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Title:	Design of a two stage inverter for grid connected transformerless single phase PV systems
Authors:	Mohsen Shayestegan (P72520)
Supervisor:	Nowshad Amin, Prof. Dr.
Keywords:	Electrical energy Photovoltaic power systems
Issue Date:	16-Mar-2018
Description:	In power generation and distribution, high efficiency is required to deliver energy from photovoltaic (PV) systems to the utility grid. It is essential to track the maximum power point/position of the output characteristics of PV systems at ever changing surrounding conditions. The aim of this work is to develop a noble concept to supply electrical energy more efficiently from the PV system to the utility grid. Currently, transformerless inverters are getting attention as they have abilities to attain high efficiency, low cost, and smaller size. These inverters do not have electrical isolation between DC and AC circuits. In this respect, this study introduces the design of a two-stage inverter for grid connected transformerless single-phase PV systems. There are some disadvantages such as high number of components, hard switching, and complexity of system, which needed to be considered and optimized. For maximum power point tracking (MPPT) controllers, still have the problem of convergence speed and algorithm complexity. Impact of non-ideal condition on the leakage current were not considered in previous transformerless inverters. Moreover, the cost, power losses have some disadvantages in damping methods. The proposed inverter consists of a new DC/DC converter that is operated by soft switching technique at the first stage and a DC/AC inverter with a high order LCL filter at the second stage. The topology provides step-up capabilities and a nearly constant efficiency over a wide operating range. Then, a MPPT controller is developed for the converter to deliver the maximum power to the second stage. The controller technique is applied to the converter engaging adjustable frequency-duty cycle modulation control. The ground current issue is considered in designing the proposed transformerless inverter. Moreover, the effect of junction capacitance integrated to the power switches of the proposed inverter are analyzed in details. In this respect, the current control and the voltage control are designed and analyzed. Simulation and experimental results are presented to prove the effectiveness of the proposed DC/DC converter system. The results have shown that the zero current switching (ZCS) operation is successfully maintained over the whole operation by adapting the duty cycle with the frequency from the proposed controller. The proposed topology shows practically constant efficiency (84%) over a wide operating range. The simulation results of the whole system illustrate the improved inverter upon the proposed controller and found that sinusoidal pulse width modulation (SPWM) could inject the input power into the grid with lower harmonic distortion (THD=2.6%) along with nearly unity power factor. Finally, the ground voltage and the ground current of proposed inverter is compared with other inverter topologies to validate and justify the conformance. It is found that the developed topology is more capable than other topologies to minimize the leakage current, as the noteworthy success of the study.,Certification on Master's/Doctoral Thesis" is not available
Pages:	183
Call Number:	TK1087.S533 2018 3 tesis
Publisher:	UKM, Bangi
Appears in Collections:	Faculty of Engineering and Built Environment / Fakulti Kejuruteraan dan Alam Bina

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