An Improved Model Predictive Direct Torque Control for Induction Machine Drives

Wenxiang Song,Shengkang Le,Xiaoxin Wu,Yi Ruan 전력전자학회 2017 JOURNAL OF POWER ELECTRONICS Vol.17 No.3

The conventional model predictive direct torque control (MPDTC) method uses all of the voltage vectors available from a two level voltage source inverter for the prediction of the stator flux and stator current, which leads to a heavy computational burden. This paper proposes an improved model predictive direct torque control method. The stator flux predictive controller is obtained from an analysis of the relationship between the stator flux and the torque, which can be used to calculate the desired voltage vector based on the stator flux and torque reference. Then this method only needs to evaluate three voltage vectors in the sector of the desired voltage vector. As a result, the computational burden of the conventional MPDTC is effectively reduced. The time delay introduced by the computational time causes the stator current to oscillate around its reference. It also increases the current and torque ripples. To address this problem, a delay compensation method is adopted in this paper. Furthermore, the switching frequency of the inverter is significantly reduced by introducing the constraint of the power semiconductor switching number to the cost function of the MPDTC. Both simulation and experimental results are presented to verify the validity and feasibility of the proposed method.

An Improved Model Predictive Direct Torque Control for Induction Machine Drives

Song, Wenxiang,Le, Shengkang,Wu, Xiaoxin,Ruan, Yi The Korean Institute of Power Electronics 2017 JOURNAL OF POWER ELECTRONICS Vol.17 No.3

The conventional model predictive direct torque control (MPDTC) method uses all of the voltage vectors available from a two level voltage source inverter for the prediction of the stator flux and stator current, which leads to a heavy computational burden. This paper proposes an improved model predictive direct torque control method. The stator flux predictive controller is obtained from an analysis of the relationship between the stator flux and the torque, which can be used to calculate the desired voltage vector based on the stator flux and torque reference. Then this method only needs to evaluate three voltage vectors in the sector of the desired voltage vector. As a result, the computational burden of the conventional MPDTC is effectively reduced. The time delay introduced by the computational time causes the stator current to oscillate around its reference. It also increases the current and torque ripples. To address this problem, a delay compensation method is adopted in this paper. Furthermore, the switching frequency of the inverter is significantly reduced by introducing the constraint of the power semiconductor switching number to the cost function of the MPDTC. Both simulation and experimental results are presented to verify the validity and feasibility of the proposed method.

Unraveling the Morphology-Function Relationships of Polyamide Membranes Using Quantitative Electron Tomography

Song, Xiaohui,Smith, John W.,Kim, Juyeong,Zaluzec, Nestor J.,Chen, Wenxiang,An, Hyosung,Dennison, Jordan M.,Cahill, David G.,Kulzick, Matthew A.,Chen, Qian American Chemical Society 2019 ACS APPLIED MATERIALS & INTERFACES Vol.11 No.8

<P>An understanding of how complex nanoscale morphologies emerge from synthesis would offer powerful strategies to construct soft materials with designed structures and functions. However, these kinds of morphologies have proven difficult to characterize, and therefore manipulate, because they are three-dimensional (3D), nanoscopic, and often highly irregular. Here, we studied polyamide (PA) membranes used in wastewater reclamation as a prime example of this challenge. Using electron tomography and quantitative morphometry, we reconstructed the nanoscale morphology of 3D crumples and voids in PA membranes for the first time. Various parameters governing film transport properties, such as surface-to-volume ratio and mass-per-area, were measured directly from the reconstructed membrane structure. In addition, we extracted information inaccessible by other means. For example, 3D reconstruction shows that membrane nanostructures are formed from PA layers 15-20 nm thick folding into 3D crumples which envelope up to 30% void by volume. Mapping local curvature and thickness in 3D quantitatively groups these crumples into three classes, “domes”, “dimples”, and “clusters”, each being a distinct type of microenvironment. Elemental mapping of metal ion adsorption across the film demonstrates that these previously missed parameters are relevant to membrane performance. This imaging-morphometry platform can be applicable to other nanoscale soft materials and potentially suggests engineering strategies based directly on synthesis-morphology-function relationships.</P> [FIG OMISSION]</BR>

Optimal pulse pattern with negative pulses and third harmonic mixed injection

Qinqing Zhang,Wenxiang Song,Tianqing Shui,Hongzhang Lyu 전력전자학회 2022 JOURNAL OF POWER ELECTRONICS Vol.22 No.3

Adding negative pulses into a neutral-point clamped three-level inverter is an optimal pulse pattern (OPP) that can help restrain the neutral-point (NP) voltage fluctuation. However, this method can also cause the current harmonic distortion to be increased so that it becomes difficult to quantify the negative pulse width. Third harmonic injection can suppress neutralpoint potential fluctuation without increasing the switching frequency and it can also be automatically eliminated. Based on current harmonic minimization pulse width modulation (CHMPWM), a new optimal pulse pattern containing negative pulses and third harmonics is presented, which can inhibit NP voltage. Regarding the re-expression of the fundamental voltage expression, the optimal third harmonic content can be determined by constructing the analytical relationship between the fundamental voltage and the neutral-point current under the harmonic voltage. Combining this with a fitness function, sequence quadratic programming (SQP) is utilized to solve the new switching angles, which means that the CHMPWM is injected by negative pulses and third harmonics. Through simulations and experiments on a three-level inverter with a resistance-inductance load, it is verified that the proposed method can effectively suppress the voltage fluctuation at the neutral-point of the DC bus while taking the current harmonic distortion rate into account.

Suppression of DC-Link Voltage Fluctuation in the Motor Drive System with Reduced Capacitance

Lin Hongmin,Song Wenxiang 대한전기학회 2021 Journal of Electrical Engineering & Technology Vol.16 No.5

For general household appliances with large inertia, such as air conditioning compressor, the control system does not require high speed accuracy of motor control. In order to reduce the cost and volume of the controller, reducing the DC-link capacitance within a reasonable range has been paid more and more attention. In this paper, the permanent magnet synchronous motor (PMSM) drive system with reduced capacitance is studied. Aiming at the DC-link voltage fl uctuation caused by reducing the capacitance, a voltage fl uctuation suppression strategy is proposed, which transfers the DC side oscillation energy to the motor side. The proposed method adopts the sampled DC-link voltage to control the motor to suppress the power fl uctuation on DC-link. At the same time, to ensure the suppression eff ect, a preprocessing of over-modulation strategy without changing the output power is proposed also. The experimental results of 220 μF and 110 μF as DC-link capacitance verify the eff ectiveness of the proposed control method.

Subsection Synchronous Current Harmonic Minimum Pulse Width Modulation for ANPC-5L Inverter

Feng, Jiuyi,Song, Wenxiang,Xu, Yuan,Wang, Fei The Korean Institute of Electrical Engineers 2017 Journal of Electrical Engineering & Technology Vol.12 No.5

Medium voltage drive systems driven by high-power multi-level inverters operating at low switching frequency can reduce the switching losses of the power device and increase the output power. Employing subsection synchronous current harmonic minimum pulse width modulation (CHMPWM) technique can maintain the total harmonic distortion of current at a very low level. It can also reduce the losses of the system, improve the system control performance and increase the efficiency of DC-link voltage accordingly. This paper proposes a subsection synchronous CHMPWM approach of active neutral point clamped five-level (ANPC-5L) inverter under low switching frequency operation. The subsection synchronous scheme is obtained by theoretical calculation based on the allowed maximum switching frequency. The genetic algorithm (GA) is adopted to get the high-precision initial values. So the expected switching angles can be achieved with the help of sequential quadratic programming (SQP) algorithm. The selection principle of multiple sets of the switching angles is also presented. Finally, the validity of the theoretical analysis and the superiority of the CHMPWM are verified through both the simulation results and experimental results.

Subsection Synchronous Current Harmonic Minimum Pulse Width Modulation for ANPC-5L Inverter

Jiuyi Feng,Wenxiang Song,Yuan Xu,Fei Wang 대한전기학회 2017 Journal of Electrical Engineering & Technology Vol.12 No.5

Medium voltage drive systems driven by high-power multi-level inverters operating at low switching frequency can reduce the switching losses of the power device and increase the output power. Employing subsection synchronous current harmonic minimum pulse width modulation (CHMPWM) technique can maintain the total harmonic distortion of current at a very low level. It can also reduce the losses of the system, improve the system control performance and increase the efficiency of DC-link voltage accordingly. This paper proposes a subsection synchronous CHMPWM approach of active neutral point clamped five-level (ANPC-5L) inverter under low switching frequency operation. The subsection synchronous scheme is obtained by theoretical calculation based on the allowed maximum switching frequency. The genetic algorithm (GA) is adopted to get the highprecision initial values. So the expected switching angles can be achieved with the help of sequential quadratic programming (SQP) algorithm. The selection principle of multiple sets of the switching angles is also presented. Finally, the validity of the theoretical analysis and the superiority of the CHMPWM are verified through both the simulation results and experimental results.

A Compensation Method of Dead-Time and Forward Voltage Drop for Inverter Operating at Low Frequency

Lingyun Zhao,Wenxiang Song,Jiuyi Feng 대한전기학회 2019 Journal of Electrical Engineering & Technology Vol.14 No.2

The dead-time is introduced to prevent the upper and lower power devices of the same leg from conducting simultaneously. However, it will cause the actual output voltage deviate from the desired voltage and the load current distortion will occur, which is especially unexpected when the inverter operates at a low frequency. In addition, a voltage drop is produced when the current fl ows through the power device, which further aggravates the current distortion. This paper presents a simple compensation strategy for the dead-time and the forward voltage drop. The current polarity is obtained accurately by fi ltering the three-phase currents in the synchronous rotating coordinate. The driving signals in the SVPWM is adjusted according to the current polarity to compensate the dead-time. The forward voltage drops are equivalent to an error voltage vector by using the approximate average threshold voltage and average diff erential resistance model, which is added to the given voltage to suppress the eff ects of the forward voltage drops. The compensation quantities are set to change based on a piece wise linear function to eliminate the occurrence of the current clamp and the instantaneous zero-crossing switch. Finally, the proposed compensation strategy is verifi ed by the simulation and experiment.

Apple residues derived porous carbon nanosheets synthesized with FeCl3 assisted hydrothermal carbonization for supercapacitors with high rate performance

Li Qiqi,Zhang Yingnan,Song Ya,Yang Huawei,Yang Lixia,Bai Liangjiu,Wei Donglei,Wang Wenxiang,Liang Ying,Chen Hou 한국탄소학회 2023 Carbon Letters Vol.33 No.2

Biomass carbon materials with high rate capacity have great potential to boost supercapacitors with cost effective, fast charging–discharging performance and high safety requirements, yet currently suffers from a lack of targeted preparation methods. Here we propose a facile FeCl3 assisted hydrothermal carbonization strategy to prepare ultra-high rate biomass carbon from apple residues (ARs). In the preparation process, ARs were first hydrothermally carbonized into a porous precursor which embedded by Fe species, and then synchronously graphitized and activated to form biocarbon with a large special surface area (2159.3 m2 g−1) and high degree of graphitization. The material exhibited a considerable specific capacitance of 297.5 F g−1 at 0.5 A g−1 and outstanding capacitance retention of 85.7% at 10 A g−1 in 6 M KOH, and moreover, achieved an energy density of 16.2 Wh kg−1 with the power density of 350.3 W kg−1. After 8000 cycles, an initial capacitance of 95.2% was maintained. Our findings provide a new idea for boosting the rate capacity of carbon-based electrode materials.

Exosome-mediated lnc-ABCA12-3 promotes proliferation and glycolysis but inhibits apoptosis by regulating the toll-like receptor 4/nuclear factor kappa-B signaling pathway in esophageal squamous cell carcinoma

Junliang Ma,Yijun Luo,Yingjie Liu,Cheng Chen,Anping Chen,Lubiao Liang,Wenxiang Wang,Yongxiang Song 대한약리학회 2023 The Korean Journal of Physiology & Pharmacology Vol.27 No.1

Esophageal squamous cell carcinoma (ESCC) is a kind of malignant tumor with high incidence and mortality in the digestive system. The aim of this study is to explore the function of lnc-ABCA12-3 in the development of ESCC and its unique mechanisms. RT-PCR was applied to detect gene transcription levels in tissues or cell lines like TE-1, EC9706, and HEEC cells. Western blot was conducted to identify protein expression levels of mitochondrial apoptosis and toll-like receptor 4 (TLR4)/nuclear factor kappa-B (NF-κB) signaling pathway. CCK-8 and EdU assays were carried out to measure cell proliferation, and cell apoptosis was examined by flow cytometry. ELISA was used for checking the changes in glycolysis-related indicators. Lnc-ABCA12-3 was highly expressed in ESCC tissues and cells, which preferred it to be a candidate target. The TE-1 and EC9706 cells proliferation and glycolysis were obviously inhibited with the downregulation of lnc-ABCA12-3, while apoptosis was promoted. TLR4 activator could largely reverse the apoptosis acceleration and relieved the proliferation and glycolysis suppression caused by lnc-ABCA12-3 downregulation. Moreover, the effect of lnc-ABCA12-3 on ESCC cells was actualized by activating the TLR4/NF-κB signaling pathway under the mediation of exosome. Taken together, the lnc-ABCA12-3 could promote the proliferation and glycolysis of ESCC, while repressing its apoptosis probably by regulating the TLR4/NF-κB signaling pathway under the mediation of exosome.