System of Interconnected Microgrids -...
Transcript of System of Interconnected Microgrids -...
System of Interconnected Microgrids
Challenges and Solutions
Dr Farhad Shahnia
Overview
Microgrids
Importance of Microgrids to Australia
Microgrid Projects in WA
On-going Research Topics
A New Research Avenue :
System of Interconnected Microgrids
Application and Benefit
An Example
Research Questions to be Addressed
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Microgrid
Microgrids are defined as
interconnected networks of loads and resources (distributed energy resources-DERs)
can function in grid-connected or islanded modes
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Microgrids are a way for utilities to:
Reduce loss, emissions, cost of energy
Upgrade aging systems
Build sustainable futures
Importance of Microgrids to Australia
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Importance of Microgrids to Australia
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Importance of Microgrids to Australia
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Microgrid Projects in WA
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http://reneweconomy.com.au/w-plans-australias-biggest-solarstorage-micro-grid-onslow-39857/http://www.energymatters.com.au/renewable-news/renewables-microgrid-wa-em5793/https://onestepoffthegrid.com.au/p2p-energy-sharing-start-brings-brooklyn-microgrid-smarts-australia/http://www.energynetworks.com.au/news/energy-insider/what-could-customers-save-standalone-systems-microgrids
On-going Research Topics
Structure:
AC microgrids
DC microgrids
AC-DC microgrids
Energy Sources:
Inertial Sources
Converter-dominated microgrids
Control Techniques:
Decentralized
Centralized
Hierarchical
Distributed Control
Power Sharing among Sources:
Sharing based on source ratings
Sharing based on economics
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A New Research Avenue
New possibility:
Temporary Interconnection of Neighboring Islanded Microgrids
or
Microgrid Clusters
Considered possibilities:
Grid-connected microgrids
Islanded (isolated/standalone/off-grid)
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Application and Benefit
Application:
• Remote large towns with no access to a utility feeder
• Presence of two or more microgrid owners (operators) in the town
Importance (Benefit):
• Reducing load-shedding possibility due to unexpected overloading of the microgrid
• Reducing renewable energy curtailment due to unexpected excessive generation
• Improving the self-healing, reliability, and resiliency of the electrical system of remote town
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An example
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Research Questions to be Addressed
• Q-1: What are the criteria based on which the necessity of interconnection is defined?
• Q-2: How to select the most suitable neighboring microgrid?
• Q-3: What must be the suitable structure and topology of the microgrids to enable the coupling?
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• Q-4: How to synchronize the selected microgrids?
Research Questions to be Addressed
• Q-5: How to prevent an interconnection, which may cause instability for the system of coupled microgrids, after their interconnection?
• Q-7: How should the interconnected system operate?
• Q-6: When to isolate a system of coupled microgrids into its contributing microgrids?
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Q-1: Defining Criteria on the necessity of interconnection
Centralized Approach
• Active and reactive power generation of each source
Decentralized approach• A frequency-based technique
E Pashajavid, F Shahnia, A Ghosh (2017) Development of a self-healing strategy to enhance the overloading resilience of islanded microgrids, IEEE Trans Smart Grid 8(2):868-880
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Q-2: Selecting the suitable neighboring microgrid(s)?
Decision-Making
• Fast but not optimal
Optimization• Optimal but slow
A Arefi, F Shahnia (2017) Tertiary controller-based optimal voltage and frequency management technique for multi-microgrid systems of large remote towns, IEEE Trans Smart Grid in-pressF Shahnia, S Bourbour, A Ghosh (2017) Coupling neighboring microgrids for overload management based on dynamic multi-criteria decision-making, IEEE Trans Smart Grid 8(2):969-983
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Q-3: Suitable Structure and Topology
Planning Study
• Cost• Frequency of interconnection• One or more system of coupled micreogrids
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Power Exchange Highway:
• Three-phase ac link
• Single-phase ac link
• DC link
Interconnecting Switch:
• Conventional Circuit breaker
• Power electronics-based switch
• Back-to-back power converters
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Q-3: Suitable Structure and Topology
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Q-4: Synchronization
MG-N-1
MG-N
(a) MG-2
MG-k
MG-1
MG-N-1
(b) MG-2
MG-k
MG-1
MG-N
MG-N-1
(c) MG-2
MG-k
MG-1
MG-N
MG-N-1
(d) MG-2
MG-k
MG-1
MG-NMG-N-1
(e) MG-2
MG-k
MG-1
MG-N
MG Central
Controller
Network
Controller
OMT
Synchronization
Module
ISS
ISS
Controller
UPC, PDL
Selected
MGs
On/Off
Synchronize,
Close, DR
CC, DR
Synchronize,
Close, Open, DR
CC, DR
Open, DR
S Bourbour and F Shahnia (2016) A suitable mechanism for the interconnection phase of temporary coupling of adjacent microgrids,” IEEE PES Innovative Smart Grid Technologies Asian Conference (ISGT-Asia), Melbourne.
Q-5: Stability Analysis
Small-signal stability analysis
• Will the system of coupled microgrids become stable after
their interconnection?
Transient Analysis
• Will the overloaded microgrid become unstable before the
synchronization is achieved and they are coupled?
F Shahnia, A Arefi (2017) Eigenanalysis-based small signal stability of the system of coupled sustainable microgrids, Int Journal of Electrical Power & Energy Systems 91:42-60F Shahnia (2016) Stability and eigenanalysis of a sustainable remote area microgrid with a transforming structure, Sustainable Energy, Grids & Networks, 8:37-50 19
Q-6: Isolation of microgrids
Defining Criteria to detect
• Interconnection necessity has been alleviated.
• Generation/demand imbalance
• Faults
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Q-7: Dynamic Operation
Challenges:
• Level of allowed voltage and frequency variations
• Primary controllers of DERs fighting against each other
• Central controllers of microgrids fighting against each other
• Communication link failure
• Coordination of energy storages (e.g. batteries) with interconnection
• Power trade among interconnected microgrids
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*F Shahnia, R Chandrasena, S Rajakaruna, A Ghosh (2014) Primary control level of parallel distributed energy resources converters in system of multiple interconnected autonomous microgrids within self-healing networks, IET Gen. Trans. & Dist. 8(2):203-222E Pashajavid, F Shahnia, A Ghosh (2017) Provisional internal and external power exchange to support remote sustainable microgrids in the course of power deficiency, IET Gen. Trans. & Dist. 11(1):246-260T Mehr, A Ghosh, F Shahnia (2017) Cooperative control of battery energy storage systems in microgrids, Int Journal of Electrical Power & Energy Systems 87:109-120
Discussion