Flying-Capacitor Boost Circuit for PV String Voltage Matching
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Solution Overview
Problem
Current DC-DC voltage conversion circuits in photovoltaic power generation systems require multiple photovoltaic components connected in series, leading to increased inconsistency and reduced reliability due to varying current capabilities, making it challenging to match the output voltage of photovoltaic strings with the high-voltage direct current bus without increasing the number of components.
Innovation Solution
A voltage conversion circuit incorporating an inductor, multiple switch modules, and flying capacitors that operate in inductor charging, flying capacitor charging, and boost discharging modes to achieve a higher boost ratio, reducing the number of photovoltaic components needed in series while maintaining voltage consistency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If dozens of photovoltaic components are connected in series to increase output voltage, then the voltage matching with DC bus is improved, but the reliability and consistency of the photovoltaic string deteriorates
Solution Approach 1:
The patent divides the voltage boosting function into multiple stages using N second switch modules and N third switch modules with flying capacitors. Each stage contributes to the overall voltage multiplication, achieving high boost ratio without requiring excessive series connection of photovoltaic components. This segmentation allows the system to reach the required DC bus voltage with fewer photovoltaic components in series, thereby improving reliability while maintaining voltage matching capability.
2Adaptability or versatility
If more photovoltaic components are connected in series to match DC bus voltage, then the voltage compatibility is improved, but the risk of component inconsistency and failure increases
Solution Approach 1:
The patent transitions from a single-dimensional series connection approach to a multi-dimensional voltage conversion architecture. By introducing multiple switch modules arranged in series-parallel configurations and utilizing flying capacitors for voltage multiplication, the system achieves voltage matching through a different dimensional approach. This allows fewer photovoltaic components to be connected in series while still achieving the required DC bus voltage compatibility, thereby reducing inconsistency risks.
3Power
If a conventional boost DC-DC circuit is used to increase voltage, then the voltage conversion is achieved, but the boost ratio is limited and requires many photovoltaic components in series
Solution Approach 1:
The patent implements a nested structure where N third switch modules are connected in series, with each module containing second switch modules and flying capacitors nested within. This nested configuration enables the circuit to achieve a multiplication effect on the boost ratio, where the overall voltage conversion ratio becomes the product of individual stage ratios. Consequently, the system achieves high voltage conversion with fewer photovoltaic components connected in series, reducing device complexity while maintaining effective voltage conversion capability.
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
The proposed solution enables a higher boost ratio, reducing the risk of inconsistency and improving the reliability of photovoltaic strings by allowing fewer components to be connected in series, thus enhancing the stability and efficiency of the power generation system.
Implementation Method 1
an inductor, a first switch module, N second switch modules connected in series, N third switch modules connected in series, and N−1 flying capacitors
Implementation Method 2
N−1 flying capacitors. N is an integer greater than or equal to 2. One terminal of an ith flying capacitor in the N−1 flying capacitors is connected to a connection point between an ith second switch module and an (i+1)th second switch module
Data Source
AI summary
A voltage conversion circuit includes: an inductor, a first switch module, N second switch modules connected in series, N third switch modules connected in series, and N−1 flying capacitors. One terminal of the first switch module is separately connected to one terminal of the N second switch modules connected in series and one terminal of the N third switch modules connected in series. The other terminal of the N third switch modules connected in series is connected to a positive electrode of a high-voltage power supply. The other terminal of the first switch module and the other terminal of the N second switch modules connected in series are connected to a negative electrode of the high-voltage power supply. A low-voltage power supply is connected to the two terminals of the first switch module through the inductor.