Power Conversion Device Control Using Phase-Specific Carrier Patterns
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Solution Overview
Problem
Existing power conversion devices generate high levels of electrical noise due to switching frequencies, which can harm other electronic devices and cause electromagnetic noise, especially in multi-phase inverters with multiple half-bridge circuits, where noise diffusion is ineffective and peak values remain high.
Innovation Solution
A power conversion device control method and device that use PWM signals and carrier change patterns defined by average switching frequency, spectral diffusion index, and repetition frequency to sequentially switch switching frequencies for each phase, ensuring that at least one phase's carrier change pattern differs from others, thereby dispersing electrical noise and reducing peak values.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-generated harmful factors
If the switching frequency is varied from one half-bridge circuit to another, then the electrical noise is diffused more, but the peak value of electrical noise generated by each half-bridge circuit remains high
Solution Approach 1:
The patent applies local quality by assigning different carrier change patterns to different phases. Specifically, the U-phase uses a different carrier change pattern (different spectral diffusion index or different switching frequency sequence) compared to the V-phase and W-phase. This localized differentiation ensures that each phase contributes to noise diffusion while preventing peak superimposition, thereby reducing both the diffusion quality and peak noise levels simultaneously.
Solution Approach 2:
The patent utilizes parameter changes by varying the spectral diffusion index β and the switching frequency sequence for each phase. The carrier change patterns are defined by parameters including the spectral diffusion index β which controls the degree of frequency spreading, and the switching frequency sequence which determines the order of frequency transitions. By adjusting these parameters differently for each phase, the patent achieves effective noise diffusion while preventing constructive interference that would create high peak values.
2Device complexity
If the same switching frequency is set for all phases and switched sequentially, then the control is simplified, but the electrical noise increases in proportion to the number of half-bridge circuits
Solution Approach 1:
The patent resolves this contradiction by introducing local quality through phase-specific carrier change patterns. While maintaining the overall sequential switching framework, each phase is assigned a unique pattern characterized by different spectral diffusion indices or switching frequency sequences. This approach preserves the relative simplicity of centralized control while effectively reducing electrical noise through differentiated phase patterns, preventing the noise accumulation that would occur with identical patterns across all phases.
Solution Approach 2:
The patent applies dynamics by implementing time-varying switching frequencies that change sequentially within each phase according to defined carrier change patterns. The switching frequency is not static but dynamically transitions through a sequence of frequencies (f1, f2, f3, ...) over time, with each phase having its own dynamic pattern. This dynamic approach allows the system to maintain simplified control architecture while achieving noise reduction through temporal frequency variation and phase differentiation.
3Object-generated harmful factors
If noise countermeasure parts such as snubber circuits or noise filters are arranged on the power conversion device, then the electrical noise is controlled, but the cost and device size increase
Solution Approach 1:
The patent extracts the noise control function from physical hardware components (snubber circuits, noise filters) and implements it through software-based carrier change pattern generation. By removing the need for additional noise countermeasure parts and instead using controlled variations in switching frequencies and carrier patterns, the patent achieves effective electrical noise control while significantly reducing device size and cost. The noise control functionality is extracted from the hardware domain and implemented in the control algorithm domain.
Solution Approach 2:
The patent replaces the mechanical/electrical noise filtering system with a control-theoretic approach. Instead of using physical filters and snubber circuits to passively attenuate noise, the patent actively controls the switching behavior through dynamically varied carrier patterns and spectral diffusion. This substitution of mechanical filtering with intelligent control algorithms achieves superior noise control performance while eliminating the need for bulky and expensive passive components.
Data Source
AI summary
Provided are a power conversion device control device and a power conversion device control method, which are capable of reducing harm to other electronic devices and electromagnetic noise due to a switching frequency compared to the related art. Carrier change patterns of the respective phases, which are defined by parameters of an average switching frequency, a spectral diffusion index, and a repetition frequency, are generated so that at least the carrier change pattern of one phase differs from the carrier change patterns of the other phases. Semiconductor switching elements are controlled as instructed by duty command values while the switching frequency is switched for each phase separately, from one frequency to another sequentially based on carriers output in patterns that follow the generated carrier change patterns.