The Challenges of Small Scale Islanded Power Systems Craig Harrison 12 th November 2014.

The Challenges of Small ScaleIslanded Power Systems

Craig Harrison12th November 2014

Presentation Overview

Summary of Challenges

Focus on the Technical Challenges – Engineering

Real Life Perspective – Examples

Renewable Energy & its Impact on Generation

Generation Dynamics & Modelling

The Challenges

Political – short term objectives, optimistic plans & promises, corruption

Environmental – limited land, volcanic islands & atolls, global warming & rising sea levels

Funding – Capex - ADB, World Bank, IRENA, EU Agencies, SPREP, Australian, NZ and Japanese Governments, US Aid Agencies (US Territories)

Opex – limited utility funding!

Engineering Skills – low skill levels, low staff retention, system complexity limits

Technical Challenges – improving generation efficiencies, integration of RE, reduce losses (technical & non technical)

The Reality

FSM, Pohnpei, Power Station

FSM, Pohnpei, Power Station

FSM, Pohnpei, Power Station

Typical Island Power Station

Multiple Generators Different Sizes Different Ages & Condition

A Day in the Lifeof a

Nauruan Genset

High Speed V & I Recordings

With a self powered iba PADU-C data acquisition unit high speed recording of genset voltage and current signals can be recorded for several days.

iba PADU-C

1250kVA415V

1740A

1kHz Sampling & Recording, All Day Long

100s Span

50ms Span

0.5s Span

This Particular 24hr Period Calculations for RMS voltage & current, real & reactive power flow over 24hrs (@1000pts/s!)to get an overview of the day.

RMS Voltage (pu)

RMS Current (A)

Real Power (kW)

Reactive Power (kVar)

Flag Transient Points of InterestRaise a flag whenever the rms voltage deviates by >5% and inspect more closely.

Example1 Example2Example3

Example 1 – Effect of Sudden Load Shed on Voltage & Frequency

Example 2 – Effect of Sudden Load Changes on Voltage & Frequency

Example 3 – Transformer Inrush EventNote change of scales to cope with magnitude of event (current reaches 3500A, ~2pu). See next slide for zoom in on raw data.

Initial speed/frequency response

Example 3 - Zoom In on Raw Data

Clipped at 4000A (PADU input range limit for CT’s used)

Sub Transient

The Island Vision – 100% RE

Impediments as above!

Current Activities

PV systems being installed – small scale as % of generation capacity

Small number of battery systems – small scale

Large number of RE studies being funded – e.g. IRENA

* desk top studies focused on “hosting capacity”* input data often estimated values* generation dynamics is not known or considered

Some unsatisfactory outcomes - building on weak base!

Outcomes – The Evidence

American Samoa – 19MW Demand – 1.6MW PV Installed

* PV fluctuations audible in slow speed engines – slow response* Small High Speed Sets being run as additional spinning reserve!* Net outcome is questionable!

Tonga – 7MW Demand – 2 * 1MW PV & LA battery storage

* Cloud Events cause the PV to trip – gen. frequency variations* Batteries ineffective for demand shifting – inadequate ratings

Island Power SystemsSome Problem Areas

Low Fault Levels – Weak

Generation Dynamic Behaviour – Poor (e.g. Nauru)

Protection Discrimination – Black Outs

Island Power SystemsProblem Areas

Generation Dynamic Behaviour

Parallel Generators – Droop Load Share

Most Common Generator ConfigurationDroop typically 3 to 5%

Parallel Generators – Droop Load Share

Step Load Response

Movement downthe droop curve

Engine Model – Droop Mode

Engine & Governor – Basic Model

Governor

Engine Model – Droop Mode

Governor – Model

Governor – Transfer Function

GovernorTime Constant

Engine Model – Droop Mode

Engine & Governor – Complete

Two Poles2nd Order System

System Modelling

2nd Order Response

H(s)

Opportunities for Optimisation

Improve Generator Control Dynamics

Reduction of Spinning Reserve

Improved Performance & Fuel Efficiency

End with a Good News StoryGroote Eylandt

3% fuel saving = $300k pa Improved dynamics behaviour – reduced trips & blackouts

Thankyou

Questions