual and independent way to describe uninterrupted movement of generalized, in terms of the number of freedom degrees, dynamic system with lumped parameters in the fundamental Cauchy problem, which is formulated in the first case in terms of real time functions, and in another case – in terms of their complex images, which allows directly to set one of the said forms of Cauchy problem based on the other one both in the generalized form as to the order of differential equation and in particular form under given conditions, regardless of the physical nature of the system under examination.

Transmission loss allocation for a bilateral contract in deregulated electricity market

A new method for transmission losses allocation in and multiple-transaction system is presented. The proposed scheme is based on expressing losses explicitly in terms of the transactions in the system and requires power flow solution. The advantage of this method is that, unlike other proposed approaches, it does not require any simplifying assumptions. The loss allocation process emphasizes current rather than power injections, an approach that is leads to a natural separation of system losses among the network nodes.

Matching of renewable source of energy generation graphs and electrical load in local energy system

The paper contains the method of matching generation graph of photovoltaic electric stations and consumers. Characteristic feature of this method is the application of morphometric analysis for assessment of non-uniformity of the integrated graph of energy supply, optimal coefficients of current distribution, that enables by mean of refining the powers, transferring in accordance with the graph , to provide the decrease of electric energy losses in the grid and transport task, as the optimization tool.

Modeling of Physical Subsystem Using an Example of Electromagnetic Exciter of Low-Frequency Oscillations

This work is devoted to modeling of physical subsystem, considering an electromagnetic exciter of low-frequency oscillations (EME LFO) as it, which is a classic example of an electromechanical system. For the simulation of electromagnetic exciter of low frequencies Simscape was chosen. Based on the principle of operation (reciprocating motion due to the configuration of the resonance circuit), and the structure of the apparatus, there is detected the operation character with several types of energy conversion: electrical to magnetic and magnetic to mechanical. And the main requirement to the developed model is the conservation of energy and power under the corresponding transformations.