DC-DC Converter Overvoltage Protection via Permanent Current Path
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Solution Overview
Problem
Existing DC/DC converters in photovoltaic systems are designed for a limited input voltage range around the optimal operating point, making them vulnerable to overvoltage during no-load conditions, such as sunrise or temporary shading, which can lead to damage if not properly managed.
Innovation Solution
The method involves configuring the DC-DC converter's switching elements to form a permanent current path between the solar modules and the intermediate circuit during transitional phases, using a main contactor and additional switching elements to prevent no-load voltage buildup, allowing the system to safely operate beyond the converter's input voltage limits.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If the DC-DC converter is designed for a limited input voltage range around the optimal operating point, then the converter cost is reduced, but the converter becomes vulnerable to overvoltage damage during no-load conditions
Solution Approach 1:
The control system activates switching elements to form a permanent current path before the overvoltage condition can damage the converter. During transitional phases (sunrise, shading), the control unit preemptively switches on additional current paths that prevent no-load voltage buildup, protecting the converter before overvoltage occurs.
Solution Approach 2:
The control unit acts as an intermediary between the solar modules and the DC-DC converter. It monitors voltage conditions and activates auxiliary switching elements that create alternative current paths, mediating the voltage transfer to prevent overvoltage from reaching the converter while maintaining normal operation during optimal conditions.
2Reliability
If switching elements are activated to form a permanent current path during transitional phases, then overvoltage protection is achieved, but the system complexity increases
Solution Approach 1:
The existing switching elements of the DC-DC converter are made multi-functional. The same switching elements serve both the normal voltage conversion function and the protective current path function. By controlling the switching elements to form additional current paths during transitional phases, the system achieves overvoltage protection without adding separate protective components.
Solution Approach 2:
The DC-DC converter's own switching elements are utilized to protect the converter itself. The control unit leverages the existing switching infrastructure to create protective current paths, allowing the system to self-protect using its own components rather than requiring external protection circuits.
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 approach prevents damage to the DC-DC converter by maintaining a stable voltage during idle states and ensures seamless transition to optimal power consumption once the system is loaded, enhancing the operational reliability and efficiency of photovoltaic systems.
Implementation Method 1
Photovoltaic systems are used to convert solar radiation into electrical energy
Implementation Method 2
a DC voltage converter, which DC voltage makes available to a DC voltage intermediate circuit
Implementation Method 3
the intermediate circuit, which in a second stage converts the DC voltage from the intermediate circuit into an AC voltage
Data Source
Figure 1
AI summary
The invention relates to a method for operating a photovoltaic system comprising solar modules, at least one DC-DC converter and a DC-DC link, characterized in that, during a transition phase between the unloaded and loaded state of the solar modules, the switching elements of the DC-DC converter are brought into a switching state that forms a permanent current path between the output of the solar modules and the DC-DC link.