Integrating High PV Penetrations Into the U.S. Distribution System … · 2019-12-26 · DNV-BEW T&D Department James MacPherson, Power Systems Engineer November 8, 2011 Integrating

DNV-BEW T&D Department James MacPherson, Power Systems Engineer

November 8, 2011

Integrating High PV Penetrations Into the U.S. Distribution System,

Experiences with SynerGEE Electric

© Det Norske Veritas AS. All rights reserved.

Update on High PV Penetration on Transmission and Distribution Grids

Overview Background on High PhotoVoltaic (PV) Penetration Studies

- Hawaiian Electric Company (HECO) - Sacramento Municipal Utility District (SMUD), CPUC CSI RD&D project - Objective: Enable capability to reliably plan and operate with high

penetration of variable renewable resources on the grid - Using SynerGEE to study steady-state limitations of renewable resources

Model Development - Model creation & maintenance - Adding 1000’s of existing & potential PV units to model - PV penetration sweep (load-flow and fault analysis) - Conversion to balanced 3-phase model

Example Results

2



Distribution Modeling Analytical Tools

• SynerGEE Electric – GL Noble Denton – Steady State Analysis – Voltage Analysis – Balanced and unbalanced load flow – Fault current studies

• Equivalent inverter modeling for steady state and fault analysis

– Harmonics – Time sequential analysis (hourly) – Switching routines – Tap changer impacts – Capacitor control and regulation impacts

• PSS/Sincal – Siemens PTI – Steady State and Dynamic Capability – Same as SynerGEE for steady state

analysis, but also includes – Detailed inverter modeling for fault current

studies – Dynamic/Transient Modeling of

Generators – Sub hourly irradiance data input

3



PV Penetration Limits at Different System Levels

4

46kV:12kV

Load Pocket

15 kW Distributed Residential PV

Large Customer PV

NO

3.6 MVAr

W1

W4

W3

W2

46kV:12kV

Area 1

Area 3

Feeder Transformer

Substation



Model Creation & Maintenance

5

• GIS database continually updated by utility

• Convert GIS database to SynerGEE format

• Run in SynerGEE and identify errors (BEW)

• Identify corrections and where to correct (BEW/utility)

• Propose updates to GIS database



Model Development: Adding Existing PV to Model

Done in Excel & Access

Input from utility - Address - Rated kW Capacity - Feeder - Phasing at point of interconnection

For each existing PV unit - Convert address to geographical coordinates

(X,Y) - Match to nearest node with same feeder &

phasing

Aggregate existing PV units as necessary

6 Source: HECO 6



Model Development: Allocating Potential PV



Model Development: Sweeping Potential PV Capacity with Recipe Objective: Create a Recipe to run multiple analyses, changing PV output, and

saving results to CSV files

• Identify potential PV units • Set Generator Output to “Specify Output %”

• Initialize potential PV % outputs (e.g. 0%)

• Run Analyses (e.g. Load-Flow, Fault, etc.)

• Export Results to Excel (.csv)

• Increment PV % outputs (e.g. +1%, +5%)

Loop Until 100%



Example Results: Hi Potential PV Sweep

Effect of PV Penetration on - Min/Max Voltage, Max Loading, Tap

Position

9

Backfeeding at - Feeders, Transformers, and Substation - Minimum Daytime Load

0

2

4

6

8

10

12

0.0

20.0

40.0

60.0

80.0

100.0

120.0

140.0

128

180

232

280

337

386

442

491

546

594

643

905

1166

1423

1681

1939

2203

2462

2719

2981

3237

Tap

Posi

tion

Max

Loa

ding

(%),

Volt

age

(120

V b

ase)

Total PV Generation (kW)

"Feeder A" Potential PV Sweep ResultsMinimum Voltage Maximum Voltage Maximum Loading Depot Rd TSF TP

0 1000 2000 3000 4000 5000 6000 7000 8000 9000 10000

Feeder 4

Feeder 3

TSF 2

Feeder 2

Feeder 1

TSF 1

Substation

Total kW of PV When Backfeeding Occurs

Total kW of PV When Backfeeding Occurs for Feeders, Transformers, and Substation

≈ Sum of TSF 1 & 2

≈ Sum of Feeders 1 & 2

≈ Sum of Feeders 3 & 4



Model Development: Fault Analysis with Distributed PV Inverters not yet

modeled in SynerGEE Electric

Need another means of modeling a current source for fault analysis

Current method time-consuming and difficult to automate in PV sweep

PSLF, Sincal - Dynamics &Transient

stability - Inverter dynamic models

from IEEE and WECC guidelines

Equivalent Inverter Model

Low Voltage Network

Representation

Generator

Transformer

3 PH Fault Current on Distribution

Line

Equivalent Fault Contribution from

Inverter

Switch



Example Results: 3-Phase Fault Current Analysis

0% 1% 2% 3% 4% 5% 6% 7% 8% 9%

10% 11% 12% 13% 14%

0 1000 2000 3000 4000 5000 6000 7000

% C

hang

e in

Fau

lt C

urre

nt fr

om N

o PV

Cas

e

PV Generation on Feeder (kW)

Feeder Max. 3P Fault Current vs. PV Generation

Distributed Potential PV Potential PV at Start of Feeder Potential PV at END of Feeder

5% FC Increase

10% FC Increase

15% PV penetration FC



Results: Time of Day with PV Irradiance Profiles

Separate solar irradiance profile applied to each feeder

Recipe used to loop through 24 hours

-16

-12

-8

-4

0

4

8

12

16

0

200

400

600

800

1000

1 2 3 4 5 6 7 8 9 101112131415161718192021222324

Tap

Posi

tion

PV G

ener

atio

n (k

W)

Hour

Time of Day PV Generation ProfilesFeeder 1 Feeder 2 TSF Tap Position



Model Development: Converting SynerGEE Unbalanced 1-P Model to 3-P Balanced Model

Purpose - Need to study dynamic/transient impacts of

distributed PV

Problem - No automatic conversion between SynerGEE and

other load flow software

Solution - Manually convert models into CIM format

Steps for Conversion - Perform single and two phase “roll up” to three

phase in SynerGEE - Export to Excel database - Manual manipulation of SynerGEE data into CIM

format - Import to other load flow software

Investigating the automation of this conversion process

13

Comparison of voltages at specified distances along the feeder



Summary

Working with SynerGEE to accomplish steady-state load-flow, fault current, harmonics studies

Key needs from SynerGEE: - Inverter PQ model for fault current

analysis - Transient analysis capability - Sub-hourly irradiance inputs

14



Contact James MacPherson Engineer, Power Systems BEW Engineering, Inc. 2303 Camino Ramon, Suite 220 San Ramon, CA 94583 Email: [email protected] Main: 1-925-867-3330 Phone: 1-925-327-3030

15



16

Safeguarding life, property and the environment

www.dnv.com

Documents

Integrating High PV Penetrations Into the U.S. Distribution System … · 2019-12-26 · DNV-BEW T&D Department James MacPherson, Power Systems Engineer November 8, 2011 Integrating