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RISS 인기검색어
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- 저자 : Mengshi Li (검색결과 4 건)
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Power System Harmonic Estimation Based on Park Transform
Ya Chen,Tianyao Ji,Mengshi Li,Qinghua Wu,Xuejian Wang 대한전기학회 2016 Journal of Electrical Engineering & Technology Vol.11 No.3
This paper presents a novel method for power system harmonic estimation based on the Park transform. The proposed method firstly extends the signal to a group of three-phase signals in a-b-c coordinate. Then, a linear fitting based method is adopted to estimate the fundamental frequency. Afterwards, the Park transform is utilized to convert the three-phase signals from a-b-c coordinate to d-q- 0 coordinate. Finally, the amplitude and phase of a harmonic component of interest can be calculated using the d-axis and q-axis components obtained. Simulation studies have been conducted using matrix laboratory (MATLAB) and power system computer aided design/electromagnetic transients including direct current (PSCAD/EMTDC). Simulation studies in MATLAB have considered three scenarios, i.e., no-frequency-deviation scenario, frequency-deviation scenario and the scenario in the presence of inter-harminics. The results have demonstrated that the proposed method achieves very high accuracy in frequency, phase and amplitude estimation under noisy conditions, and suffers little influence of the inter-harmonics. Moreover, comparison studies have proved that the proposed method is superior to FFT and Interpolated FFT with the Hanning Window (IpFFTHW). Finally, a popular case in PSCAD/EMTDC has been employed to further verify the effectiveness of the proposed method.
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Power System Harmonic Estimation Based on Park Transform
Chen, Ya,Ji, Tianyao,Li, Mengshi,Wu, Qinghua,Wang, Xuejian The Korean Institute of Electrical Engineers 2016 Journal of Electrical Engineering & Technology Vol.11 No.3
This paper presents a novel method for power system harmonic estimation based on the Park transform. The proposed method firstly extends the signal to a group of three-phase signals in a-b-c coordinate. Then, a linear fitting based method is adopted to estimate the fundamental frequency. Afterwards, the Park transform is utilized to convert the three-phase signals from a-b-c coordinate to d-q-0 coordinate. Finally, the amplitude and phase of a harmonic component of interest can be calculated using the d-axis and q-axis components obtained. Simulation studies have been conducted using matrix laboratory (MATLAB) and power system computer aided design/electromagnetic transients including direct current (PSCAD/EMTDC). Simulation studies in MATLAB have considered three scenarios, i.e., no-frequency-deviation scenario, frequency-deviation scenario and the scenario in the presence of inter-harminics. The results have demonstrated that the proposed method achieves very high accuracy in frequency, phase and amplitude estimation under noisy conditions, and suffers little influence of the inter-harmonics. Moreover, comparison studies have proved that the proposed method is superior to FFT and Interpolated FFT with the Hanning Window (IpFFTHW). Finally, a popular case in PSCAD/EMTDC has been employed to further verify the effectiveness of the proposed method.
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Analysis of Operation Characteristics of a Diesel Generator Set with Constant‑Power Pulsed Load
Meng Shi,Puyu Wang,Jinquan Wang,Haichao Li,Ye Xu,Kefeng Huang,Jianke Li 대한전기학회 2019 Journal of Electrical Engineering & Technology Vol.14 No.6
To improve the power quality of a diesel generator set with a pulsed load in a microgrid, this paper studied the operation characteristics of the system and proposed pulsed load conditions for an actual project based on test data. For a low average pulse power and a high peak power, a new mathematical model of the pulsed load in diferent operation modes was proposed. Then, a simulation model of the microgrid was established in MATLAB/Simulink, and the operation of the system was studied considering changes in various pulsed load parameters (the peak power Pk, output duty cycle D and switching period Ts). It was verifed by tests that the simulation model is efective and can refect the operation of the system. Based on the simulation model, the operation characteristics of the system with a bivariate pulsed load were studied, and qualifcation conditions for the diesel generator set in an actual project were proposed.
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Meng Shi,Zhaoyu Liu,Hong Liang Wang,Chuanxin Shi,Ling Liu,Junjun Wang,Defa Li,Shuai Zhang 아세아·태평양축산학회 2019 Animal Bioscience Vol.32 No.3
Objective: This experiment was conducted to determine the chemical composition, digestible energy (DE) and metabolizable energy (ME) contents of corn germ meals (CGM) and to develop equations to predict the corresponding energy contents based on the chemical characteristics of individual CGM. Methods: Sixty-six barrows (initial body weight = 51.3±4.6 kg) were allotted to 11 diets including a basal diet and 10 CGM test diets in a completely randomized design. In the test diets, CGM was included in replacement of 30% of the energy-providing ingredients in the basal diet, resulting in a final inclusion rate of 29.1%. Each diet was fed to 6 barrows housed in individual metabolism crates for a 7-d acclimation period followed by a 5-d total but separate collection of feces and urine. Results: Considerable variation was observed in acid-hydrolyzed ether extract, ether extract, ash, calcium (Ca) and total phosphorus contents among the CGM samples. On dry matter (DM) basis, the DE and ME contents of the CGM ranged from 10.22 to 15.83 MJ/kg and from 9.94 to 15.43 MJ/kg, respectively. The acid detergent fiber (ADF) contents were negatively correlated with the DE and ME contents of CGM samples. The best-fit prediction equations for the DE and ME values (MJ/kg DM) of the 10 CGM were: DE = 26.85–0.28 insoluble dietary fiber (%)–17.79 Ca (%); ME = 21.05–0.43 ADF (%)–11.40 Ca (%). Conclusion: The chemical compositions of CGM vary depending on sources, particularly in ether extract and Ca. The DE and ME values of CGM can be predicted based on their chemical composition in growing pigs.
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