Multi-Level Converter Structure for String-Level MPPT Control
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Solution Overview
Problem
Solar power generation systems with single converters face challenges in tracking the maximum power point for each solar cell string due to varying sunlight conditions, and they require additional devices for voltage detection and auxiliary power supply, which increases complexity and cost.
Innovation Solution
A power conversion device with multiple converters connected to each solar cell string, featuring a voltage detection unit using resistors and a control unit that generates synchronized control signals for each converter, enabling efficient maximum power point tracking and auxiliary power supply in a multi-level structure.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a single converter is used for the entire solar cell module, then the device complexity is reduced, but the maximum power point tracking control for individual cell strings becomes impossible when sunlight conditions differ
Solution Approach 1:
The patent divides the solar cell module into multiple cell strings, each with its own converter. This segmentation allows each converter to independently perform maximum power point tracking for its respective cell string, even when sunlight conditions differ across the module. The modular structure resolves the contradiction by enabling individualized control while maintaining manageable system complexity through standardized converter units.
Solution Approach 2:
The patent introduces a multi-level hierarchical control structure where converters are organized in levels (first level, second level, etc.). This dimensional organization allows for both individual cell string control and coordinated system-wide control. The multi-level architecture enables maximum power point tracking at the cell string level while maintaining overall system efficiency, resolving the contradiction between granular control and system simplicity.
2Adaptability or versatility
If multiple converters with multi-level structure are used for each cell string, then the maximum power point tracking for individual cell strings is enabled, but the device complexity increases
Solution Approach 1:
The patent merges multiple converters into a coordinated multi-level system where converters at different levels work together. The first-level converters handle individual cell string control, while second-level converters provide coordinated control across multiple cell strings. This merging approach enables comprehensive maximum power point tracking while reducing overall complexity by eliminating redundant control functions and sharing resources across the hierarchical structure.
Solution Approach 2:
The patent designs converters with multi-functional capabilities that can operate in different modes depending on their level in the hierarchy. Converters can function as first-level converters for individual cell string control or as second-level converters for coordinated system control. This universality reduces device complexity by using standardized multi-functional units rather than requiring specialized converters for each control function.
3Device complexity
If the same ground is used for solar cell module, dc/dc converter, controller, and auxiliary power, then the auxiliary power circuit configuration is simplified, but voltage detection becomes problematic in multi-level structure
Solution Approach 1:
The patent introduces isolated converters as intermediary devices between the auxiliary power circuit and the multi-level converter structure. These isolated converters provide galvanic isolation, allowing voltage detection in the multi-level structure without creating ground loops or reference potential conflicts. The intermediary isolators enable accurate voltage measurement while maintaining the simplified auxiliary power circuit configuration, resolving the contradiction between circuit simplicity and measurement accuracy.
4Difficulty of detecting and measuring
If isolated converters are used for auxiliary power supply in multi-level structure, then voltage detection and auxiliary power supply are simplified, but the number of components increases
Solution Approach 1:
The patent implements self-service functionality where the isolated converters used for auxiliary power supply also perform voltage detection functions. By integrating these functions into the existing isolated converter components, the patent avoids adding separate voltage detection devices, thereby reducing the overall component count. The isolated converters serve multiple purposes: providing galvanic isolation for auxiliary power and enabling accurate voltage detection in the multi-level structure, thus resolving the contradiction between measurement capability and component quantity.
Data Source
AI summary
A power conversion device according to one embodiment of the present invention comprises: converters that are connected to respective cell strings; a voltage detection unit for detecting an input voltage and/or an output voltage of each of the plurality of converters; and a control unit which generates a control signal for each of the plurality of converters by using the voltage detected by the voltage detection unit and applies same, wherein the plurality of converters have a multi-level structure.