Solar inverter is one of the essential core components in solar power generation applications. In addition to affecting the power generation of the entire system, it also plays a key role in whether the entire system can operate stably.

Therefore, an inverter such as 2000w pure sine wave inverter or power inverter 3000w, with excellent performance, should have complete inverter protection functions or measures to deal with various abnormal situations that occur during actual use, so as to protect the inverter itself and other components of the system from damage.

This article will introduce you to some common functions of solar inverter protection.



1. Input overvoltage protection

When the DC side input voltage is higher than the maximum DC array access voltage allowed by the inverter, the inverter shall not start, or stop within 0.1s (when running), and a warning signal will be issued at the same time. After the DC side voltage returns to the allowable operating range of the inverter, the inverter should be able to start and operate normally.

2. Input reverse polarity protection

When the positive input terminal and negative input terminal of the inverter are reversely connected, the best solar inverter should be able to activate automatic inverter protection. After the polarity is connected correctly, the device should be able to work normally.


3. Input overcurrent protection

After the photovoltaic modules are connected in series and parallel, each string is connected to the DC side of the solar inverter. After MPPT disturbance is performed, when its input current is higher than the allowed maximum DC input current set by the inverter, the inverter Stops MPPT disturbance (while running) and issues an alert signal. After the DC side current returns to the allowable operating range of the inverter, the inverter should be able to start and operate normally.

4. Output overcurrent protection

The AC output side of the grid-connected inverter should be equipped with inverter protection for overcurrent. When a short circuit is detected on the grid side, the grid-connected inverter should stop supplying power to the grid within 0.1s and issue a warning signal at the same time for inverter protection. After the fault is eliminated, the grid-connected inverter should work normally.

5. Output short circuit protection

When the inverter output is short-circuited, inverter protection for short circuit should be provided. The short-circuit inverter protection action time should not exceed 0.5s. After the short-circuit fault is eliminated, the equipment should be able to operate normally.

6. AC and DC surge protection

The inverter should have inverter protection against lightning, and the technical indicators of its lightning inverter protection device should be able to ensure the absorption of expected impact energy.


7. Anti-islanding protection

The anti-islanding inverter protection is mainly developed for the islanding phenomenon caused by abnormal voltage or frequency in solar power stations. When the anti-islanding device loses power on either the grid side or the photovoltaic side, it will quickly send a trip signal to the grid-connected circuit breaker, allowing the circuit breaker to open to protect the maintenance personnel on both sides of the photovoltaic system.

The anti-islanding protection device is based on the islanding phenomenon of distributed power sources (solar power generation, hydropower, etc.) in smart grids. Combined with microcomputer protection technology, it realizes the protection and control of microgrids and provides an effective solution for the prevention of islanding phenomena. Islanding refers to the islanding phenomenon caused by unstable voltage and insufficient reactive power or power loss in the power grid.

Once islanding occurs, it will cause serious harm to the power system and have a great impact on equipment safety. Inverter protection for anti-islanding will help improve the reliability of power grid operations.


8. Output over/under voltage, over/under frequency protection

On the AC output side of the grid-connected inverter, the grid-connected inverter should be able to accurately determine the over/under-voltage, over/under-frequency and other abnormal conditions of the power supply grid (wiring) for inverter protection.

The grid-connected inverter should perform operation according to the required time. And a warning signal should be issued when inverter protection is activated and cut off. When the grid voltage and frequency return to the allowable voltage and frequency range, the inverter should be able to start and operate normally.

9. Internal short circuit protection

When a short circuit occurs inside the grid-connected inverter, the electronic circuits, fuses and other inverter protection within the inverter should act quickly and reliably.

10. Over temperature protection

The grid-connected inverter should have inverter protection functions for overheating, such as alarm for excessive ambient temperature in the machine (such as excessive temperature in the chassis caused by fire) and inverter protection of key internal components (such as IGBT, Mosfet, etc.) from excessive temperature.


11. Automatically restore grid-connected protection

After the grid-connected inverter stops supplying power to the grid due to a grid failure, the grid-connected inverter should be able to automatically re-send power to the grid 20s to 5 minutes after the voltage and frequency of the grid return to the normal range for inverter protection. The power should be increased slowly without any impact on the power grid.

12. Insulation resistance monitoring

The inverter has a complete insulation resistance monitoring function for inverter protection. When the live part of the equipment is grounded, the insulation monitoring system should be able to immediately detect the fault status of the inverter, shut down and alarm.

The inverter detects the voltage of PV+ to ground and PV- to ground, and calculates the resistance of PV+ and PV– to ground respectively. If the resistance on either side is lower than the threshold, the inverter will stop working and an alarm will display "PV low insulation resistance”.


13. Arc fault circuit interrupter (AFCI) protection

The inverter has a complete arc fault circuit interrupter (AFCI) inverter protection function. When the inverter is running, the leakage current is monitored in real time, and when the monitored residual current exceeds the limit, the inverter should disconnect from the grid within 0.3s and issue a fault signal.

14. Zero/low voltage ride-through protection

When an accident or disturbance in the power system causes a voltage sag in the voltage at the grid connection point of the solar power station, within a certain voltage drop range and time interval, the solar power station can ensure continuous operation without disconnecting from the grid. This function is implemented by the inverter.

The cause of the voltage sag is that when a short-circuit fault occurs in a certain branch of the power system, the current increases sharply. At this time, the inverter protection device in the faulty branch operates to isolate the fault point, and the voltage returns to normal.

From fault occurrence to detection and disconnection, which takes a while, it will cause the voltage of each branch to drop suddenly, resulting in a short-term voltage drop. At this time, if the solar power station is removed immediately, it will affect the stability of the power grid, and even other non-faulty branches will be disconnected, causing a large-scale power outage. At this time, the photovoltaic inverter needs to be able to support for a period of time (within 1 second) until the grid voltage returns to normal.

15. Intelligent anti-PID protection

The PID (Potential Induced Degradation) effect of photovoltaic modules refers to a situation where the performance of the module will gradually decay after working for a long time.

The direct harm of the PID effect is that a large amount of charge accumulates on the surface of the LFP battery. It will cause passivation on the surface of the battery, which reduces the fill factor (FF), open circuit voltage, and short circuit current of the battery component, which will reduce the output power of the solar power station, thus reduce the power generation, and reduce the income of the photovoltaic power station. For the best batteries, you can check the battery stores near me.

The PID effect easily occurs in humid environments, and the activity level is positively related to the degree of humidity. At the same time, the degree of contamination of the component surface by conductive, acidic, alkaline, and ion-containing objects is also related to the occurrence of attenuation phenomena.

At present, the mainstream components themselves have the function of preventing PID effect. In addition, the inverter can also add this function. By raising the N line voltage on the AC output side, the PV negative electrode voltage is indirectly raised, so that the PV negative electrode of each inverter to the ground voltage is close to 0 or slightly higher than 0 potential to achieve the purpose of suppressing the PID effect for inverter protection.

The data collector in the system connects and communicates with the inverter and the external anti-PID module, automatically collects the negative pole status information of the inverter, and automatically performs lifting adjustment, thereby realizing the intelligent anti-PID inverter protection function. ​


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