Distributed PV Harvesting with MPPT Converters
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Solution Overview
Problem
Conventional photovoltaic panel systems face inefficiencies due to serial connection of mismatched solar panels, which leads to non-optimal power draw and increased energy losses, especially under varying environmental conditions, and lack effective monitoring and verification methods for correct operation.
Innovation Solution
A distributed power harvesting system with multiple photovoltaic sub-strings connected in parallel, each equipped with a DC power converter that includes a maximum power point tracking (MPPT) loop and a bypass diode, allowing for independent optimization of power output from each panel and reducing energy losses through the conversion process.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Stress or pressure
If solar panels are connected in series to achieve required operating voltage, then voltage requirement is met, but current capability is insufficient and multiple strings must be connected in parallel
Solution Approach 1:
The system segments the solar panel array into multiple independent parallel-connected strings, each with its own DC power converter. This allows each string to operate independently at its optimal current level while contributing to the total system voltage, resolving the contradiction between achieving required voltage through series connection and maintaining sufficient current capability.
2Power
If multiple solar panels are connected in parallel to provide required current, then current requirement is met, but voltage level becomes insufficient for load operation
Solution Approach 1:
Each DC power converter independently adjusts the operating parameters (voltage and current) of its associated solar panel string to maximize power extraction. The converters transform the low-voltage high-current output from parallel-connected panels into the appropriate voltage level for load operation, resolving the voltage insufficiency while maintaining high current capability.
3Adaptability or versatility
If solar panels with different output characteristics are connected in series, then system can handle mismatched panels, but power draw becomes non-optimal due to current matching requirement
Solution Approach 1:
The system divides the solar array into separate parallel-connected strings, each with its own DC power converter. This segmentation allows each converter to independently optimize the power extraction from its associated panels without being constrained by current matching requirements of series connections, thereby maintaining high power draw efficiency while accommodating mismatched panels.
Solution Approach 2:
Each DC power converter dynamically adjusts the operating point of its associated solar panel string to maximize power extraction. This dynamic optimization allows the system to adapt to varying panel characteristics and environmental conditions, ensuring optimal power draw efficiency even when panels are mismatched.
4Reliability
If a single bypass diode is connected across the parallel-connected DC power source, then fault tolerance is improved, but individual string monitoring capability is reduced
Solution Approach 1:
The system provides electrical segmentation through parallel-connected strings with independent DC power converters, allowing faults to be isolated to individual strings without affecting the entire system. This segmentation inherently improves fault tolerance while maintaining the ability to detect and measure string-level parameters through the converter control 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 system achieves high conversion efficiency, allows for easy testing and verification, and enhances fault tolerance by enabling the use of mismatched panels and improving maintenance, thereby optimizing power harvesting and reducing installation and maintenance costs.
Implementation Method 1
A bypass diode may be connected in shunt across the input terminals of the converter. The bypass diode functions by passing current during a failure of any of the sub-strings and/or a partial shading of the sub-strings.
Implementation Method 2
A photovoltaic panel with multiple photovoltaic sub-strings including serially-connected photovoltaic cells
Data Source
AI summary
A photovoltaic panel with multiple photovoltaic sub-strings including serially-connected photovoltaic cells and having direct current (DC) outputs adapted for interconnection in parallel into a parallel-connected DC power source. A direct current (DC) power converter including input terminals and output terminals is adapted for coupling to the parallel-connected DC power source and for converting an input power received at the input terminals to an output power at the output terminals. The direct current (DC) power converter optionally has a control loop configured to set the input power received at the input terminals according to a previously determined criterion. The control loop may be adapted to receive a feedback signal from the input terminals for maximizing the input power. A bypass diode is typically connected in shunt across the input terminals of the converter. The bypass diode functions by passing current during a failure of any of the sub-strings and/or a partial shading of the sub-strings. The bypass diode may be a single bypass diode connected across the parallel-connected DC power source. The DC power converter may convert the input power at high current to the output power at a lower current. The output terminals may be connectible with wire cables to a load, and the DC power converter is configured to reduce energy loss through the wire cables to the load.