IEEE Electrification Magazine - June 2017 - 23

Time Horizon
Day D-1

Day D
UC and
Indicative Production
Scheduling
(24 h of D)

Updated UC and
Production Scheduling
(Every 20 min, with a
4 h Look-Ahead
Horizon)

ED
(Every
5 min)

DAS

RTD + AGC

Real Time

Market Participants
and NII Operator
Declarations
Load Forecast and
Nondispatchable RES
Production Forecast

Figure 8. Management cycles of NII generation.

xx
The first includes the standard

Three main
processes constitute
the day-ahead and
intraday generation
management: rolling
day-ahead
scheduling (RDAS),
dispatch scheduling
(DS), and real-time
dispatch (RTD).

day-ahead UC problem, over the 24
hours of the following dispatch
day D, using one-hour dispatch
intervals. RDAS is performed on
day D−1, preceding dispatch day D,
to initially determine a commitment schedule for the system's
dispatchable generating units.
Input data to the RDAS problem
are the declarations of the relevant market participants (load
representatives and dispatchable
generators), as well as load and
nondispatchable RES power forecasts carried out by the NIIPS operator. Participants' declarations and
NIIPS operator forecasts are submitted by 18:00 of D−1, whereas
the results of the RDAS optimization should be available
by 21:00 of the same day, for all 32 NIIPSs.
xx
The second RDAS process constitutes an intraday
revision of the UC problem, for the second half of
the dispatch day D (B's RDAS period), using updated
and more accurate data mainly in terms of RES
power and energy forecasts. The updated participants' declarations should be submitted by 08:00 of
day D, while the results of the updated RDAS process
for the second half of dispatch day D should be
announced by the NIIPS operator by 10:00 of the
same day.

The NIIPS market differs from the
standard electricity markets mainly in
that market participants do not submit
priced bids. Rather, UC and load dispatch are performed based on the
objective variable operating cost of
conventional units, while RES energy
enjoys priority dispatch. Hence, generator entities participating in the RDAS
submit availability declarations for
their units, and dispatchable RES stations submit either energy offers
regarding the total quantity of available
energy to be dispatched in day D (see
S. Papaefthimiou et al.) or hourly generation schedules.
DS is a core optimization problem
related to the intraday management of
NIIPS generation, aiming at determining, at a time closer to the actual operation, the final commitment status of dispatchable units and the initial output
scheduling (ED). DS is executed periodically every 15 or
20 min, using a four-hour look-ahead horizon, while in
small and medium-sized NIIPS with no dispatchable RES
units, DS may be executed at longer intervals. Inputs for the
DS problem are updated short-term forecasts, data received
from the NII SCADA system, and the actual availability and
operating status of all generating units. Further, DS incorporates all necessary operating reserve requirements (primary, secondary, and tertiary reserves) to ensure secure
operation of the system. DS results constitute the
IEEE Electrific ation Magazine / j une 2 0 1 7

Table of Contents for the Digital Edition of IEEE Electrification Magazine - June 2017