Energy management of microgrids
The innovative shape of traditional power systems has been developing towards more intelligent, flexible and efficient entities. In the name of microgrids, the transformation of physical structure has gradually blurred the boundaries between generation, transmission and distribution network from...
Saved in:
Main Author: | |
---|---|
Other Authors: | |
Format: | Theses and Dissertations |
Language: | English |
Published: |
2018
|
Subjects: | |
Online Access: | http://hdl.handle.net/10356/73775 |
Tags: |
Add Tag
No Tags, Be the first to tag this record!
|
Institution: | Nanyang Technological University |
Language: | English |
Summary: | The innovative shape of traditional power systems has been developing towards
more intelligent, flexible and efficient entities. In the name of microgrids,
the transformation of physical structure has gradually blurred the boundaries
between generation, transmission and distribution network from centralization to
decentralization topologies. With much smaller scales, microgrids are comprised
of local distributed generation, energy storage systems (ESSs) and load, making it
quite possible to enhance reliability with distributed generation, increase efficiency
with reduced transmission distance, and implement capability in ease use of
alternative energy resources and storages. However, public concern has been
raised due to progressive stability and reliability issues regarding different aspects
related with fast developing system infrastructure and emerging electricity market.
On the other hand, it might sometimes become a serious issue for microgrids on
the trade-off between economy and reliability, since operating reserves are much
incomparable to variations from both generation and consumption sides in most
cases.
Against the background of exploring better configuration for microgrids to
be not only reliable but also economic, many conducted research has mainly
focused on autonomous operation, droop control, hierarchical control, low-voltage
protections, state estimations and power electronics studies and so forth. In terms
of modeling and control strategy, this thesis gives an overall comprehensive
methodology about effective planning and efficient operation of microgrids.
Firstly, optimal power flowalgorithms are investigated in a novelway that provides
the minimum operating cost and maintains the highest possible reliability levels.
In order to deal with stochastic behaviors of RESs and loads in microgrids,
scenario reduction techniques are extended by imposing auxiliary constraints so
that the optimal solution space is narrowed down. By implementing the fine-tuned
algorithm, case studies with benchmarks have well validated the reliability has
been significantly enhanced at little cost of additional expenditure.
Large-scale energy storage systems have provided promising potentials for
multiple applications in microgrids by providing additional spinning reserve,
regulating voltage, frequency and power factors, as well as offering economic
benefits by participating into demand response and facilitating the integration of
renewable energy sources (RESs). A dynamic optimal power flow (OPF) model
with adaptive operation costs is thus proposed to address influential consequences
of ESS implementation in microgrids, specifying the dynamic characteristics of
energy storage in multiple time periods. Conclusive results have shown that the
proposed model and algorithm can be utilized not only to meet system ramping
requirements, but also to help flatten the load profile in peak hours.
In microgrids, participation of renewable energy sources in combination
of ESSs has further expanded the potential benefits to end uses as well as to
system operators. In consideration of economic operation, a two-layer predictive
energy management system (EMS) for microgrids with hybrid ESS is proposed
incorporating respective degradation costs, so that high system robustness at
minimum operational cost is well maintained. The hierarchical dispatch model is
well designed, that total operational cost is achieved in the upper layer EMS while
the lower layer EMS deals with more cumbersome tasks resulted in intermittencies
and forecast errors. The novelty of the proposed algorithm has been demonstrated
by intensive scenario tests incorporating different pricing schemes, prediction
horizon lengths and forecast accuracies.
Clustering microgrids in different distribution networks, microgrid commu-
nity has enabled individual members to be more operationally flexible by resource
sharing with minimizing dependency on the main power grid during normal
conditions and more self-sustainable with enhanced power system reliability
under extreme events. This thesis further investigated the hierarchical EMS in
the context of interconnected microgrid community, in which pairing strategy is
proposed so that community-level EMS to explicitly determine the power flow
between microgrids and with the upstream distribution grid. Such the profit can
be fairly shared by each participating microgrid in the community, without user
privacy being compromised.
All the proposed methodologies and algorithms throughout the research have
been verified in MATLAB, with regards to different system topologies involving
multiple data of RESs, ESSs and loads. |
---|