[Introduction]Vanadium battery system has unique characteristics that other lithium batteries and lead-acid batteries do not have, and will play an important role in the new energy industry. As a system, monitoring the operating status of each component in a flow battery is an essential process.
Vanadium battery, the full name is all-vanadium flow battery, is a redox battery in which the active material is in a circulating liquid state, and it is also a new type of clean energy storage device. Among many energy storage solutions, compared with other energy storage technologies, all-vanadium redox flow battery energy storage technology has become one of the preferred technologies for large-scale energy storage due to its outstanding advantages such as long service life, large scale, safety and reliability. The energy storage industry has immeasurable development potential in the future. Large-scale energy storage batteries have three basic requirements: high safety, cost-effective life cycle, and environmentally friendly life cycle. Due to its outstanding performance advantages, the Hall current sensor is selected by more and more battery manufacturers. As a component of battery system power monitoring, it can meet the three basic requirements of large-scale energy storage batteries.
Hall current sensor is a magnetic field sensor made according to the Hall effect. According to the principle, it can be divided into two working modes: open-loop (direct type) and closed-loop (magnetic balance type). Based on the open-loop (direct type) principle in practical applications, the sensor structure is relatively compact, the power consumption is low, and the cost is low. The open-loop (direct type) principle Hall current sensor is generally used in the on-line current monitoring of the battery system. Open-loop Hall current sensor, also known as direct discharge Hall current sensor, is composed of primary circuit, magnetic focusing ring, Hall element, amplifier, etc. The measured current passes through the perforation of the sensor, and the soft magnetic material plays a role of magnetization. The Hall element located in the air gap can detect the magnitude of the magnetism and output a weak voltage signal. After the weak voltage signal is amplified by the operational amplifier, It is conditioned into standard signals DC0-5V, DC4-20mA, etc. The output voltage signal has a linear proportional relationship with the measured current.
Application: Monitoring of vanadium battery systems
As a high-efficiency energy storage device, vanadium redox flow battery has many advantages. The play of this advantage depends on the systematic monitoring of various components in the system, and no failure is allowed, otherwise all advantages will cease to exist. In a vanadium redox flow battery system, there are two containers that hold the liquid solutions of the positive and negative electrodes, respectively. The exchange of the solution depends on the reliable operation of an efficient electromagnetic pump. Once the pump fails, the exchange activity will stop, and the battery will also will stop running. Therefore, in the entire battery system, the magnetic drive circulating pump, as the only component with mechanical movement, must be monitored reliably to ensure the safe operation of the system. Therefore, the current of the magnetic drive circulating pump must be monitored. In addition, the discharge current of the stack, as well as the charging current during charging, should also be monitored to monitor whether a fault occurs inside the stack.
Precautions for use
1. Check whether the equipment on the site has been installed. The sensor is divided into open and closed. The accuracy of closing is high, but the accuracy of opening is poor. In the case of the line that cannot be broken, the opening needs to be selected, and the maintenance of the equipment in the future needs to be considered. When the sensor is replaced, can it be disconnected;
2. When a large DC current flows through the primary coil of the sensor during use, and the secondary circuit is not powered on | the voltage stabilizer or the secondary side is open, the magnetic circuit will be magnetized, resulting in residual magnetism, which affects the measurement accuracy (so When using it, turn on the power supply and the measuring terminal M), and when this happens, demagnetize it first. The method is that the secondary side circuit does not add power, and the AC current of the same level is passed through the primary side coil and its value is gradually reduced;
3. When selecting the Hall current sensor and voltage sensor for monitoring the battery pack, it is necessary to pay attention to whether it is necessary to monitor the reverse current and voltage, because the battery has charging and discharging problems;
4. In order to obtain better dynamic characteristics and sensitivity, attention must be paid to the coupling of the primary coil and the secondary coil. To be well coupled, it is best to use a single wire and the wire completely fills the aperture of the Hall sensor module;
5. In most occasions, the Hall sensor has a strong ability to resist external magnetic field interference. Generally, the magnetic field interference caused by a current twice the working current Ip between 5-10cm from the module can be ignored. But when there is a stronger magnetic field interference, appropriate measures should be taken to solve it.
The usual methods are:
① Adjust the direction of the module to minimize the influence of the external magnetic field on the module;
② Add an anti-magnetic metal shield to the module;
③ Select the module with double Hall element or multi-hall element;
④ The best measurement accuracy is obtained under the rated value. When the measured current is much lower than the rated value, to obtain the best accuracy, multiple turns can be used on the primary side, namely: IpNp=rated ampere-turns. In addition, the primary feeder temperature should not exceed 80 ℃.
The inherent advantages of vanadium redox flow batteries are about to be widely promoted, and high-reliability systems depend on the effective operation of high-reliability monitoring systems. Due to its many advantages, the Hall current sensor ensures the safe and reliable operation of the battery system by accurately detecting and controlling the large current. In the whole monitoring system, the Hall current sensor is one of the core devices, which can deal with abnormal conditions in time, which directly determines the reliability and long-term stability of the system, and provides a solid and reliable guarantee for the vanadium battery system.