A Novel Approach for Real-Time Monitoring of Power Losses of DC-Link Capacitors in Traction Inverters Subject to Various Periodic Modulation Strategies

摘要

The dc-link capacitor is a crucial component within the traction inverter of electric vehicles. Due to its limited robustness with regard to thermal degradation, the temperatures within the capacitor have a great impact on reliability and lifetime of the inverter. In fact, harmonics occurring in the dc-link current significantly affect the electrical and thermal stress of dc-link components. In real-life operation, the electric drive is used with different modulation strategies that may have a remarkable influence on those harmonic characteristics. For thermal monitoring and protection, in a corresponding online temperature model the actual losses need to be known. This paper presents a generic approach for the loss calculation of the dc-link capacitor based on a simplified Fourier decomposition using the switching pattern of periodic modulation strategies, which is appropriate for real-time application within the inverter's software. Furthermore, the methodology is verified by measurements.