How to Test For Anti-Islanding Using a Grid Simulator & Load
First, what is Anti-Islanding and why does it matter?
As the demand for distributed energy resources (DERs) and electrification grows, ensuring safety and grid stability has become more critical than ever. One of the key safety mechanisms is anti-islanding protection—designed to prevent a solar inverter, for example, from continuing to feed power onto the grid when the grid has shut down.
Islanding occurs when a local energy generator continues to feed power into the grid during a grid outage, creating a hazardous “island” of energized equipment. Anti-islanding protection ensures that DERs or grid connected systems like EV chargers promptly disconnect from the grid during such events, safeguarding utility workers, customers, and equipment.
Why Does Testing for Anti-Islanding Matter?
Anti-Islanding Test Applications
What is a Typical Anti-Islanding Test Configuration?
A typical anti-islanding test setup is designed to evaluate whether a grid-tied inverter or distributed energy resource (DER) can reliably detect and respond to a loss of grid connection—an event known as unintentional islanding.
A Typical Anti-Islanding Set-up
- grid simulator
- a device under test (DUT)
- controllable RLC load bank
- measurement equipment
Together, these components replicate real-world scenarios in which the inverter must cease to energize an isolated section of the grid. This controlled environment allows for precise assessment of the inverter’s anti-islanding protection capabilities, as required by standards such as IEEE 1547, UL 1741, and IEC 62116.
The Pacific Power Source's AZX/GSZ Grid Simulator and Load eliminates the need for additional equipment by providing the built-in RLC and integrated measurement capabilities.
Figure 1: Balanced Generation to Load Unintentional Islanding Test Configuration, source: IEEE Std 1547.1-2020 standard page 125
Example Grid Simulator Unintentional Islanding Test Configuration
Figure 2: AZX Series AC & DC Power Source, Load
Below is an example of a test procedure based on IEC 62116 & UL 1741 SA/SB:
- Connect the System: Connect the DUT to a grid simulator, RLC load, and measurement equipment. This forms the test circuit.
- Configure the Load: Adjust the R, L, and C elements to closely match the inverter’s output power—this simulates the worst-case scenario for islanding detection.
- Establish Steady-State: Run the system under normal grid conditions. Verify stable voltage, frequency, and phase before proceeding.
- Simulate Grid Disconnection: Open the switch between the DUT/load and the grid simulator to create an islanded condition. The inverter now powers the load independently.
- Monitor and Record: Measure the time from disconnection to inverter shutdown. Record voltage and frequency behavior throughout the test.
- Apply Pass/Fail Criteria: The inverter must cease energizing within the allowed time (typically ≤ 2 seconds per IEEE 1547). Failure to do so indicates non-compliance.
RLC Load Capability
One of the required anti-islanding tests is to verify that DER ceases to energize and trip from the area EPS as specified in IEEE Std 1547 when an unintentional island condition is present. This requires an adjustable RLC load as part of the required test setup.
The AZX/GSZ regenerative test solutions support islanding condition emulation when set to RLC Electronic Load mode by performing a real-time simulation of an RLC circuit.
It also accurately measures the disconnection time based on a programmable current threshold after it removes the simulated grid voltage to the DER test setup. This simplifies the required setup and time needed to perform IEEE 1547 PV Inverter and other distributed energy resources (DER’s) Anti-Islanding testing.
Figure 3: Single Phase PV Inverter Test Set Up Example
