DYNAMIC ECONOMIC LOAD DISPATCH OF A DISTRIBUTED GENERATION SYSTEM

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1 International Journal of Electrical Engineering & Technology (IJEET) Volume 9, Issue 4, July-August 2018, pp , Article ID: IJEET_09_04_007 Available online at ISSN Print: and ISSN Online: Journal Impact Factor (2016): (Calculated by GISI) IAEME Publication DYNAMIC ECONOMIC LOAD DISPATCH OF A DISTRIBUTED GENERATION SYSTEM C. Durga Prasad Department of Electrical Engineering, College of Engineering (A), Andhra University, Visakhapatnam. A.P, India Prof. G.V. Siva Krishna Rao Department of Electrical Engineering, College of Engineering (A), Andhra University, Visakhapatnam. A.P, India ABSTRACT The increased power demand, atmospheric pollution and population growth makes it essential to design a new power system with low atmospheric pollution and transmission losses. The growing price and limited availability of fossil fuels makes installation of conventional power plants uneconomical. Installation of nonconventional power plants is essential to meet the increased load demand and environmental pollution standards. The inter connection of conventional and nonconventional power plants is essential to meet the growing energy demand and atmospheric pollution standards. Distributed generation with renewable energy sources is one of the best methods to meet increased load demand with low transmission losses and pollution levels. The output of renewable energy sources like wind and solar systems is not reliable because they depend on atmospheric conditions. To find a solution to dynamic economic load dispatch of distributed generation system with renewable energy sources is a difficult problem because of unreliable nature of solar and wind plants. This paper will explain a solution to dynamic economic load dispatch of a distributed generation system using λ -iterative method. Key words: Dynamic Economic Load Dispatch, Distributed generation, distributed generation types & technologies. Cite this Article: C. Durga Prasad, Prof. G.V. Siva Krishna Rao, Dynamic Economic Load Dispatch of a Distributed Generation System. International Journal of Electrical Engineering & Technology, 9(4), 2018, pp INTRODUCTION The conventional power generation methods are costly. They need large amounts of coal and water to produce power. They are located nearer to the coal fields and water resources like rivers. They need large area of site at low price to construct the power plant. They are mostly located at remote places far away from the load centers. To transmit the generated power to 67 editor@iaeme.com

2 Dynamic Economic Load Dispatch of a Distributed Generation System load centers they need long transmission lines. These long transmission lines needs huge capital investment and creates more power loss. The conventional power generation methods produce more pollution due to burning of large amounts of fossil fuels like coal. The limited availability and growing price of fossil fuels makes conventional generation infeasible in a long run. The growing population, raising atmospheric temperatures and invention of new electrical power operated gadgets creates more demand for electrical power. The growing demand for electric power can be met by installing additional conventional power plants or by reducing transmission losses. An installation of additional conventional power plants produces more pollution and they need more resources like fossil fuels, land and water. Limited availability of resources like fossil fuels, land and water make transmission loss reduction is the only solution to meet growing power demand. The transmission loss can be reduced by increasing the cross sectional area of the existing transmission line conductors by replacing them with new heavy gauge conductors or reducing the amount of current flowing through the existing conductors. Replacement of existing conductors requires more capital and long installation time. The amount of current flowing through the existing transmission line conductors can be reduced by installing new low capacity non-conventional power plants near load centers. This process of decentralized electric power generation is called as Distributed Generation. The distributed generation can be defined as electric power generation within distribution networks. It may be explained in simple terms that are small-scale power plants. The International Energy Agency (IEA) define distributed generation as a generating plant, transfer a customer on-site or providing support to a distribution system connected to the grid at distribution-level voltages [1]. Electric Power Research Institute (EPRI) defines a distributed generation as the generation from a few kilowatts up to 50 MW [2]. Distributed Generation Sources are also used for system black-start to start generation and restore a portion of the utility system without outside support after a system collapse [3]. They also restore the system within a short time during natural disasters like cyclones and earthquakes. Distributed generation with renewable energy sources is one of the best solutions to meet the growing energy demand at low power loss without creating any environmental pollution. There is no need to replace the existing transmission and distribution lines with higher cross sectional area conductors, because renewable energy sources can be installed at very nearer to the load centers. It reduces the transmission loss and improves the efficiency of the system. Compared with the conventional generation systems, the distributed generation system with renewable energy sources can reduce the environmental pollution and the cost of generation. There is no need to acquire land for installation of renewable energy sources particularly solar plants because they can be installed on roof of a house also. Distributed generation with renewable energy sources will improve the security and reliability of power supply. The dynamic economic load dispatch solution determines the optimal combination of power outputs for all committed generation units over a certain period of time in order to minimize the total fuel cost while satisfying dynamic operational constraints and load demand in each interval of time editor@iaeme.com

3 C. Durga Prasad, Prof. G.V. Siva Krishna Rao 2. TYPES OF DISTRIBUTED GENERATION SYSTEMS DG systems may be broadly categorized as conventional and nonconventional Conventional Distributed Generators Conventional Distributed Generators use Micro Turbines and Gas Turbines as prime movers. Micro turbines are a new type of combustion turbines they produces both heat and Electricity on a small scale. Micro turbines offer a clean and efficient solution to direct Mechanical drive markets such as compression and air conditioning [4]. Micro turbines are small combustion turbines with outputs of 25 kw to 500 kw. The MTs run at less pressure, temperature and faster speed, which sometimes require no gearbox [5]. The advantages of Micro turbines are cheap, compact in size, light in weight, more efficient and have less emission [6], Advance power electronic interface between the MT and the load or grid increases its flexibility to be controlled efficiently [7]. Gas turbines produce high pressure gas at high temperature. This high pressure gas rotate Turbine shaft, which in turn drives an alternator. Gas turbines are always used above 1MW, but nowadays we can generate electricity through a small micro-gas turbine of 200kW size [5] Non-Conventional Distributed Generators The non-conventional Distributed generators include Electrochemical Devices, Storage devices and Renewable devices Electrochemical Devices The fuel cell (FC) is a device used to generate electric power and provide thermal energy from chemical energy through electrochemical processes. It can be weigh as a battery supplying electric energy as long as its fuels are continued to supply. Unlike batteries fuel cell, do not need to be charged for the consumed materials during the electrochemical process since these materials are continuously supplied [8]. FC capacities vary from few kw to MW for portable and static units, respectively. They provide clean power and heat for several applications by using gaseous and liquid fuels [9]. FCs can use a variety of hydrogen-rich fuels such as natural gas, gasoline, biogas or propane [10]. FCs operates at different pressures and temperatures which vary from atmospheric to hundreds of atmospheric pressure and from 20 to 200 C, respectively [10] Storage Devices Storage devices consists of flywheels, batteries, and other devices, they are charged during low load demand and used when required. They are usually combined with other kinds of DG types to supply the required peak load demand [7]. These batteries have a charging controller for protection from overcharge and over discharge as it disconnects the charging process when the batteries have full charge. The sizes of these batteries find the battery discharge period. However, flywheels systems could be charge and provide 700kW in 5 s [7] Renewable Devices Renewable devices commonly used for DG s are Photovoltaic panels and Wind turbines Photovoltaic (PV) Panels Photovoltaic (PV) panels generate electrical power by converting solar radiation into direct current electricity using semiconductors. PV power generation employs solar panels. They have number of solar cells with photovoltaic material. Solar Cells absorb light energy from the sunlight, where the light photons force cell electrons to flow, and transfer it to dc electricity. Practically, each cell supply 2 4A according to its size with a 0.5V output voltage. Usually an array, cells connected in series, provides 12V to charge batteries PVs consist of modular which can be connected to provide a variety of power ranges but on the 69 editor@iaeme.com

4 Dynamic Economic Load Dispatch of a Distributed Generation System other hand there are many restrictions. Photovoltaic devices provide low output power, the cost of land is expensive where PVs installed and it is restricted to certain weather and geographic features [6] Wind Energy Systems Modern wind energy systems consist of three basic components: a tower on which the wind turbine is mounted; a rotor (with blades) that is turned by the wind; and the nacelle. Their shape was capsule-shaped component which houses the instrument, including the generator that converts the mechanical energy in the spinning rotor into electrical energy. Rotor blades need to be strong and light in order to be aerodynamically efficient and to withstand prolonged use in high winds. The rotor, which spins when driven by the wind, supports blades that are designed to capture kinetic energy from the wind. The advantages of Wind Turbines does not cause greenhouse gases or other pollutants, great resources to generate energy in remote areas A typical configuration of a Doubly Fed Induction Generator (DFIG) wind turbine is shown schematically in Fig-1. It uses a Wound Rotor Induction Generator (WRIG) with slip rings to take current into or out of the rotor winding and variable-speed operation is obtained by injecting a controllable voltage into the rotor at slip frequency [11]. The rotor winding is fed through a variable-frequency power converter, typically based on two AC/DC IGBTbased voltage source converters (VSC) linked by a DC bus. The power converter decouples the network electrical frequency from the rotor mechanical frequency, enabling variablespeed operation of the wind turbine. The generator and converters are protected by voltage limits and an over-current crowbar. A DFIG system can deliver power to the grid through the stator and rotor, while the rotor can also absorb power, depending on the rotational speed of the generator. Figure 1 Doubly Fed Induction Generator (DFIG) 3. BENEFITS OF DISTRIBUTED GENERATION Easy and quicker installation on account of prefabricated standardized components Lowering of cost by avoiding long distance high voltage transmission 70 editor@iaeme.com

5 C. Durga Prasad, Prof. G.V. Siva Krishna Rao Environment friendly where renewable sources are used Running cost more or less constant over the period of time with the use of renewable sources Possibility of user-operator participation due to lesser complexity More dependability with simple construction, and consequent easy operation and maintenance 4. PROBLEM FORMULATION The main objective of Dynamic Economic Load Dispatch of a Distributed Generation System is to minimize the total fuel cost of the system by considering all constrains of the individual generating plants and overall system. The objective function is to minimize the total generating cost of all power plants. In this case the output of Distributed Generated System are taken as constant and they are treated as a negative load on system. Where - Total fuel cost of all generators - Total number of generators - Active power output of th generator The fuel cost of individual generator is represented by the following quadratic equation Where are fuel cost function coefficients of individual generators. The inequality constraint is The equality constraint is Where total power demand of system total power transmission loss Active power output of th Distributed Generator 71 editor@iaeme.com

6 Dynamic Economic Load Dispatch of a Distributed Generation System 5. SIMULATIONS AND EXPERIMENTAL RESULTS The cost coefficients and min. and max. limits of generating plants are shown in the following Table-I Table 1 Data of six generating units Generating Cost Coefficients Unit a i b i c i P i min P i max P P P P P P The total fuel cost of system is shown in Table-II for different load demand Table 2 Total Fuel Cost S.No. Demand (MW) Fuel Cost in (Rs/hr) CONCLUSIONS The penetration of Distributed Generation Systems is increasing day by day to meet increased load demand and to reduce pollution levels. The inter connection of conventional and Nonconventional sources is necessary. To maintain security and stability of combined system a method is proposed to solve Dynamic Economic Load Dispatch of a Distributed Generation System(DELDDGS). This paper demonstrates the technique to solve DELDDGS problem by satisfying all constrains. The technique was implemented with the help of a MATLAB program. REFERENCES [1] Distributed Generation in Liberalized Electricity Market, IEA Publication (2002), available at: nppdf/free/2002 /distributed2002.pdf. [2] A. Thomas, A. Göran, S. Lennart, Distributed generation: a definition, Electric Power System Research, vol. 57, pp , Dec [3] L.L.Lai and T.F.Chan, Distributed Generation: induction and permanent magnet generators, Wiley, [4] Sibasish Patnaik and Ankur Sachdev, Design and Development of Micro Turbine Graduation dissertation, Department of Mechanical Engineering National Institute of Technology Rourkela editor@iaeme.com

7 C. Durga Prasad, Prof. G.V. Siva Krishna Rao [5] M. Suter, Active filter for a microturbine, in: Proceedings of the Telecommunications Energy Conference, INTELEC 2001, Twenty- Third International, pp , Jan [6] J.L. Del Monaco, The role of distributed generation in the critical electric power infrastructure, in: Proceedings of the Power Engineering Society Winter Meeting IEEE, vol. 1, pp , Feb [7] B. Lasseter, Microgrids, distributed power generation, in: Proceedings of the Power Engineering Society Winter Meeting IEEE, vol. 1, pp , [8] M.W. Ellis, M.R. Von Spakovsky, D.J. Nelson, Fuel cell systems: efficient, flexible energy conversion for the 21st century, in: Proceedings of the IEEE, vol. 89, pp , Dec [9] M. Farooque, H.C. Maru, Fuel cells the clean and efficient power generators, in: Proceedings of the IEEE, vol. 89, pp , Dec [10] Wm. L. Hughes, Comments on the hydrogen fuel cell as a competitive energy source, in: Proceedings of the Power Engineering Society Summer Meeting IEEE, vol. 1, pp , July [11] Olimpo Anaya-Lara, Nick Jenkins, Janaka Ekanayake, Phill Cartwright, and Mike Hughes, Wind energy generation : modelling and control.: John Wiley & Sons Ltd, editor@iaeme.com