PV Power Conditioning Unit Shading Management
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Solution Overview
Problem
Photovoltaic (PV) panels under partial shading lose efficiency and can suffer damage due to hotspots, as existing systems rely on bypass diodes that incur significant voltage loss and can fail, and existing power conditioning units do not effectively manage power harvesting under shaded conditions.
Innovation Solution
A photovoltaic power conditioning unit with a shared DC link, input power converters for each sub-string, energy storage capacitors, and a common output conversion stage, along with sensors and bypass controllers to detect shading and manage power flow, reducing voltage loss and preventing hotspot formation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If bypass diodes are used to protect shaded cells, then cell protection is improved, but voltage loss and power dissipation increase significantly
Solution Approach 1:
The patent replaces passive bypass diodes with active power electronic converters (DC-DC converters) that use switching devices and control circuits to bypass shaded sub-strings. This substitution eliminates the significant forward voltage drop inherent in diode-based bypassing, reducing power losses while maintaining cell protection functionality through controlled switching operations.
Solution Approach 2:
The invention changes the operating parameters of the bypass mechanism by using controllable switching devices instead of fixed diode characteristics. The power electronic converters dynamically adjust their operation based on shading detection, optimizing the bypass behavior to minimize voltage loss while providing necessary protection against hotspot formation in shaded cells.
2Power
If series-connected solar cells are used to form sub-strings, then voltage output is improved, but susceptibility to shading damage increases
Solution Approach 1:
The patent segments the series-connected solar cell string into multiple independently controllable sub-strings with tap connections. Each sub-string can be independently monitored and bypassed by dedicated power converters, allowing the system to maintain high voltage output from unshaded portions while isolating and protecting shaded segments, thus reducing overall susceptibility to shading damage.
Solution Approach 2:
The invention introduces power electronic converters as intermediary devices between the series-connected solar cell sub-strings and the load. These converters act as mediators that can detect shading conditions and actively manage power flow, protecting the series-connected cells from shading-induced damage while preserving the voltage output benefits of series configuration.
3Productivity
If active bypassing is implemented, then power harvesting efficiency is improved under shading, but device complexity increases
Solution Approach 1:
The patent designs the power electronic converters to perform multiple functions: they serve as both power harvesting optimizers and bypass controllers for shaded sub-strings. This multi-functionality reduces the need for separate dedicated bypass circuits, thereby managing device complexity while maintaining improved power harvesting efficiency under partial shading conditions.
Solution Approach 2:
The invention merges the bypass control functionality with the power conversion stages. The same power electronic converters that convert DC power from solar sub-strings are also used to implement active bypassing of shaded portions, consolidating multiple functions into unified circuitry and reducing overall system complexity compared to having separate bypass and conversion systems.
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 power harvesting from PV panels even under partial shading by actively bypassing shaded sub-strings, reducing voltage loss, and preventing damage, thus improving overall panel efficiency and longevity.
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
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.