Ingenieur Vol. 75 ingenieur July 2018-FA | Page 46

INGENIEUR
demand and future availability of generators. The
power system must thus be able to manage both
variability and uncertainty.
Today, various combinations of hydro and
thermal generation are used to manage variability,
and these operate as a portfolio to meet demand.
Each generator has various characteristics, but
the most important one for this article relates to
flexibility.
Daily and weekly patterns of system demand
often involve short-term forecasting. Knowing the
time horizon over which significant ramps (MW per
minute) take place such as during the morning
demand rise has allowed operators to plan and
implement effective strategies for flexibility.
Traditionally, long-term resource planning
with conventional thermal and hydro generation
requires little information about the variability of
the net demand/load in time scales of minutes to
days, whereas characterising the daytime cycle
is an important feature of day-ahead operational
generation dispatch planning. Power system
planners/operators are familiar with the ‘system
needs’ in order to ensure that the balance between
supply and demand is maintained continuously
by refining the generation output and demand
delivered by the wholesale electricity market.
These ‘system needs’ in the order they are
required from real time are:
- System Inertia and Rate of Change of
Frequency (RoCoF)
- Frequency Response
- Reserve
- Reactive Power/Voltage Support
- Blackstart
System Inertia comes from the rotational
energy stored in the synchronous generators of
gas-fired, coal-fired and hydro power plants. Inertia
determines how quickly the 50Hz Alternating
Current (AC) system frequency will change when
there is an imbalance between generation and
demand; Inertia stabilises the frequency and
reduces the RoCoF. The lower the level of Inertia
on the system, the higher the RoCoF will be in the
event of a sudden generation or demand loss.
As levels of solar photovoltaic/distributed
renewable energy generation continue to increase
in our future national energy generation mix
portfolio, System Inertia is expected to decrease.
Thus, the challenging issue of managing System
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Inertia and RoCoF is of utmost importance in
order to secure the future Malaysian power grid
against increased probability of partial system
collapse.
One characteristic that variable renewable
generation (VG) resources, such as solar
photovoltaic, have in common is that their
generation output is governed by atmospheric/
climatic conditions and are consequently difficult
to predict over some time scales. Thus, large-
scale penetration/integration of VG would lead
to increases in the variability and uncertainty in
the system’s generation output, driving a need for
greater flexibility; this is required in order to ensure
the overall demand-generation balance [50Hz
system frequency] is maintained at all times.
In this same Policy Paper [Ref.2], it was
recommended that the Government design and
shape its future long-term (at least up to 2050)
electricity generation energy mix with clear targets
for each primary fuel portfolio based on the
following factors:
• extent of concern about domestic energy
security;
• availability and price of ‘legacy’ indigenous
natural gas for electricity generation;
• extent of penetration/integration of
renewable variable generation, particularly
• large-scale solar PV plants (LSS);
• cost and availability of imported coal for
electricity generation;
• cost and availability of the nuclear option
for electricity generation; and
• environmental policy objectives expected
over the next decade.
Each of these key factors requires supportive
policies and regulatory processes to enable
appropriate commercial decisions to be taken in a
prudent and timely manner.
RENEWABLE AND DISTRIBUTED
GENERATION
Variable Generation (VG)
According to the MGI Report [Ref. 1], solar and
wind power could represent 15 to 16% of global
electricity generation in 2025, up from only 2%
in 2013. The incremental economic impact of
this growth could be US$165 billion to US$275