Existing, Advanced and Smart Grid Technologies for Renewable Integration

Presented toIEEE PES San Francisco Chapter

Integration of Renewable Resources -Challenges & Solutions

By Merwin Brown, DirectorElectric Grid Research

This presentation is based in part on work sponsored by the California Energy Commission, but does not necessarily represent the views of, nor has it been approved or disapproved by, the Energy Commission.

November 15, 2010

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For most of the 20th Century, transmission had a relatively simple role moving electricity from central power plants to the consumers.

Transmission system behavior was predictable, and under the close control of an operator -much like conducting an orchestra.

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But conducting the 21st

century electric grid is becoming a more hair raising experience:

• Being connected to the world’s largest machines, i.e., a multi-state, multi-country, brittle power grid

• Accommodating competitive wholesale power markets

• Serving growing and changing electric loads that are becoming part of the “orchestra”

• Dealing with economic and public policy pressures

Being instrumental for meeting aggressive renewable energy goals

But to grid operators, looks like this…

Renewable resources portfolio mix for33% 2020 might look like this…

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Wind Biomass

Geothermal

Solar

~20,000 MW of New Generation

The Saga of Renewable Generation and Grid Integration reveals many challenges.

But renewable resources portfolio mix for33% 2020 might look like this to grid operators

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The Saga of Renewable Generation and Grid Integration reveals many challenges.

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The Saga of Renewable Generation and Grid Integration

...

. .... . ....... . ... ...

Most central station generation will be located remote from customers.

HIGH WINDS

Provide AccessBuilding new transmission lines is becoming increasingly difficult and taking longer.

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Building new transmission lines is becoming increasingly difficult and taking longer.

• Proving need and value• Distributing benefits & allocating costs

• Assessing and mitigating environmental, land use & aesthetic impacts

• Getting approval from multiple agencies and jurisdictions

New LineNIMBY$X

Delay in siting & building new transmission is often cited as major barrier to meeting renewable generation policy goals.

The Continuing The Saga of Renewable Generation and Grid Integration

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Renewable Power Plant

...

. .... . ....... . ... ...

Some renewable generation is unique, e.g.,• Intermittent• Fast Ramp-Rates• Over Supply• Low Inertia The power grid

system must accommodate generation’s unique behaviors.

PV output on sunny day in NV (10 sec sampling)

PV output on partly cloudy day in NV (10 sec sampling)

Source: NERC Report - Accommodating High Levels of Variable Generation – March 2009

Solar generation can vary widely from day to day and hour to hour.

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Wind generation can vary widely from day to day and hour to hour.

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Tehachapi-area, April 2005

Typical load & wind profiles are almost inverse images

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CAISO Load -- Summer 2006

22,000

24,000

26,000

28,000

30,000

32,000

34,000

36,000

38,000

40,000

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24

Hours

MW

Load

Total Wind -- Summer 2006

200

300

400

500

600

700

800

900

1,000

1,100

1,200

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24

Hours

MW

Wind Generation

Creates issues with load-following ramping and oversupply.

Thanks to

Variable generation can increase the need for system flexibility.

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Thousands of MW of new rapidly dispatchable generation required for regulation and load-following ramping.

Source: NERC Report - Accommodating High Levels of Variable Generation – March 2009

Projected Profiles of Wind and Solar Combined

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Wind and solar generation combined appear to make ramping worse.

Thanks to

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Imbalance between Generation and Load

Typical Oversupply Conditions –Usually at night in spring

Summary: Transmission must accommodate supply uncertainty, rapid up- and down-ramp rates, and over generation.

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...

. .... . ....... . ... ...

The Continuing The Saga of Renewable Generation and Grid Integration

Increase Capacity

Renewable Power Plant

• Difficulties with siting new or upgrading existing transmission

• Thermal Limits• Stability Constraints (Voltage, Transient, Dynamic)

• “N-1” Contingencies

Existing infrastructure is constrained.

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...

. .... . ....... . ... ...

There are essentially two options for successful expansion and operations of T&D:

Renewable Power Plant

…Improved or new T&D functionalities to make expansion and operations easier and less costly.

The traditional “build” solutions, i.e., investments in wires, towers, poles and power plants, and…

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• …traditional “build” solutions, i.e., investments in wires, towers and power plants, can’t do it alone.

• New technologies will be needed to make renewable integration easier and less costly…

For now we can “build” our way out of these problems, but at higher renewable penetrations…

…especially technologies that make the grid smarter

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New Technologies to Provide Faster Access for New Renewable Plants…

… by putting new power lines in a better light.• Underground Transmission • High Voltage Direct Current • Engineered Compact

Designs• Advanced Transmission

Line Conductors• Distributed Renewables &

Demand Response• Web-based Interactive

Stakeholder Siting Tools• Cost Allocation & Strategic

Benefit Analysis Tools

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New Technologies to AccommodateUnique Renewable Generator

Behaviors…

• Energy Storage & Intelligent Agent (temporal power flow control)

• Solar and Wind Forecasting Tools

• Generator and Load Modeling

• Demand Response • Synchrophasor Monitoring• Power Flow Control (spatial)• Distributed Generation • Advanced Intelligent

Protection Systems• Statistical and Probabilistic

Forecasting Tools

Tehachapi Wind Generation - April 2005

IntermittencyRamp RateInertiaOver Supply

…through a smarter and more flexible grid.

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New Technologies for Increased Grid Power Capacity…

North-South COI

California –Desert Southwest

• Dynamic Thermal Ratings• Real-Time System Ops

(synchrophasors) • Power Flow Control (spatial)• Energy Storage (temporal

power flow control)• High Voltage Direct Current • Distributed Generation &

Demand Response• Advanced Intelligent

Protection Systems• Statistical & Probabilistic

Analysis & Planning Tools• Advanced Transmission

Line Conductors

… by optimizing the grid for greater power flow.

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Example: Increase Capacity of Transmission Corridors via New Line Materials.

• High-Temperature, Low-Sag Conductors: New composite core materials replace steel.

• > 2X power flow through transmission corridor.

• Upgrade transmission conductor without rebuilding transmission towers

• 3M’s version being tested at San Diego Gas and Electric.

3M High-Temperature Low-Sag Conductor

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Station transformer is

where the individual wind turbines come together as a power plant

Collector system with several

overhead and underground feeders

Power Grid

POIIndividual wind turbines have

specific dynamic model based on technology type.

Updating dynamic wind power plant models reduces chances of grid problems.

Example: Accommodate Renewable Generation Unique Behaviors

Invalid models fail to predict potential risk.

Four basic topologies based on grid interface:o Type 1 – conventional induction generatoro Type 2 – wound-rotor induction generator with variable rotor

resistanceo Type 3 – doubly-fed induction generatoro Type 4 – full converter interface

generator

full power

PlantFeeders

actodc

dctoac

generator

partia l power

PlantFeeders

actodc

dctoac

generator

Slip poweras heat loss

PlantFeeders

PF controlcapacitor s

actodc

generator

PlantFeeders

PF controlcapacitor s

Type 1 Type 2 Type 3 Type 4

Wind Dynamic Model

Types of Wind Turbine Generator

Taken from, Ed Muljadi, NREL, CEC Wind Turbine Dynamic Modeling Project, October 25, 2010

Combined Regulation Services between CAISO and BPA

Cost of Regulation in CAISO$300M/yearDouble every 3 years

Proposed system configuration2 resources: (flywheel & hydro) BPA & CAISO conventional regulation signalsThe hydro unit provides smooth/slow regulation and helps maintain the desired energy level in the flywheelThe flywheel provides the fast regulation, helps minimize the stress on the hydro unit and keeps its output within the limits

Modeled Benefits of the Wide-Area Energy Management & Storage Concept

• Reduce regulation reserve by up to 30% • Provide fast, cost-effective, and efficient ancillary services

o Minimize wear-and-tear of conventional regulating unitso Operate conventional regulating units close to their most

efficient operating point.o Allow the storage devices to excel in specific applications that fit

their characteristics Allow the flywheel to serve biased regulation signals and support

the flywheel by maintaining a reasonable state-of-charge (SOC)• Easy scalable technology• Compatibility:

o Fully compatible with the existing BPA and CAISO AGC systems

o Fully compatible with the other technologies such as ACE Diversity Interchange (ADI)

• Can be used with the other Balancing Authorities

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Two Views: August 10th, 1996, California-Oregon Intertie Power Flow During Generator Trip

Simulated COI Power (initial WSCC base case)

What the operator saw

Observed COI Power (Dittmer Control Center)

Simulated COI Power (initial WSCC base case)

What the operators saw

What synchrophasors showed

This event triggered an inter-area power oscillation and ended in a wide-area power outage in western US.

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A number of these oscillations are showing up annually, and are a cause of growing concern.

North – South0.25- 0.3 Hz

East-West 0.6- 0.7 Hz

California –Desert Southwest 0.5 Hz

Alberta 0.45 Hz

These oscillations have caused transmission capacity to be derated by thousands of MW in the western interconnection, restricting the export/import of renewable power. System inertia is thought to be a factor.

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Some renewable generators have low or no inertia.

If large amounts of renewables worsen the oscillation threat, how will the grid operator be able to respond?

• Traditional (thermal) power plants have inertia in the rotational mass of their turbine-generators.

• Some renewables exhibit traditional inertia

• Wind and some solar exhibit low or no inertia.

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HVDC Terminal

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Projected WSCC Monitors, 1995

jfh01/24/95

Power System Analysis Monitor (BPA)

Power System Monitor

Phase-Angle Measurement Unit (Macrodyne)

Dynamic System Monitor (PTI/Hathaway)

Portable Power System Monitor (BPA)

*Proposed installation

PMU

DSM

PSMPPSM

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PMU

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PSAM

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PMUs (Phasor Measurement Units)

WECC

Synchrophasor Measurements –The Basis of the “Smart Grid”

Transmission

Data 425

450

475

500

525

550

575

30 60 90 120 150 180 210 240

Time - seconds

Vol

tage

- kV

John Day Malin Summer L Slatt McNary

Grizzly reactor #2

Grizzly reactor #3

Ashe reactor

Time Synchronous Data

GPS Satellite

Time-Stamp

Control Center

Courtesy of EPRI

Useful Real-Time Information

Are like “X-ray” to “MRI” improvements in diagnostics capability.

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Before Synchrophasor Measurements

PowerSystem

Unobserved Response

Disturbances

Traditional Real-Time Data Rate = Every 4-5 seconds

Addition of synchrophasor measurements throughout the western electric grid would create a dramatic change in speed and applications for situational awareness of the power system.

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After Synchrophasor Measurements

PowerSystem

Unobserved Response

Disturbances

Traditional Real-Time Data Rate = Every 4-5 seconds

Automatic ControlObserved Response

Information

System Planning

System Operation

Decision Processes

Measurement Based Information System

WECC

30/second^

Synchrophasors^

An unprecedented ability to see, know, plan and control for increased reliability and economic efficiencies.

CAISO, SCE, PG&E, and SDG&E Are Pioneering the Use of Phasor Technologies in California

Compliments of CERTS

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Mode Estimate: Example

Poorly Damped ModeOs

cillat

ory F

requ

ency

(Hz)

Damping Ratio (%)

Alert Threshold<5% damping

Alarm Threshold<3% damping

Photo courtesy CERTS

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Other Synchrophasor ApplicationsAngle/ Frequency/Voltage/FlowMonitoring , Trending &Alarming

Applications for Renewables &DG

Planned Power SystemSeparation

Wide Area PSS Stabilization

Improved State Estimation

Congestion Management

Smart Grid Applications

Linear State Measurement

Oscillations Damping

Voltage Stability Monitoring

Adaptive Protection

Wind Site Voltage Control Interconnection WideDynamic State Estimation

Power System Restoration

Steady-state System Baselining (e.g., based on angle separation)

1 to 3 Years 3 to 5 Years > 5 Years

Necessary and Critical

Critical with Added Benefits

Moderate Need, Added Benefits

Requires More Investigation

Deployment Challenge

LOW MED HI

PMU Placement Strategies

Phasor Data Network &Storage

Event &Performance Analysis

System Dynamic Model Validation

Mode Meter and Mode Shape Identification

Dynamic Nomograms

Dynamic State Estimation

Voltage Stability Control

Transient Stability Control

System Inertia Monitoring

Frequency Response Monitoring

Advanced Remedial Action Schemes

Wide Area Frequency Response

Real Time Transient Stability Margin

Box Colors:

√√

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• Expand situation awareness to automated control, intelligent protection and decision support O&M.

• Integrate operator intelligence with physical system actions, e.g., power flow control, restoration, congestion management, storage, demand response, distributed generation…

• Enhance rate and level of understanding and acceptance by planners, policy makers, regulators and public

• Expand into system security from assaults, e.g., earthquakes, wildfires.

• Integrate the customer into the decision making processes

Some Other “Smart” Aspects of New Grid Technologies

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For additional information or discussion, contact :

Merwin BrownDirector, Electric Grid Research Voice: 916-551-1871Fax: 916-551-1874Merwin.Brown@uc-ciee.orgwww.uc-ciee.org

“People tend to overestimate what can be accomplished in the short run but to underestimate what can be accomplished in the long run.” Arthur C. Clarke

And he’ll find someone to help you.