UL1741 SA, Rule 21, and what it means for you

Josh Brister

Sr. Manager, Product Management and Tech Sales

Contents

• What are these requirements?

• UL versus IEEE versus Rule 21, etc

• How will this help support the grid?

• How will this be implemented?

• How do I remain compliant?

What is UL1741 SA?

• Officially called “UL 1741: Standard for Inverters, Converters, Controllers and Interconnection System Equipment for Use with Distributed Energy Resources”

• In essence, the test standard by which inverters are certified for interconnection to the grid, with particular respect to:

‒ Grid Voltage

‒ Grid Frequency

• Intended to supplement and be used in conjunction with IEEE 1547 (Standard for Interconnecting Distributed Resources with Electric Power Systems) and IEEE 1547.1 (Standard for Conformance Test Procedures) in accordance with NEC

• Developed by workgroup representing Inverter industry, electric utilities, NREL, EPRI

• SA is short for Supplement A, an addition to the existing UL 1741 standard

‒ Designed to create a standard for inverters more capable of dealing with a volatile grid

‒ “Future-Proofing” by creating a standard for inverters to actively manage grid functions

UL vs. Rule 21 vs. 14H

UL 1741 SA

CA Rule 21 HI Rule 14H

PG

&E

SCE

SDG

&E

Product Certification Standard

State Interconnection Requirements, also called Source Requirements Document (SRD)

Local Interconnection RequirementsH

ECO

MEC

O

KU

IC

How will UL 1741 SA be implemented?

All projects permitted and approved for interconnection on or after September 8th 2017 will need to be certified to UL 1741 SA

‒ In Hawaii

‒ In California

‒ In other utility districts running pilot programs, such as

• APS

• Green Mountain Power

Source: Outback Power

Labelling Requirements

• In addition to being approved on state lists, product will need to be physically labelled as “Grid Support Inverter” rather than simply “Grid Interactive”

‒ You may hear these referred to as “Smart Inverters” or “Advanced Inverters”

What does UL 1741 SA test?

Mandatory

• Anti-Islanding

• Low/High Voltage Ride Through

• Low/High Frequency Ride Through

• Ramp Rate

• Specified Power Factor

• Volt/Var mode

Optional (Depends on SRD)

• Frequency Watt

• Volt Watt

Why is this needed?

Source: SolarEdge

• Grids are facing higher penetration rates of PV, and in some cases, saturation

• Existing UL 1741 standards had very strict thresholds for operation and shutdown

• Imagine cases with high PV penetration and• Intermittent clouds (Ramp Rate)• Aging transformers (VRT)• Afternoon confluence of higher loads and PV

dropping offline (VRT and FRT)

UL vs. Rule 21 vs. 14H

Source: Outback Power

Examples of Grid Support Features

Low/High Frequency Ride-Through

Source: SolarEdge

Voltage Ride-Through

Source: SMA

Volt-Var Mode

1. Grid voltage nominal, purely active power

2. Grid voltage high, add ‘inductive’ reactive power

3. Grid voltage low, add ‘capacitive’ reactive power

1

2

3

Adjusting VArs keeps grid voltage from oscillating; acts like a shock absorber Intended result is automatic stabilization of grid voltage

Source: SMA

Ramp Rate (Normal and Soft Start)

Power Gradient

These parameters define how the inverter will gradually ramp up to the preset active and reactive power during:• Normal Operation• Soft Start

Defined as a % of Inom / Second

Source: ABB

Frequency Watt (Optional by SRD)

Support grid frequency by changing inverter wattage output 1. Grid frequency nominal,

inverter at max output 2. Grid frequency high,

inverter curtails power 3. Grid frequency low,

inverter increases powerif available

1

2

3

Source: SolarEdge

Which inverters are compliant?

Company Product Expected Date of Certification AEE Availability

Enphase IQ6-60-2-US Certified Now Available Now

Enphase IQ6PLUS-72-2-US, IQ6PLUS-72-5-US Certified Now Available Now

Enphase IQ6-60-ACM, IQ6PLUS-72-ACM Certified Now Available Now

Fronius Primo 3.8-1 208-240; 5.0-1; 6.0-1; 7..6-1; 8.2-1 Certified Now Available Now

FroniusPrimo 10.0-1 208/240; 11.4-1; 12.5-1; 15.0-1;

Symo 10.0-3 208/240; 12.0-3 208/240 Expected date of cert Oct 2017 Available Now

Fronius Symo 15.0-3 208 Expected date of cert Oct 2017 Available Now

FroniusSymo 10.0-3 480; 12.5-3; 15.0-3; 20.0-3; 22.7-3;

24.0-3 Certified Now Available Now

SolarEdgeSE3000A-US/ 3800/ 5000/ 6000/ 7600/ 10000/

11400 Certified Now Available Now

SolarEdge SE3000H-US/ 3800/ 5000/ 6000/ 7600 Certified Now Available Now

SolarEdgeSE9KUS, SE14.4KUS, SE10KUS, SE20KUS,

SE33.3KUS Certified Now Available Now

SMA SB3.0-1SP-US-40/3.8/5.0/6.0/7.0/7.7 Certified Now Available Now

Outback Radian/VFXR/FXR Certified Now Available Early September

Ginlong Solis-1P3k-4G-US-SA/3.6/4.6/5/6/7/7.6/8/9/10k Certified Now Available Now

ABB PVI-3.0/3.6/3.8/4.2; PVI-5000/6000; UNO-

7.6/8.6; UNO-DM-PLUS-3.0/3.6/3.8/4.2/5.0 Certified Now Available Now

Where can I learn more?

• CEC Approved Inverter List

• Hawaii Approved Inverter List

• Calseia compliance list

• CPUC Rule 21 page

• UL 1741 SA Webinar made by UL

• NREL White Paper

Questions?

Joshua BristerSr. Manager, Product Management and Technical SalesJoshua.brister@aeesolar.com

Appendices

Rule 21 Rollout

Phase 1

• Autonomous Control

• Effective 9/8/2017

Phase 2

• Communications (SEP 2.0) Required

• Expected in 2018

Phase 3

• Interoperability

• Signalling from utility, etc.

• NOC required

• No timeline