Conference publications (Engineering)
http://hdl.handle.net/10059/243
2017-07-05T22:06:19ZRecovery of VOC from offshore and onshore shuttle tankers using structured Y-type zeolite membranes.
http://hdl.handle.net/10059/2329
Recovery of VOC from offshore and onshore shuttle tankers using structured Y-type zeolite membranes.
Habiba, Shehu; Ajayi, Adebayo; Okon, Edidiong; Gobina, Edward
The emissions of volatile organic compounds (VOCs) from onshore and offshore facilities are studied and an alternative technology for the recovery of methane and propane by the use of membrane technology is explored. Permeation tests were carried out with a zeolite membrane consisting of an α - Al2O3 support. The permeance of nitrogen, carbon dioxide, helium, methane and propane through the membrane at varying pressures was determined. The permeance of CH4 was in the range of 1.44 x 10-6 to 3.41 x 10 -6 mols-1m-2Pa-1 and a CH4/C3H8 selectivity of 3.3 at 293 K was obtained. The molar flux of the gases was found to have an average linear regression coefficient value R2 of 0.9892. On the basis of the results obtained it can be concluded that separation of the hydrocarbon gases can be achieved with the zeolite membrane. The main mechanism governing the flow of gases through the zeolite membrane was molecular sieving although there is evidence of deviation from this mechanism. To achieve higher selectivity of the target gas there is need for further modification of the membrane. The morphology of the membrane was determined using the scanning electron microscope, which showed the pore size of the membrane and the support layer.
2017-03-13T00:00:00ZAveraged model of modular multilevel converter in rotating DQ frame.
http://hdl.handle.net/10059/2283
Averaged model of modular multilevel converter in rotating DQ frame.
Sinha, Yashwant; Nampally, Ashok
This paper proposes an average model of Modular Multilevel Converter (MMC) in rotating DQ frame. The proposed MMC model has a modular structure and can be linked with other power elements such as AC and DC subsystems. Modelling in DQ frame has numerous advantages over traditional ABC frame in terms of simulation speed and convenience for linearization. The main challenge of developing DQ model of MMC is to deal with the multiplication terms of dynamic equations of MMC. To overcome this complexity, a generic form is first introduced for each product variable mathematical equations of the average MMC model in ABC frame and then the multiplication results are transferred to DQ frame after ignoring the higher harmonics. The detailed model and the proposed DQ average model are implemented in PSCAD/EMTDC. The simulation results of the two models show very good matching which in turn confirms the accuracy of the proposed model. Also, the DQ average model is considerably faster than the detailed and even ABC average models.
2016-11-20T00:00:00ZLinearized DQ averaged model of modular multilevel converter.
http://hdl.handle.net/10059/2282
Linearized DQ averaged model of modular multilevel converter.
Sinha, Yashwant; Nampally, Ashok
This paper proposes a linearized model of Modular Multilevel Converter (MMC) in DQ frame. The proposed MMC model has a modularstructure and can be linked with other power elements such as AC and DC subsystems.The main challenge of developing DQ model of MMC is to deal with the multiplication terms in dynamic equations of MMC. In this paper, the multiplication terms are done in ABC frame and results are transferred to DQ frame after ignoring the higher harmonics. The detailed model is implemented in PSCAD/EMTDC and the proposed linearized model is implemented in Matlab in a modular form. The results of the two models show very good matching which in turn confirm the accuracy of the proposed model. Therefore, thismodelpermits modern control designtechniques to be employedon MMC,including eigenvalues studies and frequency domain analysis.
2016-11-20T00:00:00ZModular multilevel converter modulation using fundamental switching selective harmonic elimination method.
http://hdl.handle.net/10059/2281
Modular multilevel converter modulation using fundamental switching selective harmonic elimination method.
Sinha, Yashwant; Nampally, Ashok
This paper address the issue of low order harmonics in a modular multilevel converter (MMC). Using fundamental switching selective harmonic elimination (SHE), the control angles are calculated from nonlinear equations by Newton-Raphson method. The selective harmonic elimination equations are solved in such a way that the first switching angle is used to control the magnitude of the fundamental voltage and the remaining angles are used to eliminate the lowest odd, non-triplen harmonics components as they dominate the total harmonic distortion of the converter. The concept is validated using a 9-level detailed model of MMC in PSCAD/EMTDC®. The simulation result shows a good agreement with theoretical analysis and in comparison with conventional sinusoidal pulse width modulation (SPWM), the proposed method, eliminates low order harmonics, leading to a low total harmonic distortion.
2016-11-20T00:00:00Z