What Is The Islanding Effect of a PV Station?

The Islanding Effect of PV power station refers to the fact that distributed electricity generation systems (e.g., PV power stations) still supply power to the local grid or loads in the event of grid power loss, creating an isolated power system. This situation may pose security risks and power quality problems, and therefore requires special attention and prevention.

How does the islanding effect occur?

1. Power grid failure: When a power grid failure or power outage occurs, if the photovoltaic system fails to detect and stop supplying power to the grid in a timely manner, it may continue to supply power to local loads, forming an islanding effect.

2. System protection failure: The PV inverter or other protection devices fail to detect a grid power failure in time, causing the PV system to continue to operate.

3. Load matching: the power demand of the local load matches the power generated by the PV system, allowing the PV system to continue to operate stably without the grid

Impact of the islanding effect when it occurs

1. Safety risk: When dealing with grid faults, maintenance staff of power companies may mistakenly believe that the grid has been completely disconnected, but in fact the islanded area is still electrified, leading to the risk of electrocution.

2. Power quality problems: In an islanded state, the PV system may not be able to maintain a stable voltage and frequency, affecting the quality of power supply.

3. Device damage: The islanding effect may cause damage to electrical equipment due to overvoltage or frequency instability.

4. Laws and regulations: In many countries and regions, power regulations require distributed generation systems to be automatically disconnected during grid outages to avoid the islanding effect.

What are the detection and protection measures for islanding effect?

1. Passive detection methods: Detecting the islanding effect by monitoring changes in grid voltage and frequency. These methods include undervoltage/overvoltage protection, underfrequency/overfrequency protection, etc.

1. Undervoltage/overvoltage protection:

Monitors changes in grid voltage. When the voltage exceeds the set range, the system will automatically disconnect the PV power staion from the grid.

  b. Underfrequency/overfrequency protection:

Monitor the change of grid frequency. When the frequency exceeds the set range, the system will automatically disconnect the PV power staion from the grid.

2. Active detection methods: The PV inverter actively injects small perturbations into the grid, and the response to these perturbations is detected to determine whether an islanding effect occurs. These methods include active frequency offset method, active voltage change method, etc.

3. Active frequency offset method (AFO):

The inverter actively changes the output frequency and observes whether the frequency change is fed back normally. If the feedback is abnormal, it is judged as islanding effect.

4. Active voltage change method:

The inverter actively changes the output voltage and monitors the voltage response. If the voltage response is abnormal, it is judged as islanding effect.

Synchronisation detection method: using synchronisation detection devices, when the power grid is disconnected, the device detects the asynchronous state and automatically disconnects the photovoltaic system.

Methods to prevent the islanding effect:

1. Install suitable inverters: choose ADAYO solar inverters with islanding effect detection and protection functions.

2. Configure protection devices: Configure voltage protection, frequency protection and lightning protection devices to ensure that the system is automatically disconnected under abnormal conditions.

3. Regular testing and maintenance: Regularly test and maintain the islanding detection and protection devices to ensure that they work properly.

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