IEEE Power & Energy Magazine - September/October 2019 - 65

describing device capabilities and limitations, sending and
acknowledging instructions, and updating device status and
measurements, as shown in Table 1.

Software Integration Platform
The home gateway software platform used in EFR-II is
the Distributed Energy Flexibility Platform and Interface
(dEF-Pi), an open source IoT platform. As shown in Figure 3,
dEF-Pi is the software integration platform that hosts several
software components. dEF-Pi contains a management dashboard for orchestrating a large number of user processes. It
also provides the end user with a dashboard that contains
device-specific operational data and insights, including control functionalities.
By starting off with a declarative description of the service
interfaces, code generators automatically create the code skeleton, ensure compatibility with other services, and handle service runtime management, such as (re)configuration or redeployment of software from a gateway to the cloud.
EFI protocol refers to device drivers as resource managers (RMs) to communicate steering instructions with the
devices and runs monitoring activities for verification purposes. The RM's role is to translate status information and
control parameters to the EFI as well as adding knowledge
about the behavior of the device at hand. Therefore, the
RM implementation requires specific customizations (for
example, device-specific protocols or control actions) that
depend on the device at hand. Figure 5 shows the battery
driver, which communicates using Modbus over Transmission Control Protocol (TCP), whereas the PV switch uses
ZigBee (based on the IEEE Standard 802.15.4), and the solar
panel inverters are interfaced with using WebSockets to an
external cloud service.

The CEM sends aggregated bids for all connected devices to the auctioneer and, in turn, receives a set point,
represented as a market clearing price from the auctioneer.
Note that, for EFR-II, this price was fictional and did not
represent a real monetary value. In a fully operational rollout, this price should reflect the true market value of the
traded flexibility. These prices are translated to power set
points, which are then sent to the devices. For every EFIconnected device, a corresponding device agent implements
the bidding strategy (price and load) based on the EFI class
the device falls in. A power set point is converted to an
instruction (if applicable) and sent to the device over the
dEF-Pi connection.
The aggregator hosts the external logic (from the household's point of view), which, in EFR, is the PowerMatcher
Central Logic (PMCL), where the auctioneer agent is hosted.
This entity receives aggregated bids from all household
CEMs and sends back the price, which meets a desired

EFI

Dispatch Control Algorithm
The RMs report the devices' status and open up control
possibilities through the EFI to each household's customer
energy manager (CEM) (see Figure 5). The CEM is specific
for the aggregator control algorithm, which, in this case, is
PowerMatcher.

figure 4. The EFI acts as a standardized protocol,
allowing different control algorithms to communicate
with different devices.

table 1. The four categories of devices with regard to their energy flexibility capabilities, as defined by the EFI.
Description

Examples

Inflexible

Cannot be controlled and has no flexibility (with the exception of
curtailment), but it is measurable and may provide forecasts.

PV panels, conventional domestic loads
(nonsmart devices), and windmills

Adjustable

Flexible in production/consumption level and not constrained by a
buffer. They have a wide range of control possibilities without many
restrictions and therefore usually offer considerable flexibility.

Generators, dimmable lighting, heat
pumps, and gas boilers

Shiftable

Process that can be shifted in time, i.e., it has a deadline.

Washing machines, dryers, and
dishwashers

Storage

Flexible in production/consumption level but bounded by a
buffer. Deadlines and required fill levels constrain the flexibility
of this category.

Freezers, combined heat and power,
thermal buffers, stationary batteries,
and electric vehicles

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IEEE Power & Energy Magazine - September/October 2019

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