Page 57 - Energize September 2022

TECHNICAL

as voltage regulators and capacitors such as the addition of voltage regulators and capacitors, can
• Tertiary: The hosting capacity with grid upgrades such as line improve the amount of PV generation that a distribution circuit
upgrades, energy storage and smart inverters. can accommodate This includes advanced tap changers. Voltage
regulators can be installed along the length of the feeder to provide
Initial hosting capacity limits are illustrated in Figure 7. localised voltage control.
In the initial hosting capacity, none of the criteria are impacted Tertiary hosting capacity is the capacity which can be achieved
and no changes are required to assess the initial hosting capacity, with major changes to the network. This includes smart tap
the operation of legacy devices is included in the calculation of changers, voltage regulators, capacitors, strengthening the network
capacity. It should be noted that there is a delay in the operation of by re-cabling, replacement or upgrade of distribution transformers,
legacy control devices. Thus, the feeder may record an overvoltage the use of voltage control on PV inverters, and storage at PV
condition for a few minutes until the control device operates. generators to absorb excess generation.
The devices operate based on the local information and control An interesting option to achieve tertiary capacity is the
settings, and thus do not require an external communication installation of network storage at the distribution transformer. The
interface. ESS stores excess generation during the day and re-injects it into
Secondary hosting capacity is the capacity that can be achieved the grid during the peak period at night (at a premium), preventing
without major changes to the feeder or to the PV generators. reverse power flow.
Operational changes in the voltage regulation equipment,
References
1. P Apadhyay: “Distributed Energy Resources (DERs): Impact
of Reverse Power Flow on Transformer”, Cigre Science &
Engineering, number 19, October 2020.
2. P Aston: “What is reverse power flow”, Roadknight Taylor, April
2022 https://roadnighttaylor.co.uk/connectology/what-is-
reverse-power-flow/#
3. GE: “Voltage Regulators”, GE digital energy
4. S Jothibasu, et al: “Cost of integrating distributed photovoltaic
generation to the utility distribution circuits”, White Paper
UTEI/2016-01-1, 2016, http://energy.utexas.edu/the-full-cost-of-
Figure 7: Example of initial hosting capacity limits electricity-fce/
5. I Majeed: “Impact of reverse power flow on distributed
transformers in a solar PV integrated low voltage network”,
University of Johannesburg, https://ssrn.com/abstract=4172636
6. A Akinyemi, et al: “Analysis of voltage rise phenomena in
electrical power network with high concentration of renewable
distributed generations”, DUT Scientific reports, 2022
6. S Hasemi: “Methods and strategies for overvoltage prevention in
low voltage distribution systems with PV”, IET Renewable Power
Generation, 2017, Vol. 11, Issue 2

Figure 8: Effect of voltage regulation on PV inverters Send your comments to rogerl@nowmedia.co.za

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