Primary-side sensing for a yback converter in both continuous and discontinuous conduction mode

Primary-side sensing is an observer-based approach to estimate the out- put voltage of yback converters from a primary winding (or an auxiliary winding). Various observer-laws have been recently developed for yback converters operating in discontinuous conduction mode (DCM). The extension to continuous conduction mode (CCM), however, has not been considered due to the diculties in compensating for the voltage drop in the secondary winding. From the possibility to predict the winding volt- age drop using the magnetizing current and the transformer model, this paper presents a new observer method that can work accurately and smoothly in both CCM and DCM. The methodology can be combined with any controller to provide either output voltage regulation or output current regulation. The proposed sensing technique is veried by simulation

Non-linear Dynamic Transformer Modelling and Optimum Control Design of Switched-mode Power Supplies

With recent advances in semiconductor manufacturing and computational technology, digital control systems have grown to a relatively mature stage, and will soon become a viable replacement for their analogue counterparts in the design of isolated and non-isolated DC-to-DC converters in general, and yback converters in particular. Inspired by this possibility, the thesis adopts the first-ever digital control design in the field for wide-operating range yback converters, based on a low-cost microcontroller. Accurate transformer modelling is a necessary exercise for the study of the yback converters as well as for model-based controller design. Therefore, a non-linear dynamic model, which allows an accurate representation of both linear dynamics and non-linear core behaviour in a practical transformer, is proposed. The parameters of the proposed transformer model are obtained using time-domain system identification based on experimental data. In order to reduce the round-of error typically occurring in the collected time-domain data, a method which is based on adjusting the value of the current sensing resistor is also adopted. To facilitate control design, a control-oriented model is developed based on the full converter model through a simplification step. As demonstrated in the thesis, the control-oriented model is able to preserve the bulk of the full converter model fidelity, critical for a control design step, while at the same time requiring a significantly shorter execution time for simulation when compared with the full converter model. For the purpose of implementing isolated-feedback control within a low-cost microcontroller, a magnetic sensing principle, which can operates in both continuous and discontinuous conduction modes of the yback converter, is developed. The proposed sensing principle is also based on the bias winding voltage of the yback transformer to estimate the converter output voltage; however, the sampling instant is chosen at the point where the secondary current is known, instead of the knee point where the secondary current is zero. The implementation of the proposed sensing technique, based on analogue circuitry and a microcontroller, is also studied. Finally, optimum digital control for a wide-operating range yback converter is developed and implemented. The control architecture is purposely designed to perform a variety of tasks, including efficiency optimisation, magnetic sensing, and valley switching operation, in addition to the main task of regulating the output voltage. Three different methods for synthesizing optimum compensators, based on mixed-sensitivity H1 robust control theory, gain-adaptive predictive functional control (GAPFC) theory, and gain-adaptive quantitative feedback theory (GAQFT), are also studied. In order to improve the performance of the robust controllers, parametric variations of the yback converter models are minimized before applying the robust control. Two possibilities for reducing converter parametric model uncertainty, based on adapting the converter open-loop gain and varying the sampling rate of the digital controller, are also demonstrated

Non-linear Dynamic Transformer Modelling and Optimum Control Design of Switched-mode Power Supplies

With recent advances in semiconductor manufacturing and computational technology, digital control systems have grown to a relatively mature stage, and will soon become a viable replacement for their analogue counterparts in the design of isolated and non-isolated DC-to-DC converters in general, and yback converters in particular. Inspired by this possibility, the thesis adopts the first-ever digital control design in the field for wide-operating range yback converters, based on a low-cost microcontroller. Accurate transformer modelling is a necessary exercise for the study of the yback converters as well as for model-based controller design. Therefore, a non-linear dynamic model, which allows an accurate representation of both linear dynamics and non-linear core behaviour in a practical transformer, is proposed. The parameters of the proposed transformer model are obtained using time-domain system identification based on experimental data. In order to reduce the round-of error typically occurring in the collected time-domain data, a method which is based on adjusting the value of the current sensing resistor is also adopted. To facilitate control design, a control-oriented model is developed based on the full converter model through a simplification step. As demonstrated in the thesis, the control-oriented model is able to preserve the bulk of the full converter model fidelity, critical for a control design step, while at the same time requiring a significantly shorter execution time for simulation when compared with the full converter model. For the purpose of implementing isolated-feedback control within a low-cost microcontroller, a magnetic sensing principle, which can operates in both continuous and discontinuous conduction modes of the yback converter, is developed. The proposed sensing principle is also based on the bias winding voltage of the yback transformer to estimate the converter output voltage; however, the sampling instant is chosen at the point where the secondary current is known, instead of the knee point where the secondary current is zero. The implementation of the proposed sensing technique, based on analogue circuitry and a microcontroller, is also studied. Finally, optimum digital control for a wide-operating range yback converter is developed and implemented. The control architecture is purposely designed to perform a variety of tasks, including efficiency optimisation, magnetic sensing, and valley switching operation, in addition to the main task of regulating the output voltage. Three different methods for synthesizing optimum compensators, based on mixed-sensitivity H1 robust control theory, gain-adaptive predictive functional control (GAPFC) theory, and gain-adaptive quantitative feedback theory (GAQFT), are also studied. In order to improve the performance of the robust controllers, parametric variations of the yback converter models are minimized before applying the robust control. Two possibilities for reducing converter parametric model uncertainty, based on adapting the converter open-loop gain and varying the sampling rate of the digital controller, are also demonstrated

Non-linear Dynamic Transformer Modelling and Optimum Control Design of Switched-mode Power Supplies

With recent advances in semiconductor manufacturing and computational technology, digital control systems have grown to a relatively mature stage, and will soon become a viable replacement for their analogue counterparts in the design of isolated and non-isolated DC-to-DC converters in general, and yback converters in particular. Inspired by this possibility, the thesis adopts the first-ever digital control design in the field for wide-operating range yback converters, based on a low-cost microcontroller. Accurate transformer modelling is a necessary exercise for the study of the yback converters as well as for model-based controller design. Therefore, a non-linear dynamic model, which allows an accurate representation of both linear dynamics and non-linear core behaviour in a practical transformer, is proposed. The parameters of the proposed transformer model are obtained using time-domain system identification based on experimental data. In order to reduce the round-of error typically occurring in the collected time-domain data, a method which is based on adjusting the value of the current sensing resistor is also adopted. To facilitate control design, a control-oriented model is developed based on the full converter model through a simplification step. As demonstrated in the thesis, the control-oriented model is able to preserve the bulk of the full converter model fidelity, critical for a control design step, while at the same time requiring a significantly shorter execution time for simulation when compared with the full converter model. For the purpose of implementing isolated-feedback control within a low-cost microcontroller, a magnetic sensing principle, which can operates in both continuous and discontinuous conduction modes of the yback converter, is developed. The proposed sensing principle is also based on the bias winding voltage of the yback transformer to estimate the converter output voltage; however, the sampling instant is chosen at the point where the secondary current is known, instead of the knee point where the secondary current is zero. The implementation of the proposed sensing technique, based on analogue circuitry and a microcontroller, is also studied. Finally, optimum digital control for a wide-operating range yback converter is developed and implemented. The control architecture is purposely designed to perform a variety of tasks, including efficiency optimisation, magnetic sensing, and valley switching operation, in addition to the main task of regulating the output voltage. Three different methods for synthesizing optimum compensators, based on mixed-sensitivity H1 robust control theory, gain-adaptive predictive functional control (GAPFC) theory, and gain-adaptive quantitative feedback theory (GAQFT), are also studied. In order to improve the performance of the robust controllers, parametric variations of the yback converter models are minimized before applying the robust control. Two possibilities for reducing converter parametric model uncertainty, based on adapting the converter open-loop gain and varying the sampling rate of the digital controller, are also demonstrated

Primary-side sensing for a yback converter in both continuous and discontinuous conduction mode

Primary-side sensing is an observer-based approach to estimate the out- put voltage of yback converters from a primary winding (or an auxiliary winding). Various observer-laws have been recently developed for yback converters operating in discontinuous conduction mode (DCM). The extension to continuous conduction mode (CCM), however, has not been considered due to the diculties in compensating for the voltage drop in the secondary winding. From the possibility to predict the winding volt- age drop using the magnetizing current and the transformer model, this paper presents a new observer method that can work accurately and smoothly in both CCM and DCM. The methodology can be combined with any controller to provide either output voltage regulation or output current regulation. The proposed sensing technique is veried by simulation

Primary-side sensing for a yback converter in both continuous and discontinuous conduction mode

Primary-side sensing is an observer-based approach to estimate the out- put voltage of yback converters from a primary winding (or an auxiliary winding). Various observer-laws have been recently developed for yback converters operating in discontinuous conduction mode (DCM). The extension to continuous conduction mode (CCM), however, has not been considered due to the diculties in compensating for the voltage drop in the secondary winding. From the possibility to predict the winding volt- age drop using the magnetizing current and the transformer model, this paper presents a new observer method that can work accurately and smoothly in both CCM and DCM. The methodology can be combined with any controller to provide either output voltage regulation or output current regulation. The proposed sensing technique is veried by simulation

Primary-side sensing for a yback converter in both continuous and discontinuous conduction mode

Primary-side sensing is an observer-based approach to estimate the out- put voltage of yback converters from a primary winding (or an auxiliary winding). Various observer-laws have been recently developed for yback converters operating in discontinuous conduction mode (DCM). The extension to continuous conduction mode (CCM), however, has not been considered due to the diculties in compensating for the voltage drop in the secondary winding. From the possibility to predict the winding volt- age drop using the magnetizing current and the transformer model, this paper presents a new observer method that can work accurately and smoothly in both CCM and DCM. The methodology can be combined with any controller to provide either output voltage regulation or output current regulation. The proposed sensing technique is veried by simulation

Projected Evolution of Drought Characteristics in Vietnam based on CORDEX-SEA Downscaled CMIP5 Data

In this study, the projected drought characteristics over Vietnam for the future periods of the middle (2046–2065) and end of the 21st century (2080–2099) were investigated under the Representative Concentration Pathway (RCP) scenarios RCP4.5 and RCP8.5. The drought characteristics (duration, severity, intensity, inter-arrival time, and geographic extent) were estimated based on the Palmer Drought Severity Index (PDSI). The PDSI was calculated using temperature and precipitation data from six regional climate downscaling experiments and their ensemble conducted by the Coordinated Regional Climate Downscaling Experiment-Southeast Asia (CORDEX-SEA) project. Projected changes of drought characteristics in the future periods were determined with respect to those in the baseline period 1986–2005. Results show biases in the regional climate model (RCM) outputs, namely an underestimation of temperature and an overestimation of precipitation, which also affect the representation of drought characteristics by overestimating the PDSI. In terms of projections, substantial increases of drought duration, severity and intensity, and decreases in the inter-arrival time are found over the Red River Delta, northern parts of the North Central sub-region, parts of the Central Highlands and over southern Vietnam. The droughts are projected to be more widespread under scenario RCP8.5 than RCP4.5, especially in southern Vietnam. With the increasing likelihood of droughts in Vietnam as a result of climate change, sustainable water resources management should be taken into account for agriculture, natural ecosystems and social development