Abstract
In this paper design and implementation of a wide input range Cascaded Buck and Boost (CBB) converter is presented with a robust power controller. Four new control strategies are proposed and tested for this converter based on input voltage and duty cycle of the control signals. Robust feature of the proposed control system ensures constant output DC current required to charge the Lead-Acid batteries in bulk charge mode. The robust feedback controller of the power converter is developed using a microcontroller which is acting as smart controller of the CBB converter. DC-DC converters which are used for battery charging applications with variable power sources should be able to both step-up and step-down the input voltage and provide high efficiency in the whole range of operation. The CBB converter with power switches and diodes is used to achieve above objective. CBB converter is constructed by cascading a Buck and a Boost Converter and eliminating the output capacitor of the buck converter.
Highlights
Duty cycle of the control signal is used as the control parameter when it is required to transit from boost mode to buckboost mode or from buck mode to buck-boost mode
The CBB converter was tested with control strategy 1 which is based on the input voltage
To overcome the deficiencies in control strategy 3, the CBB converter was tested with a control strategy which is completely based on the duty cycle of the MOSFETs control signals (Control strategy 4)
Summary
Control strategy of the controller is for maintaining a constant output current from the CBB converter as the converter load and input voltage changes. Control algorithm of the converter is based on the duty cycle of the control signal, input voltage and output current. 2.1 Control strategy 1 - Input voltage based control strategy with zero initial duty cycle In this algorithm, mode of operation of the CBB converter is decided using only the input voltage. The gate control signal of the power switches are initialized with zero duty cycle. 2.2 Control strategy 2 - Input voltage based control strategy with non-zero initial duty cycle In this algorithm, mode of operation of the CBB converter is decided using input voltage. The gate control signal of the power switches are initialized with non-zero duty cycle. The duty cycle of the power switch is calculated to give minimum dips in the output current as the converter changes its mode of operation
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