Multiple-Frequency Inverter for Portable Generator Weight Reduction
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Solution Overview
Problem
Internal combustion engine driven generators have large device parameters and high internal resistance due to common inversion technologies, limiting their non-linear load capability and resulting in a larger, heavier apparatus with poor sinusoidal voltage output under harmonic currents.
Innovation Solution
A multiple-frequency inversion method that adjusts the proportionality coefficient of sine waves with a 180-degree phase difference to generate PWM waves with frequency 2f, reducing the switching frequency and device parameters of the filter unit, and controls the throttle of the internal combustion engine to achieve target revolving speeds.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If common inversion technology is used, then the generator can operate, but the device parameters in the filter unit become large and the output internal resistance becomes high
Solution Approach 1:
The patent changes the inversion frequency parameter from conventional single frequency to multiple frequencies (specifically 2f frequency). By using a triangle wave carrier with frequency f and modulating with sine waves, the inverter outputs a modulated wave with frequency 2f. This frequency parameter change allows the filter unit to use smaller device parameters (inductance and capacitance values) while maintaining effective filtering, thus resolving the contradiction between reliable operation and reduced device complexity.
2Reliability
If common inversion technology is used, then the generator can operate, but the output internal resistance becomes high and non-linear load capability becomes low
Solution Approach 1:
The patent employs multiple-frequency inversion with a 2f modulated output frequency. This frequency parameter change fundamentally alters the impedance characteristics of the filter unit, resulting in lower output internal resistance. The reduced internal resistance enables the generator to maintain stable voltage under non-linear loads with harmonic currents, thereby improving adaptability and versatility without compromising reliable operation.
3Manufacturing precision
If high switching frequency is used in the inverter unit, then the output waveform quality improves, but the filter unit device parameters become large and the apparatus becomes heavier
Solution Approach 1:
The patent uses a multiple-frequency inversion scheme where the inverter unit operates with a triangle wave carrier of frequency f that generates a modulated output at frequency 2f. This specific frequency parameter configuration achieves effective waveform quality improvement while allowing the use of smaller filter components. The smaller filter components directly reduce the overall apparatus weight, resolving the contradiction between waveform quality and apparatus weight.
4Weight of stationary object
If the filter unit device parameters are reduced, then the apparatus size and weight decrease, but the output internal resistance becomes low improving non-linear load capability
Solution Approach 1:
The patent implements multiple-frequency inversion with 2f modulated frequency, which fundamentally changes the impedance characteristics of the reduced-size filter unit. This frequency parameter transformation ensures that even with smaller device parameters (lower weight), the output internal resistance is reduced to an optimal level that enhances non-linear load capability. The contradiction is resolved because the frequency change creates a new operating regime where small filters perform optimally.
Data Source
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AI summary
The present invention provides a multiple-frequency inversion method and a control apparatus for an internal combustion engine driven generator. An inverter unit employs a multiple-frequency inversion technology, controlling the inverter unit through a low switching frequency f to obtain a 2f modulated frequency, thus resolving the problem that a low frequency switching component generates a high frequency modulated waveform. Four switching tubes in the inverter unit have the same working frequency, alleviating the controller load. In addition, a high modulated frequency reduces the device parameters of the filter unit, resulting in a smaller-sized and lighter apparatus, thus giving the generator portability. Reduction of the device parameters of the filter unit means reduction of the output internal resistance of the generator, therefore increasing the non-linear load capability of the generator.