What are Ancillary Services In Power System ?

What are
Ancillary
Services
In Power System ?

Ancillary Services ensure a proper operation of the power
grid. The grid operators (transmission grid operators and
distribution grid operators) are responsible for ancillary
services.
To ensure a reliable power supply, it is necessary that
frequency, voltage, and power load remain within certain
limits.
This does not happen automatically, but through continuous
corrections: namely, ancillary services.

The most renowned service is probably the frequency
control/balancing energy.
Even in the event of a blackout, ancillary services help restart the
power grid as quickly as possible.
Ancillary services can be divided into four sections: Frequency
measure, voltage measure, supply reconstruction, and
operational management.

Frequency Measure
System Services for Frequency Maintenance
The frequency within a power grid is either 50 or 60 Hertz. It is important
that the frequency be within a defined range so that the power grid does not
collapse. In Europe, this is a positive or negative deviation of max. 0.2
Hertz from 50 Hertz. Therefore, power feed-in and power consumption
have to be in balance at all times.
This also applies in cases of unforeseen events, such as power plant
outages, a strong wind period with the resulting high feed-in of wind power,
or a sudden increase in electricity consumption. The responsibility for a
stable frequency lies with the balancing group managers, who must keep
their balancing groups in balance, and with the grid operators, who are
responsible for stabilizing the frequency in case balancing groups – and
subsequently the frequency itself – are out of balance.

Spinning Reserve
In the narrower sense, the spinning reserve is not part of the ancillary
services, since it is already created by the inertia of rotating masses: If a
heavy mass is set in rotation like a flywheel, it continues for a while, even
after the energy supply has been stopped. For the sake of completeness,
however, the spinning reserve is often mentioned in connection with
ancillary services and is a kind of preliminary stage to balancing energy.
Due to the kinetic energy of their rotors, power plant generators are able to
compensate for a short-term power failure. Renewables do not yet provide a
spinning reserve. However, it is conceivable that the kinetic energy of large
wind turbines could be used for this purpose.

Frequency Control / Balancing Energy
If the effect of the spinning reserve cannot balance the frequency sufficiently,
balancing energy is used to restore equilibrium. In some countries, balancing
energy is obtained via a market. This is often based on an auction procedure
to keep costs low. In countries with a vertically integrated energy industry,
such as China or parts of the USA, this task is performed directly by the grid
operator. Balancing energy is often divided into different products depending
on how fast they have to react.
In Germany, for example, balancing energy is divided into three products:
Frequency Containment Reserve (FCR: reaction time < 30 seconds),
Automatic Frequency Restoration Reserve (aFRR: reaction time < five
minutes), and Manual Frequency Restoration Reserve (mFRR: reaction time
< 15 minutes).

Sheddable Loads
Switchable loads, sometimes also called “sheddable loads”, are loads that
are deactivated for a short time in order to guarantee network stability.
Who provides these loads and in which procedure the needed power is
tendered, varies from country to country.
Oftentimes, heavy industries with a high degree of power consumption and
automation in their production lines, such as aluminum or steel
manufacturers, provide sheddable loads.

System Services for Voltage Compensation
In addition to the frequency, voltage must also be kept within a certain
range in order to ensure the safety of persons, equipment, and final
consumption devices.
In the event of a voltage drop, it is the task of the network operators to
contain the voltage instability.

Power Factor Correction
For alternating current (AC) to maintain its real power, active power and
reactive power need to be out of phase by 90°.
Transformers, the grid itself or various consumption processes can
destabilize the phase relation between active and reactive power, which
leads to a loss in voltage.
Grid operators need to take measures to ensure stable voltage range, such as
providing additional load.

Loss Energy
Energy losses occur during the transport of energy. Grid operators have to
forecast this power loss and purchase additional amounts of energy on the
electricity market accordingly.
The amount of power dissipated is influenced by the capacity utilization of
the networks and represents one of the largest costs of system services.
Loss energy is a by-product of power production or a system efficiency
problem, which the TSOs and DSOs try to counteract.

Ancillary Services for the reconstruction of supply after a Power Failure
After a power failure, the power supply must be restored as quickly as
possible. Usually, this is the responsibility of the TSO. Power plants that
can start up without an external power supply play a central role in
rebuilding the supply.
Black start
Many large power plants are thermal power plants. They are able to
generate large amounts of electricity but need an external power source to
start their electricity production. Without this, neither nuclear nor coal-
fired power plants can be put into operation, as there is no energy source
for the operation of the cooling and monitoring systems of the reactor and
the coal extraction plants.

Ancillary
Services
In Power System

In contrast to these types of power plants, there are power plants which
can carry out a black start. They can start up autonomously and without
external energy supply. Power plant types that are suitable for a black start
are, for example, hydroelectric power plants, compressed air storage power
plants, or gas power plants. Electricity storage facilities are also
increasingly being used on a large scale to ensure black start capability.
Ancillary Services for Operational Management & Grid Bottleneck
Management
Operational management means controlling and monitoring of the grid by
the network operators. This includes the coordination of ancillary services.
The expansion of renewables increases the demands placed on grid
operators. Different system services are used for these measures.

Redispatch
The redispatch is a means of grid congestion management - especially in
grids with a high share of renewable energies. The TSOs consider the
expected feed-in and feed-out at grid level on the previous day. They then
use this information to analyze the utilization of the electricity grid.
The TSOs use this analysis, also known as load flow calculation, to
instruct the power plant operators the day before to postpone the planned
electricity production. This avoids foreseeable potential grid bottlenecks.
This instruction to shift electricity production is called a redispatch.
The redispatch does not change the amount of electricity fed into the grid,
but its local distribution. Meanwhile, there are also pilot projects for the
use of renewable energy plants in redispatch.

Feed-In Management
Feed-in management refers to the regulation of electricity feed-in from
renewable energy systems.
If sections of the distribution or transmission grid are overloaded and the
stability of the grid is threatened, feed-in management comes into play.
The grid operator takes renewable energy systems off the grid in the event
of a drastic power surplus.

Available Capacities and Capacity Mechanisms
In addition, the provision of electricity without the factual delivery is a
popular capacity mechanism.
Services of this kind can either be grid reserves or the safety readiness of
power plants.
This gives these ancillary services a capacity market character. The
design of such reserves differs greatly from country to country.

Ancillary Services – Understanding the Basics
Have you ever heard the words ”ancillary services” referred to in the electric industry and
wondered just what does this mean? Merriam-Webster dictionary defines the word
“ancillary” as something that is “auxiliary” or “supplementary.” When most of us think about
electricity, we think about having immediate access to power for our electrical devices,
whether by the flick of a switch, or by plugging a device into the electrical wall outlet. We
may think about how the power is provided, but not about all the “ancillary” components
that are necessary to allow for that instantaneous on and off usage to take place.
Almost all electricity we utilize is produced as it is needed. As millions of consumers turn
on their lights throughout an evening, the electric grid operator must request that power
generating units increase their power output to meet the new electrical demand. For
example, when large electrical furnaces are turned on to melt metals, electrical power
generation must increase rapidly and then maintain this increased production. Generators
must also decrease output as a response to reduction in electrical usage. As each
generator’s output is increased or decreased, additional wear and tear takes place on the
equipment within the power plant.

Types of Ancillary Services
Regulation Service is an ancillary service provided by resources that can
respond quickly to the instantaneous change in electrical demand, often
represented as a regulation signal. These resources, which are typically some
type of electricity generator, demand response, or sources storing and then
releasing electricity, may offer this service based on constructed formulas.
Some of the items impacting a resource’s revenues when providing this type of
service are whether it has the ability to respond quickly or slowly to a regulation
signal and how well the resource can follow the regulation signal. A resource that
can follow the regulation signal better than other resources will receive more
revenue for this service.

Synchronized Reserve Service is an ancillary service designed to ensure that
there is enough “headroom” or unutilized energy on resources to increase output
to ensure abrupt changes in electrical supply or demand can be met. A demand
response resource, or aggregate of demand response resources, may provide
this service by rapidly reducing electricity usage. A prime example of why this
service is needed is for the sudden loss of generation or a loss of transmission
capability.
If a generator stops producing electricity due to a sudden operational issue, other
resources must respond quickly to provide the “missing” power. For the most part,
this market product clears at zero cost due to adequate supply or “headroom” on
the system. When there is high demand for electricity, the price associated with
this service could increase as the grid operator has to pay resources to be in an
operating position to provide this service.

Day-Ahead Scheduling Reserve (DASR) is cleared a day prior (day-ahead) to
the actual need of the ancillary service and is utilized to ensure a sufficient
quantity of resources, including demand response, are in the operational position
of being available to provide 30-minute reserve service in the real-time market.
There are numerous non-market-based ancillary services; however we will only
discuss two potentially expensive services.
The Federal Energy Regulatory Commission, (FERC), has oversight of the
wholesale electricity markets and approves these service-related compensation
mechanisms.

Black Start Service is an ancillary service that is paid to certain generating
resources that can begin providing electricity to the grid without first utilizing
outside power from the grid to initially start power generating stations. Black
start is necessary if there are large black outs on the power system.
The power output from these resources is utilized to start other power stations,
provide electricity to nuclear stations, and provide critical-needs services. The
compensation for resources providing this service is an annual FERC-
approved, cost-of-service rate. As new black start resources begin operation, or
as existing black start resources retire, significant changes to this charge can
occur.

Voltage Control and Reactive Service is a FERC-approved rate that provides
basic compensation for a generator to provide incremental voltage or to absorb
voltage on the transmission system. This type of service is local in nature. In
other words, you may have portions of the electrical grid with both normal and
abnormal conditions depending on the configuration of generators, loads, and
the transmission system.
These charges can grow beyond FERC-approved charges if the grid operator
must turn on or off a generator or substantially modify the output of a
generating resource to provide this service thus inhibiting the resource’s ability
to participate within the economic energy dispatch of the grid.

Frequency support Ancillary services as
the name suggests are required to support
frequency in the grid, when the frequency
in the grid fall below 0.05 Hz below the
lower operating frequency range as
specified in the IEGC for two consecutive
time-blocks.
In such a situation the nodal agency will
give instructions to the FSAS provider to
despatch in the third time block so that
the frequency can be controlled.

Black Start Ancillary Services (BSAS) &
Execution
Central Electricity Authority Regulations mandate
hydro generating stations for providing black start
facility. Incentives may be provided to all flexible
generators who provide black start facility when
such services are sought by the system operator.

What are Ancillary Services In Power System ?

What are Ancillary Services In Power System ?

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