This　paper　proposes　an　inherent　and　effective　method　for　updating　the　database　which　is　critical　for　the　model-free　predictive　controller.　In　contrast　to　existing　update　methods　which　require　complex　analytical　expressions,　a　unified　analytical　update　model　is　proposed　as　a　sum　of　the　actual　current　and　input　control　gradients.　The　effectiveness　of　the　proposed　controller　is　validated　in　a　two-level　voltage　source　inverter　connected　to　the　grid　and　an　RLE　load.　The　simulation　results　show　that　DDPC　effectively　cancels　the　stagnant　mode　and　compared　with　MPC,　DDPC　provides　better　current　performance　at　normal　conditions　and　has　higher　robustness　under　parameter　mismatches.　©　2023　IEEE.