Multi-Input Micro Inverter Resonance Circuit for Smaller Transformers
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Solution Overview
Problem
Conventional micro inverters with series-connected photovoltaic components have large transformer turn ratios, leading to increased transformer volume and associated issues such as loss, EMI, and reduced efficiency.
Innovation Solution
A micro inverter with multiple independent inputs, incorporating multiple isolated DC-DC converters and a DC-AC converter, where transformers form series resonance with capacitors in voltage-multiplying rectifiers to adjust impedance and reduce transformer turn ratios, thereby reducing volume and improving efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Volume of moving object
If a conventional isolated DC-DC converter with a single transformer is used, then the circuit is simple, but the transformer turn ratio is large resulting in large transformer volume
Solution Approach 1:
The single transformer is segmented into multiple independent transformers (first transformer and second transformer), each with smaller turn ratios. The primary windings are connected in parallel and secondary windings in series, dividing the total voltage transformation task across multiple smaller units, thereby reducing individual transformer volumes while maintaining the required overall transformation ratio.
Solution Approach 2:
Multiple transformers are combined through specific wiring configurations: primary windings connected in parallel and secondary windings in series. This merging approach allows the system to achieve the required high voltage transformation ratio through the series connection of secondary windings, while each individual transformer operates at a lower, more efficient turn ratio.
2Loss of energy
If a large transformer turn ratio is used, then voltage transformation is achieved, but power loss and EMI increase reducing efficiency
Solution Approach 1:
The voltage transformation function is segmented across multiple transformers with smaller turn ratios. By dividing the total transformation ratio into smaller stages (each transformer handling a portion of the total voltage step-up), the patent reduces copper losses, core losses, and EMI associated with large single-stage transformation, while achieving the same overall voltage transformation capability.
3Volume of moving object
If multiple isolated DC-DC converters are used with series resonance, then transformer turn ratio is reduced, but circuit complexity increases
Solution Approach 1:
The patent introduces series resonance circuits with adjustable capacitors that allow dynamic optimization of the transformer operation. The resonance frequency can be tuned to match the switching frequency, enabling soft switching and reducing the required transformer turn ratio. This dynamic adjustment capability allows the system to operate efficiently with smaller transformers despite the increased circuit structure.
4Productivity
If conventional DC-AC conversion is used, then the system operates reliably, but maximum power point tracking cannot be achieved at component level
Solution Approach 1:
The patent divides the power conversion system into multiple independent isolated DC-DC converter modules, each capable of independent maximum power point tracking (MPPT). This segmentation allows each module to operate autonomously and track its own optimal operating point, maximizing overall power extraction from photovoltaic components while maintaining system reliability through modular independence.
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 allows for adjustable voltage gain and reduced transformer volume, enhancing efficiency and stability while minimizing power consumption and device stress.
Implementation Method 1
A leakage inductor or an external inductor of the transformer forms series resonance along with a capacitor in the voltage-multiplying rectifier
Implementation Method 2
The isolated DC-DC converter includes an inverter H-bridge, a transformer, and a voltage-multiplying rectifier
Data Source
AI summary
A micro inverter having a plurality of independent inputs and a photovoltaic system are provided. The micro inverter includes multiple isolated DC-DC converters and a DC-AC converter. Each isolated DC-DC converter of the isolated DC-DC converters includes an inverter H-bridge, a transformer and a voltage-multiplying rectifier. An input terminal of the inverter H-bridges is configured to connect to a direct-current power supply. A secondary winding of the transformer is connected to an input terminal of the voltage-multiplying rectifier. An output terminal of the voltage-multiplying rectifier is connected to an input terminal of the DC-AC converter. A leakage inductor or an external inductor of the transformer forms series resonance along with a capacitor in the voltage-multiplying rectifier.