First, this paper analyzes the AC fault ride-through scheme based on the DC chopper device. Given the topological structure of a DC chopper device suitable for offshore wind power projects, its working mode and switching strategy are analyzed. Secondly, the scope and zoning of large-scale offshore wind power DC protection with a DC chopper are studied. The DC protection action strategy is determined, and each DC protection zone is focused on the protection configuration strategy. Then the influence of the switching on and off of the DC chopper on the DC protection function is studied. The focus is on the coordination strategy of DC overvoltage protection setting and the input voltage value of the chopper, and its protection function design. Finally, the above strategy is verified by simulation. This work is supported by the National Key Research and Development Program of China (No. 2016YFB0900600) and the Science and Technology Project of State Grid Corporation of China (No. 52094017000W).