PV Module Junction Box Shutdown Unit for Rapid DC Interruption
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Solution Overview
Problem
Photovoltaic systems face challenges in quickly shutting down power output when DC power exceeds permissible ranges, leading to instability and potential damage, as existing solutions like string inverters require significant time to reduce voltage to safe levels.
Innovation Solution
Incorporating a shutdown unit within photovoltaic modules that includes a capacitor unit and a switching mechanism to consume stored DC power and interrupt output when voltage exceeds permissible limits, allowing for rapid power interruption and improved system stability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If string inverter shutdown method is used, then system protection is achieved, but shutdown time is too long and voltage reduction is slow
Solution Approach 1:
The patent segments the shutdown function by placing a dedicated shutdown unit with capacitor directly at the photovoltaic module level, separate from the central string inverter. This distributed segmentation enables localized rapid shutdown independent of the central inverter's slower voltage reduction process.
Solution Approach 2:
The capacitor in the shutdown unit is pre-charged during normal operation to store energy. When shutdown is required, this pre-stored energy is immediately discharged through the shutdown switch to rapidly reduce voltage, eliminating the need to wait for the inverter's gradual voltage reduction.
2Speed
If capacitor unit is added to store DC power, then rapid power interruption capability is improved, but device complexity increases
Solution Approach 1:
The shutdown unit including capacitor and switch is merged into the junction box of the photovoltaic module, combining multiple functions (power storage, shutdown control, and existing junction box connectivity) into a single integrated component rather than adding separate distributed elements.
Solution Approach 2:
The capacitor unit serves multiple functions: storing DC power during normal operation, enabling rapid shutdown when needed, and potentially providing backup power or voltage stabilization. This multi-functionality justifies the added complexity by delivering multiple benefits from a single added component.
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
Enables quick power output interruption when DC power is outside the permissible range, enhancing system stability by consuming stored capacitor power, which is faster than traditional string inverter shutdown methods, thus protecting the system and adhering to national voltage standards.
Implementation Method 1
a capacitor unit to store a direct current (DC) power from the solar cell module
Implementation Method 2
a shutdown unit disposed at a front end of the capacitor unit and to operate to consume the DC power stored in the capacitor unit
Data Source
AI summary
Discussed are a photovoltaic module and a photovoltaic system including the same. According to an embodiment, the photovoltaic module includes a solar cell module including a plurality of solar cells, and a junction box attached to a back surface of the solar cell module, wherein the junction box includes a capacitor unit to store a direct current (DC) power from the solar cell module, and a shutdown unit disposed at a front end of the capacitor unit and to operate to consume the DC power stored in the capacitor unit and temporarily interrupt power output of the solar cell module when the DC power from the solar cell module is outside of a permissible range. Thus, when DC power outside of the permissible range is supplied, the power output can be quickly interrupted while the DC power stored in the capacitor is consumed.