Shanghai Juren Electric Powerofrhs6003tThe reverse power protection device is a device used to prevent the outflow of reverse power, and is a secondary equipment commonly used in photovoltaics, charging pile systems, energy storage systems, and projects that generate electricity in generator mode. When a PV system generates more electricity than the grid needs, the excess energy may flow back to the grid, which can lead to instability of the grid or damage to equipment. Its main function is to judge the direction of the current, when the current flows through the detection point of the reverse power, it is judged that the reverse power occurs, and then send a command to the circuit breaker to disconnect the grid-connected switch. Reverse power protection devices usually include a power detection unit and a control unit. The power detection unit is responsible for monitoring the output power of the photovoltaic system in real time, and once the reverse power is detected, the control unit will immediately take measures to cut off the connection to the grid, so as to protect the stable operation of the equipment and the power grid. In practical applications, inverter power protection devices can be used in conjunction with photovoltaic inverters. When the inverter detects that the PV system generates more electricity than the grid needs, it sends a signal to the inverse power protection device, which cuts off the connection to the grid based on the received signal.
The photovoltaic anti-backcurrent grid-connected box is to install the reverse power protection device, input switch, multi-function instrument, contactor, surge protector, photovoltaic isolation switch and other equipment in a box. The main function is to prevent the reverse flow of electrical energy back to the grid. In a photovoltaic system, when the electrical energy generated by the photovoltaic system exceeds the demand of the local load, the excess electrical energy may flow back to the grid, which can lead to the instability of the grid or cause damage to the equipment. The PV anti-backflow grid-connected box can detect this and take measures to prevent the backflow of electrical energy back to the grid. The PV anti-backcurrent grid-connected box usually includes an anti-backcurrent protection device, a grid-connected switch and related circuits. The anti-backflow protection device is responsible for detecting whether the electrical energy generated by the photovoltaic system exceeds the demand of the local load and taking corresponding measures according to the test results. When it detects that the power is flowing back to the grid, it will issue a command to the grid-connected switch to cut off the connection to the grid, thus preventing the reverse flow of power.
The function of the reverse power protection device and the anti-reverse current grid-connected box is to realize the function of "self-generation and self-use, and the surplus power is not connected to the Internet". The reverse power protection device is only a separate setting, usually to be used in conjunction with other power components, and the photovoltaic anti-reverse current grid-connected box is to install the reverse power protection device and other power equipment in a box, when the reverse current phenomenon is generated, with other power switches to the photovoltaic system to disconnect or access the operation.
When the PV system generates more electricity than the local load demands, the device can detect this and take measures to prevent the reverse flow of electrical energy back to the grid, thus protecting the stable operation of equipment and the grid. Its main functions and functions are as follows:
Reverse power detection
The main function of the reverse power protection device is the reverse power detection, which can monitor the output power of the photovoltaic system in real time according to the actual situation of the power grid and the characteristics of the photovoltaic system, and once the reverse power is detected, the corresponding protection measures will be taken immediately.
Trip control
When the reverse power is detected, the device will immediately trigger a trip signal and jump the corresponding switch to prevent the power from continuing to flow back to the grid, preventing the equipment from being overloaded or causing an impact on the grid.
Closing control
In addition to trip control, the reverse power protection device also has a closing control function. After a certain period of time, if the system returns to normal, the device will automatically close and restore normal power supply.
By detecting the real-time forward power p at the property right demarcation point (the grid system is positive for the user), P is compared with the control power fixed value Pset, and the principle is as follows:
When the p-value is negative and -pset
Enter the input criterion, if the PV is already in operation, the operation of disconnecting the switch is completed.
When the p-value is positive and pset
Enter the input criterion, if the PV has been put into operation, the execution will be completed;If the PV is not in operation, the switch is closed.
It is generally believed that the photovoltaic power generation power is not more than 20% of the capacity of the upper distribution transformer on the grid-connected side. At present, power grid companies usually require the photovoltaic grid-connected system to be a non-reversible current power generation system, that is, the electricity generated by the photovoltaic grid-connected system is consumed by the local load, and the excess electricity is not allowed to be transmitted to the upper power grid through the low-voltage distribution transformer. In the grid-connected power generation system, because the external environment is constantly changing, in order to prevent the reverse power generation of the photovoltaic grid-connected system, the system needs to be equipped with one set of anti-backflow protection devices. The power generation power of the photovoltaic power generation system is adjusted by real-time monitoring of the voltage and current signals on the low-voltage outlet side of the distribution transformer, so as to achieve the anti-backflow function of the photovoltaic grid-connected system, and its logic diagram is shown below.