Page 68 - Energize January 2022

TECHNICAL

The latest generation of voltage regulators evaluated so that the consequences of possible actions are consistent with optimised
(VRs) can provide multi-phase voltage control objectives. This could be done centrally using a substation automation system or a
regulation, so that two or three regulators distribution management system.
can be operated with the use of single In the smart grid environment, Volt/VAR optimisation (VVO) is receiving increasing
control. This capability provides a single attention. The basis of VVO is to utilise various Volt/VAR control (VVC) and supporting
point of contact for communications, true devices in an optimal way to achieve minimal losses and maximum energy savings.
multi-phase metering and fewer controls This approach is commonly referred to as integrated VVO. The accelerated
to program and maintain. VRs can be adoption of substation automation (SA), feeder automation (FA) technology, and the
equipped with integrated intelligence widespread deployment of advanced metering infrastructure (AMI) have laid the
and communications which enable them foundations for a centralized control approach, by providing the necessary sensor,
to provide functionality and intelligence actuator and reliable two-way communications between the field and the distribution
which could be used in a variety of system control centre.
operational strategies. During the process, voltage control devices at a substation and on the circuit can be
used to shrink the voltage drop from the substation to the end of the line and reduce
Reactive compensation devices the service voltage to customers while maintaining the voltage within defined limits.
Reactive compensation devices (i.e., The efficiency gains are realised primarily from a reduction in the system voltage. This
capacitor banks) are used to reduce the results in less energy being consumed by end-use equipment served by the distribution
reactive power flows throughout the system.
distribution network. The capacitor banks A typical interconnected VVO system is shown in Figure 5.
may be located in the substation or on the
feeders. Capacitor banks can be fixed or Energy conservation through smart voltage control
switched. Latest versions have metering The next step which has been applied for several years, albeit without smart controls, is
and communications capabilities. the use of voltage control to effect energy savings. Energy conservation through voltage
reduction and distributed energy storage (DES) technology have emerged as a potential
Distribution Statcom (D-Statcom) candidate for peak load relief in distribution grid. However, lack of coordination between
The D-Statcom provides the same network controls such as conservation voltage reduction (CVR) and DERs may have a
functions as the transmission Statcom detrimental impact on smart grid operations.
but on a reduced scale. The unit provides Controlling the voltage on the low side of the distribution transformer provides
closer control of voltage than the VR and significant opportunities to reduce energy. Conservation voltage reduction (CVR) is a
the capacitor bank and is able to respond technique applied in the smart grid to achieve this. Voltage control at the grid edge also
faster. reduces voltage volatility, allowing for energy savings. Despite constant energy converter-
based appliances in most consumer installations, the energy consumption depends on the
Smart Volt-VAR optimisation voltage level, and keeping the supply voltage at the lower end of the allowable window
Volt/VAR optimisation (VVO) is a process reduces energy consumption.
of optimally managing voltage levels and This technique is currently implemented on a centralised basis and is applied to the
reactive power to achieve more efficient voltage control elements in the feeder. The output is adjusted to ensure that the voltage
gird operation by reducing system losses, at the lowest point in the distribution network does not exceed allowable limits. CVO is
peak demand or energy consumption or applied to ensure that voltage at all points of connection is kept at the lower limit.
a combination of the three. Traditionally,
the voltage and VAR control devices are
regulated in accordance with locally
available measurements of, for example,
voltage or current. On a feeder with
multiple voltage regulation and VAR
compensation devices, each device is
controlled independently, without regard
for the consequences of actions taken by
other control devices. This practice often
results in optimum control actions at the
local level, which can have suboptimal
effects at the broader level.
To achieve broader level control,
information should be shared among all
voltage and VAR control devices. Control
strategies should be comprehensively Figure 5: Smart VVO system 5

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