Abstract: In order to improve the power density of the double-stage isolated medium-voltage direct-linked PV-battery (DIMD-PVB) grid-connected system, to expand its stable operation range, and to achieve adaptive inter-phase power balance, a single-stage isolated medium-voltage direct-linked PV-battery-hybrid cascade (SIMD-PVBH) cascade grid-connected system is proposed. Firstly, the single-stage isolated DC/AC converter is used to eliminate the decoupling capacitance of the intermediate DC link to achieve high power density operation, and a high voltage gain sub-module topology based on the full-bridge flip-module is proposed. Secondly, the PV-battery-hybrid cascade method is used to solve the over-modulation problem of the inner-phase power conversion cell caused by local PV shadow occlusion, which expands the stable operation range of the system. Then, the requirements of PV medium-voltage high-power grid-connected and multipath maximum power point tracking (MPPT) operation are taken into account, and a wiring method of using a common DC bus between phases and multiple DC buses within phases is adopted, which has adaptive inter-phase power balance capability on the basis of achieving multipath MPPT operation. Finally, a 10 kV/1.5 MW simulation system has been built to verify the feasibility of the proposed SIMD-PVBH cascade grid-connected system.