Abstract: For the technical requirements of on-load voltage regulation based on power electronic switches，a

thyristor-based on-load voltage regulation unit topology was given based on the analysis of the possible conduction state of each switch in the steady state and the switching law of different states. Considering that the control logic of on-load voltage regulation with multiple states is complicated，a hierarchical structure of control program for on-load voltage regulation was proposed. Further，through analizing the switching sequence of different states，a control strategy of the on-load voltage regulating transformer suitable for the given voltage regulation unit was proposed. Finally，the experimental prototype was designed，and the experimental results verify the rationality of the on-load voltage regulation unit structure and the correctness of the regulation strategy.

      Key words: on-load voltage regulation；power electronics；topology of on-load voltage regulation unit；hierarchical structure of control program；control strategy