Under the background of promoting energy conservation and emission reduction and green manufacturing, energy conservation and emission reduction has become the most frequently mentioned word in all walks of life. As a key field of energy consumption and pollution discharge, the power industry has an important impact on resources and environment due to its conversion efficiency and pollution control.
In power plants or substations, DC power supply system (battery) is an important part to ensure the safety of power operation. Reasonable use and maintenance of battery to keep it in good operation state is the key to prolong battery life and improve the reliability of DC operating power supply. After a period of use, the capacity of batteries (especially maintenance free lead-acid batteries and VRLA (valve regulated batteries) decreases or even fails due to the falling off of active substances, grid corrosion or plate deformation and vulcanization. In order to verify the quality of the battery and measure the capacity of the battery, verification discharge experiments must be carried out regularly.
The conventional discharge mode is resistance discharge, which has the advantages of low cost and simple structure, but it is bulky, red and hot, temperature rise, potential fire hazards, and technically can not meet the needs of battery constant current discharge to measure capacity. Although the use of PTC thermistor reduces the risk of fire, the disadvantage of wasting a lot of energy has not been solved.
Therefore, the way to reverse the battery energy into AC energy and feed back to the power grid is undoubtedly an ideal solution.
The benefits are:
1. High inverter efficiency, little heat consumption and low ambient temperature.
2. The discharge is stable and the record is accurate. There is no phenomenon of inaccurate current due to resistance value change caused by resistance discharge temperature rise.
3. Energy is fed back to the power grid without waste.
4. It reduces the labor intensity of maintenance personnel and is suitable for completely unattended operation of the power station.
In this system, in order to realize unattended and regular checking automatic discharge and feedback to the power grid, the most important thing is to judge whether the battery is in the floating charge state by the control system. Only in the floating charge state, the checking discharge is meaningful.
According to the self discharge rate of the battery, the floating charge current is generally small, usually 1mA / ah, in order to meet the self discharge of the battery itself. For example, the floating charge current of 100Ah battery pack is about 100mA. In this way, the current sensor here needs to be able to measure both the 0.1C average charging current (10a at 100Ah) and the 100mA floating charging current. The current Hall current sensor can not meet the requirements, and only the fluxgate current sensor can perfectly realize accurate measurement.
The other two places need to be accurately measured. Here, the current sensor measures the discharge current of the battery pack. Because the inverter device itself has a certain harmonic (generally not higher than 3%), a part of AC current component will be added to the DC current (see the attached figure). The existing Hall current sensor is a follow-up output signal, It is often unable to meet the needs of the existing acquisition system. The measurement is inaccurate at low current and the data deviation is large, which affects the capacity judgment of the battery system.
Based on the above requirements, the fluxgate current sensor FDIB-C16-H series of PAS can perfectly meet the above requirements. Due to the unique ultra-high sensitivity of fluxgate current sensor, it has a large dynamic current measurement range and can accurately measure the current from milliampere level to hundred ampere level.
Through the actual comparison test, the flux gate current sensor FDIB-C16-H of PAS can well adapt to the current measurement application of battery charge and discharge.
The current sensor FIA-C07 based on the fluxgate principle can also accurately measure the current from mA to 100 A, which is in the field test.
FDIB-C16-H is the most reasonable way. It has incomparable advantages over Hall sensor for measuring DC current within 100 A.