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

Typical Island Power Station  Multiple Generators  Different Sizes  Different Ages & Condition

A Day in the Life of 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 1250kVA 415V 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 get an overview of the day. RMS Voltage (pu) RMS Current (A) Real Power (kW) Reactive Power (kVar)

Flag Transient Points of Interest Raise a flag whenever the rms voltage deviates by >5% and inspect more closely. Example1Example2Example3

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

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

Example 3 – Transformer Inrush Event Note 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 Systems Some Problem Areas  Low Fault Levels – Weak  Generation Dynamic Behaviour – Poor (e.g. Nauru)  Protection Discrimination – Black Outs

Island Power Systems Problem Areas Generation Dynamic Behaviour

Parallel Generators – Droop Load Share Most Common Generator Configuration Droop typically 3 to 5%

Parallel Generators – Droop Load Share Step Load Response Movement down the droop curve

Engine Model – Droop Mode Engine & Governor – Basic Model Governor

Engine Model – Droop Mode Governor – Model Governor – Transfer Function Governor Time Constant

Engine Model – Droop Mode Engine & Governor – Complete Two Poles 2nd Order System

System Modelling 2 nd Order Response H(s)

Opportunities for Optimisation  Improve Generator Control Dynamics  Reduction of Spinning Reserve Improved Performance & Fuel Efficiency

End with a Good News Story Groote Eylandt 3% fuel saving = $300k pa Improved dynamics behaviour – reduced trips & blackouts

Thankyou Questions