In phase I of the Evaluation of Power Export Limiters project a review of market-ready Power Export Limiters (PEL) was undertaken, it was observed that more than half of market-ready PELs do not specify enough information to determine if they are able to comply with draft Engineering Recommendations (ER) G100 and other relevant standards.

Phase II of the Evaluation of Power Export Limiters project will test 2 PELs identified in Phase I as not specifying enough information to determine if they are able to comply with draft ER G100, to determine if these do comply in practice. The tests will include a fail-safe test and a functional test which are mandatory requirements of EREC G100 compliance.

Objectives

The aim of this project was to test the functionalities of the market-available PELs with regarding to the requirements of EREC G100 standards. The three main tasks of the project are given below:

  • Select reviewed PELs for test taking into account the following criteria: cost, market share and control methodologies
  • Set up test bed for PELs at PNDC
  • Test selected PELs using proposed testing procedures and considering the EREC G100 Standards

Method

Two PELs are firstly selected for testing based on the review conducted in the Phase 1 of the project. The two PELs testing at the PNDC was completed in two testing categories.

  1. Functional test
    The fail-safe test evaluated if the selected PELs can limit the export power under the agreed export capacity within 5 seconds
  2. Fail-safe test
    The fail-safe test evaluated if the selected ELS can limit the export power under the required threshold when any part(s) of the ELS are disabled or broken-down.

Outcome

A number of findings and conclusions are made based on the testing for the two PELs:

  • Inverters’ self-consumption and measurement errors should be taken into account when setting the ELS export limiting value (for the SMA inverter, 50-60W should be deducted from the export power threshold).
  • ELSs using “soft control” over the inverters may have difficulty complying with the EREC G100 standards.
  • ELSs using “Hard control” are more likely to comply with EREC G100 standards

Injection testing (one testing method suggested by the EREC G100 standard) is not suitable for all kinds of ELSs. For ELSs that only use current transducers to monitor export power, injection testing can be used.  However, for ELSs that use current and voltage measurement to calculate export power, injection testing is not suitable.  This is because the export voltage must also be defined and an injection tester cannot provide this voltage setting.

Results

  • 2 out of 10 market-available PELs were selected for testing at the PNDC
  • 2 testing categories for 2 PELs were performed at PNDC
  • 1 general-purpose PELs test bed was established at PNDC
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