Application of anti-reverse current meter in photovoltaic system

With the rapid development of the photovoltaic industry, the installed capacity is also increasing. In some areas, the installed capacity is saturated, and newly installed photovoltaics cannot be sold online. The power grid company requires the photovoltaic grid-connected system to be built later to be an anti-reverse current generation system.

What is anti-backflow?

What is "countercurrent"? In the power system, the power is generally sent from the grid to the load, which is called forward current. After installing the photovoltaic power station, when the power of the photovoltaic system is greater than the power of the local load, the power that cannot be consumed will be sent to the grid. Since the current direction is opposite to the conventional one, it is called "countercurrent". In the grid-connected two-way meter, the forward power is the power provided by the grid to the load, and the reverse power is the power delivered by the photovoltaic to the grid. The photovoltaic system with anti-backflow is that the electricity generated by the photovoltaic is only used by the local load and cannot be sent to the grid.

When the PV inverter converts the DC point generated by the PV modules into AC power, there will be DC components and harmonics, three-phase current imbalance, and output power uncertainty. When generating power is sent to the public power grid, it will cause harmonic pollution to the power grid, which is easy to cause grid voltage fluctuations, flicker, etc. If there are many such power generating sources to transmit electricity to the power grid, the power quality of the power grid will be seriously degraded. Therefore, this type of photovoltaic power generation system must be equipped with anti-reverse flow equipment to prevent the occurrence of reverse power.

How does backflow prevention work?

Anti-reverse current working principle: Install an anti-reverse current meter or current sensor at the grid connection point. When it detects that there is current flowing to the grid, a signal is sent to the inverter through 485 communication, and the inverter reduces the output power until the reverse output current is zero. Thereby, the anti-reverse flow function is realized. According to the different voltage levels of the system, photovoltaic systems can be divided into single-phase anti-reverse current systems and three-phase anti-reverse current systems.

How to choose an anti-reverse flow smart meter?

When the photovoltaic power generation is greater than the load demand, reverse power will be generated. We need an instrument to detect and determine the active power output of the inverter, and then the instrument sends a signal through RS485 communication to interact with the inverter data, and adjust the output power of the inverter to balance the output power and the electrical power.

The rail-mounted electric energy meter developed by EASTRON is a new generation of miniature smart meters. It adopts standard DIN35mm rail-mounted installation, modular structure design, and the width matches the miniature circuit breaker, which can be easily installed in the lighting box. The product perfectly illustrates the characteristics of "small size, large function". It can be used in various power grids such as three-phase 4-wire, three-phase 3-wire, single-phase 2-wire, two-phase 3-wire, etc. It can measure various important power parameters, such as: active power, reactive power, voltage, current, active power, Reactive power, apparent power, frequency, power factor, demand, split-phase power, total harmonic content and other parameters, and can exchange data with the host computer through the RS485 interface.

The instrument has good electromagnetic compatibility, in line with international GB/T17215, GB/T15284, GB/T17883 and power industry standards DL/T614, IEC62053-21, EN5070-1/3 standards, and passed MID (European Union Measuring Instruments Directive) B +D certified.