Frequency-Dependent Impedance Variation in Multilevel Converters with Parallel Connectivity

Multilevel converters with parallel connectivity, known for their flexibility and scalability, are extensively applied across diverse fields. Earlier studies presumed an ideal inverse relationship between the output impedance and the number of paralleled modules, an assumption we found inaccurate under variable output frequencies. To rectify this, we derived a novel analytic formula describing the changes in impedance across multiple paralleled modules as a function of the output frequency. Our simulation results closely mirrored our theoretical model. Experimental validation on a prototype confirmed the resistive impedance variation, demonstrating a 2.5 W conduction loss increase relative to low-frequency scenarios, consistent with our theoretical analysis.