PV Panel Power Conditioning Unit with Shared DC Link
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Solution Overview
Problem
Photovoltaic (PV) panels under partial shading experience reduced power generation and risk of long-term degradation due to local hotspots, and existing solutions with bypass diodes suffer from significant forward conduction voltage loss and potential diode failures.
Innovation Solution
A photovoltaic power conditioning unit with a shared dc link and input power converters for each sub-string, featuring sensors and bypass controllers to detect shading, reduce power conversion, and provide active bypassing, along with MPPT control to optimize energy harvesting, eliminating the need for bypass diodes and reducing voltage loss.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If bypass diodes are used to protect shaded cells, then cell protection is improved, but forward conduction voltage loss increases
Solution Approach 1:
The patent replaces passive bypass diodes with an active power converter system that uses electronic switching devices (MOSFETs, IGBTs) and control circuits to achieve cell protection. This substitution eliminates the inherent forward voltage drop of diodes by using controllable switches that can operate with minimal conduction loss, thereby resolving the contradiction between protection reliability and energy loss.
Solution Approach 2:
The invention changes the operating parameters of the protection mechanism by using variable switching devices instead of fixed diode characteristics. The power converter dynamically adjusts its operation based on shading conditions, allowing it to provide protection while maintaining optimal electrical parameters that minimize energy loss, unlike the fixed forward voltage drop of bypass diodes.
2Reliability
If bypass diodes are used to protect shaded cells, then cell protection is improved, but device complexity increases
Solution Approach 1:
The patent integrates multiple functions into the power converter system: it performs both the primary power conversion function and the cell protection function through the same electronic switching devices and control circuitry. This multi-functionality eliminates the need for separate bypass diode components, reducing overall device complexity while maintaining protection capabilities.
Solution Approach 2:
The invention incorporates feedback control mechanisms that continuously monitor system conditions and adjust the operation of switching devices accordingly. This feedback-based control enables the system to detect shading conditions and activate protection only when necessary, reducing the complexity of always having passive protection paths while ensuring reliable cell protection through intelligent control.
3Productivity
If active bypassing is implemented, then energy harvesting efficiency is improved, but device complexity increases
Solution Approach 1:
The patent divides the PV array into multiple independently controllable segments or modules, each with its own power converter. This segmentation allows each converter to optimize energy harvesting from its respective segment while maintaining a manageable complexity level for each individual unit. The modular architecture enables scalable implementation without proportionally increasing overall system complexity.
Solution Approach 2:
The invention employs dynamic control of the power converter operating parameters to maximize energy harvesting under varying shading conditions. By dynamically adjusting switching frequencies, duty cycles, and operating points, the system adapts to changing conditions to maintain optimal efficiency without requiring overly complex static protection circuitry, thus balancing productivity improvement with acceptable device complexity.
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
The solution enables efficient operation under partial shading, reduces voltage loss, and enhances the reliability of PV panels by preventing hotspot formation, while maintaining high energy harvesting efficiency without the drawbacks of traditional bypass diodes.
Implementation Method 1
In a photovoltaic module (panel) the panel is made up of series-connected mono crystalline or polycrystalline solar cells
Implementation Method 2
an energy storage capacitor, coupled to said shared dc link, to store power from said PV panel for delivering to said ac power supply output
Data Source
Figure 1
Figure 2a
Figure 2b
AI summary
We describe a photovoltaic (PV) panel power conditioning circuits, in particular for a PV panel with multiple sub-strings of connected solar cells. The power conditioning unit comprises a set of input power converters, one connected to each sub-string, a shared dc link to provide a common dc bus for the set of input power converters, and a common output power conversion stage coupled to the shared dc link to convert power from the shared dc link to ac power for a mains power supply output from the power conditioning unit. Local conversion of the sub-strings facilitates control of the power available from the panel and optimum energy harvesting, as well as local maximum power point tracking (MPPT) adjustment.