MOSFET Bypass Switch for Solar Cell String Protection
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Solution Overview
Problem
Large solar energy generating systems face issues with power losses and heat damage due to high currents passing through bypass diodes when solar cells malfunction or are shaded, as existing bypass diodes are not designed to handle these high currents efficiently.
Innovation Solution
The implementation of a switch, such as a metal-oxide semiconductor field-effect transistor (MOSFET), connected in parallel with the bypass diode to reroute a majority of the bypass current, reducing the load on the diode and minimizing power losses and heat generation, using a capacitor and latch circuit to control the switch's operation based on voltage thresholds.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If bypass diodes are used to allow current to bypass malfunctioning or shaded solar cells, then current can continue to flow through the string, but large currents cause unwanted power losses and heat generation that can damage the bypass diodes
Solution Approach 1:
The patent introduces an intermediary device (switching element controlled by sensor and control circuit) between the solar cell string and bypass diode. The sensor detects malfunctioning cells and triggers the control circuit to activate the switching element, which then redirects current flow to bypass the problematic cells without overloading the bypass diode with excessive current
Solution Approach 2:
The patent implements a feedback mechanism where a sensor continuously monitors the electrical characteristics of solar cells to detect malfunctioning or shaded cells. When abnormal conditions are detected, the sensor signals the control circuit to activate the bypass mechanism. This closed-loop feedback system ensures the bypass is activated only when necessary, preventing unnecessary power losses while maintaining system reliability
2Reliability
If bypass diodes are used to protect against malfunctioning solar cells, then system operation is maintained, but the bypass diodes are not designed to handle high currents efficiently leading to heat-related damage
Solution Approach 1:
The switching element acts as a mediator that controls the flow of current to the bypass diode. Instead of allowing all high currents to pass through the bypass diode, the switching element regulated by the control circuit limits and manages the current distribution, preventing excessive heat generation in the bypass diode while maintaining system operation
Solution Approach 2:
The patent employs preliminary detection and control actions by using sensors to identify malfunctioning cells before they cause excessive current flow. The control circuit activates the bypass switching element in advance to prevent high currents from reaching the bypass diode, thereby preventing heat generation before it occurs rather than reacting after damage has started
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 solution allows for efficient bypassing of current around malfunctioning or shaded solar cells, significantly reducing power losses and preventing heat-related damage to the bypass diodes, while maintaining system performance.
Implementation Method 1
A capacitor can be connected to a control of the switch (e.g., the gate of a metal-oxide semiconductor field-effect transistor) through a latch circuit. When the latch is closed or off, the capacitor cannot discharge and close, or turn on, the switch.
Implementation Method 2
a switch (e.g., a metal-oxide semiconductor field-effect transistor) connected in parallel with the bypass diode. By turning the switch on, a majority of the bypass current can be routed through the switch
Data Source
AI summary
Systems and methods are herein disclosed for efficiently allowing current to bypass a group of solar cells having one or more malfunctioning or shaded solar cells without overwhelming a bypass diode. This can be done using a switch (e.g., a MOSFET) connected in parallel with the bypass diode. By turning the switch on and off, a majority of the bypass current can be routed through the switch, which is configured to handle larger currents than the bypass diode is designed for, leaving only a minority of the current to pass through the bypass diode.