In order to carry out experimental verification on the protection and fault clearance strategy based on DC grid

we develop a four-terminal DC grid physical platform according to the network structure of Zhangbei DC grid. The pseudo-bipolar connection at DC-side is adopted in the platform

and each bridge arm is cascaded through a full-bridge modular multiple converter（MMC） sub-module. In terms of controller structure

the physical platform includes 3-level control structures

such as upper computer

crate controller

and sub-module crate

communicating through the Ethernet and optical fiber

respectively. And all control algorithm is set in FPGA of crate controller

realizing packet sequencing voltage-sharing strategy of the capacitor of sub-modules（SMs） to simplify the control method and improve response speed of controller. The good performance of physical platform is verified by the experiments of normal operation and power step change. Finally

the experiment of fault clearing is carried out.The results show that the physical platform has the hardware ability to carry out the research of DC power grid protection and fault clearing

which can provide good hardware support for the follow-up research.