The voltage unbalance remains the most critical challenge of series-connected devices in medium-voltage high-power applications. In this paper, a behavioral model considering IGBT structure properties is proposed to balance the voltage among the series-connected trench gate/field-stop (FS) IGBTs. The equivalent circuits are presented for the voltage fast-rising stage and current tail stage respectively. Furthermore, the assumption of carrier extraction effect is applied to evaluate the phenomenon of gate voltage drop in Miller platform considering the trench gate/field stop structure. As a result, the voltage sharing in series-connected IGBTs during turn-off transient is analyzed quantitatively. The accuracy of the model is experimentally verified under different operating conditions. More importantly, this paper presents a guidance based on the proposed model for voltage balancing, which can be directly used in the design of drive and snubber circuit for series-connected IGBTs.