Aidan Tuohy Technical Leader/Project Manager, EPRI ERCOT Emerging Technology Working Group (ETWG)...

Aidan TuohyTechnical Leader/Project Manager, EPRI

ERCOT Emerging Technology Working Group (ETWG)09/24/2014

Transmission System Considerations for Integrating Distributed Resources

2© 2014 Electric Power Research Institute, Inc. All rights reserved.

Overview

• Background and Potential Bulk System Impacts of Distributed Energy Resources (DER)

• Benefit/Cost Assessment Framework for Integration of DER

• Interconnection Requirements for DER


How much PV Is Possible? DOE SunShot Initiative Scenarios…

Source: NREL, “Sensitivity of Rooftop PV Projections in the SunShot Vision Study to Market Assumptions”

Optimistic, but policy objective PV assumptions, leads toRooftop PV of 120 GW in 2030 & 240 GW in 2050.

Optimistic, but policy objective PV assumptions, leads toRooftop PV of 120 GW in 2030 & 240 GW in 2050.


Inverter – Role in Power System


• Increasing amounts of distributed energy resources– Solar PV,

– Electric Vehicles

– Demand Response

– Distributed storage

– Other distributed generation

• As penetration level of these resources increases, they may impact on bulk system reliability- impacts may include:

– Ramping and Variability Impacts

– Reactive Power Control

– Loss of DR During Low Frequency and Voltage Conditions

– System Protection Considerations

– Under Frequency and Under Voltage Load Shedding (UFLS/UVLS)

– Visibility/Controllability of DR at Bulk System Level

Distributed energy resources will impact bulk system operations

EPRI Integrated Grid

Assessing Costs and Benefits of DER


Integrated Grid – Phase II3 Key Areas & Research Challenges

Benefit - Cost Framework

Benefit - Cost Framework

Interconnection Technical Guidelines

Interconnection Technical Guidelines

Grid Planning & Operations

Grid Planning & Operations

Completed Draft of Benefit-Cost Framework Presently under Internal EPRI Review

Completed Draft of Benefit-Cost Framework Presently under Internal EPRI Review


HostingHosting EnergyEnergy

CapacityCapacity

Distribution System

Bulk System

Customer or Owner

Cost/Benefits

Customer or Owner

Cost/Benefits

Societal Costs/Benefits

Societal Costs/Benefits

Benefit/Cost

1 4

5

3

2

6

Core Assumptions

Adoption/ Deployment Scenarios

Adoption/ Deployment Scenarios

Market Conditions

Market Conditions

Resource AdequacyResource Adequacy

FlexibilityFlexibility

Operational Practices & Simulation Operational Practices & Simulation

Transmission PerformanceTransmission Performance

Transmission Expansion


System Net CostsSystem

Net Costs

System BenefitsSystem Benefits

ReliabilityReliability

Integrated Grid: Benefit Cost Framework

DRAFT


Integrated Grid: Bulk System Analysis

Transmission System

Performance Studies

DER Scenarios

Resource Adequacy

Existing SystemModel(s)

Load Forecasts

Variability Profiles

Existing Generation

Existing Network Model

Resource Epxansion

LOLE/Reserve Margin & Capacity

Credit

New Resources/Expansion

Plan

Thermal / Voltage Impacts

Operational Simulations

Resource Dispatches

Transmission System

Upgrades

Technology options


Losses

Reliability ImpactsReserve &

Operational Changes

LOLE/Reserve Margin & Capacity

Credit

New Reserve & Operational

Modes

Integrated GridBulk System

Analysis Framework

Costs of new resources

Production Costs & Marginal

Costs

Costs of mitigation/upgrades

Cost of Losses

Cost of Base Case

Cost of Scenario

System Flexibility

Assessment

Flexibility Metrics

Line Type LegendData InputFinal ResultFeed-Forward ResultFeed Back Result

Frequency Impacts

Hosting Capacity PV & Demand

Profiles (See Fig. 5.3)

1 RESOURCE ADEQUCY

2 FLEXIBILITY

3 OPERATIONAL SIMULATION

4 TRANSMISSION PERFORMANCE

5 TRANSMISSION EXPANSION

DRAFT


How Will Future Electricity Resource Needs Change?

Ancillary services and capacity may become more valuable to operators causing a shift in market design

Ancillary services and capacity may become more valuable to operators causing a shift in market design

Before After?EirGrid Considerations

•Irish Simulation Study+ 40% renewable scenario+ w/ & w/o add’l A/S set (inertia, ramp, VAR res)

•Change in A/S Costs$60M $300M

•Regulator rejected study, but gives ballpark of potential

changes

EirGrid Considerations

•Irish Simulation Study+ 40% renewable scenario+ w/ & w/o add’l A/S set (inertia, ramp, VAR res)

•Change in A/S Costs$60M $300M

•Regulator rejected study, but gives ballpark of potential

changes

Interconnection Requirements

Examples of Potential Requirements and Performance from DER


General Reliability Concerns

Reliability Functions• Reactive power/voltage control• Active power control

– inertia/primary freq response• Disturbance performance

– voltage & frequency ride through

Other Considerations• Inverter capabilities• Available headroom for wind/PV• Distributed

Inverter-Based Inverter-Based Generators must Generators must supply Reliability supply Reliability Services as they Services as they

Displace Displace Conventional Conventional

Sources of those Sources of those reliability services!reliability services!

Inverter-Based Inverter-Based Generators must Generators must supply Reliability supply Reliability Services as they Services as they

Displace Displace Conventional Conventional

Sources of those Sources of those reliability services!reliability services!


Can Inverter-Based Generation be equipped with Grid Support Functionality?

What functionalities are needed and how should they be required?

Can Inverter-Based Generation be equipped with Grid Support Functionality?

What functionalities are needed and how should they be required?

Key Questions


Low Voltage Ride Through Impact (PJM)

Source: Mahendra Patel, PJM.


Updated Interconnection Rules Reduces Risk of Frequency Instability

50.8

50.6

50.4

50.2

50.0

49.8

49.6

49.4

49.2

Grid

Fre

quen

cy in

Hz

Time in Seconds

0 10 20 30 40 50 60

Source: T. K. Vrana (2011)

Previous Interconnection Rules

Updated Interconnection Rules

German Operating Frequency Limit

Germany

15,000 PV systems

Sized 10kW+

9 GW Nominal Power

Over 3 – 4 years

Costing €70 – 180 Million

Retrofitting/ Replacing


Dynamic Assessment of potential impacts

Impact on Voltages :

Delay in voltage recovery

With and without voltage ride-thru

Impact on Voltages :

Delay in voltage recovery

With and without voltage ride-thru

Impact on Frequency:

Reduction in system inertia due to change in generation mix

PV drop out due to large voltage disturbance (as per IEEE 1547)

Impact on Frequency:

Reduction in system inertia due to change in generation mix

PV drop out due to large voltage disturbance (as per IEEE 1547)


Changes in “Response to Abnormal Voltages”

IEEE 1547-2003

IEEE 1547a

Similar Similar requirement requirement

for for frequencyfrequency

Similar Similar requirement requirement

for for frequencyfrequency


Voltage Regulation – Reactive Power Support

• Power factor setting

• Constant VAR consumption/injection

• Volt-VAR control

• Voltage Setpoint

Can support Can support distribution distribution

and/or and/or transmissiontransmission

Can support Can support distribution distribution

and/or and/or transmissiontransmission


Real power control, ramping, and curtailment

050

100150200250300350400450

4.5 6.5 8.5 10.5 12.5 14.5 16.5 18.5 20.5

DC

Volta

ge &

Cur

rent

Time (s)

Vdc Idc Modbus

-400

-300

-200

-100

0

100

200

300

400A

C Vo

ltage

& C

urre

ntVa Ia

390Vdc

3 Phase Output current ramp(only phase A shown)

DC Current ramp for 100%-25%-75% Curtailment

Modbus Signal(not actual voltage)

Modbus Signal(not actual voltage)

100% 75%25% In 4 secondsIn 6 seconds


Today’s Smart Inverter TechnologyEnabling Changes in Grid Codes

Inverters converts DC energy to AC energy and interface the generating plant with electricity grid

Traditional Inverter Functionality Smart Inverter Functionality

• Matching plant output with grid voltage and frequency

• Providing safety by providing unintentional islanding protection

• Disconnect from grid based on V/f set points

• Active power reduction in case of over-frequency

• Fault Ride Through (FRT)• Reactive power and voltage

support• Communication with grid• Many more

DC Power AC Power


What if Standards are not Changed?

Source: DOE SunShot Vision Study (Total PV Capacity in U.S. 2008 – 2030)

Not changing is

not an option!

Question is

when?

Retrofitting inverters in a later date could be pretty expensive


Summary

• Increasing levels of Distributed Energy Resources– Getting out ahead is important to be able to fully utilize

these new resources

• Need framework to understand costs/benefits– EPRI Integrated Grid effort developing framework– Should inform market development

• Inverter based generation can behave in ways desirable to system operations– Need to specify requirements– EPRI white paper series coming out soon

[email protected]

Together…Shaping the Future of Electricity

Aidan Tuohy Technical Leader/Project Manager, EPRI ERCOT Emerging Technology Working Group (ETWG)...

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