Multi Objective Parameter Optimization of Variable Mode Voltage Doubling LLC Resonant Converter
Zhao Yongxiu1,2, Liu Zewei1,2, Wang Chongjie1,2, Lei Ming1,2, Yan Ming3
1. College of Electrical and Control Engineering Xi'an University of Science and Technology Xi'an 710054 China; 2. Xi'an Key Laboratory of Electrical Equipment Condition Monitoring and Power Supply Security Xi'an 710054 China; 3. Shaanxi Hanzhong State Grid Co. Ltd Hanzhong 723000 China
Abstract：LLC resonant converters can achieve electrical isolation and soft switching, exhibit high efficiency and power density advantages, and are widely used in new energy fields such as lithium battery charging. The traditional fundamental analysis method simplifies the analysis difficulty and calculation process. However, significant errors exist when far from the resonant frequency point, and the accuracy is low in wide output voltage scenarios. This paper focuses on the precise time-domain model analysis of a variable mode voltage doubling-type LLC resonant converter with wide output. A multi-objective parameter optimization design method is proposed. Firstly, the operating modes of LLC resonant converters and the characteristics of each operating mode are analyzed. The PO mode can achieve ZVS of the switching tube and ZCS of the rectifier tube, and the DC gain monotonically increases with the decrease of operating frequency. Accordingly, the PO mode is established as the optimal operating mode. Based on the working waveform of the PO mode and the equivalent circuit of P and O stages, a time-domain equation for the excitation current iLm, resonant current iLr, and resonant capacitor voltage uCr state variables in PO mode is established. The coefficients k1, k2, k3, and k4 in the state equation are solved to obtain the analytical formula for the PO mode state equation system. According to the coefficient analysis formula, it can be seen that k1, k2, k3, and k4 are related to the resonant capacitor Cr, inductance ratio coefficient K, and the conduction angle of the P mode sub-interval θ. Secondly, the parameter design of the main circuit is optimized. A multi-objective parameter optimization method is proposed based on pattern boundary constraints, resonant capacitor maximum constraints, and ZVS constraints. The multi-objective parameter optimization region and the optimal solution are obtained. The gain requirements and ZVS of the switching transistor under the most stringent operating conditions are achieved with a small cyclic reactive power, thereby improving the efficiency of the converter. Finally, simulation models and experimental prototype platforms are constructed. The correctness of multi-objective parameter optimizationis verified by simulation. Simultaneously, using the traditional fundamental analysis method and the proposed parameter optimization design method, the converter parameters are designed separately, and comparative analysis is conducted from the perspectives of switch frequency variation range and resonant network current. The experimental results show that the proposed multi-objective parameter optimization design method has a narrower operating frequency range and higher operating efficiency than traditional fundamental analysis methods, which can meet the gain requirements and ZVS operating conditions of the converter over the entire load range.
赵永秀, 刘泽伟, 王崇杰, 雷鸣, 晏铭. 变模态倍压型LLC谐振变换器多目标参数优化[J]. 电工技术学报, 2024, 39(22): 7139-7153.
Zhao Yongxiu, Liu Zewei, Wang Chongjie, Lei Ming, Yan Ming. Multi Objective Parameter Optimization of Variable Mode Voltage Doubling LLC Resonant Converter. Transactions of China Electrotechnical Society, 2024, 39(22): 7139-7153.
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2024, Vol. 39 
