Engineeringhttp://hdl.handle.net/10059/142017-04-29T15:33:44Z2017-04-29T15:33:44ZAveraged model of modular multilevel converter in rotating DQ frame.Sinha, YashwantNampally, Ashokhttp://hdl.handle.net/10059/22832017-04-24T11:22:48Z2016-11-20T00:00:00ZAveraged 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.Sinha, YashwantNampally, Ashokhttp://hdl.handle.net/10059/22822017-04-24T11:09:13Z2016-11-20T00:00:00ZLinearized 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.Sinha, YashwantNampally, Ashokhttp://hdl.handle.net/10059/22812017-04-24T10:53:09Z2016-11-20T00:00:00ZModular 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/EMTDCĀ®. 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.
2016-11-20T00:00:00ZEsterification of lactic acid and ethanol using heterogenous catalysts for the production of a bio-based chemical.Okon, EdidiongHabiba, ShehuGobina, Edwardhttp://hdl.handle.net/10059/22582017-04-14T13:52:52Z2017-03-15T00:00:00ZEsterification of lactic acid and ethanol using heterogenous catalysts for the production of a bio-based chemical.
Okon, Edidiong; Habiba, Shehu; Gobina, Edward
In this work, the batch process esterification reaction was carried out at 80 oC using different types of heterogeneous catalysts. The heterogeneous resin catalysts used for the analysis were amberlyst 15, amberlyst 36, amberlyst 16 and dowex 50W8x. The esterification product was analysed using autosampler gas chromatograph coupled with mass spectrometer (Agilent technology 7890B). The surface morphology of the resin catalysts after the esterification process was examined using scanning electron microscopy (The Zeiss EVO LS10) coupled with energy dispersive analysis of x-ray (The Oxford INCA System) (SEM/EDAX). The SEM of amberlyst 36 and 16 showed a defect-free surface in contrast to amberlyst 15 and dowex 50W8x. The EDAX spectra of the resin catalysts confirmed the presence of elements including carbon, oxygen, sulphur, and aluminium. Amberlyst 36 exhibited a large pore after the esterification process in contrast to other catalysts. Sulphur showed the highest peak on the EDAX of the resin. Dowex 50W8x and amberlyst 36 resin catalysts were found to elute faster at 1.523 and 1.527 min respectively in contrast to amberlyst 15 and amberlyst 16 at 1.521 and 1.503 min respectively. The increasing order of the retention time after the esterification process at 80 oC was dowex 50W8x > amberlyst 36 > amberlyst 15 > amberlyst 16. The liquid nitrogen adsorption at 77 K (Quantachrome 2013) was used to determine the surface area, pore size and the total pore volume of the cation-exchange reins. The BET surface area of the resin catalyst was found to be higher (14.302 m2/g) with hysteresis loop confirming a good interaction of the catalysts with the reactant solvent.
2017-03-15T00:00:00Z