Architecture of Computing Systems (Lecture Notes in Computer ...

Decentralized Energy-Management to Control Smart-Home Architectures 157
high demand in the grid during a specific timeslot. The aim of the SHMD is to
re-schedule demand sets to timeslots rated with the lowest possible signal value.
Thus, the grid’s balancing process of supply and demand is supported.
In addition to the 24h-signal, the SHMD is able to receive a short-term signal
from the grid operator. In this way, the grid operator is able to communicate the
condition of a short-term imbalance in the grid to the SHMD. The smart-home
can react to this signal e. g. by interrupting the charging process of the car in
case of requiring positive balancing power, or by starting the charging process
in case of the demand of negative balancing power. The SHMD calculates a
scheduling of every device to satisfy the given signals on the one hand and to
fit the appliance’s degree of freedom on the other hand. The signals reflect the
predicted load and short-term imbalances in the grid. In this way the SHMD is
able to schedule its appliances related to the grid’s condition.
Thus, the controller unit of the SHMD tries to match the demand set of each
appliance with a certain degree of freedom with the received signals, referred as
matching in Fig. 4. After this a set of rules can be generated and sent to each
appliance. These rules contain instructions for the appliances, in which timeslot
they should start or break its operation. The controller unit of each appliance’s
observer/controller unit contains a simple set of static rules to interact with
the appliance. It allows the local observer/controller unit to adjudicate finally,
combined with the given rule from the SHMD, whether to switch on the appliance
or not. This decision is based on the capability to operate; a washing machine
for example should only operate, if it is filled up with laundry.
In [8], a related approach is introduced. Any smart-home is equipped with
a Bedirectional Energy Management Interface (BEMI), which is able to control
smart appliances and to measure electrical values indicating the grid’s condition
locally. The BEMI is able to optimize the operation of locally connected controllable
appliances. The BEMI-approach focuses the communication between the
Energy Service Provider and his low voltage grid connection points, while the
present approach concentrates on in-house monitoring and controlling based on
external signals.
5.1 The Local Observer/Controller Unit
Most of the modern household appliances are complex devices. Thus, it is not
possible to interfere directly in the program of the appliance’s native controller.
For this reason, the appliance is monitored by a local observer, as shown in Fig. 4,
and will be managed by its local controller only with the simple command either
to operate or not. Each intelligent appliance is fitted with a set of sensors
to detect its current state. Depending on the household appliance, different parameters
may be measured, and a parameter common to all parameter sets is
the power supply. Based on the assumption that for every household appliance
there is an approximated typical demand set, we can draw conclusions from the
current state of the appliance. The potential of re-scheduling depends on the
degree of freedom each appliance has. A set of classes regarding the degree of
freedom can be defined. The operation of these appliances with a high degree of