IEEE Power & Energy Magazine - September/October 2020 - 67

✔ Communication breakdowns and energy supply break-

downs: This is the worst scenario. The breakdown of both
systems requires the assistance of intermediate systems
or aggregators, which take control and perform various
procedures to restore services.
The FSPs use the available DERs (RESs, storage, and
V2G) and the customer load to better operate the DSO grids.
The implementation of a local market to gather and transmit
information for the FSP will enable the interoperation between
the parties (TSO and DSO) and different service providers.
Of course, the local market will reward behavior intended to
reduce congestion according to grid requests. Thus, in a local
market oriented to congestion management based on FSs provided by aggregators, standard protocols, such as Open Automated DR (ADR), ensure the resource control and information exchange. This provides a scalable and reliable strategy
for the DSO to ensure the continuity of power quality and supply through distributed congestion management.

The OpenADR Standard Protocol
and Other Alternatives
OpenADR is a standard protocol developed by the OpenADR
Alliance. It provides a DR solution for asset management
(including aggregators). This open standard is based on "Energy
Interoperation 1.0" from the Organization for the Advancement
of Structured Information Standards (OASIS). However, energy
interoperation (EI) includes additional services that enable the
protocol to implement a transactive energy strategy.
The architecture of the OpenADR protocol is based on a
hierarchical organization of different nodes in which a virtual top node (VTN) could control one or several virtual end
nodes (VENs). At the same time, one VEN could act as a final
node or an aggregator, which would adopt a VTN role for
other VENs in the hierarchically lower layer. Figure 1 gives
an example of this hierarchical architecture. In this schema,
the OpenADR protocol allows only a tree-based schema. In
this way, a VEN could be placed at the head of either a smart
building or a complete power grid since the services are the
same and take effect in all aggregated resources. Thus, each
aggregator level simplifies the downstream control and regulation of the available resources. This concept, which simplifies the management of the power grid, is similar to virtual
power plants (VPPs). A VPP is a system that integrates several types of power resources to give a reliable overall power
supply, provide ancillary services to grid operators (for grid
stability), and serve as a cloud-based central or distributed
control center that takes advantage of ICTs. In this sense,
both strategies provide high scalability and reliability, simplifying the complexity of the power grid.
The main objective of the OpenADR protocol is the management of a good. Of course, this good is primarily active
power, but it is possible to manage reactive power, capacity, other characteristics of power supplies, and even goods
outside the electric energy business, such as water and gas.
The available documentation about the OpenADR protocol
september/october 2020

is completely oriented to the electric energy market. In this
way, the OpenADR protocol is the first attempt to obtain an
implementation of EI that is oriented to the electric energy
market. OpenADR has five main services:
✔ Registration message (EiRegistration, according to
the OpenADR terminology): used in the joining process between a VEN and a VTN
✔ Event message (EiEvent): enables flexibility requests
to be sent to VENs
✔ Reporting message (EiReport): facilitates sharing information among OpenADR nodes
✔ Opt message (EiOpt): used by the VEN to confirm or
deny a request and to share the availability of the node
to receive requests
✔ Pull-mode message (OadrPoll): used to know the VEN
status (used only in pull mode).
The OpenADR and EI standards are harmonized with others (Figure 2) from the International Electrotechnical Commission (IEC). For example, the 61968 [Common Interface Model
(CIM)/Distribution Management] and 61970 (CIM/Energy
Management) standards address the CIM and the component
interface specification for distribution management systems
and energy management systems. The eMIX standard (from
OASIS) is the information standard related to the OpenADR
and EI standards. The eMIX is interoperable with the other
protocols from the IEC and IEEE. The main difference is that
the IEC CIM stores the period that registers the start and end
dates and the hour (timestamp), and the eMIX registers the
initial timestamp and the duration. Additionally, there is a
high degree of interoperability with other protocols, such as
IEEE Standard 2030 (Guide for Smart Grid Interoperability
of Energy Technology and Information Technology Operation
With the Electric Power System and End-Use Applications
and Loads) and IEC 62325 (Framework for Energy Market
Communications).
Additionally, the OpenADR and EI protocols are open
access, but the standards from the IEEE and IEC are not.
Although OpenADR is an open standard, the cybersecurity that it implements is sufficient to operate in power grids
and avoid cyberattacks. Standard security is mandatory and

VTN

VEN
VTN

VEN
VEN

VEN

figure 1. The hierarchical relation among a VTN and
VENs in OpenADR for distribution system management.
ieee power & energy magazine

IEEE Power & Energy Magazine - September/October 2020

Table of Contents for the Digital Edition of IEEE Power & Energy Magazine - September/October 2020