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    Overview of the CERTS Microgrid laboratory Test Bed

    Eto, J. ; Lasseter, R. ; Schenkman, B. ; Stevens, J. ; Klapp, D. ; Volkommer, H. ; Linton, E. ; Hurtado, H. ; Roy, J.
    Integration of Wide-Scale Renewable Resources Into the Power Delivery System, 2009 CIGRE/IEEE PES Joint Symposium

    Publication Year: 2009 , Page(s): 1
    Cited by:  Papers (17)

    IEEE Conference Publications

    The objective of the CERTS microgrid test bed project was to enhance the ease of integrating energy sources into a microgrid. The project accomplished this objective by developing and demonstrating three advanced techniques, collectively referred to as the CERTS microgrid concept, that significantly reduce the level of custom field engineering needed to operate microgrids consisting of generating sources less than 100 kW. The techniques comprising the CERTS microgrid concept are: 1) a method for effecting automatic and seamless transitions between grid-connected and islanded modes of operation, islanding the microgrid's load from a disturbance, thereby maintaining a higher level of service, without impacting the integrity of the utility's electrical power grid; 2) an approach to electrical protection within a limited source microgrid that does not depend on high fault currents; and 3) a method for microgrid control that achieves voltage and frequency stability under islanded conditions without requiring high-speed communications between sources. These techniques were demonstrated at a full-scale test bed built near Columbus, Ohio and operated by American electric power. The testing fully confirmed earlier research that had been conducted initially through analytical simulations, then through laboratory emulations, and finally through factory acceptance testing of individual microgrid components. The islanding and resychronization method met all Institute of Electrical and Electronics Engineers Standard 1547 and power quality requirements. The electrical protection system was able to distinguish between normal and faulted operation. The controls were found to be robust under all conditions, including difficult motor starts and high impedance faults. The results from these tests are expected to lead to additional testing of enhancements to the basic techniques at the test bed to improve the business case for microgrid technologies, as well to field demonstrations in- volving microgrids that involve one or more of the CERTS microgrid concepts. Future planned microgrid work involves unattended continuous operation of the microgrid for 30 to 60 days to determine how utility faults impact the operation of the microgrid and to gage the power quality and reliability improvements offered by microgrids. View full abstract»

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    The extend CIM for MicroGrid

    Chun Wang ; Haixuan Liu ; Fubao Wu
    Electricity Distribution (CICED), 2012 China International Conference on

    DOI: 10.1109/CICED.2012.6508543
    Publication Year: 2012 , Page(s): 1 - 5

    IEEE Conference Publications

    This paper analyzes modeling demands of microgrid common information model (CIM), sums up detailed features of microgrid, and proposes branch concept. Depending on branch concept, it sets up different branch models for PV, wind power, energy storage equipment, etc. Microgrid CIM, which is known as high-efficient and low-carbon, was established based on these models. Microgrid CIM constructs integrated microgrid information model and applies to the design of microgrid energy management system (EMS) based on IEC61970, which provides unified interface to establish microgrid energy management system platform and lays solid foundation to develop further advanced application software of microgrid energy management system. View full abstract»

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    Review of microgrid technology

    Hartono, B.S. ; Budiyanto, Y. ; Setiabudy, R.
    QiR (Quality in Research), 2013 International Conference on

    DOI: 10.1109/QiR.2013.6632550
    Publication Year: 2013 , Page(s): 127 - 132

    IEEE Conference Publications

    The use of renewable energy source (RES) in meet the demand of electrical energy is getting into attention as solution of the problem a deficit of electrical energy. Application of RES in electricity generation system is done in a variety of configurations, among others in microgrid system. Implementation of microgrid systems provide many advantages both from the user and from the electric utility provider. Many microgrid development carried out in several countries, because microgrid offers many advantages, including better power quality and more environmentally friendly. Microgrid development concern in technology generation, microgrid architecture, power electronics, control systems, protection systems. This paper reviewing various technological developments related to microgrid system and case study about microgrid system development using grid tie inverter (GTI). Microgrid system can implemented using GTI, power transfer can occur from GTI to grid when GTI has power excess and grid supplying power to GTI when GTI power shortage. View full abstract»

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    Analysis of power sharing on hybrid AC-DC microgrid

    Hema, V.K. ; Dhanalakshmi, R.
    Emerging Research Areas: Magnetics, Machines and Drives (AICERA/iCMMD), 2014 Annual International Conference on

    DOI: 10.1109/AICERA.2014.6908184
    Publication Year: 2014 , Page(s): 1 - 6

    IEEE Conference Publications

    The proposed paper presents a Hybrid AC-DC microgrid to chop the process of multiple conversions in an individual AC microgrid or DC microgrid. The proposed hybrid microgrid compose of both AC microgrid and DC microgrid connected together by multilevel inverter. This paper concentrates on developing a control system for the hybrid AC-DC microgrid to manage power flows, which is more difficult than previously developed systems only for AC microgrid or DC microgrid. The objective is then to makeup a co-ordinated control system for power sharing within the sources in the hybrid AC-DC microgrid in proportion to the power ratings. The droop control technique is presented in this paper to control the hybrid microgrid. The droop control concept uses a suitable normalization technique for combining both the subgrids. The co-ordinated operation of DC and AC sources and multilevel inverter are investigated. Analysis of power sharing on hybrid AC-DC microgrid is done using MATLAB/SIMULINK. View full abstract»

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    Transient analysis and control for microgrid stability controller

    Han Minxiao ; Su Xiaoling ; Lin Shaobo ; Zhao Zhengkui
    PowerTech (POWERTECH), 2013 IEEE Grenoble

    DOI: 10.1109/PTC.2013.6652175
    Publication Year: 2013 , Page(s): 1 - 6
    Cited by:  Papers (1)

    IEEE Conference Publications

    This work develops a microgrid stability controller to support microgrid switching its operation mode and provide DG units in the microgrid with the additional functionality of working in island mode without changing their control strategies. When microgrid works in grid connected mode, microgrid stability controller compensate power variation and reduces power fluctuation. When the main grid is not available, microgrid operates in island mode, microgrid stability controller provide output voltage and frequency reference for DG units. Its operation is analyzed by studying its control strategies, islanding detection techniques and black box arc model of circuit breaker at the Point of Common Coupling (PCC). Furthermore this paper analyzes its transient characteristics based on the dynamic performance of the microgrid during a fault in distribution network. Simulation and experimental results validates the feasibility of the microgrid stability controller. View full abstract»

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    Power Management and Power Flow Control With Back-to-Back Converters in a Utility Connected Microgrid

    Majumder, R. ; Ghosh, A. ; Ledwich, G. ; Zare, F.
    Power Systems, IEEE Transactions on

    Volume: 25 , Issue: 2
    DOI: 10.1109/TPWRS.2009.2034666
    Publication Year: 2010 , Page(s): 821 - 834
    Cited by:  Papers (52)

    IEEE Journals & Magazines

    This paper proposes a method for power flow control between utility and microgrid through back-to-back converters, which facilitates desired real and reactive power flow between utility and microgrid. In the proposed control strategy, the system can run in two different modes depending on the power requirement in the microgrid. In mode-1, specified amount of real and reactive power are shared between the utility and the microgrid through the back-to-back converters. Mode-2 is invoked when the power that can be supplied by the distributed generators (DGs) in the microgrid reaches its maximum limit. In such a case, the rest of the power demand of the microgrid has to be supplied by the utility. An arrangement between DGs in the microgrid is proposed to achieve load sharing in both grid connected and islanded modes. The back-to-back converters also provide total frequency isolation between the utility and the microgrid. It is shown that the voltage or frequency fluctuation in the utility side has no impact on voltage or power in microgrid side. Proper relay-breaker operation coordination is proposed during fault along with the blocking of the back-to-back converters for seamless resynchronization. Both impedance and motor type loads are considered to verify the system stability. The impact of dc side voltage fluctuation of the DGs and DG tripping on power sharing is also investigated. The efficacy of the proposed control arrangement has been validated through simulation for various operating conditions. The model of the microgrid power system is simulated in PSCAD. View full abstract»

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    Microgrid Stability Characterization Subsequent to Fault-Triggered Islanding Incidents

    Kasem Alaboudy, A.H. ; Zeineldin, H.H. ; Kirtley, J.L.
    Power Delivery, IEEE Transactions on

    Volume: 27 , Issue: 2
    DOI: 10.1109/TPWRD.2012.2183150
    Publication Year: 2012 , Page(s): 658 - 669
    Cited by:  Papers (10)

    IEEE Journals & Magazines

    With the growing deployment of microgrids, it has become urgent to investigate the microgrid behavior during transient faults and subsequent islanding conditions. The load type and the manner in which distributed generations (DGs) are controlled can have substantial impacts on the dynamic performance of microgrids. In this paper, impacts of different control schemes of the inverter-based DG and microgrid load types on the microgrid stability subsequent to fault-forced islanding are investigated. A microgrid model, simulated on Matlab/Simulink software, is analyzed including a mix of synchronous and inverter-based DG and a combination of passive RLC and induction motor (IM) loads. Simulation results show that in the presence of IM loads, the microgrid may lose its stable operation even if the fault is isolated within a typical clearing time. The critical clearing time of a microgrid is highly dependent on the microgrid control strategy, DG interface control, and load type. Induction motor loads can prove problematical to microgrid transient stability, particularly in situations in which the voltage dip can cause the induction motor to “pull out”. View full abstract»

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    A Study of the Impact of Load Forecasting Errors on Trading and Balancing in a Microgrid

    Tomic, S.D.
    Green Technologies Conference, 2013 IEEE

    DOI: 10.1109/GreenTech.2013.74
    Publication Year: 2013 , Page(s): 443 - 450

    IEEE Conference Publications

    How to efficiently integrate and exploit flexible demand and distributed renewable generation in the Smart Grid is a question of high interest reflecting the societal need for energy efficiency and urge to lower carbon emissions. This question also provides strong motivation for honing the concept of a microgrid as an atomic cell of future active distribution networks as well as the smallest market entity. The microgrid locally balances demand and supply in a far more efficient way than in current practice. Complementary, the microgrid market offers basis for creating energy prices that stimulate investments in renewable generation, storage, and demand response. As similar to the current energy markets, the microgrid market can accommodate trading of the short term and the long term energy products, balancing energy and capacity. The foundation of trading is forecasting and optimization, and consequently each party involved in microgrid trading must be able to forecast its demand, supply, or flexibility. But how precise these forecasts must be? This paper focuses on the impact of forecasting errors on the economic effects of trading and balancing in the microgrid: while lower forecasting accuracy induces greater differences between forecasted and real consumption/generation, and hence higher need for balancing energy, higher forecasting precision may increase the cost of the system. We present results of an agent-based simulation study of a microgrid with a simple market integrating local suppliers and customers with flexible loads, renewable energy sources and storage capacity. These actors buy energy, sell demand reduction, and sell energy produced by their wind turbines and solar panels, or stored in their battery. The Microgrid System Operator (MSO) operates the local market and balances demand and supply. In our model MSO operates a dedicated storage and interacts with the global grid markets and performs clearing and settlement of balancing energy costs. In t- e presented study we compare the economic results of trading and balancing for different values of forecasting errors in scenarios characterized with different supply levels in the microgrid. View full abstract»

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    From laboratory Microgrid to real markets — Challenges and opportunities

    Liang Tao ; Schwaegerl, C. ; Narayanan, S. ; Jian Hui Zhang
    Power Electronics and ECCE Asia (ICPE & ECCE), 2011 IEEE 8th International Conference on

    DOI: 10.1109/ICPE.2011.5944600
    Publication Year: 2011 , Page(s): 264 - 271
    Cited by:  Papers (3)

    IEEE Conference Publications

    This paper aims to identify and briefly address major gaps between nowadays technical (laboratory/pilot) Microgrid solutions and real-life (quasi-)commercial Microgrid market demands under a global setting. Firstly, both technical and commercial aspects of Microgrid story are illustrated in parallel; both sides' inherent motivations, scopes, business models etc. are compared. Then the paper deeper identifies and discusses existing gaps for application under three different categories: Major (internal) technical gaps: 1. Grid-connected and off-grid dual mode operation support 2. Meeting Microgrid network constraints / requirements 3. Protection solution for new / upgraded Microgrids Major (external) regulatory gaps: 4. Islanding vs. anti-island vs. low voltage ride through requirements 5. Microgrid controllability definition at point of common coupling Major market gaps: 6. Acknowledgement of local consumption; 7. Extra incentives and differentiation from DG market Consequently, general gap-narrowing principles and techniques are recommended for the above listed issues. Then the corresponding responsibilities and benefits of main stakeholders (producer, consumer, Microgrid operator etc.) in a Microgrid are proposed under this framework. Finally, a global Microgrid development roadmap is envisaged taking into account of regional differences as well as potential technology advancements in future. View full abstract»

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    Active Synchronizing Control of a Microgrid

    Changhee Cho ; Jin-Hong Jeon ; Jong-Yul Kim ; Soonman Kwon ; Kyongyop Park ; Sungshin Kim
    Power Electronics, IEEE Transactions on

    Volume: 26 , Issue: 12
    DOI: 10.1109/TPEL.2011.2162532
    Publication Year: 2011 , Page(s): 3707 - 3719
    Cited by:  Papers (20)

    IEEE Journals & Magazines

    A microgrid is an aggregation of multiple distributed generators (DGs), such as renewable energy sources, conventional generators, and energy storage systems that provide both electric power and thermal energy. Typically, a microgrid operates in parallel with the main grid. However, there are cases in which a microgrid operates in an islanded mode, or in a disconnected state. Islanded microgrid can change its operational mode to grid-connected operation by reconnection to the grid, which is referred to as synchronization. Generally, a single machine simply synchronizes with the grid using a synchronizer. However, the synchronization of microgrids that operate with multiple DGs and loads cannot be controlled by a traditional synchronizer. It is needed to control multiple generators and energy storage systems in a coordinated way for the microgrid synchronization. This is not a simple problem, considering that a microgrid consists of various power electronics-based DGs as well as alternator-based generators that produce power together. This paper proposes an active synchronizing control scheme that adopts the network-based coordinated control of multiple DGs. From the simulation results using Simulink dynamic models, it is shown that the scheme provides the microgrid with a deterministic and reliable reconnection to the grid. The proposed method is verified by using the test cases with the experimental setup of a practical microgrid pilot plant. View full abstract»

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    Microgrid's operation-management containing distributed generation system

    Wang Yang ; Ai Xin ; Gao Yang
    Electric Utility Deregulation and Restructuring and Power Technologies (DRPT), 2011 4th International Conference on

    DOI: 10.1109/DRPT.2011.5993983
    Publication Year: 2011 , Page(s): 703 - 707
    Cited by:  Papers (4)

    IEEE Conference Publications

    As an effective way of power industry's sustainable development, microgrid technology provides flexible and high efficiency platform for distributed generation and renewable energy generation's integration and utilization. And research of its operation-control and management-modes has been a key part. In this paper, on the basis of summarizing microgrid's development status all over the world, according to the differences and relations between microgrid and large power system, and considering two operating modes of microgrid, the key issues of microgrid operation-management are studied. It is pointed out that microgrid's stable operation and optimal management depend on advanced unit-level control technology and system-level integration control technology, among which the dispatch of distributed energy storage and design of dynamic microgrid should be paid more attention. View full abstract»

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    Design of a photovoltaic power conditioning system for hierarchical control of a microgrid

    Wandhare, R.G. ; Thale, S. ; Agarwal, V.
    Photovoltaic Specialist Conference (PVSC), 2014 IEEE 40th

    DOI: 10.1109/PVSC.2014.6925603
    Publication Year: 2014 , Page(s): 3144 - 3149

    IEEE Conference Publications

    Recently hierarchical control of microgrid has been the focus of extensive research due to its flexibility to effectively utilize the micro-sources while ensuring reliability. The work presented in this paper is focused on the design and development of a photovoltaic (PV) power conditioning system for a hierarchically controlled microgrid application. The PV interface is equipped with multiple functionalities such as droop characteristic control for both active and reactive power sharing, centralized power sharing, adaptive power control etc. All these features make the PV interface one of the main power contributing sources. A detailed control design procedure for this microgrid PV source is given. The effectiveness of the proposed control scheme is investigated with a laboratory prototype of the microgrid with hierarchical control supported by sources like Solar PV, Wind, hydro turbine driven synchronous machine and Fuel cell based renewable energy sources. The microgrid has the capability of reconfigurable control. The Local Source Controllers (LSC) are linked with Controller Area Network (CAN) for fast data transfer and RS-485 for bulk data transfer. Battery storage is provided for prolonged energy back up and ultracapacitor for transient and momentary power support during dynamic phase. The PV interface of this microgrid is investigated under various conditions such as large variation in its radiation level, maximum power point tracking, centralized control for active power, co-ordinate active and reactive power control with de-centralized operation, hierarchical control functionality of PV source with other microgrid sources etc. The intermittent nature of photovoltaic source causes a peculiar impact on the microgrid operation. This and other important observations are analyzed for further study and investigations into the control aspects of PV sources in a microgrid paradigm. The key simulation and experimental results are included to verify proper operation- and control of the microgrid. View full abstract»

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    Network Analysis and Algorithm of Microgrid Reliability Assessment

    Yi Luo ; Longjun Wang ; Gelan Zhu ; Gang Wang
    Power and Energy Engineering Conference (APPEEC), 2010 Asia-Pacific

    DOI: 10.1109/APPEEC.2010.5448798
    Publication Year: 2010 , Page(s): 1 - 4
    Cited by:  Papers (4)

    IEEE Conference Publications

    Microgrid is profitable to mitigate the expansion pressure of transmission grid and achieve higher reliability at the same time. It also provides an ideal platform for the application of renewable energy. Network characteristics analysis is the basic element in reliability assessment of microgrid. This paper discusses two methods of microgrid construction according to China's distribution system, and constructs a microgrid based on typical 10 kV distribution network. In order to analyze the topology characteristics of a microgrid, two typical kinds of matrices are used to describe the topology of microgrid, and a more common microgrid based on RBTS Bus4 System is established to illustrate four kinds of sub-network type under different conditions. Issues analyzed in this paper clear the structure difference between the microgrid and distribution network. Accordingly, the algorithms suitable to identify the characteristics of network structure in reliability analysis of microgrid are offered. The work in this paper lays a foundation for further reliability assessment of microgrid. View full abstract»

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    Tracking network voltage based control of the microgrid mode conversion

    Yang, X. ; Bi, D. ; Wu, Z. ; Mou, X.
    Electrical Machines and Systems (ICEMS), 2011 International Conference on

    DOI: 10.1109/ICEMS.2011.6073379
    Publication Year: 2011 , Page(s): 1 - 4

    IEEE Conference Publications

    Due to the large power fluctuation in the mode conversion of Mircogrid, the single energy storage is hard to support the balance of power quickly and stably, which makes the mode conversion not stable and influences the quality of power supply. To improve the performance of microgrid conversion, a new control strategy is presented in this paper. In hybrid structure of vanadium redox battery (VRB) and supercapacitor, the supercapacitor adopts vf control to follow up the network voltage and frequency while microgrid turns into the islanded mode, making sure the voltage and frequency of microgrid and the network synchronization. VRB adopts vf/PQ control to ensure power balance of microgrid operation. This control strategy can improve the conversion rate of microgrid and ensure the stability of microgrid system. The simulation results show that the hybrid energy storage can achieve the excellent performance. View full abstract»

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    Microgrid: Control techniques and modeling

    Basak, P. ; Saha, A.K. ; Chowdhury, S. ; Chowdhury, S.P.
    Universities Power Engineering Conference (UPEC), 2009 Proceedings of the 44th International

    Publication Year: 2009 , Page(s): 1 - 5
    Cited by:  Papers (12)

    IEEE Conference Publications

    This paper presents a discussion on the control techniques required for microgrid operation and implements a simple control strategy in a microgrid model realized with Matlab. The modeling and control strategy are kept elementary. This is done in order to use developed model for teaching and student training purpose for power system curriculum in undergraduate courses. The model is helpful in introducing the microgrid concept, its advantages and operating modes, to the students, and for highlighting the basic control issues of a microgrid. The control issues related with power quality events and pre-set conditions which disconnect microgrid from the main grid and leads the microgrid in a separate islanded mode are discussed. To demonstrate the operation of a microgrid in islanded mode, the authors have simulated showing that the same is connected with the main grid and simultaneously sharing critical and non-critical loads. After being switched over to islanding mode, automatically it eliminates the non-critical loads and continues to supply power to the critical loads. The power supplied by the main grid and the microgrid are observed and studied. The authors present the issues relating to the islanded operation of microgrid including coordination of microsources and storage device to maintain the satisfactory islanding operation of microgrid. View full abstract»

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    Preliminary implementation of microgrid with photovoltaic and microturbine for stand alone operation

    Yih-Der Lee ; Yung-Ruei Chang ; Chen-Min Chan ; Yuan-Hsiang Ho
    Industry Applications Society Annual Meeting (IAS), 2012 IEEE

    DOI: 10.1109/IAS.2012.6373988
    Publication Year: 2012 , Page(s): 1 - 9
    Cited by:  Papers (1)

    IEEE Conference Publications

    This paper presents the preliminary implementation of microgrid system with photovoltaic and microturbine for stand alone operation. The microgrid test bed of the Institute of Nuclear Energy Research (INER) in Taiwan is selected for the study of impacts of high concentration photovoltaic (HCPV) and microturbine to be installed. The one line diagram of the microgrid is constructed and actual load profile supplied by the microgrid is collected. Based on the direct normal irradiation (DNI) and the corresponding power output of HCPV, the voltage variation of microgrid with a microturbine is solved according to the power flow analysis. Besides, the fault currents introduced from HCPV, microturbine and Taipower system are calculated to design the protection coordination of the microgrid. Three actual filed tests of the microgrid have been conducted to verify the effectiveness of the transition operation between grid connect and stand alone control of the microturbine. To verify the normal operation of HCPV, a fault contingency at the external utility system followed by the motor starting in the microgrid is simulated by computer software program. From the simulation results, it is concluded that the transient stability of the INER microgrid for stand alone operation can be guaranteed by installing a microturbine. View full abstract»

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    Improved microgrid energy storage device model in microgrid mode switching process

    Zhang Xiaobo ; Zhang Baohui
    Green Energy, 2014 International Conference on

    DOI: 10.1109/ICGE.2014.6835404
    Publication Year: 2014 , Page(s): 96 - 100

    IEEE Conference Publications

    Microgrid has two operating modes, that is the state of being intergrated in external grid and the state of island operation, and can switch freely between the two states. As microgrid containing renewable energy power generations which are full of randomness and there is conflict that the randomness of micro source power supply and the randomness of users electricity need is temporal mismatch between the two sides, the key to solving this problem is the introduction of an energy storage device. Therefore, the study the energy storage device has played an extremely important role in microgrid study. With further microgrid research, a lot of simulation tools are used to explore the characteristics of microgrid and verify the effects of new proposed control means, one of which is digsilent, the software has a general energy storage device model. However, in the course of using the model it was found that the model does neither meet theoretical calculation results expectations nor conform to the actual situation under certain conditions, such as microgrid island operation or mode switching, the problem has been proposed and validated. After theoretical analysis, the method to improve the energy storage model is proposed, and its improved results are validated by simulation experiments, the results show that the new improved storage model is more consistent with theoretical expectations and realities than the original model. View full abstract»

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    Investigation of the Dynamic Stability of Microgrid

    Xisheng Tang ; Wei Deng ; Zhiping Qi
    Power Systems, IEEE Transactions on

    Volume: 29 , Issue: 2
    DOI: 10.1109/TPWRS.2013.2285585
    Publication Year: 2014 , Page(s): 698 - 706

    IEEE Journals & Magazines

    Microgrid is an aggregation of distributed generators (DGs) and energy storage systems (ESS) through corresponding power interface, such as synchronous generators, asynchronous generators and power electronic devices. Without the support from the public grid, the control and management of an autonomous microgrid is more complex due to its poor equivalent system inertia. To investigate microgrid dynamic stability, a small-signal model of a typical microgrid containing asynchronous generator based wind turbine, synchronous diesel generator, power electronic based energy storage and power network is proposed in this paper. The small-signal model of each of the subsystem is established respectively and then the global model is set up in a global reference axil frame. Eigenvalues distributions of the microgrid system under certain steady operating status are identified to indicate the damping of the oscillatory terms and its effect on system stability margin. Eigenvalues loci analysis is also presented which helps identifying the relationship among the dynamic stability, system configuration and operation status, such as the variation of intermittent generations and ESS with different control strategies. The results obtained from the model and eigenvalues analysis are verified through simulations and experiments on a study microgrid system. View full abstract»

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    Cooperative control between the distributed energy resources in AC/DC hybrid microgrid

    Sung-Hwan Park ; Jin-Young Choi ; Dong-Jun Won
    Innovative Smart Grid Technologies Conference (ISGT), 2014 IEEE PES

    DOI: 10.1109/ISGT.2014.6816448
    Publication Year: 2014 , Page(s): 1 - 5

    IEEE Conference Publications

    Increase of renewable energy resource (RES) and development of energy storage system (ESS) encourage a lot of researches in DC microgrid system. AC system is used in almost power system and it is not easy to change from AC system to DC system at once. Therefore, it is necessary for DC microgrid to be connected to existing AC microgrid or power system unless it is only operated in island mode. In this paper, a strategy on improving stability and reliability of AC/DC hybrid microgrid is proposed. Battery Energy Storage Systems (BESSs) are interfaced with both AC and DC microgrids to improve the system stability by P-f, Q-v, P-v2 droop control. The AC/DC converters connected to DC microgrid maintain the DC voltage constant and balances the energy of whole system. The simulation results by PSCAD /EMTDC are analyzed in grid connected mode and island mode on a peak season of one small island. View full abstract»

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    Contribution of a smart transformer in the local primary control of a microgrid

    Vandoorn, T.L. ; Willems, W. ; De Kooning, J.D.M. ; Van de Vyver, J. ; Vandevelde, L.
    Innovative Smart Grid Technologies Europe (ISGT EUROPE), 2013 4th IEEE/PES

    DOI: 10.1109/ISGTEurope.2013.6695239
    Publication Year: 2013 , Page(s): 1 - 5

    IEEE Conference Publications

    In order to enable an easy participation of microgrids in the electricity markets, the smart transformer (ST) concept has been developed. The ST controls the power exchange between a microgrid and the utility network by only controlling its microgrid side voltage, instead of the conventional arrangement where new set points are communicated to all microgrid elements. When the voltage-based droop (VBD) control is implemented in the DG units, loads and storage elements, all microgrid units automatically respond to this change of microgrid voltage by altering their power output or consumption. However, this reference value of power exchange is dependent on (day-ahead) predictions of both consumption and (renewable) power generation. Hence, when these predictions prove to be inaccurate, the ST will still control the power exchange, but with consequently large variations of the microgrid voltage from its nominal value. It is suggested to take the real-time microgrid voltage into account when determining the reference power of the ST. This is presented in this paper by extending the ST's control strategy with a VBD control, such that the ST can contribute in the primary control. Simulations are included to analyze this primary control of the ST combined with VBD control of the other microgrid elements. View full abstract»

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    Study on microgrid operation modes switching based on eigenvalue analysis

    Zheng Jing Hong ; Wang YanTing ; Wang ZhongJun ; Zhu Shouzhen ; Wang Xiaoyu ; Shen Xinwei
    Advanced Power System Automation and Protection (APAP), 2011 International Conference on

    Volume: 1
    DOI: 10.1109/APAP.2011.6180443
    Publication Year: 2011 , Page(s): 445 - 450
    Cited by:  Papers (1)

    IEEE Conference Publications

    The purpose of this paper is to investigate the characteristics of the switching caused by the microgrid transitions based on the eigenvalue analysis. The factors, including control parameters, line parameters and load parameters, which have impact on the eigenvalues of the two operation modes of the microgrid are studied. In addition, the parameter sensitivity analysis for the dominant eigenvalues is carried out under different load levels in two operation modes of microgrid. The results show: the line parameters and the load parameters have less impact on the stability of the microgrid system than control parameters in either the grid-connected mode or islanded mode; the parameter sensitivity of kpi, the proportional parameter of inner-loop current controller, for the dominant eigenvalue is increased after the microgrid switches from grid-connected mode to autonomous mode. This may cause the microgrid instable in the autonomous mode even if transition from a stable grid-connected mode. Therefore, the parameter kpi should be adjusted to a suitable value to maintain the microgrid stable during the switching, once the island state of microgrid is detected. By comparing the change of the eigenvalues distribution in the modes switching of micro-grid, some smooth-switching control strategies are proposed. Finally several time-domain simulations are present to verify the above result. View full abstract»

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    An improved frequency control method for microgrid in islanded operation

    Yong You ; Gang Wang ; Chang-hua Zhang ; Jing-ru Lian
    Instrumentation and Measurement, Sensor Network and Automation (IMSNA), 2013 2nd International Symposium on

    DOI: 10.1109/IMSNA.2013.6743273
    Publication Year: 2013 , Page(s): 296 - 299

    IEEE Conference Publications

    Some existing microgrid frequency control methods imitated traditional power system primary frequency regulation and secondary frequency regulation. Advantages and disadvantages of this imitation are analyzed and an improved frequency error integral regulation method for islanded microgrid operation is proposed in this paper. The proposed control strategy can implement no-error adjustment of microgrid frequency. In order to overcome the drawbacks of low inertia of microgrid, motion equation of rotor of synchronous generator (SG) is supplemented to the proposed frequency control strategy, which can make frequency to reach a new steady state relatively slowly while loads fluctuate rapidly. Therefore, stability of frequency in microgrid is thus improved. Typical operation states of microgrid operated in islanded mode, such as load random fluctuation, are simulated based on MATLAB/Simulink. Simulation studies prove the effectiveness of the proposed frequency control strategy. View full abstract»

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    Performance Characterization for Photovoltaic-Vanadium Redox Battery Microgrid Systems

    Nguyen, T.A. ; Xin Qiu ; Guggenberger, J.D. ; Crow, M.L. ; Elmore, A.C.
    Sustainable Energy, IEEE Transactions on

    Volume: 5 , Issue: 4
    DOI: 10.1109/TSTE.2014.2305132
    Publication Year: 2014 , Page(s): 1379 - 1388
    Cited by:  Papers (1)

    IEEE Journals & Magazines

    The integration of photovoltatics (PV) and vanadium redox batteries (VRB) in microgrid systems has proven to be a valuable, environmentally friendly solution for reducing the dependency on conventional fossil fuel and decreasing emissions. The integrated microgrid system must be characterized to develop appropriate charging strategies specifically for VRBs, sizing microgrid systems to meet a given load, or comparing the VRB to other energy storage technologies in different applications. This paper provides a performance characterization analysis in a PV-VRB microgrid system for military installations under different conditions of load and weather. This microgrid system is currently deployed at the Fort Leonard Wood army base in Missouri, USA. View full abstract»

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    Integration of High Reliability Distribution System in Microgrid Operation

    Khodayar, M.E. ; Barati, M. ; Shahidehpour, M.
    Smart Grid, IEEE Transactions on

    Volume: 3 , Issue: 4
    DOI: 10.1109/TSG.2012.2213348
    Publication Year: 2012 , Page(s): 1997 - 2006
    Cited by:  Papers (9)

    IEEE Journals & Magazines

    In this paper, the application of high reliability distribution system (HRDS) in the economic operation of a microgrid is studied. HRDS, which offers higher operation reliability and fewer outages in microgrids, is applied to looped networks in distribution systems. The microgrid model in this study is composed of distributed energy resources (DER) including distributed generation (DG), controllable loads, and storage. The microgrid would utilize the local DER as well as the main grid for supplying its hourly load economically which is subject to power quality and reliability requirements. The HRDS implemented at Illinois Institute of Technology (IIT) is used as a case study along with the local DER to increase the load point reliability and decrease the operation cost of the IIT microgrid. The availability of distribution lines, main grid supply, and microgrid generation is considered using the Markov chain Monte Carlo simulation in the microgrid scenarios. The reliability indices based on frequency and duration of outages are measured at the microgrid level and the load point level, and the potential system enhancements are discussed for improving the economic operation of the IIT microgrid. View full abstract»

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    Coordinated control of battery energy storage system in a microgrid

    Wang, Y. ; Tan, K.T. ; So, P.L.
    Power and Energy Engineering Conference (APPEEC), 2013 IEEE PES Asia-Pacific

    DOI: 10.1109/APPEEC.2013.6837211
    Publication Year: 2013 , Page(s): 1 - 6

    IEEE Conference Publications

    Battery energy storage system (BESS) is the key element to integrate a distributed generation (DG) unit into a microgrid. This paper presents a microgrid consisting of singlephase photovoltaic (PV) arrays which function as the primary DG units and a BESS to supplement the intermittent PV power generation and demand variations in the microgrid. An energy management system is proposed to coordinate the operations of the microgrid during grid-connected and islanded modes of operation. The BESS is incorporated into the microgrid to deal with power imbalance and peak load demand during grid-connected operation and to compensate for any power shortage during islanded operation. The controller design for the voltage source inverter employs a model predictive control (MPC) algorithm which enables faster dynamic response. MATLAB/Simulink is used to simulate the proposed microgrid under different test scenarios. The simulation results show that the operations of the BESS in the microgrid can be coordinated effectively using the proposed control system to ensure stable operation of the overall microgrid. View full abstract»

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