ZSCC suppression method for parallel three‑level inverters based on model predictive control with virtual location vector

Ling Mao,Yuankai Li,Chao Pan,Jianlin Yang,Qin Hu,Yuncong Zheng,Jinbin Zhao 전력전자학회 2024 JOURNAL OF POWER ELECTRONICS Vol.24 No.4

Parallel three-level neutral point clamped (3L-NPC) inverters are widely used in power conversion applications, such as new energy generation and high voltage inverters. However, the zero-sequence circulating current (ZSCC) between two inverters degrades the whole performance of the system. To suppress the ZSCC in parallel inverters and improve the quality of output current, this study proposes an MPC strategy based on the virtual location vector. First, to reduce the computational burden of MPC, the virtual location vector is constructed by the output current of two inverters so that the control of the parallel inverters is similar to that of a single inverter. Then, the virtual location vector is obtained by using the direct power control method. Finally, the sets of candidate voltage vectors for MPC are determined on the basis of this reference voltage vector and the magnitude of ZSCC. Moreover, the optimal vectors calculated by MPC are assigned to the two inverters. Compared with the traditional MPC strategy, the MPC strategy proposed in this study has better steady state and transient performance with less computational burden. The proposed method is validated in simulation and experimental platforms.

Rational finite element method for plane orthotropic elastic problems

Mao, Ling,Yao, Weian,Gao, Qiang,Zhong, Wanxie Techno-Press 2014 Structural Engineering and Mechanics, An Int'l Jou Vol.51 No.6

The rational finite element method is different from the standard finite element method, which is constructed using basic solutions of the governing differential equations as interpolation functions in the elements. Therefore, it is superior to the isoparametric approach because of its obvious physical meaning and accuracy; it has successfully been applied to the isotropic elasticity problem. In this paper, the formulation of rational finite elements for plane orthotropic elasticity problems is deduced. This method is formulated directly in the physical domain with full consideration of the requirements of the patch test. Based on the number of element nodes and the interpolation functions, different approaches are applied with complete polynomial interpolation functions. Then, two special stiffness matrixes of elements with four and five nodes are deduced as a representative application. In addition, some typical numerical examples are considered to evaluate the performance of the elements. The numerical results demonstrate that the present method has a high level of accuracy and is an effective technique for solving plane orthotropic elasticity problems.

Study of the Effects of the Antisite Related Defects in Silicon Dioxide of Metal-Oxide-Semiconductor Structure on the Gate Leakage Current

Mao, Ling-Feng,Wang, Zi-Ou,Xu, Ming-Zhen,Tan, Chang-Hua The Institute of Electronics and Information Engin 2008 Journal of semiconductor technology and science Vol.8 No.2

The effects of the antisite related defects on the electronic structure of silica and the gate leakage current have been investigated using first-principles calculations. Energy levels related to the antisite defects in silicon dioxide have been introduced into the bandgap, which are nearly 2.0 eV from the top of the valence band. Combining with the electronic structures calculated from first-principles simulations, tunneling currents through the silica layer with antisite defects have been calculated. The tunneling current calculations show that the hole tunneling currents assisted by the antisite defects will be dominant at low oxide field whereas the electron direct tunneling current will be dominant at high oxide field. With increased thickness of the defect layer, the threshold point where the hole tunneling current assisted by antisite defects in silica is equal to the electron direct tunneling current extends to higher oxide field.

Impact of Energy Relaxation of Channel Electrons on Drain- Induced Barrier Lowering in Nano-Scale Si-Based MOSFETs

Ling-Feng Mao 한국전자통신연구원 2017 ETRI Journal Vol.39 No.2

Drain-induced barrier lowering (DIBL) is one of the main parameters employed to indicate the short-channel effect for nano metal-oxide semiconductor field-effect transistors (MOSFETs). We propose a new physical model of the DIBL effect under two-dimensional approximations based on the energy-conservation equation for channel electrons in FETs, which is different from the former field-penetration model. The DIBL is caused by lowering of the effective potential barrier height seen by the channel electrons because a lateral channel electric field results in an increase in the average kinetic energy of the channel electrons. The channel length, temperature, and doping concentration-dependent DIBL effects predicted by the proposed physical model agree well with the experimental data and simulation results reported in Nature and other journals.

Effects of Channel Electron In-Plane Velocity on the Capacitance-Voltage Curve of MOS Devices

Ling-Feng Mao 한국전자통신연구원 2010 ETRI Journal Vol.32 No.1

The coupling between the transverse and longitudinal components of the channel electron motion in NMOS devices leads to a reduction in the barrier height. Therefore, this study theoretically investigates the effects of the in-plane velocity of channel electrons on the capacitance-voltage characteristics of nano NMOS devices under inversion bias. Numerical calculation via a self-consistent solution to the coupled Schrödinger equation and Poisson equation is used in the investigation. The results demonstrate that such a coupling largely affects capacitance-voltage characteristic when the in-plane velocity of channel electrons is high. The ballistic transport ensures a high in-plane momentum. It suggests that such a coupling should be considered in the quantum capacitance-voltage modeling in ballistic transport devices.

Rational finite element method for plane orthotropic elastic problems

Ling Mao,Weian Yao,Qiang Gao,Wanxie Zhong 국제구조공학회 2014 Structural Engineering and Mechanics, An Int'l Jou Vol.51 No.6

The rational finite element method is different from the standard finite element method, which is constructed using basic solutions of the governing differential equations as interpolation functions in the elements. Therefore, it is superior to the isoparametric approach because of its obvious physical meaning and accuracy; it has successfully been applied to the isotropic elasticity problem. In this paper, the formulation of rational finite elements for plane orthotropic elasticity problems is deduced. This method is formulated directly in the physical domain with full consideration of the requirements of the patch test. Based on the number of element nodes and the interpolation functions, different approaches are applied with complete polynomial interpolation functions. Then, two special stiffness matrixes of elements with four and five nodes are deduced as a representative application. In addition, some typical numerical examples are considered to evaluate the performance of the elements. The numerical results demonstrate that the present method has a high level of accuracy and is an effective technique for solving plane orthotropic elasticity problems.

Modeling negative and positive temperature dependence of the gate leakage current in GaN high-electron mobility transistors

Ling-Feng Mao 한국전자통신연구원 2022 ETRI Journal Vol.44 No.3

Monte Carlo simulations show that, as temperature increases, the average kinetic energy of channel electrons in a GaN transistor first decreases and then increases. According to the calculations, the relative energy change reaches 40%. This change leads to a reduced barrier height due to quantum coupling among the three-dimensional motions of channel electrons. Thus, an analysis and physical model of the gate leakage current that includes drift velocity is proposed. Numerical calculations show that the negative and positive temperature dependence of gate leakage currents decreases across the barrier as the field increases. They also demonstrate that source–drain voltage can have an effect of 1 to 2 orders of magnitude on the gate leakage current. The proposed model agrees well with the experimental results.

Study of the Effects of the Antisite Related Defects in Silicon Dioxide of Metal-Oxide-Semiconductor Structure on the Gate Leakage Current

Ling-Feng Mao,Zi-Ou Wang,Ming-Zhen Xu,Chang-Hua Tan 대한전자공학회 2008 Journal of semiconductor technology and science Vol.8 No.2

The effects of the antisite related defects on the electronic structure of silica and the gate leakage current have been investigated using first-principles calculations. Energy levels related to the antisite defects in silicon dioxide have been introduced into the bandgap, which are nearly 2.0 eV from the top of the valence band. Combining with the electronic structures calculated from first-principles simulations, tunneling currents through the silica layer with antisite defects have been calculated. The tunneling current calculations show that the hole tunneling currents assisted by the antisite defects will be dominant at low oxide field whereas the electron direct tunneling current will be dominant at high oxide field. With increased thickness of the defect layer, the threshold point where the hole tunneling current assisted by antisite defects in silica is equal to the electron direct tunneling current extends to higher oxide field.

Expression of microRNA-218 and its Clinicopathological and Prognostic Significance in Human Glioma Cases

Cheng, Mao-Wei,Wang, Ling-Ling,Hu, Gu-Yu Asian Pacific Journal of Cancer Prevention 2015 Asian Pacific journal of cancer prevention Vol.16 No.5

Background: MicroRNAs are a class of noncoding RNAs which regulate multiple cellular processes during tumor development. The purpose of this report is to investigate the clinicopathological and prognostic significance of miR-218 in human gliomas. Materials and Methods: Quantitative RT-PCR (qRT-PCR) was conducted to detect the expression of miR-218 in primary normal human astrocytes, three glioma cell lines and 98 paired glioma and adjacent normal brain tissues.Associations of miR-218 with clinicopathological variables of glioma patients were statistically analyzed. Finally, a survival analysis was performed using the Kaplan-Meier method and Cox's proportional hazards model. Results: The expression level of miR-218 in primary normal human astrocytes was significantly higher than that in glioma cell lines (p<0.01). Also, the expression level of miR-218 in glioma tissues was significantly downregulated in comparison with that in the adjacent normal brain tissues (p<0.001). Statistical analyses demonstrated that low miR-218 expression was closely associated with advanced WHO grade (p=0.002) and low Karnofsky performance score (p=0.010) of glioma patients. Kaplan-Meier analysis with the log-rank test showed that patients with low-miR-218 expression had poorer disease-free survival and overall survival (p=0.0045 and 0.0124, respectively). Multivariate analysis revealed that miR-218 expression was independently associated with the disease-free survival (p=0.009) and overall survival (p=0.004) of glioma patients. Conclusions: Our results indicate that miR-218 is downregulated in gliomas and that its status might be a potential valuable biomarker for glioma patients.

Expression of HMGB1 and its Clinical Significance in T-cell Lymphoma

Mao, Xing-Jiang,Wang, Geng-Fu,Chen, Zhi-Jun,Wang, Li-Na,Zhang, Jun-Biao,Wang, Hui-Ling Asian Pacific Journal of Cancer Prevention 2012 Asian Pacific journal of cancer prevention Vol.13 No.11

Objectives: To evaluate the clinical significance of HMGB1 expression in T-cell lymphoma. Methods: Immunohistochemical staining for HMGB1 and survivin was performed with specimens from 120 cases of T-cell lymphoma and 40 cases of reactive lymphoid hyperplasia with antibodies against human HMGB1 and survivin. Results: The expression of HMGB1 and survivin was significantly higher in tissues of T-cell lymphoma than in reactive lymphoid hyperplasia. Positive expression of HMGB1 and survivin was observed in 63.7% (65/102) and 61.8% (63/102) of T-cell lymphoma cases, respectively. While was associated with gender, age, and tumor location, significant correlations with malignancy and clinical stage were observed. Spearman rank correlation analysis revealed that the expression of HMGB1 and survivin was positively correlated in T-cell lymphomas (P<0.01). Conclusions: Expression of HMGB1 and survivin in T-cell lymphomas is significantly associated with malignancy and clinical stage, but not with gender, age and tumor location. Elevated expression of HMGB1 may be an important biomarker for the development and progression of T-cell lymphoma.