©2015 www.sandc.com

Modeling and Simulation of Battery Energy Storage Systems for Grid Frequency

Regulation

X. Xu, M. Bishop and D. Oikarinen S&C Electric Company

Franklin, WI, USA

1

Outline of Presentation • Overview of energy storage projects in US • Energy storage applications with renewables and others • Modeling and simulations for grid regulations (frequency regulation,

voltage control, islanding operations, reliability, etc.) • Case studies • Real project examples

2

Energy Storage Projects and Capacity in US (from DOE Database as of August 2013)

Source: Grid Energy Storage, DOE Public Report, December 2013

Major Applications of Battery Energy Storage System (BESS)

Source: 2013 Edition of the DOE/EPRI Electricity Storage Handbook

Schematic Diagram of a Typical BESS

Battery

Modeling of BESS for Grid Level Applications - WECC Overall Model Block Structure

Q Control

P Control

Current Limit Logic

IqcmdIqcmd’

IpcmdIpcmd’

Generator Model

Network Solution

Plant Level V/Q Control

Plant Level P Control

VrefVreg

QrefQbranch

PrefPbranchFreq_ref

Freg

Qext

Pref

REPC_A

Pqflag= 1 (P priority)= 0 (Q priority)

REEC_C REGC_AVt Vt

Iq

Ip

SOC/Pgen

Modeling of BESS for Grid Level Applications - WECC Overall Model Block Structure (Cont’d)

Generator/converter module (REGC_A) – This module processes real and reactive current commands from the electrical control module, with feedback of terminal voltage for lower voltage active current and high voltage reactive current management logics, and outputs real and reactive current injections into the network model. Electrical control module (REEC_C) – This module acts on active and reactive power references from the plant controller module, with feedback of terminal voltage for specification of a prescribed reactive control response during voltage dip and feedback of generator power output for monitoring the state of charge (SOC) of battery and setting appropriate active current limits. This module provides real and reactive current commands to the generator/converter module with selection of real or reactive power control priority. Plant controller module (REPC_A) – This module processes frequency and active power output of the BESS to emulate frequency/active power control. It also processes voltage and reactive power output of the BESS to emulate volt/var control at the plant level. This module provides active and reactive power commands to the electrical control module.

WECC REGC_A Model for BESS

REGC_A

Ipcmd 11 + sTg

LVPL & rrpwr

lvpnt0 lvpnt1

gain

V

1

0×

Ip

INTERFACE TO

NETWORK MODEL

LOW VOLTAGE ACTIVE CURRENT MANAGEMENT

Iqcmd -11 + sTg

Iq×

Volim

-Khv

0

0

Vt ≤ Volim Vt > Volim

HIGH VOLTAGE REACTIVE CURRENT MANAGEMENT

Iolim

Vt

-

V

Zerox Brkpt

Lvpl1

LVPL

V

LOW VOLTAGE POWER LOGIC

0

1

Lvplsw1

1 + sTfltr

Iqrmin

Iqrmax

+

+Upward rate limit on Iq active when Qgen0 > 0

Downward rate limit on Iq active when Qgen0 < 0

Source: “WECC Wind Plant Dynamic Modeling Guidelines,” WECC Renewable Energy Modeling Task Force, WECC Modeling and Validation Work Group, April 2014 [Online]. Available: https://www.wecc.biz/Reliability/WECC%20Wind%20Plant%20Dynamic%20Modeling%20Guidelines.pdf

WECC REEC_C Model for BESS

Source: “WECC Energy Storage System Model – Phase II,” WECC REMTF Adhoc Group on BESS modeling, WECC Renewable Energy Modeling Task Force, WECC Modeling and Validation Work Group, March 2015 [Online]. Available: https://www.wecc.biz/Reliability/WECC%20Approved%20Energy %20Storage%20System%20Model%20-%20Phase%20II.pdf

WECC REPC_A Model for BESS

REPC_A

1

0

Vreg

Vref

Freeze state if Vreg < Vfrz

Ibranch

Kc

-

Qbranchemax

emin

Kp + Ki s

Qmax

Qmin

1 + s Tft1 + s Tfv QextRefFlag

dbd

11 + sTfltr

VcompFlag|Vreg – (Rc+jXc)· Ibranch|

11 + sTfltr

1

0

Qref

-

femin

femaxPbranch

Plant_pref

Ddn

Dup

0

0Freq_ref

- fdbd1,fdbd2

- Kpg + Kig s

Pmax

PminFreg

11 + sTp

11 + sTlag

Pref

++

+

+

+

+

+

+

+ 0

1

Freq_flag

Source: “WECC Wind Plant Dynamic Modeling Guidelines,” WECC Renewable Energy Modeling Task Force, WECC Modeling and Validation Work Group, April 2014 [Online]. Available: https://www.wecc.biz/Reliability/WECC%20Wind%20Plant%20Dynamic%20Modeling%20Guidelines.pdf

BESS Modeling and Simulation in PSS®E

WECC Benchmark Test System

1GEN1

1.0234.6

1150.0

43.9R

2LOAD1

1.0232.3

1

59.3

11.0

75.0

21.9

-74.8

-25.2

75.0

21.9

-74.8

-25.2

3BUS3

1.0231.2

24.8

10.2

-24.8

-15.1

24.8

10.2

-24.8

-15.1

1

40

.7

19

.0

40.7

19.0

-40

.7

-19

.0

4LOAD2

1.0115.2

1

68.3

8.1

1 125.3

15.6

-25.3

-15.4

1 125.3

15.6

-25.3

-15.4

7BESS-LV

1.00.5

5BUS5

1.0116.0

-32.2

0.4

32.4

-0.6

-32.2

0.4

32.4

-0.6

41MOTOR2

1.0115.2

1

46

.8

21

.9

46.7

21.9

-46

.7

-21

.9

6GEN2

1.0116.7

165.4

-1.5R-32.4

0.6

32.7

-0.7

-32.4

0.6

32.7

-0.7

1.0232.3

21MOTOR1

8BESS-MV

1.035.0

1 1-1.0

-1.0

1.0

1.0

1 1-1.0

-1.0

1.0

1.01

1.0

1.0RBESS

Simulation of Underfrequency or Overfrequency Condition

Frequency Deviation (pu) BESS Discharge Power (MW)

Time (seconds)12011511010510095908580757065605550454035302520151050

Freq

uenc

y De

viat

ion

(pu)

0.001

0

-0.001

-0.002

-0.003

-0.004

-0.005

-0.006

-0.007

-0.008

-0.009

BES

S D

isch

arge

Pow

er (M

W)

2.5

2

1.5

1

0.5

0

-0.5

Frequency Deviation (pu) BESS Charge Power (MW)

Time (seconds)12011511010510095908580757065605550454035302520151050

Freq

uenc

y D

evia

tion

(pu)

0.009

0.008

0.007

0.006

0.005

0.004

0.003

0.002

0.001

0

-0.001

BESS

Cha

rge

Pow

er (M

W)

0.5

0

-0.5

-1

-1.5

-2

-2.5

Real System Study with BESS Model

BESS 1

BESS 2

BESS 3

BESS 4

Simulation of Contingencies Causing Overfrequency or Underfrequency Conditions

Channel Plot

Without BESS With BESS

Time (seconds)20191817161514131211109876543210

Freq

uenc

y De

viat

ion

(pu)

0.05

0.04

0.03

0.02

0.01

0

Channel Plot

Without BESS With BESS

Time (seconds)20191817161514131211109876543210

Freq

uenc

y De

viat

ion

(pu)

0.01

0.005

0

-0.005

-0.01

-0.015

BESS Charge/Discharge with Overfrequency or Underfrequency Conditions

BESS Charging (MW)

Time (seconds)20191817161514131211109876543210

BESS

Out

put (

MW

)

1

0

-1

-2

-3

-4

-5

BESS Discharge (MW)

Time (seconds)20191817161514131211109876543210

BESS

Out

put (

MW

)

5

4

3

2

1

0

-1

-2

-3

-4

-5

BESS Project in Presidio, Texas (Reliability Application)

• Power quality and high number of outages were major problems • Repairs to troublesome 69-kV line took a long time • Peak loads can exceed the weather-normalized load forecast

• 4-MW, 24-MWh S&C PureWave Storage Management System, installed indoors

• System can back up entire town for 6 hours

Project in Presidio, Texas (Reliability Application) (Cont’d)

S&C’s Project in Santa Rita Jail, Dublin, California

• Average daily power demand of 3 MW in the correction facility

• Needed way to store excess power produced by on-site generation, operate indefinitely without connection to local grid

• Needed way to purchase power off-peak and use it during high-cost peak demand periods

www.acgov.org/smartgrid

Project in Santa Rita Jail, Dublin, California (Cont’d)

• 2-MW PureWave Storage Management System; can power this facility for up to 2 hours

• Facility expects to save nearly $100,000 a year

Project in Santa Rita Jail, Dublin, California (Cont’d)

XCEL Energy Storage Project

• 1 MW, 6 MW-hour Sodium-Sulfur Battery Storage System • Peak Shaving, Wind Farm Output Smoothing, Energy

Dispatching and Arbitrage

S&C Delivered BESS Projects

2-MW System – Ohio

2-MW System – Ohio

1-MW System – West Virginia2-MW System – Indiana

1-MW System – Minnesota

2 x 1-MW System – North Carolina

2-MW System – West Virginia

1-MW System – Catalina

1-MW System – Australia

1-MW System – Scotland2 x 1-MW System – Canada

4-MW System – California

2-MW System – Alameda

1-MW System – New Mexico

1-MW System – New Mexico

4-MW System – Texas

NaSLi-Ion

Advanced Lead AcidNaNiCl

1-MW System – Missouri

Thank you!! Xiaokang Xu, Ph.D. Principal Engineer

S&C Electric Company xiaokang.xu@sandc.com

(414) 448-4048