Three-Level AC Generating Circuit for Solar and Wind Power
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Solution Overview
Problem
Traditional three-level AC generating circuits for solar and wind power systems face inefficiencies and high switch losses due to wide input voltage variations, especially when using MOSFETs as switch components, which are exacerbated by the need for high voltage handling and reverse recovery issues in traditional half-bridge structures.
Innovation Solution
A three-level AC generating circuit is designed with a MOSFET-based inverting circuit, dividing the circuit into positive and negative halves as boost-buck circuits to manage voltage variations, allowing for high-frequency switching of only three switch components, reducing conduction and switch losses, and eliminating the need for large capacitors for energy storage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If MOSFET is used as switch component in traditional half-bridge structure, then conduction property and switch property are improved, but reverse recovery loss increases due to parasitic diode
Solution Approach 1:
The patent extracts and removes the parasitic diode from the circuit by using a body-diode-less MOSFET structure. This eliminates the reverse recovery phenomenon entirely, allowing the MOSFET to operate without the energy loss associated with diode reverse recovery while maintaining its excellent switching characteristics.
Solution Approach 2:
The patent employs a simplified switch structure that eliminates complex anti-parallel diode components. By using a MOSFET without requiring an external body diode, the design reduces component count and complexity while achieving comparable or superior performance to traditional half-bridge structures with dedicated diodes.
2Stress or pressure
If three-level inverting circuit is used for high voltage applications, then voltage endurance capability is improved, but switch component voltage stress increases reducing reliability
Solution Approach 1:
The patent segments the high voltage handling into multiple stages: the three-level inverting circuit handles the high voltage conversion while the body-diode-less MOSFETs in the boosting circuit handle only lower voltage portions. This segmentation distributes voltage stress across different components, allowing the main MOSFETs to operate within their reliable voltage ratings while still achieving high voltage output capability.
Solution Approach 2:
The patent introduces intermediate voltage levels through the three-level inverting circuit topology, which creates midpoint voltage references that reduce the voltage differential any single switch must withstand. This intermediary voltage structure allows high voltage operation without subjecting individual MOSFETs to excessive voltage stress.
3Adaptability or versatility
If two-stage circuit with pre-converter and post-inverter is used, then input voltage variation range is expanded, but efficiency decreases and capacitor interference increases
Solution Approach 1:
The patent merges the pre-converter and post-inverter functions into a single integrated three-level inverting circuit with a boosting circuit. This unified structure eliminates the need for separate conversion stages and intermediate capacitors, reducing energy losses at each conversion interface while maintaining the ability to handle wide input voltage variations through coordinated switching of the boosting and inverting stages.
Data Source
AI summary
The present invention provides a three-level ac generating circuit and the control method thereof. The three-level ac generating circuit includes a three-level boosting circuit connected to an input source and including a positive boosting portion and a negative boosting portion; and a three-level inverting circuit connected to the three-level boosting circuit and including a positive inverting portion and a negative inverting portion, wherein while the input source is a relative low voltage, the relatively low voltage is boosted via the three-level boosting circuit, inverted and output via the three-level inverting circuit; while the input source is a relatively high voltage, the relatively high voltage is inverted and output via the three-level inverting circuit andwherein the output of the three-level ac generating circuit is power grid.