Switched Capacitor DC-DC Converter for MPPT Without Electrolytic Capacitors
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Solution Overview
Problem
The widespread adoption of solar power is hindered by high installed costs and total cost of ownership, primarily due to expensive power converters and limited efficiency, as well as the short lifetime of electrolytic capacitors which affect maximum power point tracking (MPPT) algorithms in photovoltaic systems.
Innovation Solution
Implementing a multilevel output DC-DC switched capacitor power converter without magnetic components, coupled with a central inverter that provides a constant current source, allowing for per-panel MPPT control and decoupling of local and global MPPT control, thereby reducing costs and extending converter lifespan.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a large electrolytic capacitor is added to filter out 120 Hz power ripple, then the tracking ability of the MPPT algorithm is improved, but the lifetime of the power converter is reduced due to capacitor degradation
Solution Approach 1:
The patent extracts and removes the electrolytic capacitor from the system by implementing a ripple port inverter that directs the 120 Hz ripple power away from the PV unit through a transformer-coupled path, eliminating the need for large electrolytic capacitors while preserving MPPT tracking ability
Solution Approach 2:
The patent introduces a transformer-coupled ripple port as an intermediary mechanism that mediates between the PV unit and the 120 Hz ripple power, redirecting the ripple energy through a separate path that does not require electrolytic capacitors for filtering
2Power
If conventional power converters with magnetic components are used, then power conversion is achieved, but system cost and complexity increase
Solution Approach 1:
The patent substitutes magnetic field-based power conversion (inductors/transformers) with electric field-based switched capacitor circuits, eliminating magnetic components while maintaining power conversion capability and reducing system complexity
Solution Approach 2:
The patent changes the fundamental operating parameters of the power converter by using switched capacitor topology with discrete conversion ratios instead of continuous magnetic-based conversion, achieving power conversion through capacitive switching networks
3Measurement precision
If per-panel MPPT control is implemented, then tracking efficiency is improved, but converter cost increases
Solution Approach 1:
The patent segments the power conversion function into modular switched capacitor circuits with discrete conversion ratios, enabling per-panel MPPT control through simple ratio selection rather than complex continuous control, thereby reducing converter cost while maintaining high tracking efficiency
Data Source
AI summary
Switched capacitor multilevel output DC-DC converters can be used as panel integrated modules in a solar maximum power point tracking system. The system can also include a central input current-controlled ripple port inverter. The system can implement per panel MPPT without inter-panel communication, electrolytic capacitors or per panel magnetics. A Marx converter implementation of the switched capacitor module is studied. Average total efficiencies (tracking×conversion) greater than 93% can be achieved for a simulated 510 W, 3 panel, DC-DC system.