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.