Li G.-D.,Zhejiang University |
Hu Y.-Q.,CSR Zhuzhou Institute Co. |
Liu X.-G.,Zhejiang University
Zidonghua Xuebao/Acta Automatica Sinica | Year: 2015
The control vector parameterization (CVP) method is currently popular for solving optimal control problems in process industries. However, one of its main disadvantages is the low computational efficiency, because the relevant differential equations in solving the generated nonlinear programming (NLP) problem should be calculated repeatedly with the adjustment of control, which is the most time-consuming part of the CVP method. A new fast approximate approach with less computational expenses on differential equations, function values and gradients is therefore proposed to improve the computational efficiency of the CVP method in this paper. The proposed approach is demonstrated to have marked advantages in terms of accuracy and efficiency, in contrast to mature optimal control softwares, on two classic optimal control problems. Copyright © 2015 Acta Automatica Sinica. All rights reserved.
Wang Y.,Shanghai JiaoTong University |
Luo Y.,Shanghai JiaoTong University |
Liu H.,CSR Zhuzhou Institute Co.
Hanjie Xuebao/Transactions of the China Welding Institution | Year: 2015
By considering the practical assembly process of the body bolster, Welding structure analysis system (Weld-Sta) is employed to predict the welding deformation of the structure. Firstly, finite element models and welding lines of each step are constructed. Then, the welding deformation of each step is calculated in corresponding model. Thirdly, the whole welding deformation is summed up by the one from each steps. Finally, the welding deformation of the structure is calculated in one step. By comparing the welding deformation predicted by simulated results including two methods-considering welding sequence and not considering welding sequence with that of measured results, the reliability of this method is confirmed. This study can provide a guideline for the designation and determination of welding procedures on body bolster. © 2015, Harbin Research Institute of Welding. All right reserved.
Cheng S.,Central South University |
Li W.,Central South University |
Chen T.,Central South University |
Ding R.,CSR Zhuzhou Institute Co. |
Zhang G.,Central South University
Diangong Jishu Xuebao/Transactions of China Electrotechnical Society | Year: 2016
A novel open circuit fault diagnosis method and the corresponding fault tolerant scheme are proposed in this paper to prevent traction converters breakdown from one leg open circuit fault. When an open circuit occurs in any leg of the traction converter, the newly proposed method can generate an indication accurately to the faulty leg rapidly without additional sensor. Furthermore, the faulty converter can be reconfigured to maintain its full rate operation. The fault diagnosis and locate process only utilize the converter's input/output voltages, which are the most common parameters in the converter control. No extra sensors are needed. The diagnosis process and the control triggering signal are not related to the load variation. The fault tolerant process employs 5 additional switches to reconfigure the connection between the traction converter and the traction transformer without changing the original devices. All the 5 switches are working under the zero voltage and zero current condition. Simulation and experiment are proceeded to verify the effectiveness of the theoretical analysis. © 2016, The editorial office of Transaction of China Electrotechnical Society. All right reserved.
Zhong H.,University of Electronic Science and Technology of China |
Zhong H.,University of Sichuan |
Du P.,University of Electronic Science and Technology of China |
Tang F.,CSR Zhuzhou Institute Co. |
Wang L.,University of Electronic Science and Technology of China
Applied Energy | Year: 2015
Wind turbine wakes have significant effects on the production efficiency and fatigue loads, and these effects should be considered in the optimization of wind turbine structure and wind farm layouts. In this paper, a numerical model combining Lagrangian dynamic large-eddy models and actuator line methods (ALMs) is implemented to investigate the wind turbine near wakes at three representative tip speed ratios (TSRs). In the model, several model parameters that have been justified based on the existing literature and experiments are utilized to enhance the numerical stability and accuracy. These parameters are related to a physically meaningful length scale in the Gaussian smoothing function, a Prandtl tip/hub-loss factor and a 3D correction for airfoil data. The model is compared to the MEXICO measurements, in which a detailed stereo PIV measurement is carried out. According to the comparison of rotor power coefficients between the prediction and the measurements, there is a slight overestimate at TSRs of 6.67 and 10, while a slight underestimate at TSR of 4.17. Additionally, according to the comparison of streamwise traverses and spanwise distribution of axial velocities, good agreement is achieved at both TSRs of 4.17 and 6.67, while visible difference is found at TSR of 10. Moreover, the simulation result shows a helical behavior of wake tip vortices induced by the turbine rotor. This behavior gets more pronounced with a decreasing TSR. The tip vortices also give a reasonable explanation of why the maximum velocity deficit and turbulence intensity occur near the blade tip of wind turbines. © 2015 Elsevier Ltd.
Jing H.,Central South University |
Jing H.,CSR Zhuzhou Institute Co. |
Nian X.,Central South University
Gaodianya Jishu/High Voltage Engineering | Year: 2012
To improve the application of DC ice-melting technology in power grids, a new type of flexible DC ice-melting technology was proposed. Based on analysis on the equivalent model of frozen transmission lines and the heat exchange during ice-melting, the necessary anti-icing current and maximum current were calculated for a 220 kV power line. A novel flexible DC ice-melting power based on self-commutated semiconductors was designed according to the calculation results. The main circuit topology, mathematical model and control strategy of the power unit module were introduced and discussed. Finally, a full-controlled DC ice-melting device prototype was developed, of which the test has been carried out too. Test results show that the ice-melting device can regulate DC output flexibly, while the harmonic contents on line side, which is only 3.16% in the test, also meet requirements.