Distributed Energy Resource Connectivity: Closing the Communications Gaps
There are several challenges confronting utility communication system architects and engineers as they design and deploy networks to transport the increasing varieties, velocities, and volumes of data for grid management. One of the biggest challenges to connect distributed energy resource (DER) assets like solar panels or batteries to the distribution grid is the definition of standards that enable easy data integration – and allow for seamless communication and control of smart inverters and local controllers (e.g. microgrid controllers).
A tremendous amount of work has been accomplished in the development of DER communication requirements to help ensure easy integration. Since 2009, the Electric Power Research Institute (EPRI) has been involved in global activities to develop requirements and working with standards development organizations such as the International Electrotechnical Commission (IEC) to have these requirements codified.
But communications gaps persist. Compliant but NOT Interoperable
To date, functional definitions have been captured in IEC standard 61850, and this has been mapped by other standards communities into standards such as IEEE 2030.5, Modbus, and DNP3. While products are being built to these standards, EPRI testing has found that products from different vendors, built to the same standard, are not able to communicate. That means there are either gaps in the interpretation of standards, or flexibility in implementation of the standards, that allows vendors to create compliant products that are not interoperable. This gap in communications interoperability results in systems that won’t economically scale as the maintenance and customization required to support numerous interfaces makes support cost prohibitive. That has impacts to the utility and ultimately to customers.
There has been substantial progress in developing DER data integration capabilities, but more R&D is needed to build a collaborative and consensus-based methodology
Circling Back: From the Field to Central Control
The latency between events that occur at the system edge and decisions made at central control creates challenges that have given rise to the Open Field Message Bus (OpenFMB). This framework defines a logical bus in the field by which devices can communicate locally and make decisions autonomously. However, central control is not completely removed from the mix. Leaving a gap in communications between central control and distributed intelligence creates the potential for these systems to work at cross-purposes, delaying or preventing needed action for grid stability and reliability. In addition, a gap in communication between distributed intelligence and central control may restrict security monitoring and response. When decisions are made in response to events in the field, central control needs to be informed of these changes, and control goals that derive from the broader grid may need to be communicated to OpenFMB devices at the edge to modify their activity.
Supporting New Requirements and Accommodating Latest Technologies
Into this situation enters Blockchain, which is being considered by some as a better way to support the concept of transactive energy; the ability for prosumers to buy and sell energy to any other party transacting on the grid (not just the utility) while also providing a built-in mechanism for securing the transactions. As more distributed generation devices like solar and energy storage are connected to distribution grids, grid stability, reliability, and safety concerns are growing. These devices will need to be monitored and managed – but what is the best communications network architecture to answer these concerns? One likely answer is that we will need to organize individual DERs into groups that can be managed in aggregate. Grid operators have identified many levels at which such aggregation is needed, including buildings, microgrids, campuses and neighborhoods, and feeders and substations. Hierarchical methods for integration of DER allow this functionality via the IEC 61968- 5 standard for distributed energy optimization, but this effort is still in draft and may be a year from being published.
Cyber security concerns also are growing. Just a few years ago, DER deployments were low and loss of control or even malicious control had limited impacts. But the trajectory of abundant, renewable energy that society desires requires high numbers of DER that could have major impacts if grid management is disrupted. There also is increasing awareness that cyber secure communication networks are required to manage DER and ensure grid reliability, stability, and safety.
Many Moving Parts
Communication interoperability among vendors, appropriate placement of intelligence for distributed grid management, useful communications with central controls, and secure infrastructure to ensure grid stability, reliability, and safety, are only a handful of many challenges outlined in this article. Utility grid devices and DERs have different communication needs due to how they prioritize data traffic and how sensitive they are to latency or delays. The rising interest in transactive energy and potential applications of Blockchain technology create new unknowns bedeviling utility communications professionals as they attempt to discern the future demands on their networks. Just like a highway engineer bases a new road design on traffic volumes, types of vehicle traffic, and traffic patterns, network designers need guidance that doesn’t yet exist to build their data transport infrastructures. This gap in knowledge is possibly the most dangerous gap of all.
Closing the Gaps through Architecture
EPRI launched a major research effort, Information & Communication Technology and Security Architecture for DER, to address the challenges confronting utilities. This research is organized into five tracks:
• Core Architecture– Guidelines, roadmap development, RFP language, and technology transfer
• Lab Evaluation (Edge-of-Grid) – Protocols, applications, and distributed intelligence
• Lab Evaluation (Distributed Energy Resource Management Systems, Markets) – Market operations, control strategies, IoT platforms
• Lab Evaluation (Cyber Security) – Security for DER devices and systems
• Demonstrations – taking lab work into the field for evaluation at participating utilities
EPRI will continue contributions to DER communications standards development efforts, with an emphasis on scalability, manageability, and security of protocols. EPRI has published “Quick Insight” reports that provide some initial guidance to utilities about Blockchain
There has been substantial progress in developing DER data integration capabilities, but more R&D is needed to build a collaborative and consensus-based methodology, a methodology that works even before a utility has a clear plan of action and the network architecture it needs to manage DER that conforms to the overall mission of ensuring reliability, stability, and safety.