DC-DC Converter Harmonic Reduction via Phase-Shifted Switching
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Solution Overview
Problem
High-power DC-DC converters used in pulsed power applications, such as proton synchrotrons, generate low-frequency harmonics in the current, which require additional filtering, limiting voltage control bandwidth and increasing costs.
Innovation Solution
The converter modules have switching laws of the same frequency but out of phase with each other, with specific phase differences, such as 180°, to reduce low-frequency harmonics, and the power supply system includes multiple converters with synchronized control laws to further minimize harmonics.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If conventional switching control is used in DC-DC converters, then the converter can deliver current to the load, but low-frequency harmonics are generated in the current
Solution Approach 1:
The patent applies periodic switching action with multiple phases. Each module switches periodically at the same frequency but with different phase shifts (e.g., 180° for two modules, or 360°/N for N branches per module). This periodic multi-phase switching distributes the harmonic content across different frequencies, reducing low-frequency harmonics while maintaining current delivery capability.
Solution Approach 2:
The converter is segmented into multiple independent modules (H-bridge modules with switching branches). Each module operates with its own switching law that is phase-shifted relative to others. This segmentation allows the total current to be composed of multiple phase-shifted current components, whose harmonics cancel each other out, reducing overall low-frequency harmonic content.
2Object-generated harmful factors
If filters are added to reduce low-frequency harmonics, then harmonic content decreases, but voltage control bandwidth is limited and costs increase
Solution Approach 1:
The patent converts the potentially harmful low-frequency harmonics into beneficial phase-shifted current components. By designing the switching laws to be out of phase, the harmonics generated by each module cancel each other constructively at low frequencies, transforming what would be harmful distortion into a mechanism for harmonic reduction without requiring additional filtering components.
3Power
If multiple converters are used in parallel, then power capacity increases, but harmonic cancellation requires complex coordination
Solution Approach 1:
The patent changes the control parameter from simple in-phase switching to phase-shifted switching. Each converter module uses the same switching frequency but with a specific phase shift parameter (e.g., 180° between modules, or 360°/N within modules). This parameter change enables automatic harmonic cancellation through mathematical interference, simplifying the coordination requirement to just setting the phase shift angle while scaling power capacity.
Data Source
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AI summary
The converter (20) has modules (70) forming an H-bridge, where each module comprises a switching branch (72) comprising controllable electronic switches (74) connected in series between terminals (40). The controllable electronic switches are connected with each other at middle point (76). A controlling unit (80) controls the modules based on commutative law, where the law of the each module has same frequency and is phase shifted with respect to each other. An independent claim is also included for a power supply system for load comprising a control unit.