EMI Reduction in Grid-Connected Converters using the Nonlinear Behavior of Multi-Layer Ceramic Capacitors

In soft switching power converters, placing a capacitor parallel to the switching semiconductor power devices is a means to reduce electromagnetic interference. This paper investigates the application of multi-layer ceramic capacitors, MLCCs, as parallel capacitors in grid-connected converters, focusing on the nonlinear behavior of these components. Unlike traditional capacitors, MLCCs, particularly Class II ceramics like X7R, exhibit voltage-dependent capacitance characteristics, which can introduce beneficial effects for EMI reduction. The study explores different types of MLCCs, comparing NP0/C0G and X7R, and highlights their respective behaviors in controlling voltage (dv/dt) and current (di/dt) transients. Through simulation and experimental validation, it is demonstrated that EMI mitigation using nonlinear MLCCs is more effective than using linear capacitor types as parallel capacitors. The findings of this research provide insight into the selection and application of parallel capacitors in grid-connected converters, with a focus on minimizing EMI.