Single-Phase Cycloconverter Line-Cycle Energy Storage
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Solution Overview
Problem
Conventional power converters for distributed generators like PV modules use large input capacitors that are susceptible to heat degradation, limiting the size, temperature, and operational lifetime, and result in pulsating power transfer.
Innovation Solution
A single-phase cycloconverter with integrated line-cycle energy storage and filtering, which uses a line frequency energy storage device to maintain a predetermined phase difference with AC mains, allowing for constant power transfer and reducing the size of capacitors, while also providing electromagnetic compliance and surge filtering.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If large input capacitors are used in conventional power converters, then the converter can handle varying power rates from PV modules, but the capacitors are susceptible to heat degradation and limit the minimum physical size, maximum operating temperature, and overall operational lifetime
Solution Approach 1:
The patent combines the energy storage function and filtering function into a single integrated circuit architecture. The energy storage circuit includes capacitors connected to store energy during high-power intervals and release it during low-power intervals, while the filtering circuit simultaneously smooths the pulsating power transfer. This merging eliminates the need for separate large input capacitors, reducing overall size while maintaining reliability.
Solution Approach 2:
The integrated circuit performs multiple functions: energy storage, power smoothing, and filtering. The energy storage circuit and filtering circuit work together to handle varying power rates from PV modules while reducing capacitor size and heat degradation issues. This multi-functionality resolves the contradiction by achieving reliable operation with smaller components.
2Productivity
If large input capacitors are used to handle varying power rates, then power conversion is enabled, but pulsating power transfer occurs through the converter
Solution Approach 1:
The energy storage circuit and filtering circuit are merged into an integrated design where the energy storage circuit captures energy during high-power intervals and the filtering circuit smooths the output. This combination enables continuous power conversion while eliminating pulsating power transfer, as the filtered output provides stable power to the load throughout the AC cycle.
3Adaptability or versatility
If conventional power converter topology is used with large capacitors, then DC to AC conversion is achieved, but the physical size and heat degradation issues limit operational flexibility
Solution Approach 1:
By merging energy storage and filtering functions into a single integrated circuit, the patent reduces the number and size of capacitors required. This integration lowers the overall heat generation and thermal management requirements, thereby increasing the maximum operating temperature capability and operational flexibility of the converter system.
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 increases power generation capacity, reduces heating limitations, and improves serviceability by allowing for modular implementation, achieving constant power transfer and reduced ripple current.
Implementation Method 1
A single-phase cycloconverter with integrated line-cycle energy storage and filtering, which uses a line frequency energy storage device to maintain a predetermined phase difference with AC mains
Implementation Method 2
Micro-inverters are a form of power converters that are capable of converting DC power generated by the PV modules into AC power
Implementation Method 3
integrated line-cycle energy storage and filtering, which uses a line frequency energy storage device to maintain a predetermined phase difference with AC mains, allowing for constant power transfer and reducing the size of capacitors, while also providing electromagnetic compliance and surge filtering
Data Source
AI summary
A method and apparatus for line-cycle storage of a single-phase cycloconverter. The method includes receiving input power from an input port of the singe-phase cycloconverter and monitoring an AC output port of the single-phase cycloconverter. The method measures energy stored in a line-cycle energy storage circuit coupled to one line of the AC output port of the single-phase cycloconverter, and determines a phase difference between a monitored AC voltage of the AC output port and the measured voltage of the line-cycle energy storage circuit. The method controls switches in the single-phase cycloconverter to selectively store energy in the line-cycle energy storage circuit based on the phase difference.