The demand for increased renewable energy production has led to increased photovoltaic installati... more The demand for increased renewable energy production has led to increased photovoltaic installations worldwide. While the cost of PV modules has reduced strongly, the Balance of System (BoS) costs, notably the costs of the power conditioning system (PCS), have not had a corresponding decrease. Module integrated converter (MIC) technology provides an alternative approach to PCS design. This thesis examines the optimisation of DC-DC converter topologies for PCS designs with an intermediate DC bus. From among various topologies, the LLC resonant converter is chosen. Photovoltaic module power conditioning requires wide operating voltage ranges. The operating range can be extended for the LLC topology by combining variable frequency control and phase shift control. Analytical solutions exist for the converter operating with variable frequency control but these have not been fully developed for phase shift control. This thesis provides a detailed analytical solution for the modes of the p...
2017 Australasian Universities Power Engineering Conference (AUPEC), 2017
This paper explores the integration of two control methods, variable frequency control and fixed ... more This paper explores the integration of two control methods, variable frequency control and fixed frequency phase shifting control for the effective operation of LLC resonant converter over an extended voltage range that can exceed 2:1. The variable frequency method is used to regulate the output voltage while the input voltage is low to use the higher gain curve whereas the phase shifting method is used when the input voltage is higher. This dual mode control is designed in such a way that the primary switches will achieve zero voltage switching (ZVS) and secondary rectifiers will achieve zero current switching (ZCS) over the entire voltage range. Moreover, the conversion efficiency is also increased at light load condition with this proposed control. A soft transition has been achieved at transition point from one control method to other control method. To confirm the validity of this paper, an experimental prototype of 300W has been built and 98.1% peak efficiency has been achieve...
The purpose of microgrids is to deliver distributed power in distribution network. Microgrids inc... more The purpose of microgrids is to deliver distributed power in distribution network. Microgrids increase the performance and reliability of the whole system by providing grid support services during the normal operation and also in islanded mode. This paper investigates two microgrid control techniques focusing on active-reactive power control and voltage-frequency control. At the converter level, this paper focuses on two microgrid configurations such as grid forming converter and grid following converter both in time domain and phasor domain form. It is shown that the computational time is much less in phasor domain form than the time domain form.
This paper presents the steady state analysis of the full bridge LLC resonant converter. Six swit... more This paper presents the steady state analysis of the full bridge LLC resonant converter. Six switching stages are found due to the odd symmetry. Once the information about state variables are at hand, state plane trajectory can be constructed for each state. In this paper a detailed analysis has been presented for phase modulated LLC resonant converter to predict the resonant voltage and current waveforms of the operational modes. For these operational modes, two dimensional state plane trajectories are also observed. A design guideline has been proposed to assess which modes are practically useful and will have the highest efficiency.
2015 Australasian Universities Power Engineering Conference (AUPEC), 2015
Modular power conditioning systems, where each PV module has its own power converter, have been p... more Modular power conditioning systems, where each PV module has its own power converter, have been proven to yield higher output power due to their superior maximum power point tracking capabilities. In PV strings the typical operating voltages pose reasonable electrical safety problems that can be overcome in conventional modules. For certain cell constructions, such as thin film arrays deposited onto roofing sheets, it is not possible to obtain sufficient galvanic isolation. Some cells, such as the back contact cells, suffer from surface charge accumulation or polarisation effects that can be solved by isolation. This paper presents a comparative loss analysis between zero-voltage-resonant-transition half bridge converter and series resonant converters that rare intend to be used as module isolation converters. Detailed analysis of the operation of these two converters is discussed. Two low voltage hardware prototypes of 300W have been made whose efficiency is of 90% for series resonant converter and 88% for zero voltage resonant transition converter.
2013 International Conference on Informatics, Electronics and Vision (ICIEV), 2013
Variation in time between two successive heart beats occurring due to internal and external stimu... more Variation in time between two successive heart beats occurring due to internal and external stimulation causes Heart Rate Variability (HRV). HRV is a tool for indirect investigation of both cardiac and autonomic system function in both healthy and diseased condition. It has been speculated that HRV analysis by nonlinear method might bring potentially useful prognosis information into light which will be helpful for assessment of cardiac condition. In this study, HRV from two types of data sets (normal sinus rhythm and sinus arrhythmia) are analyzed which are stored in MIT-BIH (Massachusetts Institute of Technology - Beth Israel hospital) database, an extended collection of recorded physiological signals. Then two nonlinear methods, approximate entropy (ApEn) and detrended fluctuation analysis (DFA), have been applied to analyze HRV of both Arrhythmia patients and people having normal sinus rhythm. It has been clearly shown that nonlinear parameters obtained from these two methods reflect the opposite heart condition of the two types of subjects under study, healthy and diseased, by HRV measures. Thus, value of the nonlinear parameters found in this work can be used as standard when treating suspected patients for diagnosis of Arrhythmia. Also, by measuring these nonlinear parameter values, heart condition can be understood.
Variation in time between two successive heart beats occurring due to internal and external stimu... more Variation in time between two successive heart beats occurring due to internal and external stimulation causes Heart Rate Variability (HRV). HRV is a tool for indirect investigation of both cardiac and autonomic system function in both healthy and diseased condition. It has been speculated that HRV analysis by nonlinear method might bring potentially useful prognosis information into light which will be helpful for assessment of cardiac condition. In this study, HRV from two types of data sets (normal sinus rhythm and sinus arrhythmia) are analyzed which are stored in MIT-BIH (Massachusetts Institute of Technology – Beth Israel hospital) database, an extended collection of recorded physiological signals. Then two nonlinear methods, approximate entropy (ApEn) and detrended fluctuation analysis (DFA), have been applied to analyze HRV of both Arrhythmia patients and people having normal sinus rhythm. It has been clearly shown that nonlinear parameters obtained from these two methods reflect the opposite heart condition of the two types of subjects under study, healthy and diseased, by HRV measures. Thus, value of the nonlinear parameters found in this work can be used as standard when treating suspected patients for diagnosis of Arrhythmia. Also, by measuring these nonlinear parameter values, heart condition can be understood.
The demand for increased renewable energy production has led to increased photovoltaic installati... more The demand for increased renewable energy production has led to increased photovoltaic installations worldwide. While the cost of PV modules has reduced strongly, the Balance of System (BoS) costs, notably the costs of the power conditioning system (PCS), have not had a corresponding decrease. Module integrated converter (MIC) technology provides an alternative approach to PCS design. This thesis examines the optimisation of DC-DC converter topologies for PCS designs with an intermediate DC bus. From among various topologies, the LLC resonant converter is chosen. Photovoltaic module power conditioning requires wide operating voltage ranges. The operating range can be extended for the LLC topology by combining variable frequency control and phase shift control. Analytical solutions exist for the converter operating with variable frequency control but these have not been fully developed for phase shift control. This thesis provides a detailed analytical solution for the modes of the p...
2017 Australasian Universities Power Engineering Conference (AUPEC), 2017
This paper explores the integration of two control methods, variable frequency control and fixed ... more This paper explores the integration of two control methods, variable frequency control and fixed frequency phase shifting control for the effective operation of LLC resonant converter over an extended voltage range that can exceed 2:1. The variable frequency method is used to regulate the output voltage while the input voltage is low to use the higher gain curve whereas the phase shifting method is used when the input voltage is higher. This dual mode control is designed in such a way that the primary switches will achieve zero voltage switching (ZVS) and secondary rectifiers will achieve zero current switching (ZCS) over the entire voltage range. Moreover, the conversion efficiency is also increased at light load condition with this proposed control. A soft transition has been achieved at transition point from one control method to other control method. To confirm the validity of this paper, an experimental prototype of 300W has been built and 98.1% peak efficiency has been achieve...
The purpose of microgrids is to deliver distributed power in distribution network. Microgrids inc... more The purpose of microgrids is to deliver distributed power in distribution network. Microgrids increase the performance and reliability of the whole system by providing grid support services during the normal operation and also in islanded mode. This paper investigates two microgrid control techniques focusing on active-reactive power control and voltage-frequency control. At the converter level, this paper focuses on two microgrid configurations such as grid forming converter and grid following converter both in time domain and phasor domain form. It is shown that the computational time is much less in phasor domain form than the time domain form.
This paper presents the steady state analysis of the full bridge LLC resonant converter. Six swit... more This paper presents the steady state analysis of the full bridge LLC resonant converter. Six switching stages are found due to the odd symmetry. Once the information about state variables are at hand, state plane trajectory can be constructed for each state. In this paper a detailed analysis has been presented for phase modulated LLC resonant converter to predict the resonant voltage and current waveforms of the operational modes. For these operational modes, two dimensional state plane trajectories are also observed. A design guideline has been proposed to assess which modes are practically useful and will have the highest efficiency.
2015 Australasian Universities Power Engineering Conference (AUPEC), 2015
Modular power conditioning systems, where each PV module has its own power converter, have been p... more Modular power conditioning systems, where each PV module has its own power converter, have been proven to yield higher output power due to their superior maximum power point tracking capabilities. In PV strings the typical operating voltages pose reasonable electrical safety problems that can be overcome in conventional modules. For certain cell constructions, such as thin film arrays deposited onto roofing sheets, it is not possible to obtain sufficient galvanic isolation. Some cells, such as the back contact cells, suffer from surface charge accumulation or polarisation effects that can be solved by isolation. This paper presents a comparative loss analysis between zero-voltage-resonant-transition half bridge converter and series resonant converters that rare intend to be used as module isolation converters. Detailed analysis of the operation of these two converters is discussed. Two low voltage hardware prototypes of 300W have been made whose efficiency is of 90% for series resonant converter and 88% for zero voltage resonant transition converter.
2013 International Conference on Informatics, Electronics and Vision (ICIEV), 2013
Variation in time between two successive heart beats occurring due to internal and external stimu... more Variation in time between two successive heart beats occurring due to internal and external stimulation causes Heart Rate Variability (HRV). HRV is a tool for indirect investigation of both cardiac and autonomic system function in both healthy and diseased condition. It has been speculated that HRV analysis by nonlinear method might bring potentially useful prognosis information into light which will be helpful for assessment of cardiac condition. In this study, HRV from two types of data sets (normal sinus rhythm and sinus arrhythmia) are analyzed which are stored in MIT-BIH (Massachusetts Institute of Technology - Beth Israel hospital) database, an extended collection of recorded physiological signals. Then two nonlinear methods, approximate entropy (ApEn) and detrended fluctuation analysis (DFA), have been applied to analyze HRV of both Arrhythmia patients and people having normal sinus rhythm. It has been clearly shown that nonlinear parameters obtained from these two methods reflect the opposite heart condition of the two types of subjects under study, healthy and diseased, by HRV measures. Thus, value of the nonlinear parameters found in this work can be used as standard when treating suspected patients for diagnosis of Arrhythmia. Also, by measuring these nonlinear parameter values, heart condition can be understood.
Variation in time between two successive heart beats occurring due to internal and external stimu... more Variation in time between two successive heart beats occurring due to internal and external stimulation causes Heart Rate Variability (HRV). HRV is a tool for indirect investigation of both cardiac and autonomic system function in both healthy and diseased condition. It has been speculated that HRV analysis by nonlinear method might bring potentially useful prognosis information into light which will be helpful for assessment of cardiac condition. In this study, HRV from two types of data sets (normal sinus rhythm and sinus arrhythmia) are analyzed which are stored in MIT-BIH (Massachusetts Institute of Technology – Beth Israel hospital) database, an extended collection of recorded physiological signals. Then two nonlinear methods, approximate entropy (ApEn) and detrended fluctuation analysis (DFA), have been applied to analyze HRV of both Arrhythmia patients and people having normal sinus rhythm. It has been clearly shown that nonlinear parameters obtained from these two methods reflect the opposite heart condition of the two types of subjects under study, healthy and diseased, by HRV measures. Thus, value of the nonlinear parameters found in this work can be used as standard when treating suspected patients for diagnosis of Arrhythmia. Also, by measuring these nonlinear parameter values, heart condition can be understood.
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