Secondary Frequency Modulation Strategy for SiC Inverters Based on Periodic Spread Spectrum Modulation

Area of Science:

• Electrical Engineering
• Power Electronics
• Electromagnetic Compatibility

Background:

• Silicon carbide (SiC) motor controllers are crucial for electric vehicles, but electromagnetic interference (EMI), device loss, and voltage/current ripple are significant challenges.
• Existing spread spectrum modulation strategies offer some mitigation but require further optimization for comprehensive performance improvement.

Purpose of the Study:

• To design an advanced modulation strategy for SiC motor controllers that minimizes EMI, device loss, and voltage/current ripple.
• To develop and evaluate a novel "secondary frequency modulation" technique for enhanced EMI reduction within a constrained spread spectrum range.

Main Methods:

• Construction of an equivalent evaluation model for inverter input voltage, output current, and switching loss under periodic spread spectrum modulation.
• Establishment of quantitative relationships between spread spectrum modulation parameters and key performance indicators (EMI, loss, ripple).
• Evaluation of inverter performance and loss under various spread spectrum modulation strategies, leading to the proposal of the "secondary frequency modulation" strategy.

Main Results:

• The proposed "secondary frequency modulation" strategy effectively reduces the peak value of inverter-conducted EMI.
• This reduction in EMI is achieved without any increase in the inverter's voltage/current ripple or device loss.
• Experimental validation confirms the superior EMI mitigation capabilities compared to single periodic signal spread spectrum modulation.

Conclusions:

• The "secondary frequency modulation" strategy offers a significant advancement in reducing conducted EMI for SiC motor controllers in electric vehicles.
• This technique provides a practical solution for achieving low EMI, low loss, and low ripple simultaneously, enhancing overall system performance.
• The findings pave the way for more efficient and electromagnetically compatible electric vehicle powertrains.