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Harmonic Analysis and Compensation Strategy for Grid-connected Inverter with LCL Filter Xiaowei Dong; Yize Sun; Yujie Chen; Jie Yang
Indonesian Journal of Electrical Engineering and Computer Science Vol 12, No 2: February 2014
Publisher : Institute of Advanced Engineering and Science

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In this paper, the harmonic components of grid-connected current are systemically and quantitatively analyzed, including the high-frequency harmonics caused by the modulation, and the low-frequency harmonics injected by the inherent non-linear characteristics and dead-time effects of switching tubes along with the DC voltage secondary pulsation and the grid disturbance. Furthermore, a combined control scheme of repetitive control and state feedback is brought forward, in which the feedforward decoupling for DC voltage and the feedforward compensation for grid voltage are added. The proposed control strategy can eliminate resonance peak of LCL filter, suppress and compensate the low-frequency harmonics, so that quick response and tracking without static error of the system can be realized. Finally, the rationality of the presented harmonic analysis and the validity of the presented combined control scheme are verified on the 3kW inverter experiment system.DOI : http://dx.doi.org/10.11591/telkomnika.v12i2.3578

Study on Chinese College Teachers’ Professional Beliefs and Ways to Improve Their Professional Beliefs Yang, Jie; Yao, Chunlin
Jurnal VARIDIKA Volume 35, No 1 June 2023
Publisher : Faculty of Teacher Training and Education, Universitas Muhammadiyah Surakarta

Show Abstract | Download Original | Original Source | Check in Google Scholar | DOI: 10.23917/varidika.v1i1.21869

Modern information technology has brought great benefits to education and challenged teachers’ professional beliefs. This study collects data about Chinese college teachers’ professional beliefs with the methods of questionnaire surveys and individual interviews. Based on 682 valid questionnaires, the study finds that Chinese college teachers’ professional beliefs are positive in general. Their research capabilities and their sense of research achievements are lower than their teaching abilities and their sense of teaching achievements. In addition, they expect to improve their information technology capabilities eagerly. Given research findings, this study proposes strategies to reconstruct the teachers’ professional beliefs, such as offering training and further education opportunities for college teachers, improving their research capabilities, intensifying the reform of colleges to establish a classified evaluation system, and providing information technology training for college teachers.

Study on Thermal-Fluid-Solid Coupling Characteristics for Helicopter Intermediate Spiral Bevel Gear Reducer Sheng, Dongping; Yang, Jie; Su, Chun
Journal of Mechanical Engineering Science and Technology (JMEST) Vol 8, No 2 (2024)
Publisher : Universitas Negeri Malang

Show Abstract | Download Original | Original Source | Check in Google Scholar | DOI: 10.17977/um016v8i22024p345

In the helicopter transmission system, the intermediate reducer is particularly special. It uses bevel gear pairs to change the transmission direction and to transfer the rotational speed effectively. Therefore, an in-depth study of the spiral gear pair is crucial to improve the overall performance of the helicopter rotor system. This study focuses on the study of the thermal-fluid-solid coupling characteristics and one-way steady-state thermal finite element analysis are conducted based on volume of fluid multiphase flow simulation theory to provide strong support for the design and optimization of the helicopter intermediate reducer. Several conclusions could be obtained. Firstly, it could be found that the negative pressure of the gear engagement occurs and the absolute value increases with the rotation speed of the gear moving wall in the flow field. Secondly, the effect force such as the gear decreases with the increase of the rotational speed of the gear moving wall in the flow field. Thirdly, the contact stress could be affected significantly at different working speed while considering the thermal-fluid influence; Finally, by reasonably controlling the speed of the gear, the stress level between the teeth can be reduced while ensuring the transmission efficiency, as well as improving the service life and reliability of the gear reducer.

Dynamic Analysis and Fatigue Life Evaluation of Single Herringbone Planetary Gear System with Crack Fault Sheng, Dongping; Yang, Jie; Su, Chun
Journal of Mechanical Engineering Science and Technology (JMEST) Vol 9, No 1 (2025)
Publisher : Universitas Negeri Malang

Show Abstract | Download Original | Original Source | Check in Google Scholar | DOI: 10.17977/um016v9i12025p026

The herringbone planetary gear transmission is widely used due to its exquisite compact structure, excellent load-bearing capacity, and stable transmission characteristics. However, root crack is one of the most common failure modes of gears. A cracked herringbone planetary gear system is taken as research object. The sun gear with crack fault is studied from the aspect of modal and transient dynamic analysis, and the related results are compared with the healthy gear. Based on the transient dynamic analysis of the herringbone teeth with cracks, a fatigue life evaluation is conducted. Firstly, the results show that no significant difference between the natural frequencies and main vibration modes of healthy gears and faulty gears could be observed. Secondly, through transient dynamic analysis, it can be found that, during the rotation process of gears and with the increase of crack depth, the stress at the crack area increases gradually. As the crack penetration length increases, the stress at the crack endpoint of the gear increases almost linearly. Additionally, by comparing cracks with different depths and penetration lengths, the depth of the crack has a greater impact on the stress of the gear compared to the crack penetration length. Finally, based on the fatigue life analysis, the depth of the crack has a significant impact on the gear life; even if the depth of the crack is not very large, it will still have a significant impact. The related research is valuable and could guide the design and optimization of herringbone planetary gear system from the point of practical application.

Study on Chinese College Teachers’ Professional Beliefs and Ways to Improve Their Professional Beliefs Yang, Jie; Yao, Chunlin
Jurnal VARIDIKA Volume 35, No 1 June 2023
Publisher : Faculty of Teacher Training and Education, Universitas Muhammadiyah Surakarta

Show Abstract | Download Original | Original Source | Check in Google Scholar | DOI: 10.23917/varidika.v1i1.21869

Modern information technology has brought great benefits to education and challenged teachers’ professional beliefs. This study collects data about Chinese college teachers’ professional beliefs with the methods of questionnaire surveys and individual interviews. Based on 682 valid questionnaires, the study finds that Chinese college teachers’ professional beliefs are positive in general. Their research capabilities and their sense of research achievements are lower than their teaching abilities and their sense of teaching achievements. In addition, they expect to improve their information technology capabilities eagerly. Given research findings, this study proposes strategies to reconstruct the teachers’ professional beliefs, such as offering training and further education opportunities for college teachers, improving their research capabilities, intensifying the reform of colleges to establish a classified evaluation system, and providing information technology training for college teachers.

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