Three Terminal Common-Mode EMI Modeling and EMI Mitigation Strategy for Full SiC UPS
This paper investigates EMI mitigation strategy for full SiC UPS. First, a three-terminal CM EMI model for a UPS with an active battery charger is developed. The model reveals that the dc-dc stage deteriorates output CM EMI via additional noise generation and multiple resonances with the parasitics of the battery cabinet. Second, different topologies and pulse width moudlation (PWM) schemes have been compared to determine the best solution for noise mitigation. Special focus has been given to dc-dc stage topologies and PWM schemes. A 20 kW full SiC UPS prototype has been built to verify the model and mitigation strategy, as shown in Fig. 2 (a). The results show that there is a large increase on CM noise when dc-dc converter operates, as shown in Fig. 2 (b). Experimental results illustrate that selecting the dc-dc converter topology and PWM scheme plays a critical rol in EMI mitigation.
With the proposed combination, CM EMI has been reduced by 14 dB over a wide frequency reange.