Units In Power System Research Articles

DESIGN OF FUZZY SELF TUNING PID LOAD FREQUENCY CONTROLLER FOR THE EGYPTIAN POWER SYSTEM

In this paper, a fuzzy self tuning is designed to update the proportional, integral, and derivative PID (FST-PID) gains which are optimized based on the Ant Colony System ACS. The design procedure is performed through two steps. Firstly, the PID gains are obtained using ACS algorithm and denoted by ACS-PID. Secondly, a fuzzy self-tuning is designed to self tune such gains. The developed approach is applied to the load-frequency control LFC of the Egyptian power system EPS as a single area with multi unit power system. The studied power system comprises three power plants; non-reheat, reheat, and hydro generation plants. The proposed PID controller is designed on an average point of four loading conditions of the EPS during summer and winter of 2008. The effectiveness of the FST-PID controller in the presence of the system inherent nonlinearity generation rate constraint GRC and uncertain system parameters under different disturbances locations are carried out using MATLAB-SIMULINK simulation program. The results prove that the proposed method is very useful in self tuning the PID controller gains for the LFC Egyptian Power System.

Model of Short-Term Forecast of Electrical Energy Consumption of Ural United Power System by Separating of a Maximal Similarity Sample into the Positive and Negative Levels

The article considers a model to forecast electrical energy consumption on the basis of the forecasting algorithm with the division of the maximal similarity sample into positive and negative levels with different approximation equations for positive and negative values. Model is tested with actual daily data of United Energy System of the Wholesale Electrical Energy and Power Market in Russia. Namely, we use Ural United Energy System data from 2009 to 2015. Based on the proposed algorithm, a forecast for the first five days of January 2016 is obtained. A forecasting error achieves 0.98 % during test. We substantiate and describe step by step an algorithm to construct a model to forecast a time series. Such algorithm is more stable for stationary series. Therefore pre-time we bring a time series of electrical energy consumption to a stationary form. To this end, we find variances of the original time series of electrical energy consumption. The proposed scientific tools are recommended in the operating activity of electrical energy subjects for short-term forecast of the basic parameters of the Energy Market to reduce the penalties by improving the forecasting accuracy.

Instability prediction of the inter-connected power grids based on rotor angle measurement

The online detection and prediction of the unstable conditions for interconnect power grids are important tasks to avoid blackout. The increasing installation of phasor measurement units (PMUs) in power systems and the development of the wide-area measurement systems (WAMS) make it possible to analyze the system dynamics using a large amount of real-time synchronous data. This paper proposes a rotor angle measurement based application for online out-of-step monitoring and predicting of the interconnected power systems. An improved Prony analysis method is presented to determine whether and when a power oscillation will lead to power system instability. The accuracy and reliability of the model free dynamic prediction are obtained by adopting an energy-like weight coefficient approximation of the decomposed signals. The self-adaptive resampling of the data and the changeable time-window are designed to make the method suitable for both transient instability and oscillation instability conditions. The effectiveness of the proposed scheme is verified on three test power systems.

Performance Analysis of SMES Integrated with Offshore Wind Farms to Power Systems through MT-HVDC

<p>With the increase in the development of offshore wind farm (OWF) around the world, this paper describes OWF consisting of permanent magnet synchronous generator (PMSG) wind turbines connected to Active network (AC grid) and Passive network (loads) through Multi Terminal High voltage direct current(MT-HVDC) transmission system. This paper discusses the effect of using a Superconducting Magnetic Energy Storage (SMES) unit in a hybrid power system that contains OWF. In this paper, we have aggregated 300 wind turbines of 1.5 MW PMSG using an aggregation technique (multi full aggregated model using equivalent wind speed (MFAM_EWS)). Furthermore, we have used a detector to detect any tripping of any wind turbine and substitute the shortage of power due to this loss of wind turbines immediately through SMES. The Active network in this paper should have a minimum of 150 MW power to be supplied by controlling the SMES unit (absorbing or providing power according to the system requirement). Simulation has been carried out by MATLAB/Simulink program to test the effectiveness of the SMES unit during tripping some of the wind turbines, fluctuation in wind speeds, load change and voltage dips. </p>

Improving the Investment Potential of the Evenkiiskaya HPP When Working Jointly with HPPS of the Volga – Kama Cascade

The capability is studied of improving the investment potential of the Evenkiiskaya HPP by using the power it generates in the United Power System of the European part of Russia by transitioning to a compensated electrical regime of water reservoir resource usage. A quantitative assessment of Evenkiiskaya HPP usage is presented using daily load demand. Increasing the guaranteed HPP power is proposed as an alternative to new nuclear power stations.

Organizing an Automatic Centralized Emergency Control System for the United Power System of Eastern Russia

The configuration of and algorithm for the centralized automatic emergency control system of the unified power system of Eastern Russia are described briefly.

System for Monitoring Automatic Excitation Regulators of Synchronous Generators with Brushless Excitation Systems

An algorithm for a monitoring system for automatic excitation regulators in synchronous generators is described. It takes the features of brushless excitation systems into account and provides effective monitoring of their operation. Results from a test of a prototype of the system on a digital-analog physical test stand at the Scientific and Technical Center of the United Power System are also reported.

How to model the cycling ability of thermal units in power systems

For thermal units in power systems, the importance of quick load changes increases along with the share of volatile renewable feed-in. An adequate representation of the cycling abilities of thermal units is therefore important in energy system modeling. Five different model techniques used in the literature to describe the cycling ability of thermal generation units are applied in the optimizing energy system model PERSEUS-NET-TS. The model calculates the dispatch of German generation units while restrictions of the transmission grid are considered. Differences in the cumulated dispatch of coal, lignite, and gas combined-cycle units in Germany due to the different modeling techniques are analyzed based on the PERSEUS-NET-TS results as well as the resulting dispatch of two exemplary single generation units. While the cumulated dispatch for Germany does not show any major differences for coal and lignite units, the cumulated dispatch of gas units differs slightly depending on the approach. Moreover, the dispatch of individual generation units may differ significantly. Even though the real commissioning strategies are not publicly known, it could be identified that the mostly applied modeling approaches based on technical restrictions increase computing time unnecessarily and that cost based approaches reduce on/off cycling more.

Solving Unit Commitment Problem Employing Proposed Hybrid BBO-discrete Hopfield Neural Network

A novel hybrid approach is developed based on the hybridization of Biogeography Based Optimization and Discrete Hopfield Neural Network. BBO algorithm is employed to tune for the optimal weights of discrete Hopfield Neural Network leading to the minimization of energy function. The proposed hybrid BBO-DHNN is implemented for 10, 20, 40 and 60 units power system under consideration. Based on the simulation results presented, it is clearly noted that the proposed HBDHNN approach results in better solutions for the unit commitment problem considered and this in turn reduces the computational burden to a significant extent. The proposed approaches are developed in MATLAB environment version 7.8.0.347 and executed in a PC with Intel core 2 Duo processor with 2.27 GHz speed and 2 GB RAM with 64 bit operating system.

A Novel Approach to Solve Environmental Economic Dispatch Problem using Gauss Newton based Genetic Algorithm

The electric power generation system has always the significant location in the power system, it should have an efficient and economic operation. This consists of the generating unit's allocation with minimum fuel cost and also considers the emission cost. This paper presents a new optimization algorithm named Gauss Newton based genetic algorithm, to solve Economic load dispatch and Emission Dispatch. Economic load dispatch is an important optimization problem to schedule the generation among generating units in power system. Due to the harmful effects of the emission released by fossil fueled electric power plants, along with economic dispatch and emission dispatch plays an important role in power industry. The main objective of the paper is to minimize the total fuel cost and the emission cost. In this paper Gauss Newton method is added to the genetic algorithm for improving the speed of optimization. The proposed framework is applied to 40 unit test systems in order to evaluate its optimized result with better computational efficiency.

Using Synchrophasors to Detect Transient and Voltage Instability in Transmission Networks and in Active Distribution Networks

Abstract: This paper summarizes three prospective applications of synchronized phasor measurement units (PMU) in electric power systems (EPS). Two applications focus on system wide stability of generation/transmission networks, whereas one application focuses on the stability of active radial distribution feeders with synchronous-machine-based distributed generation. The paper highlights that the application of synchrophasors to detect the proximity of voltage instability has been implemented with actual PMU measurements in two EPS. The paper also presents the application of synchronized measurements in out-of-step protection both in bulk transmission and in radial active distribution networks.

Lifetime estimation of superheater header

The safe operation of thermal power plants (TPPs) is largely determined by the reliability of main components of steam systems of power units, to which belong the headers of boiler superheaters.The aim of the study is to estimate the residual lifetime of superheater header starting from the initial defect size and up to the maximum allowable one. The above-mentioned lifetime is affected by the fluctuations of temperature under steady mode of operation of TPP superheater header. Superheaters headers operate in a steamy environment under the pressure of 15.5 MPa at temperature of 545 ºС. The header is a thick-walled cylinder made of 12Cr1MoV steel with a length of 2314 mm, outer diameter of 325 mm and thickness of 50 mm.To estimate the residual lifetime of header, the registered operational data of steam temperature in header were used. The temperature range of header under quasi-stable operational mode was divided into three classes: the temperature range (1) T < 10 °C; (2) 10 °C < T < 30 °C; (3) T > 30 °C. The local minima and maxima were determined using the obtained steam temperature history. The stresses in the wall of header for the given temperature fluctuations were calculated by finite element method (FEM).The residual durability was evaluated taking into account the effect of thermo-mechanical stresses and also the stresses caused by internal steam pressure. The stress intensity factors at the crack tip in the ligament between the holes of superheater collector were estimated by FEM. Based on the analysis of header defects, the proposed front shape was taken in the form of semi-ellipse. The crack growth at 500 ° C was modelled by Paris equation.With the increase of temperature difference between the external and internal header surfaces from 10 °С to 50 °С, the number of cycles, that is necessary for the crack to reach 35 mm in depth, decreases approximately in 25 times. It was calculated, that the average value of temperature fluctuations is 15°С for the Class 1, and is 46.2 °С for the Class 2. The lifetime of header can be extended due to the decrease of fluctuations of temperature range and their frequency.

Hourly Electricity Demand Response in the Stochastic Day-Ahead Scheduling of Coordinated Electricity and Natural Gas Networks

This paper studies the role of hourly economic demand response in the optimization of the stochastic day-ahead scheduling of electric power systems with natural gas transmission constraints. The proposed coordinated stochastic model (referred to as EGTran) considers random outages of generating units and transmission lines, and random errors in forecasting the day-ahead hourly loads. The Monte Carlo simulation is applied to create multiple scenarios for representing the coordinated system uncertainties. The nonlinear natural gas network constraints are linearized and incorporated into the stochastic model. Numerical results demonstrate the benefits of applying the hourly economic demand response for enhancing the scheduling coordination of natural gas and electricity networks. It is demonstrated that electricity demand response would offer a less volatile hourly load profile and locational marginal prices, and less dependence on natural gas constraints for the optimal operation of electric power systems. The proposed model for EGTran could be applied by grid operators for the hourly commitment and dispatch of power system units.

Firefly algorithm with multiple workers for the power system unit commitment problem

This paper proposes an improved firefly (FF) algorithm with multiple workers for solving the unit commitment (UC) problem of power systems. The UC problem is a combinatorial optimization problem that can be posed as minimizing a quadratic objective function under system and unit constraints. Nowadays, highly developed computer systems are available in plenty, and proper utilization of these systems will reduce the time and complexity of combinatorial optimization problems with large numbers of generating units. Here, multiple workers are assigned to solve a UC problem as well as the subproblem, namely economic dispatch (ED) in distributed memory models. The proposed method incorporates a group search in a FF algorithm and thereby a global search is attained through the local search performed by the individual workers, which fine tune the search space in achieving the final solution. The execution time taken by the processor and the solution obtained with respect to the number of processors in a cluster are thoroughly discussed for different test systems. The methodology is validated on a 100 unit system, an IEEE 118 bus system, and a practical Taiwan 38 bus power system and the results are compared with the available literature.

Energy Consumption Modelling Using Neural Networks of Direct Distribution on Example of Russia United Power System

Energy Consumption Modelling Using Neural Networks of Direct Distribution on Example of Russia United Power System

Реальний потенціал маневреної потужності ТЕЦ України з впровадженими електротепловими регуляторами

One of the sharp problems of the United Power System of Ukraine is the shortage of maneuvering power. It is particularly significant during the "night dip" of the electrical load diagram and results in the forced stop of 200-300 MW coal power units, which are used for regulation. This mode of operation of the coal power units reduces their lifetime and leads to overstated fuel consumption and increase in the expenditures for their operation, current and capital repairs. According to different estimates, this practice causes total losses of 2.2 billion UAH year. We propose an approach to increasing the maneuvering power for the United Power System of Ukraine by using electrothermal regulators (ETR) at our CHP. A result of performed, investigations, we identified large Ukrainian CHP, which are most promising for the provision of system services. As ETR, we propose to use electric boilers and heat pumps. We analyzed three options for the implementation of ETR at CHP. For each option, we determined the potential of maneuvering power and the parameters of efficiency with regard for the actual heat loads. We also discuss possible variants of including ETR into the technological scheme of CHP. It is shown that the actual technical potential of maneuvering power of the Ukrainian CHP, working for the whole year, is 763.7 MW.

Modelling, Simulation and Optimization of Small-Scale CCHP Energy Systems

The article defines and discusses techno-economic models of CCHP system based on a power system with an internal combustion engine or a gas turbine with electric power of 0, 2–1 MW including an absorption or vapour-compression refrigeration unit. The thermodynamic, ecological and economical features of the CCHP system under different load situations are analysed in relation to the basic model of energy generation with boiler and vapour-compression refrigeration unit. Based on the data of the equipment manufacturer, functional dependency curves of individual components are created in dependency to the load, which enables the construction of a system model composed of a power system (internal combustion engine or a gas turbine), single-stage or two-stage absorption refrigeration unit and boiler. A program solution has been developed applying the object-oriented programming language Modelica that enables the insight into the behaviour and techno-economic validity of usage of the analysed systems in transformable operating conditions. The article examines various energetic models, defining for the influential parameters (electric energy and fuel prices, investment costs and the level of heat recovery) the value of total energy efficiency, the return period on investment costs and the environmental impact concerns.

Short-term unit consignment solution using real-coded grey wolf algorithm

This paper presents a new real-coded grey wolf optimization (RCGWO) algorithm for power system unit commitment (UC). RCGWO is an expansion of the grey wolf algorithm. This appears to be potential for solving the UC. The fitness function is constructed from the total operating cost of the generating units. Here, the scheduling variables are coded as real variables. Therefore, the minimum up/down time constraints can be handled directly. Different test case contains 3 units, 38 units, 10 units and multiples of 10 units (large scale system) are presented. The most important advantage of the proposed method is highly robust and good convergence. The proposed algorithm shows competitive performance with the best of the other methods reported for the past two decades.

Possibility of Four-Phase Grids Application in Russian Power System

This paper is devoted to four-phase electrical grids of high and extra-high voltage, principles of its formation and its possible operation and maintenance in united power system of Russia. Development of new simulation model of four-phase power grid for further realization in software is under consideration. Special attention is given to compliance with present both technical and economical requirements of this model in Russian Federation. Economic analysis of four-phase power system applying is done by means of comparison of different kinds of transmission Ural – Siberia.

Firefly algorithm optimized fuzzy PID controller for AGC of multi-area multi-source power systems with UPFC and SMES

In this paper, a Firefly Algorithm (FA) optimized fuzzy PID controller is proposed for Automatic Generation Control (AGC) of multi-area multi-source power system. Initially, a two area six units power system is used and the gains of the fuzzy PID controller are optimized employing FA optimization technique using an ITAE criterion. The superiority of the proposed FA optimized fuzzy PID controller has been demonstrated by comparing the results with some recently published approaches such as optimal control and Differential Evolution (DE) optimized PID controller for the identical interconnected power system. Then, physical constraints such as Time Delay (TD), reheat turbine and Generation Rate Constraint (GRC) are included in the system model and the superiority of FA is demonstrated by comparing the results over DE, Gravitational Search Algorithm (GSA) and Genetic Algorithm (GA) optimization techniques for the same interconnected power system. Additionally, a Unified Power Flow Controller (UPFC) is placed in the tie-line and Superconducting Magnetic Energy Storage (SMES) units are considered in both areas. Simulation results show that the system performances are improved significantly with the proposed UPFC and SMES units. Sensitivity analysis of the system is performed by varying the system parameters and operating load conditions from their nominal values. It is observed that the optimum gains of the proposed controller need not be reset even if the system is subjected to wide variation in loading condition and system parameters. Finally, the effectiveness of the proposed controller design is verified by considering different types of load patterns.