Research Center for Renewable Energy Generation Engineering

Nanjing, China

Research Center for Renewable Energy Generation Engineering

Nanjing, China
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Chen Z.,Hohai University | Chen Z.,Research Center for Renewable Energy Generation Engineering | Li Z.,Jiangsu Electric Power Company | Ma H.,Hohai University | Ma H.,Research Center for Renewable Energy Generation Engineering
International Journal of Applied Electromagnetics and Mechanics | Year: 2017

Electromagnetic torque model is built in this paper for permanent-magnet synchronous machine (PMSM) with nonsinusoidal back electromotive force (back-EMF) and current. Electromagnetic torque is divided into four parts depending on the different combinations of fundamental and harmonic component. Effects of current harmonic order, amplitude and initial angle on average torque and torque ripple are investigated based on the mathematic model. Desired harmonic parameters are obtained from the analysis, in order to suppress the torque ripple as much as possible. Further, a method for reducing the 5th and 7th harmonic components of torque ripple is proposed, according to the characteristics of back-EMF harmonic distribution. The proposed method is greatly simplified and more feasible by only injecting 5th and 7th harmonic currents. The theoretical analysis validity has been proved by finite element (FE) simulation, and the FE results show that torque ripple would be more effectively reduced by injecting proper harmonic current than weakening it merely. © 2017 - IOS Press and the authors. All rights reserved.


Li Z.,Jiangsu Electric Power Company | Chen Z.,Hohai University | Chen Z.,Research Center for Renewable Energy Generation Engineering | Lu S.,Jiangsu Electric Power Company | And 3 more authors.
19th International Conference on Electrical Machines and Systems, ICEMS 2016 | Year: 2016

In order to analysis the influence of current harmonic on electromagnetic torque, a model of electromagnetic torque is proposed considering back electromotive force (back-EMF) harmonics in permanent-magnet synchronous machine (PMSM). Based on this model, electromagnetic torque is divided into four parts. The amplitude and phase angle of harmonic current are solved to minimize torque ripple of each part and their effects on average torque value are discussed. Further, conclusions are applied to torque ripple suppression in permanent magnet synchronous machine, which is validated by finite element (FE) method. Results show that, when back-EMF waveform is non-sinusoidal, lower torque ripple can be obtained by injecting proper current harmonic components into the fundamental current than just reducing current harmonics. © 2016 The Institute of Electrical Engineers of Japan.


Chen Z.,Hohai University | Chen Z.,Research Center for Renewable Energy Generation Engineering | Ma H.,Hohai University | Ma H.,Research Center for Renewable Energy Generation Engineering | Li Z.,Jiangsu Electric Power Company
19th International Conference on Electrical Machines and Systems, ICEMS 2016 | Year: 2016

Surface-mounted and interior hybrid permanent magnet synchronous machine (SIHPMSM) is introduced in this paper. Finite element model of SIHPMSM is built to investigate its no-load and load characteristics. In order to study the effects of surface-mounted permanent magnet (SPM) and interior permanent magnet (IPM) on this machine, three FE models are built and analyzed. Flux density, back-EMF and torque performances of them are compared. Results show that surface-mounted magnets have greater impact on no-load characteristic of this machine than interior permanent magnet, while the load characteristic is mainly affected by interior permanent magnet. © 2016 The Institute of Electrical Engineers of Japan.


Wang Q.,Hohai University | Ma H.,Research Center for Renewable Energy Generation Engineering | Cao S.,Nantong University | Chen B.,Jiangsu Province Key Laboratory of Environmental Engineering
Mathematical Problems in Engineering | Year: 2015

Thrust bearing is one part with the highest failure rate in hydroturbine generator set, which is primarily due to heavy axial load. Such heavy load often makes oil film destruction, bearing friction, and even burning. It is necessary to study the load and the reduction method. The dynamic thrust is an important factor to influence the axial load and reduction design of electromagnetic device. Therefore, in the paper, combined with the structure features of vertical turbine, the hydraulic thrust is analyzed accurately. Then, take the turbine model HL-220-LT-550, for instance; the electromagnetic levitation load reduction device is designed, and its mathematical model is built, whose purpose is to minimize excitation loss and total quality under the constraints of installation space, connection layout, and heat dissipation. Particle swarm optimization (PSO) is employed to search for the optimum solution; finally, the result is verified by finite element method (FEM), which demonstrates that the optimized structure is more effective. © 2015 Qingyan Wang et al.


Yang G.,Hohai University | Yang G.,Research Center for Renewable Energy Generation Engineering | Yang K.,Hohai University
Energy Education Science and Technology Part A: Energy Science and Research | Year: 2014

With regard to the complexity of hydraulic metal structures, the diagnosis work turns out to be multi-level and multi-criterion. Hence, the ultimate diagnosis consequence can barely be accurate enough if merely a single qualitative or quantitative evaluation method is implemented. Based on comprehensive integration theory and method, combining respective advantages of fuzzy comprehensive evaluation method and analytic hierarchy process and the mature complementarity between them, this paper researched and established the multi-layer fuzzy comprehensive evaluation model for hydraulic metal structure health diagnosis. Thus, the multi-layer fuzzy comprehensive evaluation method is brought forward, being applicable in hydraulic metal structure health diagnosis. This method converts incomplete and uncertain information into certain fuzzy concepts, quantifying qualitative problems simultaneously improving the accuracy and credibility of diagnosis results. By effectively combining with the membership degree and subordinate function from both qualitative perspective and quantitative perspective, which makes it more convenient to perform multi-level processing, the method can vastly enrich the diagnosis result information so that the hydraulic metal structure health status can be more accurately reflected. Through the analysis of the diagnosis results of project examples, the ultimate diagnosis conclusion proves to be quite close to the actual situation of equipments. Therefore, this has verified the comprehensive health diagnosis model, based on FAHP, more scientific, reasonable and dependable, providing a brand new idea for hydraulic metal structure health diagnosis. © Sila Science. All Rights Reserved.


Qian Y.,Research Center for Renewable Energy Generation Engineering | Qian Y.,Hohai University | Zhu L.,Hohai University | Wang B.,Hohai University
Chinese Control Conference, CCC | Year: 2012

Stator Inter-turn Short-circuit Fault is one of the common faults of doubly-fed induction generation (DFIG). It affect directly the stabilization and safety of wind power generation system. Based on coupled-circuit method, this paper sets up a fault mathematics model, and then analysis the fault mechanism. This paper also builds a MATLAB/SIMULINK model of DFIG with the help of S-Function. Finally the simulation is carried out, and the result shows that the MATLAB/SIMULINK model based on S-Function is reliable. © 2012 Chinese Assoc of Automati.


Yang G.,Hohai University | Yang G.,Research Center for Renewable Energy Generation Engineering | Yang K.,Hohai University | Huang Y.,Hohai University | Jing P.,Hohai University
Shuili Fadian Xuebao/Journal of Hydroelectric Engineering | Year: 2014

Hydraulic metal structural health diagnosing system is a multi-level, multi-standard and multi-factor comprehensive system. Diagnosis indexes are the basis and key elements to development of such system and determination of their weight coefficients has a direct effect on diagnosis results. The importance degree of each index is calculated and analyzed using the fundamental principle of information gain and the information carried by each index for determination of a health grade in the health diagnosis process. This method can eliminate the subjectivity in specifying the weights of the indexes and hence improves the weighting process and diagnosing results. Its calculations of the importance degrees of weight coefficients are close to those by FAHP method. It can be used for guiding data collection and analysis and also for simplification of index system for concise and effective diagnosis analysis. © Copyright.


Chen Z.,Hohai University | Chen Z.,Research Center for Renewable Energy Generation Engineering | Li Z.,Jiangsu Electric Power Company | Ma H.,Hohai University | Ma H.,Research Center for Renewable Energy Generation Engineering
International Journal of Applied Electromagnetics and Mechanics | Year: 2016

Two kind of nonuniform slot distribution models, the unit machine shift model (Model 1) and the single slot shift model (Model 2), are proposed for reducing cogging torque of surface-mounted permanent magnet (SPM) machines. Further, based on exact subdomain model and Maxwell stress tensor, an analytical model is further built for calculating cogging torque in SPM machines with nonuniformly distributed stator slots. Its accuracy and feasibility have been validated by finite element (FE) method. With the analytical model, effects of slot shift angle on cogging torque are investigated for an 8-pole/12-slot SPM machine. Meanwhile, coupling relationships between shift angle and other design parameters (slot/pole number, pole arc coefficient and slot opening) are analyzed. In addition, influences of slot shift on back-EMF and electromagnetic torque are also studied. Conclusions are drawn from the analysis and indicate that Model 1 is much better than Model 2 in improving the performances of SPM machine. © 2016 -IOS Press and the authors. All rights reserved.


Zhou D.,Research Center for Renewable Energy Generation Engineering | Chen S.,Research Center for Renewable Energy Generation Engineering | Li C.,Research Center for Renewable Energy Generation Engineering
Paiguan Jixie Gongcheng Xuebao/Journal of Drainage and Irrigation Machinery Engineering | Year: 2013

Through the establishment of unsteady state process of three-dimensional turbulence numerical simulation, operation characteristics of a new low head pit turbine without governor device were simulated under both the constant and varied runner rotation speed conditions while the inlet pressure was changing periodically. The numerical results show that, with 14% changing of the inlet pressure, the rotation speed change is up to 0.76% and down to 0.21% and the rotation speed fluctuation is 0.25 cycle delayed than that of the inlet pressure. In addition, the flow rate change is up to 8% and 2.5% at the peak value, as well as the efficiency change is down to 10.76% and up to 4%. The variation law of turbine torque, flow rate, power and efficiency with time was revealed, and in the variation process of the runner, the transient performance of runner flow in both conditions was analyzed, which can provide rational basis and suggestions for the electrical control equipment selection of a power station.


Wen D.-Y.,Research Center for Renewable Energy Generation Engineering | Sun L.-X.,Research Center for Renewable Energy Generation Engineering | Huang H.,Research Center for Renewable Energy Generation Engineering | Ju P.,Research Center for Renewable Energy Generation Engineering
Journal of Hohai University | Year: 2012

In order to reduce the calculating time and to improve the analytical speed in an electric power system, the dynamic equivalence technique can be used in the excitation system with the uniform standard transfer function in a low order. The parameters of the equivalent excitation system were determined using the weighted average method, the method of least squares (LS) in discrete time domain, and the piecewise linear polynomial function (PLPF) method. The genetic algorithm was used for parameter identification. Different methods for aggregation of the excitation system were compared, and their differences and advantages, as well as their disadvantages were summarized. A case study indicates that, in genera, the method of least squares in discrete time domain has good performance.

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