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Standard Overview Products Used in Testing Related Compliance Standards

Standard Overview

UL1741 is an inverter testing standard from the UL global safety science organization that aims to ensure power system performance and grid support functionality. 

1.1 The UL1741 inverter testing requirements cover inverters, converters, charge controllers, and interconnection system equipment (ISE) intended for use in stand-alone (not grid-connected) or utility-interactive (grid-connected) power systems. Utility-interactive inverters, converters, and ISE are intended to be operated in parallel with an electric power system (EPS) to supply power to common loads.

1.2 For utility-interactive equipment, the UL1741 inverter testing requirements are intended to supplement and be used in conjunction with the Standard for Interconnecting Distributed Resources With Electric Power Systems, IEEE 1547, and the Standard for Conformance Test Procedures for Equipment Interconnecting Distributed Resources with Electric Power Systems, IEEE 1547.1.

1.3 The UL1741 inverter testing requirements cover AC modules that combine flat-plate photovoltaic modules and inverters to provide AC output power for stand-alone use or utility interaction, and power systems that combine other alternative energy sources with inverters, converters, charge controllers, and interconnection system equipment (ISE), in system specific combinations.

1.4 The UL1741 inverter testing requirements also cover power systems that combine independent power sources with inverters, converters, charge controllers, and interconnection system equipment (ISE) in system-specific combinations.

1.5 The products covered by the UL1741 inverter testing requirements are intended to be installed in accordance with the National Electrical Code, NFPA 70.

User-defined waveforms permit the generation of non-sinusoidal voltages: asymmetrical inflections, transient anomalies, voltage harmonics

Equipment for Inverter Testing

​Grid Simulators are the most common equipment for UL1741 inverter testing standard and are widely popular in PV testing. The grid simulator can emulate sub-cycle transients, phase jumps, and multi-cycle line conditions as required. The equipment used for interver testing include: 

  • PV inverters
  • Grid simulators
  • Regenerative loads
  • AC/DC power supplies

Testing Elements for Inverter Testing



Inverter testings aim to evaluate behavior during voltage and frequency fluctuations on the grid through a stand-alone instrument or with an automated test system. The testing elements for UL 1741 standard include:

  • Phase imbalance 
  • Voltage fluctuations
  • Frequency changes
  • Harmonic injection

Retrieved from UL.com at 11-15-2013



 

Related UL Standards

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UL 1414 Section 16: Impulse Voltage Test
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UL 1449: Surge Protective Devices (SPD)
UL's safety and performance standard for Surge Protective Devices (SPD), formerly known as Transient Voltage Surge Suppressors (TVSS), is UL 1449. This standard applies to end-users, manufacturers, and specifiers. As a generalization, UL addresses electrical product safety in areas that involve a risk of fire, electric shock, or injury to persons. UL verifies the safe operation of SPDs through a listing or component recognition process including a series of stringent destructive and non-destructive tests. These ensure safe operation during normal operation and at the unit's end of life. End-of-life characteristics are particularly important because SPDs are placed in harm’s way and can affect the rest of the electrical distribution system. Areas of interest include fault current testing, thermal issues, touch-safety, etc. Nationally Recognized Testing Laboratories (NRTLs – such as UL, CSA, Intertek, MET Labs, etc.) provide a valuable service to specifiers and end-users by testing the performance of all SPDs the same way. This is the only ‘common’ testing format in the industry, making it an important barometer of performance. Retrieved from Nemasurge 11-14-2013
UL 1703: Flat-Plate Photovoltaic Modules and Panels
1.1 These requirements cover flat-plate photovoltaic modules and panels intended for installation on or integral with buildings, or to be freestanding (that is, not attached to buildings), in accordance with the National Electrical Code, NFPA 70, and Model Building Codes. 1.2 These requirements cover modules and panels intended for use in systems with a maximum system voltage of 1000 V or less. 1.3 These requirements also cover components intended to provide electrical connection to and mounting facilities for flat-plate photovoltaic modules and panels. 1.4 These requirements do not cover: a) Equipment intended to accept the electrical output from the array, such as power conditioning units (inverters) and batteries; b) Any tracking mechanism; c) Cell assemblies intended to operate under concentrated sunlight; d) Optical concentrators; or e) Combination photovoltaic-thermal modules or panels.  
UL 508A: Industrial Control Panels
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