Integrated modelling review - Modelling Distributed Energy Resources in Energy Service Networks - page 23

PHEV operation brings to electrical engineering could be seen as analogous, although
with its particular differences, to the many issues and principles that surround
hydrothermal power plant coordination studies [121].
The chance of electric battery vehicles to behave as meaningful storage facili-
ties has made academia and industry develop the V2G power concept. This field of
research aims to devise schemes that allow vehicle batteries to inject power back to
the grid whenever the utilities require the service [102]. As it can be expected, in order
for V2G services to function properly a set of monitoring and control equipment is
required alongside advanced power electronics, allowing these devices to facilitate
proper communication between PHEVs and grid operators [74,122]. Hence, despite
it is still far from application, theoretical work on modelling V2G and formulating its
business model has emerged recently in the literature [123].
Two key features are needed to add V2G capability to a PHEV. The storage
units need both on-board power electronics and real-time controls, so the DNO can
request power exactly when needed. According to these intrinsic characteristics, the
greatest near-term promise for business applications is quick-response high-value
services. Therefore, it is plausible, when penetration is considerable, for PHEVs to
play a novel ancillary role in maintaining grid reliability that supports the delivery of
electricity [124].
It has been proposed V2G services in a given area could help alleviate localised
distribution system issues; some ancillary services offered could include [125]:

Peak power : Injections required at times of day when high demand is expected;

●

Direct load control : Demand increments or reductions from multiple vehicles
based on grid conditions or electricity costs;

●

Spinning reserves : Refers to generating capacity that is up and running ( i.e. in
sync with the grid but not actually contributing power);

●

Regulation services : Are used to fine-tune the balance between power generation
and demand ( i.e. in terms of the voltage and the frequency of the grid).

●

Recently some practical research of V2G applications has been performed and
reported in the literature. Reference 126 proposes an aggregation function to repre-
sent an impartial body between grid operators and multiple PHEV owners, in which
the body sends wireless dispatch commands to the vehicles. The study indicates that
the value created by V2G services exceeds the battery wear out costs under most
operating assumptions. Meanwhile, Reference 127 states that the most profitable
V2G services for the PJM utility (US based grid operator) are meant to be frequency
regulation and spinning reserve functions.
Although not many, this section finalises by commenting on various publications
that have assessed the impacts optimal PHEV operation strategies might have on
electric network operation.
Since non-coordinated PHEV charging can lead to increased voltage fluctuations
in local networks, a coordinated charging strategy is proposed to minimise power
losses and to maximise the grid load factor [103]. The study develops a sequential
quadratic optimisation to solve the load flow analysis. Results provide a glimpse at
how voltage profiles can breach operating limits if proper monitoring and controls
are not in place.