Interconnected Microgrids Challenges and Solutions Dr Farhad - - PowerPoint PPT Presentation

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

2

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

• r

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
• verloading 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-press F Shahnia, S Bourbour, A Ghosh (2017) Coupling neighboring microgrids for

• verload 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 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

• f coupled sustainable microgrids, Int Journal of Electrical Power & Energy

Systems 91:42-60 F Shahnia (2016) Stability and eigenanalysis of a sustainable remote area microgrid with a transforming structure, Sustainable Energy, Grids & Networks, 8:37-50

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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):203-222 E 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):246-260 T 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