Operation of a Hydrothermal System with Increased Renewable - - PowerPoint PPT Presentation

Operation of a Hydrothermal System with Increased Renewable Generation:

New Zealand Case Study

Hydro Power Scheduling Workshop – Stavanger, Norway

By Luke Schwartfeger, Dr. Alan Wood, Gari Bickers 12-13th September 2018

Contents

• Background of New Zealand System
• Context of Study
• Model and Modelling Tool
• Analysis

Hydro

North and South Island Inflow Percentiles

Hydro

North and South Island Inflow Percentiles

Demand

New Zealand Demand Percentiles

• Hydro-Demand temporal and geographical

mismatches overcome the limited hydro storage

Context

• Near 100% Renewable Generation target by 2035
• > 80% Renewable at present
• Candidate generation:
• Rely on fossil fuel (FF) generation during low inflow years (dry years)
• Electricity Market energy payment based

– Disincentive to construct renewable generation

GREEN Grid 7

Generation Type Installed Cap. (MW) Consented Cap. (MW) Wind 689 2500 Geothermal 978 300

Context

• Challenges in Islanded, Highly Renewable System:

– Dry year risk – Supplying peak demand – Incentivise market to construct renewable generation

• Purpose of Study:

– Examine FF generation operation (capacity factors) in New Zealand with additional wind and geothermal generation – Determined with an optimal hydrothermal dispatch tool

Model

• 2 AC systems connected by a “bi-pole” HVDC link
• 2 node, 2 reservoir

– Island’s hydro schemes are aggregated

• HVDC ‘one-pole trip’ risk

Modelling Tool – ISO DP

Part 1 Part 2

Modelling Tool – ISO DP

• DP

– 2 year time span; 2nd year to estimate end-of-year WVs – 30 minute time interval to capture capacity constraints – 6 x 21 storage levels (126 discrete storage points)

• Both DP and Forward Dispatch use a Optimal

Generation Dispatch

Generation Dispatch (1)

• Linear programming formulation

– Capacities of storage, generation and transmission; Demand satisfaction; Transmission losses approximated with piecewise linear function; HVDC one pole trip

• Objective Function:

min Ƹ 𝑑ℎ ∙ ො 𝑕ℎ + Ƹ 𝑑𝑔𝑔 ∙ ො 𝑕𝑔𝑔 + Ƹ 𝑑𝑜 ∙ ො 𝑕𝑜 Ƹ 𝑑𝑔𝑔 = 10 100 1000 𝑈 𝑂𝑎𝐸 ; ො 𝑕𝑔𝑔

𝑑𝑏𝑞 = 385

500 748 𝑈 𝑁𝑋

• ො

𝑕𝑜 - Fictious Non-Supply Generation

Generation Dispatch (2)

• Outputs:

1. DP: WVs per node. Shadow prices of demand satisfaction or one-pole trip risk constraints 2. Forward Dispatch: Optimal generation dispatch ( ො 𝑕∗)

• Input: Net Demand, Hydro costs ( Ƹ

𝑑ℎ)

– DP: Ƹ 𝑑ℎ t interpolated from ෢ 𝑋𝑊 𝑢 + 1 – Forward Dispatch: Average WV function

Analysis: Case Study

• NZ 2015 generation portfolio and data
• 9 generation portfolios
• Scaled 2015 Wind and Geothermal production to emulate additional

generation

System Fossil Fuel Generation Capacity Factors

Wind Geothermal Wind / Geo

Duration Curves of FF Generation: Wind

Least Cost FF ($10) Moderate Cost FF ($100) Highest Cost FF ($1000)

Duration Curves of FF Generation: Dry Years

Least Cost FF Moderate Cost FF

100% Capacity Factors for 0 – 300 MW Geothermal

Future Work

• Benchmark against ESO formulation
• Evaluate importance of 30 min. time interval WV functions
• Include more wind profiles

Thank you to our industry members of the Power Engineering Excellence Trust 20