dc.description.abstract |
Proliferation of solar photovoltaics (PV) in low-voltage (LV) distribution networks
is inciting technical challenges in network design and operation with regard to the
quality of power. Violations of operational performance limits are increasingly evident
at higher solar PV penetration levels, in particular, local voltage rise has
become the major issue of concern in LV distribution networks. As the solar PV
industry continues to grow, emerging challenges need to be addressed by adopting
best policies and practices at a utility level. Thus, to comply with stipulated
network operational limits, distribution network operators (DNOs) are compelled to
develop comprehensive techniques to determine acceptable levels of solar PV hosting
capacity (HC) and explore HC enhancement options.
Complexity of modelling distribution networks is a barrier for DNOs to decide
levels of maximum solar PV penetration using stochastic approaches. Thus, there
is a necessity to develop a systematic approach to assess solar PV HC, considering
factors such as geographic layout of networks and their electrical characteristics.
This thesis extends the knowledge of managing of solar PV integration in LV
networks by developing systematic approaches to evaluate solar PV HC subjected
to over voltage curtailment. In this regard, a novel feeder based solar PV HC
evaluation approach was developed to address the diverse network characteristics of
multi feeder systems in LV distribution networks. To assess the voltage violations
and critical factors a ecting the solar PV HC, a comprehensive analysis of potential
power quality issues was conducted on a practical LV distribution network in Sri
Lanka.
The approach proposed in this thesis establishes a safe limit for solar PV HC
for a given distribution feeder based on the locational and operational aspects of
the solar PV units deployed on a LV network. The safe limit for HC was developed
employing a number of sensitivity analyses considering factors in
uencing solar PV
HC. Further, the proposed feeder based solar PV HC approach was extended to
develop a generic method to quantify solar PV HC under di erent operating con- ditions of PV inverters. Thus, it can be used as an approximate guide or a rule
of thumb to evaluate solar PV HC at a given point on an LV feeder without using
complex stochastic techniques.
With the increasing demand for solar PV systems, development of both solar
PV HC assessment and enhancement techniques is essential in managing network
voltage. DNOs have recognised the need for smart PV inverter technologies to
maintain acceptable voltage levels in distribution networks. Smart PV inverters
possess fast and
exible active and reactive power control functions such as; Volt-VAr
and Volt-Watt control modes which can be used to manage over-voltage conditions
that often limit the solar PV HC. At present, most of solar PV connection standards
provide a set of rules and guidelines to mitigate voltage violations by enabling VoltVAr
and Volt-Watt control modes of the inverters. In particular, it is imperative
to analyse the impact of such solar PV connection standards on HC assessment
and its potential to enhance solar PV HC. Thus, a detailed analysis of smart solar
PV inverter capabilities and a comparative evaluation of solar PV HC enhancement
facilitated by di erent connection standards are presented in this thesis.
Electricity utilities around the world seek to develop strategies to increase solar
PV integration while maintaining acceptable network performance. Hence, more
generalised and straightforward tools are required to rapidly assess solar PV HC
without complex and extensive network modelling and simulations. Extending the
deterministic outcomes, a nomogram based solar PV HC assessment approach is
proposed in this thesis to determine HC values speci c to any location of a given
conductor. Further, solar PV connection criteria is proposed which permits the
electric utilities to approve new solar PV connections which facilitates reasonable
modelling insights to assess HC. The proposed nomogram based solar PV HC assessment
approach and solar PV connection criteria cover technical and regulatory
aspects to manage PV integration in LV distribution networks.
For the continued development of solar PV as a distributed generation, accuracy
of PV connection approval process is crucial to correctly and easily allow PV connections that will not cause issues. Therefore, grid codes, distribution codes or
guidelines on interconnection of solar PV require to be re ned or re-written in relation
to solar PV HC assessment/enhancement and approval criteria for new PV
connections in LV distribution networks. The solar PV HC assessment/enhancement
and solar PV connection criteria proposed in this thesis shall be a contribution to
further improvement of the available guidelines/standards on solar PV installation
in LV networks.
All network modeling and simulations presented in this thesis were carried out
in DIgSILENT PowerFactory platform. |
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