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Jing Lyu

Publications and source records attributed to Jing Lyu.

57 records · Page 4Linked to original sources

Assessing Attendance by Peer Information

Attendance rate is an important indicator of students' study motivation, behavior and Psychological status; However, the heterogeneous nature of student attendance rates due to the course registration difference or the online/offline difference in a blended learning environment makes it challenging to compare attendance rates. In this paper, we propose a novel method called Relative Attendance Index (RAI) to measure attendance rates, which reflects students' efforts on attending courses. While traditional attendance focuses on the record of a single person or course, relative attendance emphasizes peer attendance information of relevant individuals or courses, making the comparisons of attendance more justified. Experimental results on real-life data show that RAI can indeed better reflect student engagement.

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Harmonic State Space Modeling of a Three-Phase Modular Multilevel Converter

This paper presents the harmonic state space (HSS) modeling of a three-phase modular multilevel converter (MMC). MMC is a converter system with a typical multi-frequency response due to its significant harmonics in the arm currents, capacitor voltages, and control signals. These internal harmonic dynamics can have a great influence on the operation characteristics of MMC. However, the conventional modeling methods commonly used in two-level voltage-source converters (VSCs), where only the fundamental-frequency dynamic is considered, will lead to an inaccurate model that cannot accurately reflect the real dynamic characteristics of MMC. Therefore, the HSS modeling method, in which harmonics of state variables, inputs, and outputs are posed separately in a state-space form, is introduced in this paper to model the MMC in order to capture all the harmonics and the frequency couplings. The steady-state and small-signal dynamic HSS models of a three-phase MMC are developed, respectively. The validity of the developed HSS model of a three-phase MMC has been verified by the results from both the nonlinear time domain simulation model in MATLAB/Simulink and the laboratory prototype with 12 submodules per arm.

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Impedance Analysis of Modular Multilevel Converter Based on Harmonic State-Space Modeling Method

The small-signal impedance modeling of modular multilevel converter (MMC) is the key for analyzing resonance and stability of MMC-based ac power electronics systems. MMC is a converter system with a typical multi-frequency response due to its significant steady-state harmonic components in the arm currents, capacitor voltages, and control signals. Therefore, traditional small-signal modeling methods for 2-level voltage-source converters (VSCs) cannot be directly applied to the MMC. In this paper, the harmonic state-space (HSS) modeling approach is introduced to characterize the harmonic coupling behavior of the MMC. On this basis, the small-signal impedance models of the MMC are developed according to the harmonic linearization principle, which can include all the steady-state harmonic effects of the state variables, leading to the accurate impedance models. Furthermore, in order to reveal the impact of the internal dynamics and closed-loop control on the small-signal impedance of the MMC, three cases are considered in this paper, i.e., open-loop control, ac voltage closed-loop control, and circulating current closed-loop control. Finally, the analytical impedance models are verified by both simulation and experimental results.

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