By AHM Jakaria, Engineer/Scientist III, Electric Power Research Institute (EPRI)
Distributed energy resources (DER), including solar photovoltaics (PV), battery energy storage (BES) and electric vehicles (EV), play an increasingly significant role in decarbonizing the electric sector. In recent years, DERs have increased capabilities, including grid-supportive smart inverter functions. However, increased DER capability means increased complexity.
In 2018, the Institute of Electrical and Electronics Engineers (IEEE) released a standard that is central to solar and battery storage systems. The standard, IEEE 1547-2018, applies to all kinds of DER and defines grid-supportive functions and standard communication capability aimed at enabling more to be deployed without causing voltage, thermal or other violations on the power grid. As interconnection codes are updated, states and utilities are typically requiring these new capabilities.
The functionalities defined in IEEE 1547-2018 involve a large number of settings — the parameter values that are programmed into a plant or device to set it up. One example is a function called Volt-Var control. As illustrated in Figure 1, this function defines how the plant’s reactive power (Vars) must automatically adjust as the local voltage varies. The settings for this function include a set of <X,Y> points that trace out a piece-wise linear “curve” that the plant is to follow.
While grid-support capability provides many benefits, it also brings the challenge of increased complexity and the additional steps required to (a) receive settings from the local utility, (b) program devices and (c) provide evidence that the process was completed correctly.
Depending on the situation in a given region, required settings may be the same for all DER or may vary by DER size, type or the feeder where they are being connected. In some cases, unique settings may even be determined for each DER during the interconnection application process.
Why this is an issue
As quantities of DER rise, it is critical that settings are correct. However, with manual processes and high complexity, mistakes are common. Detecting and correcting these mistakes can be expensive and cause delays in commission testing. Getting them wrong could result in damage to consumer equipment or the grid itself.
The diversity of settings is compounded in the variety of ways in which they are exchanged between parties. There are thousands of utilities in the U.S. and until recently, each one had to come up with its own format when sharing required settings, such as an Excel spreadsheet or PDF document. Not only are the file types different, but also the way the information is organized inside the file, the names used to identify each setting and the format of numbers all may differ from one company to the next. This makes it challenging to interpret the provided settings and get a DER site configured properly.
It is not just a one-way problem. When developers provide evidence of configured settings back to utilities, how should they report it? Some use a series of photographs taken of the display screens of inverters. Others use inverter-vendor-specific files that include hundreds of parameters with unrecognized labels, leaving utilities to figure out which ones are the required items. These verification processes are time-consuming and error-prone, adding cost and delays for all parties.
The solution: A common file format
Two years ago, EPRI and industry stakeholders set out to fix this problem. An open working group was formed, including experts from academia, consultancies, utilities, DER manufacturers and national laboratories. The group met weekly, debated options and found consensus on how to address the issue.
The solution was to define a common file format for the exchange and storage of configuration settings for DER. The chosen format is human-readable so that it is possible to inspect without any special tools, but can also be used electronically by software systems that automatically generate, exchange and apply settings without a human in the loop. The file format was designed to serve three key uses:
- Utilities expressing required DER settings to developers
- DER developers providing evidence of as-programmed settings to utilities
- DER settings storage and tracking throughout software systems
The new file format was designed to be consistent, to the extent possible, with certification results reporting format identified in IEEE 1547.1-2020, which defines a test procedure for DER, based on the IEEE 1547-2018 standard. Two aspects were kept consistent:
- A comma-separated values (CSV) file format was used. A CSV file is lightweight in terms of size and the processing required to parse it. CSV can be opened or created by almost any text editor or Excel.
- Parameter labels, data types, units and possible value options in the new settings file format were kept as consistent as possible with the performance capability indicators identified IEEE 1547.1.
The specification for the standard file format is available for free download here. The document explains the criteria needed to create a DER settings file in the standard format. Developers, installers and utilities are encouraged to use this specification to create DER settings files for exchange with other parties.
How can companies benefit from this development? Let’s consider a few application examples:
Application example 1: Utility-specified settings
A new solar or storage device is being interconnected and the local utility must convey to the developer what settings are required. Whether these settings are uniform system-wide or site-specific, the need is the same. The utility provides the developer with a CSV file through download, for example, from an online application-management system.
The utility has created the file in the standard format. This eliminates ambiguity regarding what content is in the file, the labels for each parameter, the units for each value, etc.
When the developer receives the file, they understand its content because they are familiar with it. It is the same format used by utilities everywhere. Because the format is broadly used, the developer’s software systems and site-programming tools load, parse and apply it to DER. Staff can inspect the file, but the programming of settings to the DER is handled electronically and automatically.
Application example 2: Developer-applied settings
During commissioning testing, or at some time thereafter, a developer wants to read the configuration from a solar or storage DER so they can provide it to the utility. The developer connects their field tools to the DER’s communication interface and reads the settings. The tools save or export these settings in the standard CSV file format which is later uploaded to the utility’s online application management system.
When the utility receives the file, its content is understood because they are familiar with it. It is the same format used by developers everywhere. The utility’s software systems are able to handle the file electronically and instantly compare the applied-settings to what was specified, to verify that everything is correct. In the ideal case, the entire process of DER configuring, read-out and verification by the utility could happen in seconds.
While the main purpose of the standard file format is the error-free exchange of settings, it could also be used as the native storage format in systems-of-record for utilities or developers. For example, a developer may maintain a database of all the DER they have deployed, including the settings that they applied to each. If in the future, there is a need to review this information, it could be accessed and directly shared with others in the CSV format.
AHM Jakaria works as an Engineer/Scientist III at the EPRI in the Distributed Energy Resources (DER) group. Smart DER configuration settings and DER management systems (DERMS) are some of his research areas and can be reached at email@example.com. The outcome of this work will contribute to future developments of the IEEE 1547 standards.