Photovoltaic Generator Junction Box with DC-DC Converters
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Solution Overview
Problem
Large photovoltaic systems with multiple module strings connected in parallel face issues such as high cabling costs, electrical safety risks, yield losses due to string fuses and diodes, complex maintenance, limited input voltage range, and inflexible design, leading to reduced efficiency and increased costs.
Innovation Solution
Arranging DC-DC converters within a single generator connection box with a control device for string current monitoring and communication to a central inverter, allowing for individual MPP regulation of each module string, eliminating the need for string fuses and diodes, and using galvanically isolating DC-DC converters to simplify cabling and enhance system flexibility.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If multiple module strings are connected in parallel to a central inverter, then the system can handle larger power capacity, but cabling costs and electrical safety risks increase
Solution Approach 1:
The system divides the photovoltaic installation into multiple independent module string units, each with its own DC-DC converter. This segmentation allows each unit to be independently managed and connected to the central inverter, reducing the complexity of parallel connections while maintaining high power capacity.
Solution Approach 2:
DC-DC converters are introduced as intermediary devices between module strings and the central inverter. These converters standardize voltage levels and provide galvanic isolation, simplifying the cabling architecture and reducing electrical safety risks associated with direct parallel connections.
2Reliability
If string fuses and diodes are installed in the generator connection box, then electrical safety is improved, but yield losses occur and costs increase
Solution Approach 1:
The invention extracts the safety and protection functions from traditional string fuses and diodes, integrating them into the DC-DC converters. This eliminates the need for separate protective components that cause yield losses, while maintaining electrical safety through the converter's inherent protection mechanisms.
Solution Approach 2:
The DC-DC converters provide self-protection functions including overcurrent protection, overvoltage protection, and galvanic isolation. Each converter monitors and protects its own module string without requiring external protective components, eliminating yield losses associated with traditional protection devices.
3Device complexity
If all module strings are connected to a single central inverter, then system simplicity is maintained, but input voltage range limitations and design inflexibility occur
Solution Approach 1:
Each DC-DC converter is configured with specific voltage conversion ratios tailored to its connected module string's characteristics. This local optimization allows each unit to operate at its optimal voltage range while feeding the central inverter, expanding the overall system's adaptability to different module configurations and technologies.
Solution Approach 2:
The DC-DC converters provide dynamic voltage adjustment capabilities, allowing the system to adapt to varying module string voltages based on operating conditions. This dynamic adjustment expands the acceptable input voltage range and enables flexible design with different module technologies and string configurations.
4Productivity
If DC-DC converters are distributed to individual module strings, then voltage management and MPP regulation are improved, but device complexity and cabling costs increase
Solution Approach 1:
Multiple DC-DC converters are merged into a single generator connection box, consolidating their control and monitoring functions. This merging approach maintains the voltage management benefits of individual converters while reducing overall system complexity through centralized management and shared communication infrastructure.
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 reduces cabling costs, enhances electrical safety, improves yield by optimizing voltage management, and simplifies maintenance, while allowing for flexible module string lengths and technologies, resulting in increased efficiency and reduced operational losses.
Implementation Method 1
DC voltage converters, which are also referred to as DC/DC converters
Implementation Method 2
converted into an AC voltage by means of an inverter
Data Source
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AI summary
The photovoltaic installation comprises a generator junction box (5) and the photovoltaic modules (1) that are interconnected at multiple module strands (2). The module strands are connected with a direct current converter (3) in the generator junction box which is arranged separate from an inverter (4).