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Distributed Generation (distributed + generation)

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Engineering93%

Selected Abstracts

Computation of locational and hourly maximum output of a distributed generator connected to a distribution feeder

ELECTRICAL ENGINEERING IN JAPAN, Issue 2 2009
Yasuhiro Hayashi
Abstract Recently, the total number of distributed generation such as photovoltaic generation systems and wind turbine generation systems connected to a distribution network has drastically increased. Distributed generation using renewable energy can reduce the distribution loss and emission of CO2. However, the distribution network with the distributed generators must be operated while maintaining the reliability of the power supply and power quality. In this paper, the authors propose a computational method to determine the maximum output of a distributed generator under operational constraints [(1) voltage limit, (2) line current capacity, and (3) no reverse flow to bank] at arbitrary connection points and hourly periods. In the proposed method, a three-phase iterative load flow calculation is applied to evaluate the above operational constraints. The three-phase iterative load flow calculation has two simple procedures: (Procedure 1) addition of load currents from the terminal node of the feeder to root one, and (Procedure 2) subtraction of voltage drop from the root node of the feeder to terminal one. In order to check the validity of the proposed method, numerical simulations are performed for a distribution system model. Furthermore, the characteristics of locational and hourly maximum output of a distributed generator connected to a distribution feeder are analyzed using several numerical examples. © 2009 Wiley Periodicals, Inc. Electr Eng Jpn, 167(2): 38,47, 2009; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/eej.20610 [source]

Local control of photovoltaic distributed generation for voltage regulation in LV distribution networks and simulation tools

EUROPEAN TRANSACTIONS ON ELECTRICAL POWER, Issue 6 2009
Stefania Conti
Abstract The increasing connection of distributed generation (DG) in distribution networks may affect the quality of power offered to customers. One of the most relevant issues is the possibility to have unacceptable voltage rise at the point of common coupling (PCC). This work focuses on the problem of voltage control in LV distribution networks in the presence of photovoltaic (PV) DG. The paper presents a local voltage control method based on PV generation curtailment as an alternative to ,on/off' operation, typically required by distribution operators to prevent overvoltage at the PCCs by means of overvoltage protections embedded in the PV unit. To show the effect of the proposed local voltage control, a simulation tool, developed in MATLAB®,Simulink® environment, is presented. Appropriate numerical models for network components and PV generators are provided in order to describe computer simulation implementation of the test system. The final results show that the control system is able to adjust the active power output of local generators to keep the voltage profile of the feeder, in which DG is installed, within the range allowed by Norm EN 50160. Copyright © 2008 John Wiley & Sons, Ltd. [source]

Autonomous power system for island or grid-connected wind turbines in distributed generation

EUROPEAN TRANSACTIONS ON ELECTRICAL POWER, Issue 7 2008
Grzegorz Iwanski
Abstract Modern power generation systems for wind turbines are often based on the rotor fed slip-ring machines. Power electronics converter provides the slip power, and also the reactive power for excitation of the generator during standalone operation. This way the isolated load can be supplied even if the grid has failed. Stator voltage in an autonomous operation is controlled using vectorial phase locked loop (PLL) structure; therefore the information about mechanical speed or angular position of the rotor is eliminated from the control method. The second PLL is also used for synchronization of the generated voltage with the grid voltage. Voltages synchronization is necessary for soft connection and protection of the supplied load from the rapid change of the supply voltage phase. The grid-connected doubly fed induction generator (DFIG) can be useful after grid fault; however, the mains outage detection methods are necessary for fast disconnection after grid failures. Copyright © 2008 John Wiley & Sons, Ltd. [source]

Optimal allocation of distributed generation and reactive sources considering tap positions of voltage regulators as control variables

EUROPEAN TRANSACTIONS ON ELECTRICAL POWER, Issue 3 2007
Mohamad Esmail Hamedani Golshan
Abstract In this paper, by defining and solving an optimization problem, amount of distributed generators (DGs) and reactive power sources (RSs) in selected buses of a distribution system are computed to make up a given total of distributed generation for minimizing losses, line loadings, and total required reactive power capacity. The formulated problem is a combinatorial problem, therefore Tabu search algorithm is applied for solving the optimization problem. Results of solving the optimization problem for a radial 33-bus distribution system and a meshed 6-bus system are presented. When using less amount of reactive capacity, regarding tap positions of voltage regulators as control variables has considerable role in loss reduction and improvement of voltage profile. In the case of meshed systems, including line loadings in the cost function can significantly change results of solving the optimization problem such as amount of the required reactive capacity and how to assign DGs and RSs to the selected buses. Copyright © 2006 John Wiley & Sons, Ltd. [source]

State estimation of networks with distributed generation

EUROPEAN TRANSACTIONS ON ELECTRICAL POWER, Issue 1 2007
Iñigo Cobelo
Abstract The nature and control of existing distribution networks limits the amount of distributed generation that can be connected. To increase the penetration of distributed generation a distribution management system controller (DMSC) can be used. The use of a DMSC requires a state estimator algorithm that provides an estimate of the network state in real time. In this paper, a state estimation algorithm based on the methods used on transmission networks is presented. The application of these methods into distribution networks requires existing measuring systems to be supplemented with the addition of new real-time measurements, and the use of load estimates. Copyright © 2006 John Wiley & Sons, Ltd. [source]

Investigation of the distributed generation penetration in a medium voltage power distribution network

INTERNATIONAL JOURNAL OF ENERGY RESEARCH, Issue 7 2010
G. N. Koutroumpezis
Abstract This paper investigates the results of the distributed generation penetration in a weak medium voltage power distribution network. The connected distributed generation resources are in their entirety small hydroelectric plants. Their locations are predetermined. Specifically, the influence of distributed generation on the network branch currents and voltage profile as well as on the short-circuit level at the medium voltage busbars of the infeeding substation are examined using a commercial-grade software package. The arising problems are explored and alternative technical solutions to deal with them are proposed. Finally, an initial proposal for an optimum distributed generation penetration in the predetermined network positions is given. A real-world study case, rather than a simplified academic network, is selected to be analysed in order to specify, as accurately as possible, the arising practical problems and to use this experience in the future in the development of a fast and reliable method for the determination of optimal distributed generation allocation in random network positions. Copyright © 2009 John Wiley & Sons, Ltd. [source]

Membrane reformer PEM cogeneration systems for residential applications,Part A: full load and partial load simulation

ASIA-PACIFIC JOURNAL OF CHEMICAL ENGINEERING, Issue 3 2009
Stefano Campanari
Abstract This two-part paper investigates the performances and economic potential benefits of a fuel cell cogeneration system based on a membrane reformer (MREF), using polymer electrolyte membrane (PEM) fuel cells, applied to residential cogeneration. Part A of this work focuses on the thermodynamic analysis and simulation of the system at full and partial load conditions, discussing its performance by means of a sensitivity analysis carried out under different operating conditions. Part B presents the technoeconomic analysis of the proposed system integrated into a real residential application, dealing with the energy savings and the economic balances, and proposes a preliminary design of the cogeneration unit. The system is based upon a PEM fuel cell, integrated with a membrane reformer (MREF) to form a small-scale, highly efficient cogeneration unit, potentially suitable for application to distributed generation in the residential field. The high purity hydrogen fuel required by the PEM fuel cell is produced in the membrane reformer through hydrogen selective membranes based on a Pd-Ag alloy. The analysis is carried out aiming to define the system energy balances in all the conditions occurring under real operation, including the influence of ambient temperature and of the expected fuel cell efficiency decay with time. The discussion reveals the relevant potential advantages of the MREF solution with respect to fuel cell units based on steam reforming (SR) or auto-thermal reforming (ATR): when compared to these solutions, MREF exhibits a 10% points higher electrical efficiency and requires a much simpler plant layout. These results are the basis for the detailed system technoeconomic analysis carried out in Part B of the work. Copyright © 2009 Curtin University of Technology and John Wiley & Sons, Ltd. [source]

Optimal Control of Voltage in Distribution Systems by Voltage Reference Management

IEEJ TRANSACTIONS ON ELECTRICAL AND ELECTRONIC ENGINEERING, Issue 5 2009
Tomonobu Senjyu Student member
Abstract Recently, renewable energy technologies such as wind turbine generators and photovoltaic (PV) systems have been introduced as distributed generations (DGs). Connections of a large amount of distributed generations may cause voltage deviation beyond the statutory range in distribution systems. A reactive power control of DGs can be a solution of this problem, and it also has a possibility to reduce distribution loss. In this paper, we propose a control methodology of voltage profile in a distribution system using reactive power control of inverters interfaced with DGs and tap changing transformers. In the proposed method, a one-day schedule of voltage references for the control devices are determined by an optimization technique based on predicted values of load demand and PV power generation. Reactive power control of interfaced inverters is implemented within the inverter capacity without reducing active power output. The proposed method accomplishes voltage regulation within the acceptable range and reduction of distribution loss. The effectiveness of the proposed method is confirmed by simulations. Copyright © 2009 Institute of Electrical Engineers of Japan. Published by John Wiley & Sons, Inc. [source]

Distributed-series compensator for controlling voltage in distribution line with clustered distributed generations

IEEJ TRANSACTIONS ON ELECTRICAL AND ELECTRONIC ENGINEERING, Issue 3 2009
Rejeki Simanjorang Member
Abstract A method of controlling voltage profile in distribution line with many distributed generations (DGs) using distributed-series compensator (D-SC) is proposed. These DGs are assumed to be clustered photovoltaics (PVs) which are installed at residential area. A large power injected by PVs may result in reverse power flow from PVs to main source, which can lead to overvoltage in the distribution line. To mitigate this problem, it is proposed to install D-SCs close to pole transformer of the distribution line. A D-SC is a series compensator that can imitate characteristic of negative resistance and reactance, while reverse power flow occurs in distribution line. This is carried out by injecting active and reactive power to the distribution line through voltage injection. Providing active power for the D-SC is done by a bidirectional rectifier which is connected to the secondary side of a pole transformer. The effectiveness of the proposed method is achieved by the improvement of voltage profile with small capacity of D-SC and bidirectional rectifier. Theoretical analysis is discussed and simulation results are shown to verify the proposed method. Copyright © 2009 Institute of Electrical Engineers of Japan. Published by John Wiley & Sons, Inc. [source]

Advanced and intelligent technologies for reliable operation of power systems and electricity markets

IEEJ TRANSACTIONS ON ELECTRICAL AND ELECTRONIC ENGINEERING, Issue 5 2008
Ryuichi Yokoyama Senior Member
Abstract Deregulation of power industries is still progressing in many countries, aiming at reduction of the electricity price, diversity of customer diverse choices, services and promotion of new business and keeping supply reliability. Many countries are testing this notion in anticipation of lower power prices through open competition. In such a competitive situation, it is necessary for suppliers to take on the responsibility of keeping supply reliability at the load end in order to prevent outages, for instance, independent power producers (IPP) placing distributed generations (DGs) close to the load or conventional utilities utilizing advanced and intelligent system operation/control technologies that are costly. Usually, customers pay one price for power that is good enough for ordinary use, therefore not necessarily highly consistent in quality of voltage, current, frequency or reliability. However, if customers desire better quality power, additional fees are added according to the particular characteristics desired, thus customers are supplied with this type of better power that they choose. Under such a worldwide new trend in power systems and markets, this article is edited for the purpose of introducing the most advanced technologies and the newest issues related to reliable and stable operations of power markets and systems in the competitive environment. © 2008 Institute of Electrical Engineers of Japan. Published by John Wiley & Sons, Inc. [source]