Power Electronics Converters Impedance Characterization Device for Low Frequency EMI Analysis

Knowing the impedance of power converters is crucial for designing effective electromagnetic interference filters and predicting electromagnetic interference behaviour in system-level investigations. This paper introduces a novel impedance characterization device for power converters, designed to operate while the converter is in its active state. The device employs transformer-based injection of predefined arbitrary waveforms to capture real-time impedance measurements of the converter. A key innovation of the device is the development of a compact and cost-efficient digital amplifier, which enhances the overall efficiency of the characterization process. The device has been thoroughly tested and shown to provide accurate measurements, with performance extending up to 150 kHz, limited by the specific characteristics of the injection transformer. It has been successfully utilized to characterize both the artificial main network impedance and the differential-mode impedance of a single-phase converter, achieving precise and reliable results.