In order to study the unique dynamic behavior of the lithium-ion battery system in the periodic high-rate pulse discharge, a frequency-domain impedance model and a dynamic extraction method of impedance parameters are proposed. Moreover, a 24 kWh lithium battery system is built to carry out the pulse-discharged cycle experiment. The harmonic characteristics in high and low frequency pulse discharge are studied by harmonic analysis method. Besides, the impedance characteristics of the 24 kWh lithium battery system under different SOC and different cycle are analyzed quantitatively. The results show some new characteristics and verify that the proposed frequency-domain impedance model and impedance extraction method are well qualified to analyze the frequency-domain characteristics and dynamic behavior of the periodic pulse-discharged lithium battery system.

This article reports on a case study designed to examine the implementation of flipped classroom in the EFL classroom in Taiwan. In addition, students’ perception of flipped classroom was also investigated. Sixty-one senior high school students participated in this study; data were gathered from students’ English midterm exam score and questionnaire. The data then were quantitatively analyzed by using T-test and descriptive statistics. The results show that students’ English proficiency in flipped classroom was not significantly different with students in traditional classroom. However, the results reveal that students’ perception of flipped classroom were generally favorable. Students’ contended that flipped classroom enhanced their motivation in learning English, as they liked the self-pace through the course and they stated that flipped classroom gave them more class time to practice English. The results presented here may facilitate improvements in the implementation of flipped classroom in EFL class. Furthermore, suggestions for further research are also presented.

The OLTC (on-load tap changer) transformer is an effective means to solve the voltage quality problem dynamically. There are many problems for conventional mechanical OLTC transformers, such as small regulating amplitude, low precision, slow speed and circulating current. In this paper, a voltage regulation topology and method based on power electronic transition branch is proposed. By controlling the zero-crossing switch of power electronic switch and the state transformation of the switch, smooth switching of the regulating windings is realized, so as to adjust the equivalent turns on the high voltage side. The simulation analysis and prototype experiment show that the scheme can realize the wide range arcless automatic voltage regulation and has practical application value.

For the problem of consistency decline during the long-term use of battery packs for high-voltage and high-power energy storage systems, a dynamic timing adjustment balancing strategy is proposed based on the charge–discharge topology. Compared with the traditional balancing strategy, the dynamic timing adjustment balance strategy is more suitable for the transient high-frequency pulse and high-rate output of a high-power energy storage system. It gives full play to the pulse output adjustment function of the integrated charge–discharge topology. The advantages of this strategy include improving the balance between battery groups, the operating capacity of the system, and improving the continuous working ability of the system. Combined with the work condition of the high-power energy storage system, a balance control model is established, and a cycle charge–discharge test platform of battery packs is built. The effectiveness and advantages of the balance strategy of dynamic timing adjustment are verified by the experiment and simulations. The balancing time is less than 2 min, and the voltage difference is less than 6 mv.