miso & neighboring u.s. electric grid operators

MISO & neighboring U.S. electric grid operators

1

MISO 15 states +

Manitoba

42 million customers

$30 billion market

> 6,600 generation units with 175,000 MW capacity

68,500 miles of high voltage transmission lines

> 180 member utilities

> 460 market participants MISO Control Centers:

Eagan, Indianapolis (HQ), Little Rock

Renewable Integration Impact Assessment (RIIA) seeks to find inflection points of renewable integration complexity

2

0 10 20 30 40 50 60 70 80 90 100

Ren

ewab

le In

tegr

atio

n C

ompl

exity

Renewable Energy Penetration (steps of 10%)

Illustrative example

Inflection points are milestones where complexity significantly

increases.RIIA begins by

modeling the current system.

Focus AreasRESOURCE ADEQUACY

Having the sufficient capacity of resources to reliably serve peak demand

Ability to withstand unanticipated component losses or disturbances

Ability to provide energy in all operating hours throughout the year

ENERGY ADEQUACY

OPERATING RELIABILITY

Base 10% 20% 30% 40% 50%

Rene

wab

le In

tegr

atio

n Co

mpl

exity

Renewable Energy Penetration Levels

Resource Adequacy

Energy Adequacy (Hourly)

Operating Reliability (Steady State)

Operating Reliability (Dynamics)

Total

3

Inflection point

Results indicate integration complexity increasing sharply post 30% renewable penetration

0.00%

0.01%

0.02%

0.03%

0.04%

0.05%

0.06%

0

10

20

30

40

50

60

70

80

90

0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23

Loss

of l

oad

prob

abili

ty

Net l

oad

diur

nal p

rofil

e* (G

W)

Hour (EST)

Base

50%

100%

As renewable penetration increases, the risk of losing load shifts and compresses to a smaller number of hours

4

RISKNet peak load shifts from 3 pm to 6 pm.

• Probability of losing load is targeted at one day in ten years over all penetration levels.

• While aggregate risk remains constant, the risk in particular hours increases.

*Profile shapes represent hourly averages across all days of the 6 study years.

5

Increasing variability due to renewable generation will require generators to perform differently than today

More hourly variability from renewables…

…requires increased flexibility (curtailments and ramp capability)

Wind Curtailment (Thousands of MW)

Coal and Gas Ramp (% of capacity)

Renewable Output(Thousands of MW)

24 hours1 day

24 hours1 day

24 hours1 day

20

10

0

30

4

2

0

6

15

5

0

20

10

Wind at 40%*

Solar at 40%

Windat 10%

Solar at 10%

At 40%*

At 10%

At 40%*

At 10%

* All %’s in labels refer to MISO-wide renewable penetrations levels

Energy adequacy solutions are needed at the 40% milestone to utilize the diverse variable resources across the footprint

6

• Introduced new transmission expansion optimization technique to develop solutions

• Evaluated 11,300 transmission candidates in MISO and selected ~80 cost effective solutions

Renewable Energy Penetration

Target Base (without Energy adequacy solutions)

With Energy adequacy solutions

40% 34.7% 38.5%

Complexity

High

Low

Power delivery from low short circuit areas may need transmission technologies equipped with dynamic support capabilities

7Heat Map represents Short Circuit Ratio (SCR) at 40% Milestone

Low SCR

High SCR

Low SCR

High SCR

New HVDC links

AC linksDynamic reactive power support devices(STACOM, Synchronous Condensers)

Upgrading Existing HVDC link

HVDC Upgrade AC Line +Caps +SynchronousCondensers

AC Line upgrades

HVDC Technology

Sync Condenser

Sync Condenser

Cos

t

AC-Only Technology

Stability Fixes

To mitigate low SCR issues, feeding wind into HVDC terminals and upgrading HVDC capacity may be cheaper than installing large number of synchronous condensers and mitigating small signal stability issues created

Qualitative cost comparison for different transmission technologies for equal reliability performance

8

Frequency response is stable up to 40% renewable penetration, but at 50%, planned headroom is required to remain above Under Frequency Load Shed (UFLS) threshold

No headroom on renewable resources assumed

Frequency curves for ~4500 MW trip

Base

20%

30%

50%

40%

UFLS Threshold= 59.5 Hz

Xcel Energy Service Territory

9

Northern States Power

Public Service Company of Colorado

Southwestern Public Service

8 states 3 Planning Regions 2 RTOs 2 Interconnections

Carbon Reduction80% by 2030100% by 2050

What is System Reliability?

10

Facility Ratings

Planning Reserves

Operating Reserve

Contingency Analysis

Basic Building Blocks

11

Every-Hour Energy Adequacy

Essential Reliability Services

Car

bon-

Free

Res

ourc

es

Adv

ance

d Te

chno

logy

Disp

atch

Cap

abili

ty

Clean Energy Future

Education

Implementation

Inclusion

atcllc.com

Challenges to Maintaining Renewable ModelsRobert Krueger, P.E.American Transmission Company, [email protected]

atcllc.com 13

• Retirement of fossil fuel generation– Older facilities retiring requiring additional transmission and/or

replacement generation• High penetration of renewables

– Rarely in areas with strong networks and high load• Space requirements for large-scale renewable facilities

– Weak grids are likely to exist in these areas.• Potential for control systems interaction

– Interaction between renewable and rotating machines– Interaction between multiple renewables facilities

Changes in System Topology and Inertia

atcllc.com 14

• PSS/E/TSAT Studies for G-T, etc. • Manufacturer Models – detailed studies

– Most accurate representation of Renewable Facilities– Pressures manufacturers to produce data for studies– Manufacturers must update models for future software releases

• Generic Models –system wide studies– One Size Fits All Approach – Limited model options

• May not fully represent the facility accurately– Manufacturers provide parameters for all modules

The Traditional Way of Doing Things

atcllc.com 15

• Positive Sequence, RMS Model (PSSE/TSAT, etc) – Simplified control system representation– May overestimate stability, or represent protection and controls in

insufficient detail– Potential simulation convergence issues

• 3-Phase, EMT Model (PSCAD)– Able to evaluate interactions between control systems

• More detailed modeling• Actual control systems modeled

– Models require more manufacturer engagement

Comparison of Planning Tools for Transient Studies

atcllc.com 16

Case: Worst N-1 Contingency - PSS/E

atcllc.com 17

Case: Worst N-1 Contingency - PSCAD

atcllc.com 18

• Generic Models– Manufacturers may update parameters when issues identified

• Initial parameterization may not be accurate – Extensive number of manufacturers and volume of data

• Manufacturer Models– Difficulties getting updated DLLs

• Manufacturer may want GO to pay for updates– Manufacturers leaving market place or not supporting older technology

• PSCAD Models– Many manufacturers are not equipped to translate control systems for use

in PSCAD– Manufacturers may need to contract consultants to build models

• Allowance for this activity may delay study efforts in the G-T process

Challenges to Maintaining Various Model Types

Integrating High Levels of Renewable ResourcesPanelist: Douglas BrownCo-Author: Nelson Bacalao

siemens.com/digitalgridUnrestricted © Siemens 2019

Unrestricted © Siemens 2019November 2019

Integrated Resource Plan for Puerto Rico Electric Power Authority

20-year planning horizon, 2019 to 2038

Peak load: approximately 2,250 MW

Renewable Portfolio Standard• Act 82, 2010• 20% by 2035

• Puerto Rico Energy Public Policy Act, 2019• 40% by 2025• 50% by 2040• 100% by 2050

Puerto Rico Transmission System [Source: NREL]


Transition from Fossil Fuels to RenewablesBy end of planning horizon in 2038:• 79% of installed capacity consists of renewable generation,

battery energy storage (BESS), or CHP distributed generation.

• Renewable generation accounts for 63% of total production


Storage Enables RenewablesIRP recommends installation of 2,967 MW of utility-scale solar, 1,014 MW of residential solar and 1,640 MW of battery storage.

Primary Storage Benefits• Decouple energy supply and demand• Provide primary and secondary frequency

regulation• Creation of self-reliant minigrids for resiliency

Load

From Storage

Storage Level

Energy to Storage


SCR Limitations of Grid Following InvertersIRP study utilized existing inverter technologies for PV and BESS inverters.

Grid-following inverters track the voltage angle of the grid to control their output and require a “stiff” system voltage.

IRP recommends converting 8 generators to synchronous condenser operation to maintain short circuit ratio of 1.5• Condensers at three locations• Total generator rating approximately 2,200 MVA

Grid Following Inverter Structure [Source: Siemens]


Leverage Storage to Maintain StabilityWind and solar projects in Puerto Rico must comply with Minimum Technical Requirements (MTR). • Voltage and frequency ride-through• Voltage regulation• Steady-state and dynamic reactive power controls• Frequency response and frequency regulation controls• Ramp-rate controls

Model assumptions for new solar and BESS projects• Satisfy MTR• Following fault clearing, inverter returns to pre-

contingent active power output in 100 msec

When system is inverter dominated, lack of generation immediately following fault clearing causes frequency dip.

System frequency for three-phase fault.


Leverage Storage to Maintain StabilityFrequency dip can be addressed by changing BESS controls.• Change frequency droop setting• Programmable synthetic inertia• Fast frequency response

IRP recommends reducing BESS frequency droop setting from 5% to 3%.

System frequency for three-phase fault.


System Operation with 100% Non-Synchronous Generation

ChallengeOperation of Hawai`i Island’s power system with up to 100% PV and wind generation?

SolutionOperator Support system for online adaptation of controller parameters for diverse generation components to maximize N-1 resiliency

ReNew100 ObjectiveDemonstrate Operator Support System for N-1 secure operation • in real-time simulation of Hawai`i Island’s power system• embedded in a commercial EMS solution• under changing conventional and renewable generation mix• including 100% non-synchronous generation from wind and solar

Project data• Timeline: April 2019 – March 2022• Partners: Siemens Digital Grid, Siemens Research Center, HECO, PNNL,

OPAL-RT


Douglas BrownSenior Manager, Power System ConsultingSiemens Power Technologies International10900 Wayzata BoulevardMinnetonka, MN [email protected]

siemens.com

mailto:[email protected]

miso & neighboring u.s. electric grid operators

Documents