Battery Management System Insulation Monitoring
SKIM1500EV Insulation Monitoring in BMS (Battery Management System)
With the increasing demand for energy storage from clean energy sources such as solar power and wind power, as well as the widespread use of new energy electric vehicles and the demand for charging pile energy storage batteries, the management and development of battery energy storage systems have been greatly expanded. As one of the most important management aspects of electrical safety, effective monitoring and management of the insulation performance of energy storage batteries is an important content. Therefore, countries have also introduced national standards for insulation monitoring of energy storage batteries, which stipulate that BMS (Barry Management System) needs to perform insulation testing on all components of the power battery system when they are integrated, and the insulation resistance value is used to measure the insulation status. At present, two main techniques are used for insulation monitoring of energy storage batteries: balanced electric bridge method and low-frequency AC injection method. We summarize the characteristics of two methods for reference and selection.
1. Balanced Electric Bridge
The balanced electric bridge method for insulation detection is a passive insulation detection method, which calculates the value of the resistance to be tested by comparing the resistance values of the bridge circuit. Used in the Barry Management System to detect the insulation resistance of the positive and negative poles of the battery to ground, in order to ensure the safe operation of the battery system. The basic principle of the balanced electric bridge method is that when the potential of two specific contacts in the bridge is equal, the output of the bridge is zero, which is called a balanced electric bridge. By parallel connecting a larger detection resistor to the positive and negative insulation resistors, when one side's insulation resistance decreases, the voltage on that side will quickly drop, thereby detecting faults and resistance values. However, it is impossible to identify situations where both sides' insulation resistance decreases. Additionally, because the equation principle is used, the circuit takes a long time to reach stability and the detection time is long. It belongs to the passive detection method. The technical principle of the balanced electric bridge method is simple, the technical difficulty is not high, and the production cost is low. Currently, it is widely used in electric vehicles and battery management systems. However, the significant disadvantage of the balanced electric bridge method is that it cannot recognize situations where the insulation resistance on both sides is reduced, which can easily result in false alarms and false alarms of insulation information. Moreover, the insulation detection reaction time is long, and effective detection cannot be achieved in environments with large distributed capacitance.
2. Low frequency AC injection method
Low frequency AC injection method is an active insulation detection method, which involves connecting the instrument between the IT system (ungrounded system) and the PE line, injecting low-frequency AC signals at the center point of the IT system, and detecting the response of the injected signals in the circuit through sampling circuits and A/D quantization. FIR filters and DFT algorithms are used to extract the injected signals, and the insulation resistance and distributed capacitance of the system are calculated. Due to the complex large distributed capacitors such as various battery packs, compressors, motor controllers, motors, and vehicle power supplies, the AC injection method generally uses low-frequency injection to meet the insulation detection requirements of large distributed capacitors. The SKIM1500EV launched by Sikcon is a low-frequency AC injection insulation tester specifically designed for energy storage, charging stations, and new energy needs. It can meet the rated voltage of IT systems up to 1500V and uses a low-frequency injection method of 0.25 Hz. Low frequency AC injection has the advantages of strong anti-interference ability, fast detection response speed, and low false alarm rate when used in BMS systems. However, due to the difficulty in developing and producing low-frequency AC injection instruments, the cost is higher than that of balanced bridge methods. Therefore, it is mainly used in some high-end energy storage systems.
Therefore, adopting the technical advantages of low-frequency injection method while taking into account the cost advantages of balanced electric bridge method has always been Sikcon's goal of development. Our company's SKIM1500EV not only demonstrates the technical advantages of low-frequency injection method, but also shows superior performance in cost control. For more information, please contact us info@sikcon.com
