The unbalanced capacitance voltage of series supercapacitor banks is a major problem in current supercapacitor energy storage applications. Achieving voltage balance of series supercapacitors can extend the service life of supercapacitors, increase stored energy, and improve the reliability of energy storage systems. Therefore, it is possible to achieve This goal can lead to major breakthroughs in the application of supercapacitors. This article discusses supercapacitor voltage equalization methods that are currently being studied and have been applied. These methods are of great significance to supercapacitor energy storage systems and have high practical value for improving power quality. Supercapacitor is a new energy storage component that uses the electric double layer principle to directly store electrical energy. At present, supercapacitor energy storage is widely used in distributed power generation systems and hybrid vehicles, and has good development prospects. Supercapacitors have the advantages of high power density, fast charging speed, high charge and discharge efficiency, wide operating temperature range, and long cycle life. Therefore, the application of supercapacitors in the field of power systems has high practical value. Since the rated voltage of supercapacitors is very low, generally 1-3 volts, and the voltage levels in practical applications are often very high, a large number of supercapacitors need to be combined in series in practical applications. Supercapacitors of the same type and specification have inconsistencies in parameters such as voltage, internal resistance, and capacity. From U=Q/C, it can be seen that when charging in series, Q on each supercapacitor unit is the same, and U and C are Inversely proportional. Voltage inconsistency has a great impact on the energy storage capacity and service life of supercapacitor modules. Therefore, it is crucial to make the voltages on each single capacitor in series consistent. For this purpose, the supercapacitor series voltage equalization method can be used. Research on the series voltage equalization method of supercapacitors 1. Zener tube method When the working voltage of the supercapacitor exceeds the breakdown voltage of the Zener tube, the charging current will flow through the Zener tube, and the voltage of the capacitor will no longer rise, preventing Supercapacitor overvoltage. The advantages of this method are simple circuit structure and low cost. The disadvantage is that the charging energy is completely consumed on the voltage regulator tube, which will seriously heat up and waste energy. Moreover, the breakdown voltage accuracy of the voltage regulator tube is low, the dispersion is poor, and the working reliability of the voltage balancing circuit is not high. 2. Switched resistance method: When the working voltage of the supercapacitor reaches a given reference voltage value, the bypass switch S is closed, and the charging current will flow through the resistor and switch, so that the voltage on the supercapacitor will no longer rise or the rising rate will drop significantly. . This method is more flexible than the voltage regulator tube method. It can set the bypass resistance according to the size of the charging current. It has the advantages of high voltage monitoring accuracy, good balancing effect, and high reliability. The disadvantage is that it consumes energy and the resistance generates a lot of heat. This method is suitable for applications with low charging power. 3. Flying capacitor voltage equalization method This method is divided into multi-flying capacitor voltage equalization method and single flying capacitor voltage equalization method. 1) Multi-flying capacitor voltage equalization method The multi-flying capacitor voltage equalization method uses multiple ordinary capacitors with small capacities as intermediate energy storage units to transfer part of the energy in the high-voltage supercapacitor to the low-voltage supercapacitor. A voltage equalization method. Through the reciprocating switching of the switch, the voltage equality between adjacent supercapacitors is achieved, thereby balancing the voltage of the entire supercapacitor module. Experimental results show that the multi-flying capacitor voltage balancing circuit has fast voltage balancing speed in low-power applications, and the voltage consistency of the supercapacitor module is greatly improved, so it has high application value. 2) Single flying capacitor voltage equalization method The single flying capacitor voltage equalizing method uses an ordinary capacitor with a small capacity as an intermediate energy storage unit to transfer the energy in the high voltage supercapacitor to the low voltage supercapacitor. A method of voltage equalization. Experimental results show that the single flying capacitor voltage equalization method has a fast voltage equalization speed and can greatly improve the voltage consistency of the supercapacitor module. It is suitable for use in small and medium power applications and has high application value. 3) Comparison of the two flying capacitor voltage balancing methods. The flying capacitor voltage balancing method wastes a lot of energy because it passes through many other supercapacitors during the voltage balancing process. And because the voltage balancing speed of multiple flying capacitors depends on the balancing speed of all flying capacitors, when the voltage difference between adjacent supercapacitors is very small, the voltage balancing speed of the entire supercapacitor module will decrease. The single-flying capacitor voltage equalization method directly transfers the energy in the high-voltage supercapacitor to the low-voltage supercapacitor. The voltage equalization speed only depends on the maximum voltage difference in the series supercapacitor module and the equivalent series resistance of the discharge loop. Therefore, the voltage equalization speed is much higher than that of the multi-flying capacitor method. In the same way, the single flying capacitor voltage equalization method consumes less loss during the energy transfer process, so the working efficiency is much higher than the multi-flying capacitor voltage equalization method. 4. Inductor energy storage voltage equalization method This method is divided into average inductor energy storage voltage equalization method and adjacent comparison inductor energy storage voltage equalization method. 1) The experimental results of the average inductor energy storage voltage equalization method show that the average inductor energy storage voltage equalization circuit not only balances the uneven voltage rise rate caused by the difference in capacity of the four supercapacitors during the charging process, but also greatly reduces the voltage rise rate. The initial voltage difference between them is reduced and the voltage consistency of the supercapacitor module is improved. Through constant load discharge simulation, during the discharge process of the supercapacitor module, due to the effect of the average inductor energy storage voltage balancing circuit, the voltages of the four supercapacitors are always consistent. 2) The experimental results of the adjacent comparison inductor energy storage voltage equalization method show that the adjacent comparison inductor energy storage voltage equalization circuit greatly improves the voltage consistency of the supercapacitor module. In medium power applications, the voltage equalization effect is very obvious. , has high application value. 3) Comparison of two inductive energy storage voltage equalization methods. Since energy is not transferred from the supercapacitor with the highest voltage to the supercapacitor with the lowest voltage, both voltage equalization methods have the problem of energy waste during the working process. When there are a large number of supercapacitor modules connected in series, or when the voltages of adjacent supercapacitors are not much different, energy needs to pass through multiple supercapacitors when transferring from the supercapacitor with the highest voltage to the supercapacitor with the lowest voltage, resulting in The equalization speed of the adjacent voltage equalization method decreases, and the wasted energy also increases; while the average inductor energy storage voltage equalization method is just the opposite, and its voltage equalization speed will accelerate as the number of series connections increases. Circuit simulation verification (omitted) In order to verify the effect of series voltage equalization technology, the single flying capacitor voltage equalization method with better equalization effect was selected, and PSIM software was used to perform charging simulation on a module composed of three supercapacitors connected in series. The flying capacitor voltage equalization method is used to significantly improve the voltage imbalance of the three supercapacitors. Conclusion The current supercapacitor series technology can be divided into the above methods according to its working principle. Each method has its advantages and disadvantages, and each method has applicable occasions and has high application value. Among them, the single-flying capacitor voltage equalization method and the average inductor energy storage voltage equalization method have the best equalization effects. However, these two methods are not perfect. From the perspective of equalization speed and work efficiency, there is still a big improvement. space.

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