IEEE Electrification Magazine - September 2014 - 52

300
kN
250

SERIE 103 Tare Weight: 425 t; Power: 8,800 kW;
Maximum Speed: 350 km/h
Traction 100%
(8,800 kW)
Traction 75%
(6,600 kW)

200
150

Traction 50%
(4,400 kW)

100
50
0

Ramping Drag 25 mm
Horizontal Drag
50

100

150

200
km/h

250

300

350

-50
Rheostatic Brake
-100

-150

-200

-250

Regenerative
Brake with
Maximum
Power
(8,800 kW)

-300
Figure 2. The maximum traction and braking forces for series 103
trains from Renfe, Spain. (Figure courtesy of Luis E. Mesa.)

minimum time driving (MTD), which
corresponds to the fastest way of driving while satisfying the limits of the rolling stock and the infrastructure. The
commercial driving is normally
designed by adding some time margins
to the MTD to allow the trains to
respond to the small perturbations that
occur in real operation (typically delays).
It is important to highlight that
each driving style can lead to a very
different spatiotemporal distribution
of the power consumptions (see Figure
3) and, consequently, to significantly
different requirements for the RPS.
This flexibility is the key for conceiving smart strategies for driving the
trains for many different purposes,
such as saving energy and augmenting the traffic capacity.

I E E E E l e c t r i f i c ati o n M agaz ine / september 2014

To manage the traffic flow, each train has to fulfill a
schedule, which means that it must reach the next station
[or the next regulation point (RP)] in the specified time
(see Figure 4), within a tolerance (represented in green).
The time in these intermediate RPs is checked to allow for
a better adjustment of the train driving: if the train arrives
too early, it can slow down or, conversely, drive faster if it
is delayed.
In the last decade, many researchers have worked intensively to design ecodriving strategies, i.e., driving strategies
that minimize the energy consumption of the train. Important energy savings have been achieved by smartly adjusting
the coasting sections, which avoids consuming energy that
will be given back to the catenary (or wasted in rheostats)
later. However, coasting typically augments the trip duration,
and, therefore, a tradeoff between energy savings and trip
duration has to be found by using optimization techniques.
The design of schedules optimized to enhance operation has also been a very active research topic. For
instance, in dc railways, such as commuter trains and
metros, the synchronization of departures, arrivals, and
driving strategies has been used to improve the receptivity
of the contact line (catenary or active rail) when regenerative braking is used, leading to significant energy savings.
There are also experiences in which similar techniques
have been used to improve the traffic capacity of a line.
Both techniques, ecodriving and the smart scheduling,
have been very successful in improving the performance
of electrical railways, especially in terms of energy efficiency, when the operation is planned. As they require a
huge computational effort, their application to real-time
control is very unusual today.

the Next-Generation railway esGs
Although improving energy efficiency has often been
claimed as the main change vector toward the future
railway ESGs, it is important to highlight the enhancement of the controllability of the electrified railways that
can be achieved with RESG technologies. By managing the traffic and electrification in an integrated way, the
RESG can efficiently solve different
operation problems (capacity limitations, changes in the planned operation, etc.), including many issues that
cannot be addressed within the traditional control schemes. To allow this,
the RESG has to integrate the missions of the railway (to move trains to
transport goods and persons) and the
electrification (to supply the electricity required by the trains), as represented in Figure 5.
To explain why the RESG can
improve the operation of electrified

By managing the
traffic and
electrification in an
integrated way, the
RESG can efficiently
solve different
operation problems
that cannot be
addressed within the
traditional control
schemes.

Table of Contents for the Digital Edition of IEEE Electrification Magazine - September 2014