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Distributed Energy Resources Integration

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Microgrid Concept
CERTS Microgrid Tecogen InVerde INV100 Test Report
Klapp, D., R. Zimmerly, and J. Howard. March 2012
1.2 MB PDF, 68 pp

The CERTS microgrid project at AEP is now in its third phase. One of the milestones of this phase is to install and commission a Tecogen InVerde INV100 genset. This is a natural gas fueled, combined heat and power "CHP" genset capable of producing 100kW of electrical load. Previous phases of the project included functional testing of Tecogen 60kW prototype units, and sufficient results were gained. During that period, Tecogen developed the commercially available InVerde INV100. This new unit diverged enough from the prototype units to warrant the replacement of a prototype in the test bed with one of these commercial units.

The installation process for the InVerde INV100 utilized some of the existing connection points that belonged to the prototype unit. However, some conductor upgrades were required as well as an additional cooling tower to account for the increased electrical capacity. The associated circuit breaker, fused disconnect, and bus transformer were also replaced with larger sized equipment rated for the larger load.

With the InVerde INV100 installed in the test bed, testing was performed on the unit. This procedure was modeled after that developed for the Tecogen prototype units. For these tests, data was to be gathered on black start capacity, frequency droop, voltage droop, emergency shutdown functionality, load step response, load sharing capability, and pmax controller. Since continuous run tests were completed on the prototype units, that portion was omitted from the InVerde INV100 testing.

After the initial round of testing was complete, it was determined that the unit had voltage instability issues. In order to fix this issue, the bus transformer was taken out of service and replaced with a reactance panel. The unit was then changed from a 3 wire to a 4 wire configuration. The same run of tests was then performed, and more satisfactory results were obtained.

CERTS Microgrid Mechanical Switch Test Report 6.8 MB PDF, 61 pp

The CERTS microgrid test bed at AEP’s Dolan Technology Center includes a semiconductor static switch as a paralleling device. This equipment, along with a DSP controller, offers sub-cycle connection and disconnection between the microgrid and utility. However, similar equipment is not easily duplicated and has a high cost. Therefore, a mechanical switch alternative was produced that offers comparable performance and IEEE 1547 compliance at a reduced price.

The mechanical switch and its associated microprocessor relay used for the project were chosen from major manufacturers of utility equipment. An ABB SACE Emax UL low voltage AC circuit breaker was selected, along with a Schweitzer SEL-700GT intertie relay. Existing cabinet space and wiring was utilized to install this equipment in the test bed. However, the cost of a new installation is estimated $25,000, which compares to the estimated $150,000 cost for a semiconductor switch.

Prior to installation in the test bed, a series of IEEE 1547 compliant tests were run on the SEL-700GT. This was done using an Omicron 256 test set in a laboratory environment. Taking into account a 60ms maximum operating time of the mechanical switch, the tests demonstrated the relay’s ability to operate within the specifications of IEEE 1547. With the mechanical switch and SEL-700GT relay installed in the test bed, another series of tests were run. These tests included synchronized closing, loss of utility anti-islanding, three phase and single phase reverse power, and dead bus close.

In order to improve power quality during testing, the relay’s voltage protection elements were made more stringent. This was done as an attempt to improve the mechanical switch’s ability to operate on abnormal voltage conditions and allow the microgrid generator to remain online. As an alternative to adjusting these settings, additional voltage elements can be added to the relay’s logic that focus on power quality tripping and could ignore the IEEE 1547 reconnection timer.

Comparison of PV Inverter Controller Configurations for CERTS Microgrid Applications 588 KB PDF, 8 pp

Microgrids are highly compatible with photovoltaic (PV) sources because of their ability to internally aggregate and balance multiple PV sources without imposing restrictions on the penetration of such intermittent power sources. There are two major types of inverter control configurations that are used in photovoltaic inverters to provide an interface to a CERTS microgrid. These control configurations exhibit important duality characteristics, and both are capable of tracking maximum input power while abiding by the CERTS droop algorithms. This paper investigates and demonstrates the comparative performance characteristics of these two major controller types: 1) a gridforming droop-style controller similar to those used for controlling distributed generators; and 2) a current-regulated grid-follower controller. It is shown that only the grid-forming controller allows a PV source to operate alone in an islanded CERTS microgrid, but the grid-follower controller enjoys some inherent advantages with regard to faster dynamic response.

Smart Distribution: Coupled Microgrids
Lasseter, R.H. January 2011
547 KB PDF, 8 pp

The distribution system provides major opportunities for smart grid concepts. One way to approach distribution system problems is to rethinking our distribution system to include the integration of high levels of distributed energy resources, using microgrid concepts. Basic objectives are improved reliability, promote high penetration of renewable sources, dynamic islanding, and improved generation efficiencies through the use of waste heat. Managing significant levels of DER with a wide and dynamic set of resources and control points can become overwhelming. The best way to manage such a system is to break the distribution system down into small clusters or microgrids, with distributed optimizing controls coordinating multi-microgrids. The CERTS (Consortium for Electric Reliability Technology Solutions) concept views clustered generation and associated loads as a grid resource or a "microgrid". The clustered sources and loads can operate in parallel to the grid or as an island. This grid resource can disconnect from the utility during events (i.e. faults, voltage collapses), but may also intentionally disconnect when the quality of power from the grid falls below certain standards. This paper focuses on DER based distribution, the basics of microgrids, possibility of smart distribution systems using coupled microgrid and the current state of autonomous microgrid technology.

CERTS Microgrid Laboratory Test Bed
Lasseter, R., Fellow, IEEE, J. Eto, Member, IEEE, B. Schenkman, J. Stevens, Member, IEEE, H. Volkmmer, Member, IEEE, D. Klapp, E. Linton, H. Hurtado, and J. Roy. Submitted to IEEE Transactions on Power Delivery. 2010
5.1 MB PDF, 8 pp

CERTS Microgrid concept captures the emerging potential of distributed generation using a system approach. CERTS views generation and associated loads as a subsystem or a "microgrid". The sources can operate in parallel to the grid or can operate in island, providing UPS services. The system can disconnect from the utility during large events (i.e. faults, voltage collapses), but may also intentionally disconnect when the quality of power from the grid falls below certain standards. CERTS Microgrid concepts 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 resynchronization 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.

Control of Wound Field Synchronous Machine Gensets for Operation in a CERTS Microgrid
Krishnamurthy, S., and R. Lasseter, University of Wisconsin. March 2009
4.4 MB PDF, 185 pp

Distributed generation (DG) is any small-scale electrical power generation technology that provides electric power at or near the load site; it is either interconnected to the distribution system, directly to the consumer's facilities, or to both. Developments in small-scale power generation technologies, ranging from reciprocating engines to micro turbines to fuel cells, provide credibility for DG's central premise of electric-power generation at or near load centers. The effect of the penetration of DG's in the distribution system on system stability, their interconnection with the utility, coordination of protection schemes and their control needs to be understood. A multitude of different technologies such as PV, solar, fuel cell, batteries, wind, microturbines, IC engines etc which can be used as prime movers for DG make this issue a complex challenge.

The objective of this work is to determine how an internal combustion (IC) engine driven wound field synchronous genset can be used most effectively as a DG in a microgrid environment.The genset operates synchronously which implies that the speed of the engine needs to be regulated within a narrow range to ensure that the terminal voltages meet the desired power quality standards. The focus of this work is to study the modeling and control issues related to IC engine driven wound field synchronous generators for their operation in a distribution system that contains multiple DG's. A special challenge posed by the genset is the fact that its dynamic response is considerably slower than that of several other types of DG sources that have much faster power electronic interfaces to the microgrid. Conventional IC engine gensets utilize a voltage regulator that controls the terminal voltage to a fixed value. In a distribution system like the microgrid that has multiple sources, the regulation of the voltage to a constant value results in large circulating VAR's in the system. These circulating VAR's decrease efficiency of the system and increase the rating of components.

To improve the performance of the genset for operation in a microgrid environment this work presents the design of a state variable controller based on a system observer. The state variable controller incorporates droop curves on real and reactive power that enable the IC engine genset to respond to load changes and interact with other sources in the absence of any form of communication system. The operation of the observer and controller are demonstrated using simulation and experimental tests. The results of the tests show that using the proposed controller the IC engine based genset is able to interact with other sources during load changes and maintain system frequency and voltage within prescribed limits and maintain power quality in the microgrid system. The genset is able to reduce the circulating reactive power in the system and share load more evenly with other sources. The proposed controller enhances the integration of the diesel genset into the microgrid environment.

The work also investigates the effects of line starting induction machines in a microgrid setup with diverse sources. Using machine scaling laws the required starting kVA for a large range of induction machines was calculated and guidelines are presented on sizing the induction machine that can be started in such a manner in microgrids. The work also presents a stability analysis of the microgrid system based on Lyapunov's first method. The resulting analysis shows that for the operating conditions studied, the system is stable with all eigenvalues in the left half plane for variations in power frequency droop value as well as power reference.

Finally the work looks at the applicability of the control scheme for gensets of different ratings. The work quantifies the change in frequency during the engine delay for a step load change for machines with higher power ratings. A discussion on the tuning of the controller gains for higher rating gensets is also presented.

Distributed Generation Interface to the CERTS Microgrid
Nikkhajoei, H., Member, IEEE, R. Lasseter, Fellow, IEEE. 2008
1.4 MB PDF, 10pp

This paper focuses on the energy storage system and the power electronic interface included in microsources of the CERTS microgrid. To provide the plug-and-play feature and the power quality requirements of the CERTS microgrid, all microsources regardless of their prime mover type must have a unified dynamic performance. This necessitates attaching an energy storage module to some or all of the microsources. The storage module is attached to the prime mover through a power electronic interface that couples the microsource to the microgrid. Details of the energy storage module, the power electronic interface and the corresponding controls are described. Performance of an example microsource, which includes a synchronous generator, a storage module and an electronic interface, is studied. Dynamic performance of the example microsource when operating in the CERTS microgrid is evaluated based on digital time-domain simulations in the EMTP-RV software environment. Effectiveness of the storage module, the electronic interface and the corresponding controls in enhancing the microsource performance is verified.

The Operation of Diesel Gensets in a CERTS Microgrid
Krishnamurthy, S., Student Member, IEEE, T. Jahns, Fellow, IEEE, and R. Lasseter, Life Fellow, IEEE. 2008
402 KB PDF, 8pp

In this paper the operation of diesel engine-driven wound-field synchronous generator sets as Distributed Generators (DG's) is studied. The objective of this work is to develop the modeling and control framework for such gensets to enable their operation in a distribution system that contains multiple DG's including inverter-based sources. The paper presents experimental results for the interaction of conventional gensets with inverter-based sources in a microgrid test system. From the test results it is observed that there is significant circulating reactive power between the sources as well as frequency oscillations caused by the response of the conventional genset controller. A new controller for the genset is proposed that alleviates these issues and enables the various sources to share power and maintain power quality within the system. The operation of the new controller is demonstrated using simulation results.

Validation of the CERTS Microgrid Concept The CEC/CERTS Microgrid Testbed
Nichols, D., Member, IEEE, J. Stevens, Member, IEEE, R. Lasseter, Fellow, IEEE, J. Eto, Member, IEEE, H. Vollkommer, Member, IEEE. 2006
121 KB PDF, 3pp

The development of test plans to validate the CERTS Microgrid concept is discussed, including the status of a testbed. Increased application of Distributed Energy Resources on the Distribution system has the potential to improve performance, lower operational costs and create value. Microgrids have the potential to deliver these high value benefits. This presentation will focus on operational characteristics of the CERTS microgrid, the partners in the project and the status of the CEC/CERTS microgrid testbed.

Autonomous Control of Microgrids
Piagi, P. and R. Lasseter, University of Wisconsin-Madison. June 2006
633 KB PDF, 8pp

Application of individual distributed generators can cause as many problems as it may solve. A better way to realize the emerging potential of distributed generation is to take a system approach which views generation and associated loads as a subsystem or a "microgrid". The sources can operate in parallel to the grid or can operate in island, providing UPS services. The system will disconnect from the utility during large events (i.e. faults, voltage collapses), but may also intentionally disconnect when the quality of power from the grid falls below certain standards. Utilization of waste heat from the sources will increase total efficiency, making the project more financially attractive. Laboratory verification of the Consortium for Electric Reliability Technology Solutions (CERTS) microgrid control concepts are included. Index Terms--CHP, distributed generation, intentional islanding, inverters, microgrid, power vs. frequency droop, voltage droop.

Dynamic Distribution using (DER) Distributed Energy Resources
Lasseter, R., University of Wisconsin-Madison. May 2006
236 KB PDF, 3 pp

There are four realities facing future power systems that require rethinking the distribution system and the use distributed energy resources, DER. These realities require that the T&D system;

  • Provide for load grow with enhanced stability with minimal growth of the transmission system.
  • Make greater use of renewable such as wind and photovoltaic systems.
  • Increase energy efficiency and reduce pollution and greenhouse gas emissions.
  • Increase availability of high power quality for sensitive loads.

Currently there are DER applications that can help alleviate some of these issues, but a comprehensive solution require integrating DER with distribution in such a way as to radically changing the way distribution and transmission are used to deliver power to the customer. The basic concept is to use DER to move all load following requirements to the distribution system and allow for intentional islanding within the distribution system to enhance reliable and provide high power quality to customers with sensitive loads.

Control and Design of Microgrid Components
Lasseter, R. and P. Piagi, University of Wisconsin-Madison. January 2006
Report, 3.9 MB PDF, 257 pp
Executive Summary, 50 KB PDF, 6 pp

Economic, technology and environmental incentives are changing the face of electricity generation and transmission. Centralized generating facilities are giving way to smaller, more distributed generation partially due to the loss of traditional economies of scale. Distributed generation encompasses a wide range of prime mover technologies, such as internal combustion (IC) engines, gas turbines, microturbines, photovoltaic, fuel cells and wind-power. Most emerging technologies such as micro-turbines, photovoltaic, fuel cells and gas internal combustion engines with permanent magnet generator have an inverter to interface with the electrical distribution system. These emerging technologies have lower emissions, and have the potential to have lower cost, thus negating traditional economies of scale. The applications include power support at substations, deferral of T&D upgrades, and onsite generation.

Energy Manager Design for Microgrids
Firestone, R., and C. Marnay. LBNL-54447. January 2005
927 KB PDF, 81 pp

The technical and financial feasibility and desirability of microgrids has been shown in simulation and on paper. In order to demonstrate them in practice, an energy manager (EM) for control of microgrid equipment is needed. An all-knowing EM is not possible, an extremely information rich and intelligent but expensive EM might not be the optimal choice, and yet an EM that is too simple threatens several perceived benefits of DER. Both art and science will be required to develop the optimal EM and microgrid for a given site. This report serves to introduce the science. Further work should serve to develop this science and to gain experience on actual systems from which the art will emerge.

The CERTS Microgrid and the Future of the Macrogrid
Marnay, C., and O. Bailey. LBNL-55281. August 2004
297 KB PDF, 14 pp

The blackouts of summer 2003 underscored the dependence of western economies on reliable supply of electricity with tight tolerances of quality. While demand for electricity continues to grow, expansion of the traditional electricity supply system is constrained and is unlikely to keep pace with the growing thirst western economies have for electricity. Furthermore, no compelling case has been made that perpetual improvement in the overall power quality and reliability (PQR) delivered is possible or desirable. An alternative path to providing for sensitive loads is to provide for generation close to them. This would alleviate the pressure for endless improvement in grid PQR and might allow the establishment of a sounder economically based level of universal grid service.

Providing for loads by means of local power generation is becoming increasingly competitive with central station generation for a number of reasons, four key ones being non-technical constraints on expansion of the grid, improvements in small scale technologies, opportunities for CHP application, and the ubiquitous nature of sensitive loads in advanced economies. Along with these new technologies, concepts for operating them partially under local control in microgrids are emerging, the CERTS Microgrid being one example. It has been demonstrated in simulation, and a laboratory test of a three microturbine system is planned for early 2005, to be followed by a field demonstration. A systemic energy analysis of a southern California naval base building demonstrates a current economic on-site power opportunity.

Behavior of Two Capstone 30kW Microturbines Operating in Parallel with Impedance Between Them
Yinger, R., July 2004
1.5 MB PDF, 36pp

This report describes the tests conducted to determine the behavior of two Capstone 30 kW microturbines connected in parallel with some impedance between them. This test was meant to simulate the operation of two microturbines at nearby customer facilities. This arrangement also constitutes a simple microgrid. The goal of this test was to investigate if any voltage and power instabilities exist between the two microturbines.

Two test sequences were conducted. The first test sequence operated two microturbine/ load bank pairs using manual control of the microturbine and load bank set points. The second test sequence used the Capstone Load Following mode of operation to control generation levels of one of the microturbines. The two microturbine/ load bank sets were connected together through a 300 foot long, four conductor, #12 cable so that the impedance between them would cause up to a 5% voltage drop (depending on the load balance between the two sets). Data was collected from both Capstone microturbines, two power quality instruments and a power monitor.

Microgrid: A Conceptual Solution
Lasseter, R.H., and P. Piagi, University of Wisconsin-Madison. June 2004
447 KB PDF, 6 pp

Application of individual distributed generators can cause as many problems as it may solve. A better way to realize the emerging potential of distributed generation is to take a system approach which views generation and associated loads as a subsystem or a "microgrid". During disturbances,the generation and corresponding loads can separate from the distribution system to isolate the microgrid's load from the disturbance (providing UPS services) without harming the transmission grid's integrity. This ability to island generation and loads together has a potential to provide a higher local reliability than that provided by the power system as a whole.In this model it is also critical to be able to use the waste heat by placing the sources near the heat load. This implies that a unit can be placed at any point on the electrical system as required by the location of the heat load.

A Business Case for On-Site Generation: The BD Biosciences Pharmingen Project
Firestone, R., C. Creighton, O. Bailey, C. Marnay and M. Stadler. February 2003
1.3 MB PDF, 86 pp

Deregulation is haltingly changing the United States electricity markets. The resulting uncertainty and/or rising energy costs can be hedged by generating electricity on-site and other benefits, such as use of otherwise wasted heat, can be captured. The Public Utility Regulatory Policy Act (PURPA) of 1978 first invited relatively small-scale generators (≥1 MW) into the electricity market. The advent of efficient and reliable small scale and renewable equipment has spurred an industry that has, in recent years, made even smaller(business scale) electricity generation an economically viable option for some consumers.On-site energy capture and/or conversion, known as distributed energy resources (DER),offers consumers many benefits, such as economic savings and price predictability,improved reliability, control over power quality, and emissions reductions. Despite these benefits, DER adoption can be a daunting move to a customer accustomed to simply paying a monthly utility bill.

Microgrid Energy Management System
Kueck, J.D., R.H. Staunton, S.D. Labinov, and B.J. Kirby. January 2003
577 KB PDF, 83 pp

A microgrid is defined as an aggregation of electrical loads and generation. The generators in the microgrid may be microturbines, fuel cells, reciprocating engines, or any of a number of alternate power sources. A microgrid may take the form of shopping center, industrial park or college campus. To the utility, a microgrid is an electrical load that can be controlled in magnitude. The load could be constant, or the load could increase at night when electricity is cheaper, or the load could be held at zero during times of system stress.

The microgrid utilizes waste heat from the generators to improve overall efficiency. The purpose of the Energy Management System (EMS) is to make decisions regarding the best use of the generators for producing electric power and heat. These decisions will be based upon the heat requirements of the local equipment, the weather, the price of electric power, the cost of fuel and many other considerations. The EMS will dispatch the generators and provide an overview of the Combined Heat and Power (CHP) system.

Review of Test Facilities for Distributed Energy Resources
Akhil, A., Sandia National Laboratories; C. Marnay, Lawrence Berkeley National Laboratory; and T. Lipman, University of California, Berkeley. Report Numbers: SAND2003-1602, LBNL-51954. October 2002
1.1 MB PDF, 45 pp

Since initiating research on integration of distributed energy resources(DER) in 1999, the Consortium for Electric Reliability Technology Solutions (CERTS) has been actively assessing and reviewing existing DER test facilities for possible demonstrations of advanced DER system integration concepts. This report is a compendium of information collected by the CERTS team on DER test facilities during this period.

Integration of Distributed Energy Resources: The CERTS MicroGrid Concept
Lasseter, R., A. Akhil, C. Marnay, J. Stevens, J. Dagle, R. Guttromson, A.S. Meliopoulous, R. Yinger, and J. Eto. April 2002
Report, 242 KB PDF, 32 pp
Appendices, 299 KB PDF, 46 pp

The Consortium for Electric Reliability Technology Solutions (CERTS)MicroGrid concept assumes an aggregation of loads and microsources operating as a single system providing both power and heat. The majority of the microsources must be power electronic based to provide the required flexibility to insure operation as a single aggregated system. This control flexibility allows the CERTS MicroGrid to present itself to the bulk power system as a single controlled unit that meets local needs for reliability and security.

White Paper on Protection Issues of The MicroGrid Concept
Feero, W.E., D.C. Dawson and J. Stevens. March 2002
131 KB PDF, 24 pp

This report examines the protection problems that must be dealt with to successfully operate a microgrid when the utility is experiencing abnormal conditions. There are two distinct sets of problems to solve. The first is how to determine when an islanded microgrid should be formed in the face of the array of abnormal conditions that the utility can experience. The second is how to provide segments of the microgrid with sufficient coordinated fault protection while operating as an island separate from the utility.

As used in this discussion, the term microgrid refers to conventional distribution systems with distributed resources (DR) added. This is not to imply that the simple addition of DR to a distribution system creates a microgrid. In a microgrid the DR(s) has sufficient capacity to carry all, or most, of the load connected to that portion of the distribution system that houses the DR. In addition, a microgrid can operate as an electrical island in times of disturbance to the main utility system. Thus, there will be a well-defined interconnection point where the microgrid can be disconnected from the bulk of the electric utility system if so desired.

Industrial Application of MicroGrids
Lasseter, R., and P. Piagi. October 2001
1.2 MB PDF, 132 pp

The following report summarizes the benefits of introducing Distributed Resources within an industrial site. A detailed description of the factory is followed by steady state analysis of the system. This industry has an overall demand of 1MW and is connected to the main grid with a series of transformers. Within the plant there are three main buildings: the factory, the warehouse and the offices. The grid supplies also another plant in the immediate vicinity of the one under study. Each parameter of the system is found from tables available from the literature. Steady state analysis is used to obtain voltage profiles and power flows for the system in the following scenarios: without units, with DR's with grid connection and with DR's in isolation mode, when the connection to the main grid fails.

Power Electronics
Integration of Distributed Technologies - Standard Power Electronic Interfaces
Flannery, P., G. Venkataramanan, and B. Shi. April 2004
1.7 MB PDF, 139 pp

Distributed technologies are slated to represent a substantial portion of future additions in power generation capacity. Modern distributed generation technologies such as microturbines, fuel cells, wind turbines and photovoltaic systems invariably employ several power electronic converters such as rectifiers and inverters in them in order to provide utility grade ac power. The cost of power electronic systems represent a substantial portion of overall installation costs. This has been due to the complexity of the engineering and realization of power electronics system packaging.

It is common for families of power converter products today to be custom designed. This results in sub-optimal economic performance in terms of engineering design, packaging, manufacturing, etc. Substantial opportunity exists for wide spread application of electrical power converters if they can be made low cost, reliable, rugged,serviceable, and interchangeable. Inspiration for a new, high level approach to power converter design is found in the areas of digital electronics and computer architectures.

This report presents the results of ongoing investigations on development of high power electronic systems for distributed generation systems using standardized approaches for integrating the components that comprise a power converter. The investigations have focused on developing a modular architecture that would allow using pre-engineered and mass-produced components to develop power electronic solutions in a systematic manner.

DER Modeling and Data
Evaluation of Distribution Analysis Software for DER Applications
Rizy, D.T., and R.H. Staunton. Report: ORNL/TM-2001/215. September 2002
481 KB PDF, 38 pp

The term "Distributed energy resources" or DER refers to a variety of compact, mostly self-contained power-generating technologies that can be combined with energy management and storage systems and used to improve the operation of the electricity distribution system, whether or not those technologies are connected to an electricity grid. Implementing DER can be as simple as installing a small electric generator to provide backup power at an electricity consumer's site. Or it can be a more complex system, highly integrated with the electricity grid and consisting of electricity generation, energy storage, and power management systems. DER devices provide opportunities for greater local control of electricity delivery and consumption.They also enable more efficient utilization of waste heat in combined cooling, heating and power (CHP) applications—boosting efficiency and lowering emissions. CHP systems can provide electricity, heat and hot water for industrial processes, space heating and cooling, refrigeration,and humidity control to improve indoor air quality.

Behavior of Capstone and Honeywell Microturbine Generators during Load Changes
Yinger, R.J. July 2001
Report, 217 KB PDF, 38 pp
Appendix A, 36 KB PDF, 4 pp
Appendix B, 67 KB PDF, 14 pp
Appendix C, 117 KB PDF, 17 pp
Appendix D, 274 KB PDF, 27 pp
Appendix E, 269 KB PDF, 25 pp
Appendix F, 206 KB PDF, 4 pp
Appendix G, 316 KB PDF, 16 pp
Appendix H, 208 KB PDF, 19 pp

This report describes test measurements of the behavior of two microturbine generators (MTGs)under transient conditions. The tests were conducted under three different operating conditions: grid connect;stand-alone single MTG with load banks; and two MTGs running in parallel with load banks. Tests were conducted with both the Capstone 30-kW and Honeywell Parallon 75-kW MTGs.All tests were conducted at the Southern California Edison /University of California, Irvine (UCI) test facility. In the grid- connected mode, several test runs were conducted with different set-point changes both up and down and a start up and shutdown were recorded for each MTG. For the standalone mode, load changes were initiated by changing load-bank values (both watts and VARs). For the parallel mode, tests involved changes in the load-bank settings as well as changes in the power set point of the MTG running in grid-connect mode. Detailed graphs of the test results are presented. It should be noted that these tests were done using a specific hardware and software. Use of different software and hardware could result in different performance characteristics for the same units.

Scenarios for Distributed Technology Applications with Steady State and Dynamic Models of Loads and Micro-Sources
Lasseter R., K. Tomsovic and P. Piagi. April 2000
431 KB PDF, 90 pp

This report defines two distributed energy application scenarios with the necessary models for micro-turbines, fuel cells, inverters and induction machines. The two scenarios described in Section 1 are distribution support and a sensitive load. Each of the scenario descriptions begins with a list of objectives and constraints. There are essentially two components that are required in developing the scenarios of interest; the use of appropriate models and associated parameters for studying phenomenon of interest, and the criteria and methods for evaluation of performance.

DER Customer Adoption Model
Optimal Technology Selection and Operation of Microgrids in Commercial Buildings
Marnay, C., G. Venkataramanan, M. Stadler, A. Siddiqui, R. Firestone, and B. Chandran. June 2007
282 KB PDF, 8 pp

The deployment of small (< 1-2 MW) clusters of generators, heat and electrical storage, efficiency investments, and combined heat and power (CHP) applications (particularly involving heat activated cooling) in commercial buildings promises significant benefits but poses many technical and financial challenges, both in system choice and its operation; if successful, such systems may be precursors to widespread microgrid deployment. The presented optimization approach to choosing such systems and their operating schedules uses Berkeley Lab's Distributed Energy Resources Customer Adoption Model [DER-CAM], extended to incorporate electrical storage options. DER-CAM chooses annual energy bill minimizing systems in a fully technology-neutral manner. An illustrative example for a San Francisco hotel is reported. The chosen system includes two engines and an absorption chiller, providing an estimated 11% cost savings and 10% carbon emission reductions, under idealized circumstances.

Microturbine Economic Competitiveness: A Study of Two Potential Adopters
Firestone, R., and C. Marnay. LBNL-57985. December 2005
696 KB PDF, 49 pp

This project evaluates what $/kW subsidy on microturbines (MT's) makes them economically competitive with natural gas internal combustion engines (ICE's). The Distributed Energy Resources Customer Adoption Model (DER-CAM) is used to determine least cost solutions, including distributed generation (DG) investment and operation, to sites' energy demands.

The first site considered is a hospital in New York City. The small hospital (90 beds) has a peak electric load (including cooling) of 1200 kW, with heat loads comparable to electric loads. Consolidated Edison electricity and natural gas tariffs for 2003 are used. A 60% minimum DG system efficiency is imposed on DG operation to avoid the standby tariff, which is less amenable to DG than the parent tariff.

The second site considered is the Naval Base Ventura County commissary in Southern California. The commissary has 13,000 m2 of floor space and contains a large retail store, supermarket, food court, and other small businesses. The site peak electric load (including cooling) is 1050 kW. Electricity and natural gas supply are from direct access contracts, and delivery service is provided by Southern California Edison and Southern California Gas, respectively. 2003 supply and delivery rates are used.

Distributed Energy Resources Customer Adoption Modeling with Combined Heat and Power Applications
Siddiqui, A., R. Firestone, S. Ghosh, M. Stadler, C. Marnay, and J. Edwards. June 2003
1.2 MB PDF, 127 pp

In this report, an economic model of customer adoption of distributed energy resources (DER) is developed. It covers progress on the DER project for the California Energy Commission (CEC) at Berkeley Lab during the period July 2001 through Dec 2002 in the Consortium for Electric Reliability Technology Solutions (CERTS) Distributed Energy Resources Integration (DERI) project. CERTS has developed a specific paradigm of distributed energy deployment, the CERTS Microgrid (as described in Lasseter et al 2002). The primary goal of CERTS distributed generation research is to solve the technical problems required to make the CERTS Microgrid a viable technology, and Berkeley Lab's contribution is to direct the technical research proceeding at CERTS partner sites towards the most productive engineering problems. The work reported herein is somewhat more widely applicable, so it will be described within the context of a generic microgrid (µGrid). Current work focuses on the implementation of combined heat and power (CHP) capability. A µGrid as generically defined for this work is a semiautonomous grouping of generating sources and end-use electrical loads and heat sinks that share heat and power. Equipment is clustered and operated for the benefit of its owners. Although it can function independently of the traditional power system, or macrogrid, the µGrid is usually interconnected and exchanges energy and possibly ancillary services with the macrogrid. In contrast to the traditional centralized paradigm, the design, implementation, operation, and expansion of the µGrid is meant to optimize the overall energy system requirements of participating customers rather than the objectives and requirements of the macrogrid.

Distributed Energy Resources in Practice: A Case Study Analysis and Validation of LBNL's Customer Adoption Model
Bailey, O., C. Creighton, R. Firestone, C. Marnay and M. Stadler. February 2003
Report, 1.6 MB PDF, 209 pp
Appendix, 3.6 MB PDF, 157 pp

This report describes a Berkeley Lab effort to model the economics and operation of small-scale(<500 kW) on-site electricity generators based on real-world installations at several example customer sites. This work builds upon the previous development of the Distributed Energy Resource Customer Adoption Model (DER-CAM), a tool designed to find the optimal combination of installed equipment, and idealized operating schedule, that would minimize the site's energy bills, given performance and cost data on available DER technologies, utility tariffs, and site electrical and thermal loads over a historic test period, usually a recent year. This study offered the first opportunity to apply DER-CAM in a real-world setting and evaluate its modeling results.

DER-CAM has three possible applications: first, it can be used to guide choices of equipment at specific sites, or provide general solutions for example sites and propose good choices for sites with similar circumstances; second, it can additionally provide the basis for the operations of installed on-site generation; and third, it can be used to assess the market potential of technologies by anticipating which kinds of customers might find various technologies attractive.

A list of approximately 90 DER candidate sites was compiled and each site's DER characteristics and their willingness to volunteer information was assessed, producing detailed information on about 15 sites of which five sites were analyzed in depth. The five sites were not intended to provide a random sample; rather they were chosen to provide some diversity of business activity,geography, and technology. More importantly, they were chosen in the hope of finding examples of true business decisions made based on somewhat sophisticated analyses, and pilot or demonstration projects were avoided. Information on the benefits and pitfalls of implementing a DER system was also presented from an additional ten sites including agriculture, education, health care, airport, and manufacturing facilities.

The five sites are:

  1. A&P Waldbaum's Supermarket: A Long Island supermarket that has installed a microturbine with CHP for desiccant dehumidification.
  2. Guarantee Savings Building: An historic office building in California's central valley that has undergone a major remodel and will house two federal agencies. Three fuel cells with an absorption chiller are being installed.
  3. The Orchid: A Hawaiian resort that has installed propane fired reciprocating engines and an absorption chiller.
  4. BD Biosciences Pharmingen: A San Diego biotech company that is installing reciprocating engines with heat recovery for the almost constant space heating required because of frequent air changes needed for laboratories.
  5. USPS San Bernardino: A postal sorting facility in southern California that is considering a reciprocating engine, possibly with absorption cooling.

All of these sites provided enough information on their loads, the tariffs they face, any subsidies or incentives they expected, and their analysis of their project for a parallel DER-CAM analysis to be completed. However, their various projects were at different stages of completion, so that the accuracy of available data was not consistent. For example, the Guarantee Savings Building remodel that was in progress at the time of this study was so major that historic energy use data was of no use and had to be replaced by simulation.

Scenarios were modeled to show the potential options and the financial value of different energy system designs such as the base case energy consumption with no DER installation, unrestricted installation of DER technologies, and a replication of the site's DER installation decision. The modeling results also emphasized the importance of DER grants and included sensitivity analyses on important parameters such as the spark-spread rate, standby charges, and general tariff structures.

This study accomplished the following goals: DER site project experience was analyzed, described,and disseminated; real-world problems involved with DER adoption decision-making and system design were described; DER-CAM financial estimates and technology adoption decisions were validated; the accuracy of DER-CAM was improved and its capabilities were expanded based on real-world experience; contacts were established with relevant DER sites for future research.The results of this case study report provide information on DER system costs and benefits that can be used to analyze the financial value of the DER project using tools such as net present value(NPV) and payback analysis. Important results in the report are the head-to-head comparison of DER technologies chosen at the site and the technologies recommended by DER-CAM. Typically the DER-CAM solution involves a higher capacity installation than that chosen by the site. Some sites' technology adoption decisions differed from DER-CAM due to factors not included in the model. Comparisons of DER-CAM results to the sites' estimates of DER system costs and benefits are presented. Note that most projects were in the installation or initial operation stage and actual costs could diverge significantly because of unanticipated operating conditions.

The key results are:

  • Calculating financial costs and benefits of each DER system and using this information to validate DER-CAM's estimates.
  • In general, DER-CAM and Berkeley Lab staff were able to reproduce energy bills and other key data with reasonable accuracy, typically within about 10%.
  • DER-CAM generally found reciprocating engines often with absorption cooling to be the most attractive technology and, consequently, fairly accurately predicted its adoption for those sites installing engines. In one notable case where DER-CAM chose a reciprocating engine, the Guarantee Savings Building, the developers have adopted fuel cells in large part for reasons not incorporated into DER-CAM.
  • DER-CAM tends to choose higher capacities than sites themselves choose. This seems to suggest a quite reasonable conservatism and risk averseness on the part of customers.
  • This project has provided an excellent opportunity for Berkeley Lab to exercise DER-CAM, to learn about real world DER installations, and to develop a base of data and personal contacts that will be invaluable in future research on DER adoption.
Modeling of Customer Adoption of Distributed Energy Resources
Marnay, C., J.S. Chard, K.S. Hamachi, T. Lipman, M.M. Moezzi, B. Ouaglal, and A.S. Siddiqui. August 2001
1.3 MB PDF, 122 pp

In this study, the Distributed Energy Resources Customer Adoption Model (DER-CAM), an economic model of customer DER adoption implemented in the General Algebraic Modeling System (GAMS) optimization software is used, to find the cost-minimizing combination of on-site generation customers (individual businesses and a µGrid) in a specified test year. DER-CAM s objective is to minimize the cost of supplying electricity to a specific customer by optimizing the installation of distributed generation and the self-generation of part or all of its electricity. Currently, the model only considers electrical loads, but combined heat and power (CHP) analysis capability is being developed.

Customer Adoption of Small-Scale On-Site Power Generation
Siddiqui, A., C. Marnay, K. Hamachi and F. Rubio. April 2001
111 KB PDF, 19 pp

The electricity supply system is undergoing major regulatory and technological change with significant implications for the way in which the sector will operate (including its patterns of carbon emissions) and for the policies required to ensure socially and environmentally desirable outcomes.One such change stems from the rapid emergence of viable small-scale (i.e., smaller than 500 kW)generators that are potentially competitive with grid delivered electricity, especially in combined heat and power configurations. Such distributed energy resources (DER) may be grouped together with loads in microgrids. These clusters could operate semi-autonomously from the established power system, or macrogrid, matching power quality and reliability more closely to local end-use requirements. In order to establish a capability for analyzing the effect that microgrids may have on typical commercial customers, such as office buildings, restaurants, shopping malls, and grocery stores, an economic model of DER adoption is being developed at Berkeley Lab. This model endeavors to indicate the optimal quantity and type of small on-site generation technologies that customers could employ given their electricity requirements. For various regulatory schemes and general economic conditions, this analysis produces a simple operating schedule for any installed generators. Early results suggest that many commercial customers can benefit economically from on-site generation, even without considering potential combined heat and power and reliability benefits, even though they are unlikely to disconnect from the established power system.

CERTS Customer Adoption Model
Rubio, F., A. Siddiqui, C. Marnay and K. Hamachi. March 2001
1.4 MB PDF, 145 pp

This effort represents a contribution to the wider distributed energy resources (DER)research of the Consortium for Electric Reliability Technology Solutions (CERTS, http://certs.lbl.gov) that is intended to attack and, hopefully, resolve the technical barriers to DER adoption, particularly those that are unlikely to be of high priority to individual equipment vendors. The longer term goal of the Berkeley Lab effort is to guide the wider technical research towards the key technical problems by forecasting some likely patterns of DER adoption. In sharp contrast to traditional electricity utility planning, this work takes a customer-centric approach and focuses on DER adoption decision making at,what we currently think of as, the customer level. This study reports on Berkeley Lab's second year effort (completed in Federal fiscal year 2000, FY00) of a project aimed to anticipate patterns of customer adoption of distributed energy resources (DER). Marnay,et al., 2000 describes the earlier FY99 Berkeley Lab work. The results presented herein are not intended to represent definitive economic analyses of possible DER projects by any means. The paucity of data available and the importance of excluded factors, such as environmental implications, are simply too important to make such an analysis possible at this time. Rather, the work presented represents a demonstration of the current model and an indicator of the potential to conduct more relevant studies in the future.

Integrated Assessment of Dispersed Energy Resources Deployment
Marnay, C., R. Blanco, K. Hamachi, C. Kawann, J. Osborn, and F. Rubio. March 2000
5.3 MB PDF, 139

The goal of this work is to develop an integrated framework for distributed energy resource (DER) deployment forecasting. Results for the Customer Adoption Model developed by this project show strong potential for future DER adoption. Factors that benefit DER include locally high electric rates or low natural gas prices. Although current regulations often prohibit the installation of small-scale generation for anything other than for emergency purposes, the strong interest in DER could soon remove this barrier. Environmental siting concerns are also an important consideration, the studied area, southern San Joaquin Valley (SJV), is under strict air quality restrictions. Siting DER in such locations is an environmental challenge, requiring proper selection of the DER technology, and, possibly, mitigation measures. The potential of GIS to geographically display numerous constraints associated with DER deployment in specified siting locations make it a powerful tool for anticipating potential barriers.Together, this work creates a framework for assessing customer adoption for DER deployment.

Research, Development, and Demonstration Needs for Large-Scale, Reliability-Enhancing, Integration of Distributed Energy Resources
Eto, J., Lawrence Berkeley National Laboratory; and V. Budhraja, C. Martinez, J. Dyer and M. Kondragunta, Edison Technology Solutions. Proceedings of the Thirty-Third Annual Hawaii International Conference on System Sciences, January 4-7, 2000
104 KB PDF, 7 pp

Distributed energy resources (DER) are in transition from the lab to the marketplace. The defining characteristic of DER is that they are active devices installed at the distribution system level, as opposed to the transmission level. While no specific size range has been defined, most distribution systems would have difficulty accommodating distributed generating resources larger than 10 MW/MVA at any single location and many systems may have even lower limits. Distributed energy resources include generation resources such as fuel cells, micro-turbines, photovoltaics, and hybrid power plants or storage technologies such as batteries, flywheels, ultra capacitors and superconducting magnetic energy storage. They may also consist of dynamic reactive power control devices and possibly customer end-use load controls.

This paper summarizes technical requirements for large-scale integration of active devices into the existing distribution infrastructure to maintain or enhance reliability. The paper is intended to lay the groundwork for a multi-year program of research necessary to facilitate the transition to such a system. The scope of the research includes consideration of control systems, including the sensors and instruments necessary to gather intelligence for real-time power management, and dispatch or coordination among distributed generation resources and with utility distribution systems. It also includes improved modeling techniques to better characterize the technologies and their impacts on the distribution (and ultimately the transmission) system.