Capacitive DC/DC Converter for Variable Voltage Efficiency
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Solution Overview
Problem
Current DC/DC power converters for renewable energy systems face inefficiencies and high losses due to variable input voltages, requiring large inductors and high-voltage switches, which affect harvesting and efficiency in both single and double conversion methods.
Innovation Solution
A DC/DC power converter topology using series-connected capacitors and resonant converters to convert variable input DC voltage into a variable output DC voltage with a smaller voltage range, allowing for improved operating conditions and efficiency in subsequent AC conversion, achieved through a capacitive voltage divider and resonant converter configuration that reduces switching and conduction losses.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a conventional DC/AC power converter with single conversion is used, then the device complexity is reduced, but the harvesting efficiency deteriorates due to inability to operate photovoltaic panel in optimum way
Solution Approach 1:
The patent divides the single conversion process into two separate conversion stages: a DC/DC conversion stage followed by a DC/AC conversion stage. This segmentation allows independent optimization of each stage, enabling the photovoltaic panel to operate at its maximum power point while the final output matches grid requirements, thereby resolving the contradiction between simplified structure and harvesting efficiency.
2Productivity
If a boost DC/DC converter is used in double conversion, then the photovoltaic panel can be operated in optimum way, but large input inductors are required and high switching losses occur
Solution Approach 1:
The patent replaces the conventional inductor-based DC/DC converter with a capacitor-based DC/DC converter. This substitution eliminates the large input inductor and reduces switching losses by using capacitive energy storage and transfer mechanisms instead of inductive ones, thereby resolving the contradiction between harvesting efficiency and energy losses.
3Power
If a conventional DC/DC power converter with inductor is used, then voltage conversion is achieved, but high conduction losses are caused
Solution Approach 1:
The patent substitutes inductive components with capacitive components in the DC/DC conversion stage. This replacement reduces conduction losses by utilizing the lower ESR (Equivalent Series Resistance) characteristics of capacitors compared to inductors, while maintaining the required voltage conversion capability through capacitive voltage transformation.
4Power
If high-voltage switches are used in conventional DC/DC converter, then the required voltage range is achieved, but the cost and losses increase
Solution Approach 1:
The patent segments the voltage conversion function across multiple capacitors connected in series, where each capacitor handles a portion of the total voltage. This voltage segmentation allows the use of lower-voltage-rated switches and capacitors, reducing both cost and conduction losses while achieving the required overall voltage range.
Solution Approach 2:
The patent changes the voltage distribution parameters by using multiple capacitors in series configuration, thereby distributing the high voltage stress across multiple lower-voltage components. This parameter change enables the use of lower-voltage switches and reduces the cost and losses associated with high-voltage components.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This configuration enhances the overall efficiency of power conversion to approximately 99% or more, reduces the need for high-voltage switches, and lowers costs by allowing the use of lower-rated semiconductor devices, while minimizing losses and improving energy harvesting from variable voltage sources.
Implementation Method 1
resonant converter configuration that reduces switching and conduction losses
Data Source
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AI summary
A DC/DC power converter 100 comprises three or more capacitors 120a-d connected in series between an output terminal 112 and a ground terminal 113, the three or more capacitors 120a-d being connected in series by means of two or more capacitor connection points 121a-c, and an input voltage switching unit 130a-130d configured to connect an input terminal 111 to one of a group of switching connection points 121a-c, 112, the group of switching connection points comprising the two or more capacitor connection points and the output terminal 112. With such a DC/DC power converter it is possible, for example, to convert a variable DC voltage at the input into a variable DC voltage at the output, wherein the voltage range of the output voltage is smaller than the voltage range of the input voltage.