Technical Specifications Flashcards

What does the CEC weighted efficiency on an inverter datasheet represent?

Answer: Efficiency averaged over several load levels, weighted to reflect typical operation

CEC weighted efficiency combines efficiencies at several power levels using weights that reflect how often the inverter typically runs at each level.

What does the 'MPPT voltage range' on an inverter datasheet specify?

Answer: The DC input voltage window in which the inverter can track maximum power

String Vmp must stay inside the MPPT window across all temperatures for the inverter to harvest full power.

A system pairs 12.5 kW DC of modules with a 10 kW AC inverter. What is the DC/AC (inverter loading) ratio?

Answer: 1.25

12.5 kW DC / 10 kW AC = 1.25.

Which maximum DC system voltage is most common in modern US utility-scale PV plants?

Answer: 1500 V

Utility-scale plants have standardized on 1500 V DC to allow longer strings and lower balance-of-system costs.

Which standard defines interconnection and interoperability requirements for distributed energy resources connected to the US grid?

Answer: IEEE 1547

IEEE 1547 (2018 revision) sets the performance requirements for DER interconnection, including ride-through and voltage/frequency support.

UL 1741 SB certification of an inverter indicates that it:

Answer: Has been tested for the grid-support functions required by IEEE 1547-2018

UL 1741 Supplement B certifies inverters against IEEE 1547.1-2020 grid-support function testing.

Inverter clipping happens when:

Answer: Available DC power exceeds the inverter's maximum AC output rating

When the array produces more DC power than the inverter can convert, output is capped at the AC rating and the excess is lost.