The Short Duration Undervoltage Disturbance Ride-Through (VDRT) test ensures inverters to respond appropriately during short duration undervoltage disturbance events to mitigate any further potential risks to power system security.

AS/NZS 4777.2 is undergoing revision to ensure the behaviour of small-scale generators, supports the reliable and secure operation of the power system. AEMO considered there is a pressing need to accelerate implementation of the VDRT Test Procedure in South Australia.

The VDRT test consists of two main tests:

  • Undervoltage (V<) disconnection test in response to event duration exceeding trip delay time
  • Undervoltage (V<) withstand test in response to event duration of less than trip delay time

The Undervoltage (V<) disconnection test requires stepping the grid voltage down to 177.5V from 230V, whilst the device under test is outputting 50% of its rated output current. The inverter shall disconnect within 2 seconds of the voltage drop, and reconnect to the grid after at least 60 seconds have passed from the grid voltage being returned to 230V.

The Undervoltage (V<) withstand test requires stepping the grid voltage down to 50V for 220ms then back up to 230V, whilst the device under test is outputting 50% of its rated output current. The inverter shall not disconnect due to this voltage drop, and the output power shall recover to within 4% of the value before the test within 1 second.

For a three phase system inverter, testing shall be conducted for each phase individually, and additionally for all three phases stepped together.

Limits

AC grid output power:

3phase output 50kVA

1phase output 20kVA

DC input power (EUT only has to output 50% power):

750Vdc, 40A, 10kW

 

If EUT has batteries, the DC input power test does not apply.

Contact Austest Labs for accredited testing to these requirements.