How to coordinate the control of inverter harmonics and EMC

Harmonic control and EMC control of frequency converters need to be carried out in tandem, as both involve power quality management. Harmonics mainly refer to low-frequency current distortion, while EMC focuses on higher-frequency conducted and radiated noise, but they can interfere with each other. Cooperative control strategies include: installing active or passive harmonic filters at the input, which can reduce input current harmonics, and their inductor and capacitor components also attenuate high-frequency conducted noise. Improving the EMC performance of the power factor correction circuit itself can prevent it from becoming a new noise source.

Optimizing PWM modulation strategies, such as using random PWM or specific harmonic cancellation techniques, can reduce low-order harmonics while dispersing noise energy, which is beneficial for EMC filtering. Output filters, while suppressing high-frequency EMI, may also affect the harmonic spectrum of the output voltage, requiring comprehensive evaluation. During system design, harmonic analysis and EMC prediction should be performed simultaneously, selecting filter topologies and parameters that balance both. Testing and verification are essential to ensure that the product meets both harmonic and EMC standards. The input filtering solutions provided by Audiotech often consider both harmonic suppression and EMI filtering requirements.