Browsing by Author "Hanif, Moin"
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- ItemOpen AccessAnalysis of single-diode and improvement of double-diode photovoltaic source modelling methods and techniques(2015) Shongwe, Samkeliso Hubert; Hanif, MoinModelling of photovoltaic systems is essential for designers of solar generation plants to do a yield analysis that accurately predicts the expected power output under changing environmental conditions. There are a few different models which are used and they all differ in their implementation and also on the accuracy. The main aim of this thesis is to analyse different PV modelling methods which are based on the single-diode and double-diode models. The study carried out, falls under two sections. The first study was to figure out which single-diode model produces the most accurate results. The second study is extended to double-diode models. Here, the thesis goes on to propose a different PV modelling method which is based on the double-diode representation of a PV module that will be verified and compared with other models and experimental data. An analysis of the various different single-diode models is done based on two commercially available PV modules: SQ80 and the KC200GT, in which the simulated results are compared with the characteristics extracted from the datasheets. Parameter estimation techniques within a modelling method are generally used to estimate the five unknown parameters in the single-diode model. Two sets of estimated parameters were used to plot the I-V characteristics of two PV modules, SQ80 and KC200GT, for the different sets of modelling equations which are classified into models 1 to 5 in this study. Each model is based on the different combinations of diode saturation current and photo generated current, plotted under varying irradiance and temperature. Modelling was done using Matlab/Simulink software and the results from each model were first verified for correctness against the results produced by their respective authors, then a comparison was made amongst the different models (models 1 to 5) with respect to experimentally measured and datasheet I-V curves. The SQ80 module is also connected in the lab and experimental values are measured from it under different environmental conditions. A comparison is then made using the different modelling methods with the experimental data to evaluate the accuracy of the models. In the second study, the new proposed double-diode PV modelling method is also implemented using datasheet information for three commercial PV modules made from different technologies: mono-crystalline, poly-crystalline and thin-film technology. This method is an improvement on an existing method and is more accurate. A comparison is made with the characteristics extracted from the datasheet to verify that it produces accurate results. A comparison of this modelling method is also made with the experimentally measured data from the SQ80 PV module. The results obtained were used to draw conclusions on which combination of parameter extraction and modelling method best emulates the manufacturer's characteristics.
- ItemOpen AccessDesign of LCL-filters for grid-connected voltage source inverters(2016) Jayalath, Sampath; Hanif, MoinLCL-filters are preferred over conventional L-filters for grid-connected voltage source inverters (VSI) due to their superior harmonic attenuation, smaller filter size and weight. The LCL-filter design process is complex and takes an iterative approach due to the coherence between the filter parameters and design requirements. The main aim of this thesis is to analyse different design variables that contribute to an efficient LCL-filter. The study carried out, falls under two sections. The first study was to understand the importance of ratio between the grid-side and inverter-side inductors, resonance frequency, reactive power production and attenuation of higher order harmonics in an LCL-filter. Based on the analysis, this thesis proposes a generalised LCL-filter design algorithm which avoids uncertainty in determining resonance frequency as the exact position of the resonance frequency is determined based on the design requirements. The proposed design method considers the LCL-filter as a single filtering unit rather than individual filtering contributions from passive components. The second study is extended to understand the limits of passive components based on the reactive power production limits (based on control structure), IEEE-519 harmonic limitations and the allowable switching losses or voltage drop across the entire filter. Based on the analysis, the thesis proposes an optimum operating point for an LCL-filter where the minimum inductance is realised to meet IEEE-519 harmonic current limitations for a given reactive power production while ensuring reasonable switching losses. Simulations and experimental results are presented to demonstrate the efficacy of the proposed two methods in terms of total harmonic distortion, harmonic attenuation and reactive power compensated.[Please note: This thesis file has been deferred until December 2016]
- ItemOpen AccessImprovement in control and gain aspects of impedance source inverters and converters(2019) Aleem, Zeeshan; Winberg, Simon; Hanif, MoinPower electronics have revolutionized the concept of power control for power conversion and for control of electrical motor drives. Power electronics has been extensively used in industrial applications since it was first discovered in 1902. Power conversion is one of the most important and prominent applications of power electronics. Impedance source networks cover the entire spectrum of electric power conversions from DC-AC (e.g. inverters), to phase and frequency conversion (AC-AC) in a wide range of applications. A wide variety of topologies and control methods using different impedance source networks have been presented in the literature to overcome the limitations and problems of traditional voltage source and current source as well as various classical buck–boost, unidirectional, and bidirectional converter topologies. Proper implementation of the impedance-source network with appropriate switching configurations and topologies reduces the number of power conversion stages in the system power chain, which may improve the reliability and performance of the power system. The main focus of this thesis is to study and analyze different impedance source inverters and their control methods, and the development of improved impedance source power systems that will comprise advanced circuitry and provide higher voltage gains needing less complex systems that together provide more cost-efficient solutions. The systems under considerations would have high frequency electrical isolation and voltage clamping across the DC-link inverter bridge that would resulting in better protection, lower overall system losses, and increased efficiencies. Then parallel techniques will be discussed, analyzed and implemented for the class of impedance source inverters. This parallel operation of ZSIs leads to reduced components stress across the inverter bridges by sharing the currents, interleaving, ease of maintenance, modularity, higher reliability, and (N+1) redundancy. The scope of impedance source networks is not limited to inverters (i.e., DC-AC power conversion), but covers a wide range of electric power conversion applications including (DC-DC and AC-AC converters). Thus, the last part of this research project will include the development of a new class of transformer based impedance source AC-AC converters with novel control strategies to increase the input to output gains and to improve the conglomerate characteristics of the AC-AC converters. Validation of the proposed structures will be done virtually using the Saber, PSIM simulations, and physically using experimental hardware prototypes. Several KW power systems will be fabricated and implemented using a DSP-kit based on the TMS320f28335 processor. Modified modulation schemes will be applied to control the switching of active devices. Furthermore, clamping techniques by minimizing the high frequency loop via clamping diode will be applied to the proposed inverters to limit the voltage overshoots caused by the leakage inductance energy. The better performance of improved impedance source network (with added benefits of HF isolation and parallelization) to design more resilient and efficient converter topology for various applications such as adjustable speed drives, distributed generation systems, super-capacitor energy storage systems, uninterruptable power supply, dc circuit breakers, electric vehicles, avionics, and electronic loads will attract researchers and professional engineers to explore it in depth.