Flying Capacitor Multilevel Converter Phase Shifting for Input Ripple
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Solution Overview
Problem
Existing interleaved power converters using phase-shifted pulse width modulation (PSPWM) in flying capacitor multi-level circuits fail to effectively interleave the peaks and valleys of inductor currents, leading to inadequate reduction of the total input current ripple.
Innovation Solution
An interleaved flying capacitor multi-level converter employing a phase-shifted pulse width modulation signal generation circuit that generates switch control signals with specific phase angle differences between upper and lower arm switches, ensuring that the peaks and valleys of input currents are interleaved across bridge arms to achieve optimal ripple suppression.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If phase-shifted PWM control with 180-degree phase difference is used in flying capacitor multi-level circuits, then the control structure is simplified, but the peaks and valleys of inductor currents are not effectively interleaved, resulting in inadequate ripple reduction
Solution Approach 1:
The patent changes the phase angle parameter from the conventional 180 degrees to a specific value θ1 that satisfies the formula θ1 = (180°/L) × (k + 0.5), where L is the number of levels and k is an integer. This parameter change enables effective interleaving of current peaks and valleys while maintaining a relatively simple control structure.
Solution Approach 2:
The patent introduces dynamic phase shifting between bridge arms, where each bridge arm has a different phase angle θi = θ1 + (i-1) × (180°/m). This dynamic phase distribution optimizes the interleaving effect of inductor currents across multiple bridge arms, effectively reducing total input current ripple.
2Ease of manufacture
If conventional PSPWM control is applied to interleaved bridge arms, then the control method is straightforward, but the ripple reduction effect is insufficient for high-power applications
Solution Approach 1:
The patent segments the control of each bridge arm with distinct phase angles, allowing independent optimization of current interleaving for each arm. This segmentation enables the system to achieve superior ripple reduction performance while maintaining straightforward PWM control implementation.
3Ease of operation
If 180-degree interleaved control is used in traditional power converters, then the control strategy is simple, but it fails to achieve optimal ripple suppression in multi-level flying capacitor circuits
Solution Approach 1:
The patent introduces asymmetric phase angle distribution among bridge arms, where each arm operates at a different phase angle θi. This asymmetric control strategy is specifically tailored for multi-level flying capacitor circuits, achieving optimal ripple suppression that symmetric 180-degree control cannot provide.
Data Source
AI summary
An interleaved flying capacitor multi-level converter includes a plurality of arms and a phase-shift PWM generation circuit. Each arm includes a flying capacitor multi-level circuit having an upper arm and a lower arm coupled at a middle node. The upper arm includes a plurality of serially coupled upper arm switches and the lower arm includes a plurality of serially coupled lower arm switches. One capacitor is correspondingly coupled between every two upper arm switches and every two lower arm switches. The phase-shift PWM generation circuit generates a plurality of switch control signals to respectively control the plurality of upper arm switches and the plurality of lower arm switches.