This quick note outlines what we found after our conversion with you and your team. As suggested, we loaded 1547-2003 source requirements document (SRD) and then went back and loaded 1547-2018 SRD. This did result in implementing the new 1547-2018 settings. This short report focuses on the frequency-watt function and shows a couple of screen shots of the parameter settings via the Mojave HMI interface and plots of the results of the inverter with FW function enabled in both default and most aggressive settings response to frequency events. The first screen shot shows the 1547-2018 selected after selecting 1547-2003.
The inverter firmware was upgraded to version 1.09 and an initial assessment was conducted on the inverter using the equipment listed above and the response of the inverter can be seen in the following plots. This work is to base-line the response of the inverter to utility conditions and commands and further work will involve the interoperability aspect of the inverter using SunSpec dashboard to conduct the tests and configure the inverter.
Renewable energy has become a viable solution for reducing the harmful effects that fossil fuels have on our environment, prompting utilities to replace traditional synchronous generators (SG) with more inverter-based devices that can provide clean energy. One of the biggest challenges utilities are facing is that by replacing SG, there is a reduction in the systems' mechanical inertia, making them vulnerable to frequency instability. Grid-forming inverters (GFMI) have the ability to create and regulate their own voltage reference in a manner that helps stabilize system frequency. As an emerging technology, there is a need for understanding their dynamic behavior when subjected to abrupt changes. This paper evaluates the performance of a GFMI when subjected to voltage phase jump conditions. Experimental results are presented for the GFMI subjected to both balanced and unbalanced voltage phase jump events in both P/Q and V/f modes.
Under its Grid Modernization Initiative, the U.S. Department of Energy (DOE), in collaboration with energy industry stakeholders developed a multi-year research plan to support modernizing the electric grid. One of the foundational projects for accelerating modernization efforts is information and communications technology interoperability. A key element of this project has been the development of a methodology for engaging ecosystems related to grid integration to create roadmaps that advance the ease of integration of related smart technology. This document is the product of activities undertaken in 2017 through 2019. It provides a Cybersecurity Plan describing the technology to be adopted in the project with details as per the GMLC Call document.
Historically, photovoltaic inverters have been grid-following controlled, but with increasing penetrations of inverter-based generation on the grid, grid-forming inverters (GFMI) are gaining interest. GFMIs can also be used in microgrids that require the ability to interact and operate with the grid (grid-tied), or to operate autonomously (islanded) while supplying their corresponding loads. This approach can substantially improve the response of the grid to severe contingencies such as hurricanes, or to high load demands. During islanded conditions, GFMIs play an important role on dictating the system's voltage and frequency the same way as synchronous generators do in large interconnected systems. For this reason, it is important to understand the behavior of such grid-forming inverters under fault scenarios. This paper focuses on testing different commercially available grid-forming inverters under fault conditions.
Historically, photovoltaic inverters have been grid-following controlled, but with increasing penetrations of inverter-based generation on the grid, grid-forming inverters (GFMI) are gaining interest. GFMIs can also be used in microgrids that require the ability to interact and operate with the grid (grid-tied), or to operate autonomously (islanded) while supplying their corresponding loads. This approach can substantially improve the response of the grid to severe contingencies such as hurricanes, or to high load demands. During islanded conditions, GFMIs play an important role on dictating the system's voltage and frequency the same way as synchronous generators do in large interconnected systems. For this reason, it is important to understand the behavior of such grid-forming inverters under fault scenarios. This paper focuses on testing different commercially available grid-forming inverters under fault conditions.
Batteries are designed to store electrical energy. The increasing variation in time value of energy has driven the use of batteries as controllable distributed energy resources (DER). This is enabled though low-cost power electronic inverters that are able to precisely control charge and discharge. This paper describes the software implementation of an open-source battery inverter fleet models in python. The Sandia BatterylnverterFleet class model can be used by scientists, researchers, and engineers to perform simulations of one or more fleets of similar battery-inverter systems connected to the grid. The program tracks the state- of-charge of the simulated batteries and ensures that they stay within their limits while responding to separately generated service requests to charge or discharge. This can be used to analyze control and coordination, placement and sizing, and many other problems associated with the integration of batteries on the power grid. The development of these models along with their python implementation was funded by the Grid Modernization Laboratory Consortium (GMLC) project 1.4.2. Definitions, Standards and Test Procedures for Grid Services from Devices.
Most inverters for use in distribution-connected distributed energy resource applications (distributed generation and energy storage) are tested and certified to detect and cease to energize unintentional islands on the electric grid. The requirements for the performance of islanding detection methods are specified in IEEE 1547-2018, and specified conditions for certification- type testing of islanding detection are defined in IEEE 1547.1. Such certification-type testing is designed to ensure a minimum level of confidence that these inverters will not island in field applications. However, individual inverter certification tests do not address interactions between dissimilar inverters or between inverter and synchronous machines that may occur in the field. This work investigates the performance of different inverter island detection methods for these two circumstances that are not addressed by the type testing: 1) combinations of different inverters using different types of islanding detection methods, and 2) combinations of inverters and synchronous generators. The analysis took into consideration voltage and frequency ride- through requirements as specified in IEEE 1547-2018, but did not consider grid support functionality such as voltage or frequency response. While the risk of islanding is low even in these cases, it is often difficult to deal with these scenarios in a simplified interconnection screening process. This type of analysis could provide a basis to establish a practical anti- islanding screening methodology for these complex scenarios, with the goal of reducing the number of required detailed studies. Eight generic Groups of islanding detection behavior are defined, and examples of each are used in the simulations. The results indicate that islanding detection methods lose effectiveness at significantly different rates as the composition of the distributed energy resources (DERs) varies, with some methods remaining highly effective over a wide range of conditions.
Photovoltaic (PV) distributed energy resources (DER) have reached approximately 27 GW in the U.S., and the solar penetration rate continues to increase. This growth is expected to continue, causing challenges for grid operators who must maintain grid stability, reliability, and resiliency. To minimize adverse effects on the performance of electrical power system (EPS) with increasing levels of variable renewable generation, photovoltaic inverters must implement grid-support capabilities, allowing the DER to actively participate in grid support operations and remain connected during short-term voltage and frequency anomalies. These functions include voltage and frequency regulation features that adjust DER active and reactive power at the point of common coupling. To evaluate the risk of these functions conflicting with traditional distribution system voltage regulation equipment, researchers used several methods to quantify EPS-support function response times for autonomous voltage regulation functions (volt-var function). Based on this study, no adverse interactions between PV inverters with volt-var functions and load tap changing transformers or capacitor banks were discovered.
Photovoltaic (PV) distributed energy resources (DER) have reached approximately 27 GW in the U.S., and the solar penetration rate continues to increase. This growth is expected to continue, causing challenges for grid operators who must maintain grid stability, reliability, and resiliency. To minimize adverse effects on the performance of electrical power system (EPS) with increasing levels of variable renewable generation, photovoltaic inverters must implement grid-support capabilities, allowing the DER to actively participate in grid support operations and remain connected during short-term voltage and frequency anomalies. These functions include voltage and frequency regulation features that adjust DER active and reactive power at the point of common coupling. To evaluate the risk of these functions conflicting with traditional distribution system voltage regulation equipment, researchers used several methods to quantify EPS-support function response times for autonomous voltage regulation functions (volt-var function). Based on this study, no adverse interactions between PV inverters with volt-var functions and load tap changing transformers or capacitor banks were discovered.
The continued exponential growth of photovoltaic technologies paves a path to a solar-powered world, but requires continued progress toward low-cost, high-reliability, high-performance photovoltaic (PV) systems. High reliability is an essential element in achieving low-cost solar electricity by reducing operation and maintenance (O&M) costs and extending system lifetime and availability, but these attributes are difficult to verify at the time of installation. Utilities, financiers, homeowners, and planners are demanding this information in order to evaluate their financial risk as a prerequisite to large investments. Reliability research and development (R&D) is needed to build market confidence by improving product reliability and by improving predictions of system availability, O&M cost, and lifetime. This project is focused on understanding, predicting, and improving the reliability of PV systems. The two areas being pursued include PV arc-fault and ground fault issues, and inverter reliability.
The Characterizing Emerging Technologies project focuses on developing, improving and validating characterization methods for PV modules, inverters and embedded power electronics. Characterization methods and associated analysis techniques are at the heart of technology assessments and accurate component and system modeling. Outputs of the project include measurement and analysis procedures that industry can use to accurately model performance of PV system components, in order to better distinguish and understand the performance differences between competing products (module and inverters) and new component designs and technologies (e.g., new PV cell designs, inverter topologies, etc.).
Increasing the penetration of distributed renewable sources, including photovoltaic (PV) sources, poses technical challenges for grid management. The grid has been optimized over decades to rely upon large centralized power plants with well-established feedback controls, but now non-dispatchable, renewable sources are displacing these controllable generators. This one-year study was funded by the Department of Energy (DOE) SunShot program and is intended to better utilize those variable resources by providing electric utilities with the tools to implement frequency regulation and primary frequency reserves using aggregated renewable resources, known as a virtual power plant. The goal is to eventually enable the integration of 100s of Gigawatts into US power systems.
Increasing the penetration of distributed renewable sources, including photovoltaic (PV) generators, poses technical challenges for grid management. The grid has been optimized over decades to rely on large centralized power plants with well-established feedback controls. Conventional generators provide relatively constant dispatchable power and help to regulate both voltage and frequency. In contrast, photovoltaic (PV) power is variable, is only as predictable as the weather, and provides no control action. Thus, as conventional generation is displaced by PV power, utility operation stake holders are concerned about managing fluctuations in grid voltage and frequency. Furthermore, since the operation of these distributed resources are bound by certain rules that require they stop delivering power when measured voltage or frequency deviate from the nominal operating point, there are also concerns that a single grid event may cause a large fraction of generation to turn off, triggering a black out or break-up of an electric power system.
Interconnection equipment that connects distributed resources (DR) to an electrical power system (EPS) are expected to do so efficiently. Standardized test procedures are necessary to establish methods for verifying inverter performance that leads to comparable results. These test procedures are provided as a repeatable, independent means of measuring inverter performance regarding maximum continuous power rating, conversion efficiency, and tare loss characteristics.
IEEE Standard 1547-2003 conformance of several interconnected microinverters was performed by Sandia National Laboratories (SNL) to determine if there were emergent adverse behaviors of co-located aggregated distributed energy resources. Experiments demonstrated the certification tests could be expanded for multi-manufacturer microinverter interoperability. Evaluations determined the microinverters' response to abnormal conditions in voltage and frequency, interruption in grid service, and cumulative power quality. No issues were identified to be caused by the interconnection of multiple devices.
The Sandia Inverter Performance Test Protocol defined two possible weighted-average efficiency values for use in comparing inverter performance, of which one definition was selected by the California Energy Commission for use in their Buydown incentive program leading to widespread use in the photovoltaic inverter market. This paper discusses the derivation of the efficiency weights originally proposed, and investigates the potential for defining new weights in light of increased array-to-inverter (DC-to-AC) system rating ratios in modern PV systems.
The high penetration of utility interconnected photovoltaic (PV) systems is causing heightened concern over the effect that variable renewable generation will have on the electrical power system (EPS). These concerns have initiated the need to amend the utility interconnection standard to allow advanced inverter control functionalities that provide: (1) reactive power control for voltage support, (2) real power control for frequency support and (3) better tolerance of grid disturbances. These capabilities are aimed at minimizing the negative impact distributed PV systems may have on EPS voltage and frequency. Unfortunately, these advanced control functions may interfere with island detection schemes, and further development of advanced inverter functions requires a study of the effect of advanced functions on the efficacy of antiislanding schemes employed in industry. This report summarizes the analytical, simulation and experimental work to study interactions between advanced inverter functions and anti-islanding schemes being employed in distributed PV systems.
Initiated in 2008, the Solar Energy Grid Integration Systems (SEGIS) program is a partnership involving the U.S. DOE, Sandia National Laboratories, private sector companies, electric utilities, and universities. Projects supported under the program have focused on the complete-system development of solar technologies, with the dual goal of expanding utility-scale penetration and addressing new challenges of connecting large-scale solar installations in higher penetrations to the electric grid. The Florida Solar Energy Center (FSEC), its partners, and Sandia National Laboratories have successfully collaborated to complete the work under the third and final stage of the SEGIS initiative. The SEGIS program was a three-year, three-stage project that include conceptual design and market analysis in Stage 1, prototype development and testing in Stage 2, and moving toward commercialization in Stage 3. Under this program, the FSEC SEGIS team developed a comprehensive vision that has guided technology development that sets one methodology for merging photovoltaic (PV) and smart-grid technologies. The FSEC team's objective in the SEGIS project is to remove barriers to large-scale general integration of PV and to enhance the value proposition of photovoltaic energy by enabling PV to act as much as possible as if it were at the very least equivalent to a conventional utility power plant. It was immediately apparent that the advanced power electronics of these advanced inverters will go far beyond conventional power plants, making high penetrations of PV not just acceptable, but desirable. This report summarizes a three-year effort to develop, validate and commercialize Grid-Smart Inverters for wider photovoltaic utilization, particularly in the utility sector.
Initiated in 2008, the SEGIS initiative is a partnership involving the U.S. DOE, Sandia National Laboratories, private sector companies, electric utilities, and universities. Projects supported under the initiative have focused on the complete-system development of solar technologies, with the dual goal of expanding renewable PV applications and addressing new challenges of connecting large-scale solar installations in higher penetrations to the electric grid. Petra Solar, Inc., a New Jersey-based company, received SEGIS funds to develop solutions to two of these key challenges: integrating increasing quantities of solar resources into the grid without compromising (and likely improving) power quality and reliability, and moving the design from a concept of intelligent system controls to successful commercialization. The resulting state-of-the art technology now includes a distributed photovoltaic (PV) architecture comprising AC modules that not only feed directly into the electrical grid at distribution levels but are equipped with new functions that improve voltage stability and thus enhance overall grid stability. This integrated PV system technology, known as SunWave, has applications for 'Power on a Pole,' and comes with a suite of technical capabilities, including advanced inverter and system controls, micro-inverters (capable of operating at both the 120V and 240V levels), communication system, network management system, and semiconductor integration. Collectively, these components are poised to reduce total system cost, increase the system's overall value and help mitigate the challenges of solar intermittency. Designed to be strategically located near point of load, the new SunWave technology is suitable for integration directly into the electrical grid but is also suitable for emerging microgrid applications. SunWave was showcased as part of a SEGIS Demonstration Conference at Pepco Holdings, Inc., on September 29, 2011, and is presently undergoing further field testing as a prelude to improved and expanded commercialization.
The Solar Energy Grid Integration Systems (SEGIS) initiative is a three-year, three-stage project that includes conceptual design and market analysis (Stage 1), prototype development/testing (Stage 2), and commercialization (Stage 3). Projects focus on system development of solar technologies, expansion of intelligent renewable energy applications, and connecting large-scale photovoltaic (PV) installations into the electric grid. As documented in this report, Advanced Energy Industries, Inc. (AE), its partners, and Sandia National Laboratories (SNL) successfully collaborated to complete the final stage of the SEGIS initiative, which has guided new technology development and development of methodologies for unification of PV and smart-grid technologies. The combined team met all deliverables throughout the three-year program and commercialized a broad set of the developed technologies.
Initiated in 2008, the Solar Energy Grid Integration (SEGIS) program is a partnership involving the U.S. Department of Energy, Sandia National Laboratories, electric utilities, academic institutions and the private sector. Recognizing the need to diversify the nation's energy portfolio, the SEGIS effort focuses on specific technologies needed to facilitate the integration of large-scale solar power generation into the nation's power grid Sandia National Laboratories (SNL) awarded a contract to Princeton Power Systems, Inc., (PPS) to develop a 100kW Advanced AC-link SEGIS inverter prototype under the Department of Energy Solar Energy Technologies Program for near-term commercial applications. This SEGIS initiative emphasizes the development of advanced inverters, controllers, communications and other balance-of-system components for photovoltaic (PV) distributed power applications. The SEGIS Stage 3 Contract was awarded to PPS on July 28, 2010. PPS developed and implemented a Demand Response Inverter (DRI) during this three-stage program. PPS prepared a 'Site Demonstration Conference' that was held on September 28, 2011, to showcase the cumulative advancements. This demo of the commercial product will be followed by Underwriters Laboratories, Inc., certification by the fourth quarter of 2011, and simultaneously the customer launch and commercial production sometime in late 2011 or early 2012. This final report provides an overview of all three stages and a full-length reporting of activities and accomplishments in Stage 3.
Grid tied PV energy smoothing was implemented by using a valve regulated lead-acid (VRLA) battery as a temporary energy storage device to both charge and discharge as required to smooth the inverter energy output from the PV array. Inverter output was controlled by the average solar irradiance over the previous 1h time interval. On a clear day the solar irradiance power curve is offset by about 1h, while on a variable cloudy day the inverter output power curve will be smoothed based on the average solar irradiance. Test results demonstrate that this smoothing algorithm works very well. Battery state of charge was more difficult to manage because of the variable system inefficiencies. Testing continued for 30-days and established consistent operational performance for extended periods of time under a wide variety of resource conditions. Both battery technologies from Exide (Absolyte) and East Penn (ALABC Advanced) proved to cycle well at a Partial state of charge over the time interval tested.
The ability to harvest all available energy from a photovoltaic (PV) array is essential if new system developments are to meet levelized cost of energy targets and achieve grid parity with conventional centralized utility power. Therefore, exercising maximum power point tracking (MPPT) algorithms, dynamic irradiance condition operation and startup and shutdown routines and evaluating inverter performance with various PV module fill-factor characteristics must be performed with a repeatable, reliable PV source. Sandia National Laboratories is collaborating with Ametek Programmable Power to develop and demonstrate a multi-port TerraSAS PV array simulator. The simulator will replicate challenging PV module profiles, enabling the evaluation of inverter performance through analyses of the parameters listed above. Energy harvest algorithms have traditionally implemented methods that successfully utilize available energy. However, the quantification of energy capture has always been difficult to conduct, specifically when characterizing the inverter performance under non-reproducible dynamic irradiance conditions. Theoretical models of the MPPT algorithms can simulate capture effectiveness, but full validation requires a DC source with representative field effects. The DC source being developed by Ametek and validated by Sandia is a fully integrated system that can simulate an IV curve from the Solar Advisor Model (SAM) module data base. The PV simulator allows the user to change the fill factor by programming the maximum power point voltage and current parameters and the open circuit voltage and short circuit current. The integrated PV simulator can incorporate captured irradiance and module temperature data files for playback, and scripted profiles can be generated to validate new emerging hardware embedded with existing and evolving MPPT algorithms. Since the simulator has multiple independent outputs, it also has the flexibility to evaluate an inverter with multiple MPPT DC inputs. The flexibility of the PV simulator enables the validation of the inverter's capability to handle vastly different array configurations.
Grid-tied PV energy smoothing was implemented by using a valve regulated lead-acid (VRLA) battery as a temporary energy storage device to both charge and discharge as required to smooth the inverter energy output from the PV array. Inverter output was controlled by the average solar irradiance over the previous 1h time interval. On a clear day the solar irradiance power curve is offset by about 1h, while on a variable cloudy day the inverter output power curve will be smoothed based on the average solar irradiance. Test results demonstrate that this smoothing algorithm works very well. Battery state of charge was more difficult to manage because of the variable system inefficiencies. Testing continued for 30-days and established consistent operational performance for extended periods of time under a wide variety of resource conditions. Both battery technologies from Exide (Absolyte) and East Penn (Advanced Valve Regulated Lead-Acid) proved to cycle well at a partial state of charge over the time interval tested.
This document provides an empirically based performance model for grid-connected photovoltaic inverters used for system performance (energy) modeling and for continuous monitoring of inverter performance during system operation. The versatility and accuracy of the model were validated for a variety of both residential and commercial size inverters. Default parameters for the model can be obtained from manufacturers specification sheets, and the accuracy of the model can be further refined using measurements from either well-instrumented field measurements in operational systems or using detailed measurements from a recognized testing laboratory. An initial database of inverter performance parameters was developed based on measurements conducted at Sandia National Laboratories and at laboratories supporting the solar programs of the California Energy Commission.
This report describes a Cooperative Research and Development Agreement (CRADA) between Salt River Project Agricultural Improvement and Power District (SRP) and Sandia National Laboratories to jointly develop advanced methods of controlling distributed energy resources (DERs) that may be located within SRP distribution systems. The controls must provide a standardized interface to allow plug-and-play capability and should allow utilities to take advantage of advanced capabilities of DERs to provide a value beyond offsetting load power. To do this, Sandia and SRP field-tested the IEC 61850-7-420 DER object model (OM) in a grid environment, with the goal of validating whether the model is robust enough to be used in common utility applications. The diesel generator OM tested was successfully used to accomplish basic genset control and monitoring. However, as presently constituted it does not enable plug-and-play functionality. Suggestions are made of aspects of the standard that need further development and testing. These problems are far from insurmountable and do not imply anything fundamentally unsound or unworkable in the standard.
Islanding, the supply of energy to a disconnected portion of the grid, is a phenomenon that could result in personnel hazard, interfere with reclosure, or damage hardware. Considerable effort has been expended on the development of IEEE 929, a document that defines unacceptable islanding and a method for evaluating energy sources. The worst expected loads for an islanded inverter are defined in IEEE 929 as being composed of passive resistance, inductance, and capacitance. However, a controversy continues concerning the possibility that a capacitively compensated, single-phase induction motor with a very lightly damped mechanical load having a large rotational inertia would be a significantly more difficult load to shed during an island. This report documents the result of a study that shows such a motor is not a more severe case, simply a special case of the RLC network.
The Million Solar Roofs Initiative has motivated a renewed interest in the development of utility interconnected photovoltaic (UIPV) inverters. Government-sponsored programs (PVMaT, PVBONUS) and competition among utility interconnected inverter manufacturers have stimulated innovations and improved the performance of existing technologies. With this resurgence, Sandia National Laboratories (SNL) has developed a program to assist industry initiatives to overcome barriers to UIPV inverters. In accordance with newly adopted IEEE 929-2000, the utility interconnected PV inverters are required to cease energizing the utility grid when either a significant disturbance occurs or the utility experiences an interruption in service. Compliance with IEEE 929-2000 is being widely adopted by utilities as a minimum requirement for utility interconnection. This report summarizes work done at the SNL balance-of-systems laboratory to support the development of IEEE 929-2000 and to assist manufacturers in meeting its requirements.
The National Photovoltaic (PV) Program is sponsored by the US Department of Energy and includes a PV Manufacturing Research and Development (R and D) project conducted with industry. This project includes advancements in PV components to improve reliability, reduce costs, and develop integrated PV systems. Participants submit prototypes, pre-production hardware products, and examples of the resulting final products for a range of tests conducted at several national laboratories, independent testing laboratories, and recognized listing agencies. The purpose of this testing is to use the results to assist industry in determining a product's performance and reliability, and to identify areas for potential improvement. This paper briefly describes the PV Manufacturing R and D project, participants in the area of PV systems, balance of systems, and components, and several examples of the different types of product and performance testing used to support and confirm product performance.
Electrical surges on ac and dc inverter power wiring and diagnostic cables have the potential to shorten the lifetime of power electronics. These surges may be caused by either nearby lightning or capacitor switching transients. This paper contains a description of ongoing surge evaluations of PV power electronics and surge mitigation hardware at Sandia.