Modular Extensible Voltage Equalization Based on Wireless Charging System
Liu Qi1, Xue Ming2, Zhang Pengcheng3, Liu Lizhou4, Yang Xinsheng2
1. Tianjin Key Laboratory of Intelligent Control of Electrical Equipment Tiangong University Tianjin 300387 China; 2. State Key Laboratory of Reliability and Intelligence of Electrical Equipment Hebei University of Technology Tianjin 300131 China; 3. Department of Electrical Engineering and Applied Electronics Tsinghua University Beijing 100084 China; 4. Department of Electronic Engineering Tsinghua University Beijing 100084 China
Abstract Wireless power transfer technology with the characteristic of physical isolation solves the power supply problem in situations where wires are inconvenient, making power delivery more flexible. It is commonly used in complex unmanned scenarios, such as drones, autonomous vehicles, and remote control devices. These scenarios have high requirements for the reliability of energy storage systems. The inconsistent initial voltages or charging currents caused by inherent parameter errors in the charging module of the energy storage system result in uneven charging voltages among multiple battery cells, leading to excessive current stress on battery devices. Excessive current stress disrupts system stability and even causes system failure. As a result, the battery's operational lifespan is reduced, and the system's safety is compromised. Traditional voltage-balanced modules have the disadvantages of complex structure, large volume, and high cost. This paper proposes a modular and scalable voltage multipliers constant system based on wireless power transfer technology. The voltage multiplier significantly decreases the number of diodes and capacitors in the system, reducing the construction cost. In the design of the wireless power transfer module, the transmitting coil side adopts the LCL-S compensation topology with constant voltage output characteristics, and the receiving coil side adopts the S-type topology to reduce the additional inductance and capacitance elements of the receiving unit. The voltage multiplier takes the two ends of the input from the receiving module in the wireless charging part. Taking a single receiving module and a voltage multiplier module as an example, the current flows in opposite directions during the positive and negative half-waves of the output voltage of the receiving coil, which complements the conducting diodes. The input is equilibrated by transition capacitors and diodes and distributed to each supercapacitor. This paper establishes an experimental model scaled down in equal proportions. The effectiveness of ideal and non-ideal charging constant voltage is verified through the system's charging curve, and a flexible constant voltage process is achieved using fewer components without additional control elements. By replacing the AC inputs of the three voltage multipliers with wireless power transfer modules, additional devices are reduced. The physical isolation characteristic of wireless power transfer technology is utilized to solve the inconvenience of wired charging, improving the reliability of the energy storage system and expanding the application scenarios for battery charging. The system's overall charging efficiency reaches 76.87% when the total voltage of the three supercapacitors is 48 V. Each energy storage unit ultimately converges to the target voltage value set under non-ideal charging positions. Setting of a threshold voltage solves the problem of inconsistent charging speeds of voltage multiplier constant voltage modules under non-ideal charging positions, enabling the system to charge more reliably. This system can be expanded to various charging scenarios, such as robots and drones.
Liu Qi,Xue Ming,Zhang Pengcheng等. Modular Extensible Voltage Equalization Based on Wireless Charging System[J]. Transactions of China Electrotechnical Society, 2024, 39(22): 6980-6989.
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2024, Vol. 39 
