Why Bi-Directional Energy Meter Applies for the Solar

Power Generation

At present, distributed PV power stations are continuously connected to household

users, and the State Grid has also issued the opinions on doing a good job in the grid

service of distributed PV power generation, which greatly promotes the

development of distributed solar energy. In this new energy power supply system,

new requirements are put forward for electric energy measurement, that is, it is

required to record the electric energy incorporated into the power grid and the

electric energy absorbed from the power grid; however, the ordinary single electric

meter can not meet this requirement, and the bi-directional energy meter emerges

as the times require.

Single direction digital power meter

Electricity meter is familiar to all of us. Every single house hold is equipped with an

electric meter. Every month, we need to pay the electricity fee according to the

electricity meter. However, the electricity meter installed in household is generally

the single direction electricity meter. That is, regardless of whether your connection

is forward or reverse, it will be charged to you according to the forward direction.

This has a certain significance in reality, and can make up for some shortcomings of

some old mechanical electric meters. But it is not very convenient in the application

of new PV solar power generation system. In the previous measurement of

distributed PV power generation system, two single directional meters were used.

That is, one meter is used to measure the electric energy transmitted by users to the

power grid, and the other meter is used to measure the electric energy in the power

grid. The specific application is shown in the following figure:

 

What is bi-directional energy meter

The bi-directional energy meter is an electric energy meter that can simultaneously

measure the electricity consumption and power generation. The power and electric

energy are directional. From the perspective of power consumption, the power

consumption is considered as positive power or positive energy, while the power

generation is considered as negative power or negative energy. The bi-directional

energy meter can measure, store and display electric energy separately in forward

and reverse directions. At the same time, the meter can be equipped with standard

RS485 communication interface to realize the remote transmission of data.

The application of the Bi-directional energy meter

The bi-directional energy meter is mainly aimed at the users who need two-way

measurement in distributed PV solar power station. When the electricity generated

by the PV solar power station is surplus, the power transmitted to the grid needs to

be accurately measured; when the PV solar power generation can not meet the

needs of users, the power consumption of the grid also needs to be accurately

measured. However, the common single one-way ammeter can not meet this

requirement, so it is necessary to use digital power meter with bidirectional

metering function to realize bidirectional metering of electric energy. The application

of bi-directional energy meter is shown in the following figure:

 

In distributed PV solar power station, if the bi-directional energy metering of power

consumption and power generation is realized, the traditional way is to use two

digital energy meters to measure power generation and power consumption

respectively, which greatly increases the use cost, increases the difficulty of wiring,

and becomes complex in future use or maintenance. In order to realize remote

meter reading, one more communication line and one meter are needed Both

increase the difficulty of use and push up the use cost, which is not conducive to a

large number of popularization and application; and the use of two-way meters, only

a two-way meter can be used to achieve the electricity fed into the grid, and the

power consumption of the grid can be measured separately. Compared with the

previous scheme of using two one-way meters, the scheme has the advantages of

lower cost, less construction difficulty, more convenient maintenance and simpler

use, which is also a photovoltaic power station The two-way electric energy

measurement based on GIS provides the best measurement application scheme.

Solar PV power generation is a process that uses PV effect to convert solar energy

into electric energy, and it is a method of using solar energy efficiently and directly.

Since the first solar cell was manufactured in the 1950s, the solar cell technology is

still in a period of rapid development. Since it is a conversion process, it is necessary

to evaluate the conversion process. We usually use the photoelectric conversion

efficiency of solar cells to evaluate the conversion process, that is, the ratio of

electric energy to input light energy. The international standard measurement

method (ground use, space batteries have other measurement standards) is to

measure the output power of solar cells per unit area under AM1.5 illumination

conditions, and its value is equal to the conversion efficiency. At present, the highest

level of the laboratory is over 42%. The production line level of the factory is about

20%, and it is estimated that the production level in the second half of the year will

be greatly improved. Taking the common polysilicon solar cell module as an

example, the size specification is about 1.6 m x 0.9 M. if the rated power is 260W,

that is to say, when the irradiation power density is 1000W / m2, and its spectral

distribution is within the standard error range specified by AM1.5, the ambient

temperature is 25℃ and the output power is 260W. In the actual use environment,

its maximum output power will be affected by lighting conditions, air temperature,

wind speed, installation conditions and other factors, generally the maximum power

will not exceed 1.3 times of the rated power, the real output power depends on the

impedance of the load connected to the output end, which is the significance of

maximum power tracking. By this means, the market demand of the bi-directional

energy meter will be increase in the coming 5-10 years.