consumption are available, it is possible to infer reaction of a
DER by the impact they have on the grid.
Heussen et.al. [6] classifie indirect control into four categories:
control with indirect functional variables, independent
local control, indirect control via price signals and control
with internal market platform. In this paper independent local
control (called here autonomous control) and control with
internal market platform (called here transactional control) are
separated from indirect control as depicted in Figure 1 and
described in section II-D. Indirect control, following [6], is
divided into two categories:
1) Control with indirect functional variables: A control
scheme in which a signal containing a functional variable is
sent from an external controller to a DER in order to influence
the DER operation. An example of a functional variable can be
a local set-point thermostat temperature in a heating system.
The external controller objective is to modify heating system
power consumption without knowledge of heaters state. Since
the state is unknown and there is no control feedback, the
system response is non-deterministic. Observable or estimated
aggregated response, for example the heating system power
consumption, can be used to generate the functional variable
signal. Statistical models can be used to reduce the mismatch
between the control objective and the system response.
2) Indirect control via price signals: A control scheme
based on issuing energy prices to DERs in order to alternate
its operation. Indirect control via price signals is further
divided into instantaneous price operation and scheduled price
operation. In the instantaneous price operation scheme the
control signal consists of a single price p and time stamp
signal that states the time when the price becomes valid. In the
scheduled price operation, the signal is a schedule s of future
prices, consisting of time series of prices and time stamps ,
where s = {(ti
, pi)}, i ∈ N