Parameters optimization design for LCL-type STATCOMs under complex power grid

Wang, Xiangyu,Wang, Minglei,Wang, Liguo,Fu, Guangjie,Qiao, Jinxin The Korean Institute of Power Electronics 2020 JOURNAL OF POWER ELECTRONICS Vol.20 No.2

LCL filter parameters and control parameters are interdependent and inter-restricted. They can all affect the stability of a static synchronous compensator (STATCOM) under the effects of a complex power grid such as harmonic grid voltage and grid impedance variation. An advanced parameters optimization method integrated with LCL filter and control strategy is proposed. At first, the ABC-Pareto algorithm (Pareto multi-objective optimization of an artificial bee colony algorithm) is used to reasonably choose the LCL filter parameters. Under the premise of using capacitor current feedback active damping control and grid voltage feedforward control, the mathematical models of the STATCOM are derived. The constraints of control performances on the control parameters are obtained. According to these constraints, it is possible to construct a satisfactory 3D space. The control parameters can be chosen reasonably by finding the optimized space when the power grid is changed. Simulation and experimental results show the effectiveness and superiority of the proposed method.

On-line identifying stator winding short-circuit approach for a submersible motor based on faulty current monitoring

Wang, Liguo,Feng, Mingliang,Tian, Zhenteng,Bai, Yang,Xu, Jianxin,Wang, Zongjie The Korean Institute of Power Electronics 2022 JOURNAL OF POWER ELECTRONICS Vol.22 No.11

To monitor, diagnose, and suppress the inter-turn short-circuit faults (ITSCFs) of a submersible motor, an approach for the on-line identification of its winding faults has been proposed based on monitoring the stator current. First, an ITSCF model with the global leakage referred to the stator is given. With this model, the detection parameter, which is equal to the ratio of the turns of the fault windings to the total turns of the windings in the healthy phase, can be derived. Second, a faulty model described by the fourth order state-space equation of the motor with a winding fault has been given. Based on sampled stator voltage and stator current, the detection parameter has been solved and used to estimate the location and the turns of inter-turn short-circuit windings of the motor in real time. The accuracy and the robustness of the proposed approach has been illustrated with a 1.5 kW motor that is fed by a 10 kW inverter. Experiment shows that the identification accuracy in terms of the number of the ITSCF windings of the motor stator is less than 3. It can give a reference for the on-line diagnose the ITSCFs of the stator windings of a submersible motor that works in 2 km deep well.

An Approach for Identifying the Temperature of Inductance Motors by Estimating the Rotor Slot Harmonic Based on Model Predictive Control

Wang, Liguo,Jiang, Qingyue,Zhang, Chaoyu,Jin, Dongxin,Deng, Hui The Korean Institute of Power Electronics 2017 JOURNAL OF POWER ELECTRONICS Vol.17 No.3

In order to satisfy the urgent requirements for the overheating protection of induction motors, an approach that can be used to identify motor temperature has been proposed based on the rotor slots harmonic (RSH) in this paper. One method to accomplish this is to improve the calculation efficiency of the RSH by predicting the stator winding distribution harmonic order by analyzing the harmonics spectrum. Another approach is to increase the identification accuracy of the RSH by suppressing the influence of voltage flashes or current surges during temperature estimation based on model predictive control (MPC). First, an analytical expression of the stator inductance is extracted from a steady-state positive sequence motor equivalent circuit model developed from the rotor flux field orientation. Then a procedure that applies MPC for reducing the identification error of the rotor temperature caused by voltage sag or swell of the power system is given. Due to this work, the efficiency and accuracy of the RSH have been significantly improved and validated our experiments. This work can serves as a reference for the on-line temperature monitoring and overheating protection of an induction motor.

Application of HHT for Online Detection of Inter-Area Short Circuits of Rotor Windings of Turbo-Generators Based on the Thermodynamics Modeling Method

Liguo Wang,Yi Wang,Dianguo Xu,Bo Fang,Qinghe Liu,Jing Zou 전력전자학회 2011 JOURNAL OF POWER ELECTRONICS Vol.11 No.5

This paper focuses on monitoring and predicting the short circuit faults of the rotor windings of large turbo-generator systems. For the purpose of increasing efficiency and decreasing maintenance cost, a method that combines the HHT (Hilbert Huang Transform) with a wavelet has been studied. This method is based on analyzing a classical Albright detecting coil. Due to the Empirical Mode Decomposition (EMD) and the Intrinsic Mode Functions (IMF) of the HHT the exact location of a short circuit of rotor windings may be given. However, a part of the useful information is eliminated by the unreasonable decomposing scale of the wavelet. Based on the thermodynamics modeling method, this study was illustrated with a 50㎿ turbo-generator system that is installed in Northern China. The analysis results, which have very good agreement with those of a previous study, show that the method of combining the HHT with a wavelet is an effective way to analyze and predict the short circuit faults of the rotor windings of large generators, such as supercritical turbo-generator systems and wind turbo-generator systems. This work can offer a useful reference for analyzing smart grids by improving the power quality of a distribution network that is supplied by a turbo-generator system.

An improved unified description of charge-carrier mobilities in disordered organic semiconductors

Liguo Wang,Huaiwu Zhang,Xiaoli Tang,Chunhong Mu,Jun Li 한국물리학회 2010 Current Applied Physics Vol.10 No.4

An improved unified description of the dependence of the charge-carrier mobility on temperature, carrier density, and electric field in disordered organic semiconductors is proposed based on the Arrhenius temperature dependence ln(μ) ∝ / 1=T and non-Arrhenius temperature dependence ln(μ) ∝ / 1=T2. The improved description of the mobility can quite well fit the numerical solution of the master equation at both the low densities and high densities, the latter of which cannot be accurately described using the model introduced by Pasveer et al. [6]. Experimental current–voltage characteristics in devices based on organic semiconductors are also excellently reproduced with this improved description. Finally, we calculate and analyze the distribution of the charge-carrier density and electric field with position in polymer layer for two organic semiconductors in detail by using the improved description.

An Approach for Identifying the Temperature of Inductance Motors by Estimating the Rotor Slot Harmonic Based on Model Predictive Control

Liguo Wang,Qingyue Jiang,Chaoyu Zhang,Dongxin Jin,Hui Deng 전력전자학회 2017 JOURNAL OF POWER ELECTRONICS Vol.17 No.3

In order to satisfy the urgent requirements for the overheating protection of induction motors, an approach that can be used to identify motor temperature has been proposed based on the rotor slots harmonic (RSH) in this paper. One method to accomplish this is to improve the calculation efficiency of the RSH by predicting the stator winding distribution harmonic order by analyzing the harmonics spectrum. Another approach is to increase the identification accuracy of the RSH by suppressing the influence of voltage flashes or current surges during temperature estimation based on model predictive control (MPC). First, an analytical expression of the stator inductance is extracted from a steady-state positive sequence motor equivalent circuit model developed from the rotor flux field orientation. Then a procedure that applies MPC for reducing the identification error of the rotor temperature caused by voltage sag or swell of the power system is given. Due to this work, the efficiency and accuracy of the RSH have been significantly improved and validated our experiments. This work can serves as a reference for the on-line temperature monitoring and overheating protection of an induction motor.

Application of HHT for Online Detection of Inter-Area Short Circuits of Rotor Windings of Turbo-Generators Based on the Thermodynamics Modeling Method

Wang, Liguo,Wang, Yi,Xu, Dianguo,Fang, Bo,Liu, Qinghe,Zou, Jing The Korean Institute of Power Electronics 2011 JOURNAL OF POWER ELECTRONICS Vol.11 No.5

This paper focuses on monitoring and predicting the short circuit faults of the rotor windings of large turbo-generator systems. For the purpose of increasing efficiency and decreasing maintenance cost, a method that combines the HHT (Hilbert Huang Transform) with a wavelet has been studied. This method is based on analyzing a classical Albright detecting coil. Due to the Empirical Mode Decomposition (EMD) and the Intrinsic Mode Functions (IMF) of the HHT the exact location of a short circuit of rotor windings may be given. However, a part of the useful information is eliminated by the unreasonable decomposing scale of the wavelet. Based on the thermodynamics modeling method, this study was illustrated with a 50MW turbo-generator system that is installed in Northern China. The analysis results, which have very good agreement with those of a previous study, show that the method of combining the HHT with a wavelet is an effective way to analyze and predict the short circuit faults of the rotor windings of large generators, such as supercritical turbo-generator systems and wind turbo-generator systems. This work can offer a useful reference for analyzing smart grids by improving the power quality of a distribution network that is supplied by a turbo-generator system.

MIL-53(Fe)@γ-Al₂O₃ nanocomposites incorporated cellulose acetate for forward osmosis membranes of high desalination performance

Tong Li,Xuelian Ba,Xiuju Wang,Zhongpeng Wang,Jie Yang,Yu Cui,Liguo Wang 대한환경공학회 2023 Environmental Engineering Research Vol.28 No.1

Forward osmosis (FO) membrane is a promising membrane technique. However, its application in desalination is limited. Thus, we synthesized MIL-53(Fe)@γ-Al₂O₃ via solvent-thermal method to fabricate MIL-53(Fe)@γ-Al₂O₃/cellulose acetate (CA) composite membranes of high desalination performance. MIL-53(Fe)@γ-Al₂O₃ and MIL-53(Fe) particles were studied using XRD, FITR, SEM, N₂ adsorption-desorption isotherms, and AFM. The structural features of MIL-53(Fe)@γ-Al₂O₃/CA membrane and MIL-53(Fe)/CA membrane were analyzed using SEM, AFM and water contact angle. The reverse salt flux and water flux of the MIL-53(Fe)@γ-Al₂O₃/CA membrane reached 1.78 g m<SUP>-2</SUP> h<SUP>-1</SUP> and 37.1 L m<SUP>-2 </SUP>h<SUP>-1</SUP>, respectively, when the deionized water and 1 M NaCl solution were the feed solution and traction solution, respectively. Compared to the MIL-53(Fe)/CA membrane, the MIL-53(Fe)@γ-Al₂O₃/CA membrane demonstrated better perviousness and selectivity properties of the membrane. This study shows a potential advantage of MOF composites as additives for improvement in the desalination performance of forward osmosis membranes.

MIL-53(Fe)@γ-Al2O3 nanocomposites incorporated cellulose acetate for forward osmosis membranes of high desalination performance

Tong Li,Xuelian Ba,Xiuju Wang,Zhongpeng Wang,Jie Yang,Yu Cui,Liguo Wang 대한환경공학회 2023 Environmental Engineering Research Vol.28 No.1

Forward osmosis (FO) membrane is a promising membrane technique. However, its application in desalination is limited. Thus, we synthesized MIL-53(Fe)@γ-Al2O3 via solvent-thermal method to fabricate MIL-53(Fe)@γ-Al2O3/cellulose acetate (CA) composite membranes of high desalination performance. MIL-53(Fe)@γ-Al2O3 and MIL-53(Fe) particles were studied using XRD, FITR, SEM, N2 adsorption-desorption isotherms, and AFM. The structural features of MIL-53(Fe)@γ-Al2O3/CA membrane and MIL-53(Fe)/CA membrane were analyzed using SEM, AFM and water contact angle. The reverse salt flux and water flux of the MIL-53(Fe)@γ-Al2O3/CA membrane reached 1.78 g m−2 h−1 and 37.1 L m−2 h−1, respectively, when the deionized water and 1 M NaCl solution were the feed solution and traction solution, respectively. Compared to the MIL-53(Fe)/CA membrane, the MIL-53(Fe)@γ-Al2O3/CA membrane demonstrated better perviousness and selectivity properties of the membrane. This study shows a potential advantage of MOF composites as additives for improvement in the desalination performance of forward osmosis membranes.

Desert classification based on a multi-scale residual network with an attention mechanism

Liguo Weng,Lexuan Wang,Min Xia,Huixiang Shen,Jia Liu,Yiqing Xu 한국지질과학협의회 2021 Geosciences Journal Vol.25 No.3

Desert classification is the fundamental for preventing and/or controlling desertification. Topographical features of desert remote sensing images change constantly due to the uncertainty of desert terrain, illumination, and other properties. Therefore, it is a very challenging task to accurately classify desert areas. In order to quickly and accurately classify desert from remote sensing images, this paper proposed a multi-scale residual network based on an attention mechanism. The network used conventional convolutions to perform preliminary feature extraction on images, and subsequently adopted a multi-scale residual module to further process the feature maps. Based on the idea of fusing multi-scale features, the multi-scale residual module effectively reduced information loss and possible gradient disappearance because of using skip connections. By introducing the attention mechanism, dependencies between feature channels were established, as a result, the network could recalibrate channel characteristic responses adaptively. Experimental results showed that the proposed network had better generalization ability and a higher accuracy on classification of multispectral desert remote sensing images compared with other methods.