Abstract: A hybrid cascaded ultra HVDC transmission technology integrated in one station layout is proposed in this paper, and the key equipments such as the DC filters, the controllable arresters and the fast bypass switches, and the coordinate control strategy are designed. In order to verify the engineering feasibility of this technology, this paper builds a low-voltage dynamic model platform with the real primary and secondary systems. The dynamic model platform not only includes the conventional DC equipments as the DC lines, the converter valves, the converter transformers, the control and protection devices and others, but also includes some special equipments such as the controllable arresters and the fast bypass switches, so it can accurately simulate the actual characteristics of the topology. The system characteristics of start-stop, single converter switching and fault ride-through are verified on the dynamic model platform. The test results show that the hybrid cascaded ultra HVDC system has smooth start-stop, flexible operation mode, reliable fault ride-through capabilities. It conforms to the design indexes and has engineering feasibility.