ISO-NE PUBLIC

A P R I L 1 1 , 2 0 1 9 | F O L S O M , C A

Kannan SreenivasacharISO-NE

SPIDERWG

Islanding Study - Impact of DER

ISO-NE PUBLIC

Disclaimer

• The results shown in this presentation do not represent the official results of ISO-NE as studies similar to this are being performed by SS-38 NPCC working group

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ISO-NE PUBLIC

Presentation Outline

• System Modeling

• PRC-006 Standard

• Impact of Inertia on island Performance

• Impact of DER and Load Shedding on island Performance

• Some solutions to improve island Performance with DER

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SYSTEM MODELING

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ISO-NE PUBLIC

System Modeling

• 2023 Summer Peak Gross Load for New England is 28176 MW

• Net Load assumed is 25976 MW

– 2200 MW of Retail-Scale Distributed Energy Resources (R-DER) assumed and 3000 MW of Utility-Scale Distributed Energy Resources (U-DER)

• Underfrequency Load Shed (UFLS) Scheme in NPCC– 4 Stages of 7% each and 1 stage of 2% anti-stall block

• Frequency settings : 59.5, 59.3, 59.1, and 58.9 Hz for 7% block• Frequency settings : 59.5 Hz for 2% anti-stall block• 7% load shed stage trips in 300 ms (relay (100ms) + breaker time (200ms))• 2% load shed stage trips if frequency is below 59.5 Hz for more than 10

seconds with breaker time of 200ms

– Up to 30% of load can be shed under UFLS

• Dynamic Load model included (CMLD)– Default protection settings used

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Load Distribution- CMLD Load Model

ZONE MOTOR A MOTOR B MOTOR C MOTOR

D ELECTNX STATIC TOTAL

60 (ME) 283 226 169 358 301 547 1884

61(NH) 400 300 200 450 400 751 2501

62(VT) 160 103 94 179 141 264 941

63(EMA) 1745 1163 678 2229 1551 2326 9692

64(WMA) 445 385 237 741 415 741 2964

65(RI) 298 259 139 518 278 498 1990

66(CT) 997 854 427 1780 1282 1780 7120

67(IND) 104 28 57 9 63 54 315

68(SS) 254 69 138 23 154 131 769

NUMBER OF LOADS WITH DYNAMIC LOAD MODEL IS = 1478TOTAL DYNAMIC MODEL LOAD IN AREA 101 = 28176 MW

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ISO-NE PUBLIC

System Modeling, contd.

• DER modeling

– 5200 MW of DER modeled (2200 MW assumed to be R-DER and 3000 MW to be U-DER)

– 2200 MW of R-DER is assumed to be part of the load and modeled to trip along with UFLS frequency trip settings

• A total of 513 MW of R-DER is set to trip at each UFLS frequency set-point of 59.5 Hz, 59.3 Hz, 59.1 Hz and 58.9 Hz (513 MW X 4 = 2052 MW)

• An additional 148 MW of R-DER set to trip at 59.5 Hz (if frequency is below 59.5 Hz for 10 seconds)

– Each block of 513 MW trips in 300 ms (relay (100ms) + breaker time (200ms))– Block of 148 MW trips if frequency is below 59.5 Hz for more than 10 seconds

with breaker time of 200ms– FRQTPAT models used

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ISO-NE PUBLIC

System Modeling, contd.

• Voltage Trip Settings Modeled for all inverter-based DER as per ISO-NE Source Requirement Document (SRD)– VTGTPAT modeled with “Required Settings”

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System Modeling, contd.

• Frequency Trip Settings for all inverter-based DER as per ISO-NE SRD (Identical with IEEE 1547-2018 Cat II default settings)

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System Modeling, contd.

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System Modeling, contd.

• R-DER and U-DER Modeling in Loadflow (for each DER)

R-DER1

R-DER2

R-DER3

R-DER4

R-DER5

U-DER

DER (–ve load) converted to 6 separate generators and feeders between load bus and DER bus

Load DER busLoad

Assume DER = -1.0 MW

Load BusLoad Bus

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System Modeling, contd.

• R-DER and U-DER Modeling in Loadflow (42 - 58 % split)

R-DER1 =0.098 MW tripped at 59.5 Hz (trips in 300ms)

U-DER = 0.58 MW (Trips on Voltage only, Frequency tripping not included for this study)

DER buses

Load (7% tripped at 59.5, 59.3, 59.1, 58.9 Hz, and 2% at 59.5 Hz)

R-DER2 =0.098 MW tripped at 59.3 Hz( trips in 300ms)

R-DER3 =0.098 MW tripped at 59.1 Hz( trips in 300ms)

R-DER4 =0.098 MW tripped at 58.9 Hz(trips in 300ms)

R-DER5 =0.028 MW tripped at 59.5 Hz with relay time of 10 seconds and breaker time of 200ms

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Load Bus

Assume DER = -1 M

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System Modeling, contd.

• U-DER Modeling– REGCAU1, REECAU1, and REPCAU1 model– Voltage control included– Plant controller included– Voltage trip model included

• R-DER Modeling– REGCAU1 and RECCAU1 model used– Voltage control not used– Constant real and reactive power mode (Unity pf)– Voltage and Frequency trip model included

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PRC-006 STANDARD

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PRC-006 Standard

• PRC-006 deals with Automatic Underfrequency Load Shedding

– Each PC shall develop a UFLS program that meets the performance characteristics in simulations of underfrequency conditions resulting from an imbalance scenario of up to 25 percent deficiency within identified Islands

• NPCC Directory - 12 Automatic UFLS Program Requirements:

– Frequency does not remain below 58.5 Hz for greater than 10 seconds, and does not remain below 59.5 Hz for greater than 30 seconds, for a generation deficiency of up to 25% of the load

• Deficiency defined as

𝑃𝑃𝑃𝑃𝑃𝑃𝑃𝑃𝑃𝑃𝑃𝑃𝑃𝑃 𝐷𝐷𝑃𝑃𝐷𝐷𝐷𝐷𝑃𝑃𝐷𝐷𝑃𝑃𝑃𝑃𝑃𝑃𝐷𝐷 =𝐿𝐿𝐿𝐿𝐿𝐿𝐷𝐷 − 𝐺𝐺𝐺𝐺𝐺𝐺𝐺𝐺𝐺𝐺𝐿𝐿𝐺𝐺𝐺𝐺𝐿𝐿𝐺𝐺

𝐿𝐿𝐿𝐿𝐿𝐿𝐷𝐷

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PRC-006 Standard, contd.

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Load Definition

• In the context of DER, there are two definitions of load

– Net Load :

• Net Load = Gross Load – R-DER (BTM)

• Net Load = 28176 - 2200 MW = 25976 MW

• 25% deficiency = 6494 MW

– Gross Load:

• Gross load = Total Load (excluding R-DER (BTM))

• Gross Load = 28176 MW

• 25% deficiency = 7044 MW

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Net Load v/s Gross Load

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Correct approach?

• Using Net Load and Gross Load for determining deficiency provides different results

• Which load definition to use for testing the performance of UFLS Schemes

– Net Load or Gross Load?

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Impact of Inertia on Island Performance

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Island Inertia

• With DER displacing Synchronous machines, system inertia decreases

– Lower inertia causes larger frequency drop

– Rate of frequency decline is higher

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Island Performance – Inertia

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Island Performance – Inertia, contd.

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Island Inertia

• What is the minimum inertia required for an island with DER resources to be stable?

– Is there an inertia index that can determine the stability of islands?

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Impact of DER tripping on Island Performance

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Impact of DER Tripping with UFLS

• With increasing R-DER penetration, island performance may deteriorate and in some cases may not meet the performance requirements– Need to consider R-DER tripping with UFLS– Reduces the effectiveness of UFLS Schemes

• In addition to R-DER and load tripping due to UFLS, there is a possibility of U-DER tripping on voltage and in the no-trip zone of the PRC-006 curve

– Adds to island generation deficiency and further deteriorates the performance

– May require compensatory load shedding

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R-DER Tripping with UFLS and U-DER Tripping on Voltage

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U-DER Tripping on Voltage Due to UFLS

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Some Solutions to Improve Island Performance

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Some Solutions to Improve island Performance• Battery Storage

– May be able to provide quick injection of real power and arrest frequency decline

– Potential for voltage control

• Convert R-DER to U-DER– Conceptual– Requires dedicated feeders (Express Feeder)

• Other Solutions– Dynamic Voltage Control Devices

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Battery Storage – 1500 MW (6 MW each at 250 buses)

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Conceptual Solution to Improve Island Performance

R-DER 10kW

UFLS Relay

If 20,000 Residents have 10 kW R-DER, the feeder will have a total of 200 MW of R-DER (0.01 *20,000 = 200 MW)

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ISO-NE PUBLIC

Conceptual Solution to Improve Island Performance, contd.

UFLS Relay

Express Feeder- 200 MW of U-DER

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Replace 200 MW of R-DER with a total of 200 MW of U-DER (0.01 *20,000 = 200 MW)

DER 10kW

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Conceptual Solution-Response

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Advantages of Express Feeders

• No R-DER trips due to UFLS

• Will improve island Performance

• Each resident can request the area Transmission Owner to install DER capacity based on their investment on an express feeder and not have it on their roof

• The revenue obtained by each resident based on their investment in DER on the express feeder could be deducted from their electricity bill

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