For better DC-link voltage response in three-level neutral point clamped (NPC) back-to-back converter, a cascaded extended state observer (CESO) is proposed in this paper. DC-link is the connection between active front ends (AFEs) and machines, whose stability is critical to both sides. However, the desired performance cannot be guaranteed when many disturbances occurred. Aiming to improve its response under disturbance, two extended state observers (ESOs) which estimate power and torque disturbance for the AFE and surface mounted permanent magnet synchronous motor (SPMSM), respectively, are realized in NPC back-to-back converter with model predictive control (MPC). Due to the cascaded structure of the back-to-back converter, power estimation in a conventional way takes a long time to converge. Thus, a CESO is proposed by introducing the torque reference to estimate power disturbance more quickly. With proper design of feedforward compensation, faster dynamic response is obtained, also, DC-link voltage barely changes when the working point of the SPMSM moves. The performance in both steady and transient states of the proposed scheme is verified by simulation results.