The solar islanding effect is a problem with the power grid, or the effects of the natural environment will stop the power supply. However, the solar grid-connected power generation system still supplies power to the surrounding loads, which creates a phenomenon that even the power company can’t control and maintains a continuous power supply.
Solar anti-islanding effect is to play a protective safety device in the solar energy system, after detection and calculation, to ensure that the power grid is not in the case of power supply, cut off the output of the safety device in the case of grid failure blackout in time with the connected solar power grid-connected power generation system to disconnect, so as to prevent the grid-connected power generation system to continue to supply the phenomenon and bring uncertainty about the security risks.
Solar islanding effect will jeopardize the safety of grid maintenance workers, the contact of the grid lines are still in the power supply state, the line will become a conductor of electricity, solar grid-connected system a direct power supply a large number of currents will affect the solar energy equipment is damaged, if the output voltage of the grid-connected system and the grid voltage between the number of differences may cause tripping, once the equipment is damaged, the maintenance of maintenance up to the maintenance costs, always supplying power will also lead to the damage of the solar energy equipment. Once the equipment is damaged, maintenance will be required to repair the cost, and the constant power supply will also result in energy waste, which cannot be completely consumed, and the voltage and current are unstable, affecting the use of the grid as usual.
Detection of islanding method is mainly divided into two kinds, one is active detection method and the other is passive detection method.
(1) The active detection method is to control the output frequency of the inverter distortion current, forming a frequency trend, so that the output voltage and current over the range of protection, you can detect the islanding distortion effect, there is also a cycle of current interference detection method, the inverter will be reduced at intervals of time to the output current of the grid-connected inverter, when the inverter is grid-connected to use, the output voltage and the grid voltage to reach equilibrium When the inverter is used on the grid, the output voltage is balanced with the grid voltage, and when the grid is disconnected, the inverter is loaded by the output voltage.
When the voltage reaches the set range, the islanding distortion effect can be detected.
(2) The passive detection method is that the voltage and output frequency where the inverter is working are within the appropriate range, and if the set value is reached, the occurrence of islanding will be detected. Voltage phase detection is to detect the occurrence of the islanding effect phenomenon by detecting the output voltage and current of the PV grid-connected inverter, and when the grid is disconnected, the phase of the voltage will change abruptly, so that the occurrence of the islanding phenomenon can be detected. Harmonic detection is when the power grid is faulty and the grid is out of balance, the input current of the PV power generation system will pass through the inverter and produce many harmonics, according to the harmonics can determine whether there is a fault.
Inverter regulation: when our family needs insufficient electricity from solar power, the grid-connected inverter will convert the electricity from the grid to the electricity needed by the family through conversion. If the solar energy generates more power, the inverter will divert more than the power to the grid, and the grid-tie inverter can also help us to realize the power supply needs at night when the solar energy system is not generating power.
To the islanding effect we need to recognize the harm it brings, the impact on us, anti-islanding is to protect the facilities maintenance personnel and our users’ personal safety, but also reduce the damage to the equipment.
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