LOW INERTIA SOURCES AND SYSTEM...

Confidential & Proprietary | Copyright © 2016

CAPER Meeting, August 7 & 8, 2017

Dino Lelic

LOW INERTIA SOURCES AND

SYSTEM STABILITY


Sources of Low Inertial /Governor Response

Slide 2

■ High Penetration of Wind and Solar Inverter Based Generation

• Synchronous machines not scheduled on at peak renewable/low load periods

■ Replacement of Induction Motor based load with Variable Speed Drive

Technologies

• Driven by energy efficiency, process control, six sigma ---

■ Some places to learn from:

• Islands: GB, Ireland

• Electrical Islands: Scandinavia, ERCOT

• Places with Highest Renewables: CA ISO, Germany

■ Other Related Issues

• Volatility and Forecasting Difficulties

• Ramping

• Dispatchability

• Maintaining Footroom / Headroom for Response and Dispatch

RELIABILITY | ACCOUNTABILITY 3

Synchronous inertia is declining……

ERSTF Enabled to Monitor Trends in Frequency

0.6

0.8

1

1.2

1.4

1.6

1.8

2

2.2

2.4

2.6

2.8

3

3.2

3.4x 10

5

2010 2011 2012 2013 2014 2015 2016 2017

Kin

etic e

nerg

y, M

Ws

ERCOT Historic Kinetic Energy Boxplots (2010–2017)

RELIABILITY | ACCOUNTABILITY 4

Anatomy of a Frequency Excursion with Recovery

60.00

59.90

59.80

59.70

59.60

59.50

59.40

Hz

T-15 T-10 T-5 0 T+5 T+10 T+15 T+20

NERC IFRO - Minimum

Protection and Stage 1 UFLS

DER Trip Offline – IEEE 1547

UFLS, Protection Mode (Equipment Damage), Instability

Vulnerable State

Recovery Mode

Normal Operating State Unit

Trip Synchronous

Inertia and

FFR

Rebound with

Primary Response,

Governor

Responsive Control

Secondary

Response,

AGC

Confidential & Proprietary | Copyright © 2016 Slide 5

The Load is Changing, Too

HVAC, Refrigeration,

pool pumps, ------

Industrial processes

where speed control

is critical to quality

Side note – resistive

load (lighting) also

decreasing

Confidential & Proprietary | Copyright © 2016 Confidential & Proprietary | Copyright © 2015

It is all Related

Slide 6

Cycles seconds minutes hours day

Balancing Energy

Regulation15 minute/

hourly scheduling

Day Ahead Scheduling

Governor Response

Inertial Response

Forecast errors & outages

Forecast errors& outages & imprecision

Lag from market to real time & imprecision in response

Volatility and intermittency in

renewables

Fluctuations in Load

Markets Set Prices & Issue Instructions

Capacity Market Sets Prices & Control

System IssuesInstructions

Autonomous Local Control Response

Autonomous Local Physical Response

Amount of inertial responseDetermines frequency response and

Drives governor response

continuous Continuous w deadband & limits Discrete time

Frequency ResponseDrives ACE and AGCRegulation Control

Balancing ActsTo Reallocate

Regulation ResponseEconomically

Lags in balancing response That are not considered can

Cause errors in next scheduling

RenewableRamping


Increased Renewables & Impacts

Slide 7

Cycles seconds minutes hours day

Balancing Energy

Regulation15 minute/

hourly scheduling

Day Ahead Scheduling

Governor Response

Inertial Response

Forecast errors & outages

Forecast errors& outages & imprecision

Lag from market to real time & imprecision in response

Volatility and intermittency in

renewables

Fluctuations in Load

Markets Set Prices & Issue Instructions

Capacity Market Sets Prices & Control

System IssuesInstructions

Autonomous Local Control Response

Autonomous Local Physical Response

Amount of inertial responseDetermines frequency response and

Drives governor response

continuous Continuous w deadband & limits

Discrete timeFrequency ResponseDrives ACE and AGCRegulation Control

Balancing ActsTo Reallocate

Regulation ResponseEconomically Lags in balancing response

That are not considered canCause errors in next scheduling

RenewableRamping

Increased Renewables

Increased Forecast Errors

Less Conventional Inertial and

Governor Response

Increased Reserves, Headroom, and Footroom in Scheduling to Accommodate

RenewablesIncreases Costs

Decreased Inertial & Governor ResponseIncreases Regulation Workload. Increased Regulation Capacity in

Scheduling Increases Costs


Responses to Increased Renewables

Slide 8

Increasing the Headroom and Footroom in Scheduling to Accommodate Renewable

Variability and Forecast Error

• Increased MW and MW/min available to balancing market

• Increased regulation capacity available

Increased Costs of Scheduling (higher LMP) due to additional constraints

Increased Costs for Regulation due to Additional Capacity Payments and Additional

Pay for Performance Payments

New Products (CA ISO Fast Ramping Service) Developed

Costs Pushed to Wind Farms (firm scheduling and balancing cost exposure) to Reduce

Direct Market Costs

• Unknown indirect effect on wind investment and on market costs

Shift from HA Scheduling to Intra-Hour (15 minute) Scheduling to reduce ramping

impacts and balancing costs

Focus on improved forecasting DA – HA – intra hour

Requiring grid connected solar and wind farms to provide governor response

Developing Rate of Change of Frequency (ROCOF) as synthetic inertial response

Making governor response and ROCOF ancillaries market products


Types of Analyses Done Today

Slide 10

Methodologies to Estimate Increased Regulation / Balancing Needs due to

Renewable Penetration (GE, NREL, DNVGL)

Simulations of Increased Renewables at Different Time Scales – Regulation to

Annual Production Costs

• Used to assess impact, validate assessments of increased

balancing and regulation costs, assess system dynamic

performance.

A very few studies of the inter-relationship of performance and costs – UK

study, for example of inter-relationship of regulation vs faster balancing

market and of delays in balancing market response.

Very few studies of the benefits of improved forecasting on scheduling and

balancing costs

Very few studies focused on impact of reduced governor and inertial response

Transient stability issues unexplored as compared to frequency response

Understanding the economics of market products for ROCOF and Primary

Response – and use of storage as adjunct to wind/solar farms

There is a need/opportunity to develop a mathematical analysis of

these interrelationships to allow trade-offs in constraints and

services procurement


Quanta Technology, LLC

4020 Westchase Blvd., Suite 300 Raleigh, NC 27607 USA

(919) 344-3000 www.quanta-technology.com

Thank You!

LOW INERTIA SOURCES AND SYSTEM...

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