Page 69 - Energize January 2022

TECHNICAL

Conservation voltage reduction
(CVR) is the intentional operation of the
distribution system to provide customer
voltages in the lower end of the acceptable
range, with the goal of achieving energy
and demand reductions for customers.
Conservation voltage reduction (CVR) is
one of the cheapest technologies that
can be intelligently leveraged to provide
considerable energy savings.

CVR and AMI advanced metering
infrastructure Figure 6: Smart VVO and CVR system 4
1
In a previous article , we emphasised the
extra facilities that can be achieved from The intermittency of PVs causes fast voltage fluctuations, while the abrupt charging of EVs
smart metering. One of the features that causes voltage sag and unbalance. Addressing these adverse impacts involves changes in the
could be combined with CVR is voltage network planning and operation.
measurement. Use of the AMI makes the
installation of extra monitoring equipment Voltage fluctuation
unnecessary. In a distribution network with SSEG, the voltage can vary depending on the position of the
DER and the energy produced. In some cases, the voltage fluctuation can be significant and
The smart distribution network and interferes with the operation of voltage regulation equipment, such as load tap changer of
SSEGs distribution transformers, line voltage regulators and capacitor banks.
The number of rooftop solar and ESS A constantly changing output voltage makes the application of CVR very difficult. If
storage systems is growing, driven by the SSEG is producing energy, this decreases the energy consumption of the consumer,
both economic and security of supply but increases the voltage at the point of connection, which in turn increases the energy
issues, and the grid needs to get smart consumption of those consumers that do not have SSEGs installed.
to accommodate this. SSEGs can The LV distribution networks are predominantly constructed with radial topology,
generate or store energy or manage meaning that power flows from upstream to downstream networks to supply customers’
its consumption depending on type. consumption. The increasing use of EVs causes the voltage level in the distribution feeders to
The term SSEG covers a wide range drop largely as more electrical loads will be added. The voltage drop will be severe towards
of technologies that are located on the end of the feeder.
customer sites such as solar photovoltaic In contrast, large scale PV eventually causes significant reverse power flows into the
(PV) assemblies and batteries upstream networks, and the voltage rises along the distribution feeders with the voltage
The parameters that are affected level at the end of the feeder likely exceeding the permissible limit. This undesired voltage
most by SSEG are voltage levels and rise potentially damages the customers’ electrical appliances. The voltage rise can also lead
voltage balance, resulting in voltage level to the generator tripping, activated by internal protection. The level and spread of voltage
fluctuations and voltage unbalance. These rise depends on the penetration level of PVs in the grid.
parameters affect the operation of the two
energy savings schemes often applied in Voltage unbalance
distribution networks, namely Volt-VAR Voltage unbalance is also perceived as a significant concern in the LV distribution network
optimisation and conservation voltage with high penetration of DERs. Voltage unbalance is quantified by a percentage term,
reduction. called voltage unbalance factor (VUF), which is allowed to be within an acceptable range
Rooftop solar systems, especially in of 2%. This voltage issue arises from unbalanced system impedances, uneven distribution
residential areas, are fitted with a variety of single-phase loads and unbalanced power generation from PVs. The intermittency of PV
of inverters, ranging from barely compliant output powers can also lead to voltage unbalance. Moreover, voltage fluctuation can further
to complex systems that provide reactive deteriorate voltage unbalance. The use of EVs adds more stress on voltage unbalance. 4
power support and full-blown energy Voltage unbalance increases at the end of the feeder.
management systems, and trying to
predict the behaviour of these systems is
complex to say the least.
Massive integration of DERs in
low-voltage (LV) and medium-voltage
(MV) grids has adverse impacts on the
network operation and power quality. Figure 7: Effect of PV 2

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