DC Charging Station Switching Frequency Variation for EMI Suppression
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Solution Overview
Problem
DC charging stations for electric vehicles face challenges in reducing Electromagnetic Compatibility (EMC) disorders caused by high-frequency pulse patterns used to control semiconductor switches, which increase switching losses and EMC interference radiation.
Innovation Solution
The solution involves continuously and randomly varying the switching frequency of the pulse pattern controlling the semiconductor switches, which smears the spectral components of the pulse pattern, reducing EMC interference and enhancing tolerance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If high switching frequency and high edge steepness are used to reduce power loss, then power loss is reduced, but EMC interference increases
Solution Approach 1:
The patent applies dynamics by continuously and randomly varying the switching frequency of the pulse pattern instead of using a fixed frequency. This dynamic adjustment smears the spectral components of the pulse pattern, reducing the peak interference levels while maintaining the benefits of high-frequency operation for reduced power loss
Solution Approach 2:
The patent changes the frequency parameter of the pulse pattern dynamically. By varying the switching frequency within a range rather than maintaining a constant value, the spectral energy is distributed more evenly, reducing the amplitude of individual frequency components that cause EMC interference while preserving the overall high-frequency operation needed for low power loss
2Manufacturing precision
If high switching frequency is used to reduce residual ripple of DC charging voltage, then residual ripple is reduced, but switching losses increase
Solution Approach 1:
The patent uses dynamic frequency variation to achieve a balance between ripple reduction and switching loss. By operating at high frequencies with random variation, the system maintains low ripple while the dynamic nature prevents the system from settling into a fixed high-loss operating point
Solution Approach 2:
The patent employs periodic pulse patterns with randomly varied periods to control the semiconductor switches. This periodic action with varying periods achieves effective ripple filtering while distributing the switching losses across different frequency components
3Object-generated harmful factors
If active and passive filters are used to reduce EMC interference, then EMC interference is reduced, but efficiency of power electronics decreases
Solution Approach 1:
The patent extracts the EMC filtering function from separate passive filter components and integrates it into the control system through dynamic frequency variation. This eliminates the need for additional filter hardware that would consume power and reduce overall system efficiency
Solution Approach 2:
The control system performs the EMC interference suppression function itself through intelligent frequency modulation, rather than relying on separate passive filter components. The system uses its own control capabilities to smear spectral components and reduce interference, making the system self-sufficient for both power conversion and EMC compliance
Data Source
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AI summary
The invention relates to a method for suppressing EMC interference in a DC charging station (2) for electric vehicles (8), wherein the DC charging station (2) comprises at least one power converter circuit (10, 14) with semiconductor power switches (20) controlled by a pulse pattern with a switching frequency (fs). The method according to the invention comprises the steps of providing an AC voltage from an AC power supply system (4), rectifying the AC voltage into a DC intermediate voltage (12), and converting the DC intermediate voltage (12) into a DC charging voltage (6), wherein the switching frequency (fs) of the pulse pattern (30, 40) for controlling the semiconductor power switches (20) is varied continuously and randomly. The method is applicable analogously to a charger in an electric vehicle (8).