In order to avoid frequent power regulation of DC transmission lines,a dynamic reactive power optimization model of AC /DC power systems,which takes into consideration the DC power regulation limits,is established and then solved by using the generalized Benders decomposition.In the decomposition process,the power variables of DC transmission lines are divided in the master problem together with integer variables,so that the sub-problem can be transformed into a set of independent AC /DC optimization problems in single time section.At the same time,a tightened Benders cut is used to transfer the sub-problem information into the master problem.Moreover,in order to obtain the optimal power of DC transmission lines in a successive linear way,a dynamic step adjustment strategy is proposed.The results on a real large-scale AC /DC interconnection power grid demonstrate the correctness and effectiveness of the proposed method in restricting the regulation times of DC power.Finally,the effect of maximum regulation limit on the dynamic reactivepower optimization results is analyzed.