Transient optimization control strategy of hybrid capacity regulating transformer

•A hybrid capacity regulating transformer (HCRT) based on transient optimization control strategy has been developed for energy saving in power distribution system.•The controller can greatly shorten the time of the transient process of adjusting the capacity.•There is no arc in the process of adjusting the capacity with the load voltage maintained continuously without distortion.•The transient optimization control strategy can avoid overcurrent and internal short circuit to prolong the service life of HCRT. In order to overcome the problems of the traditional capacity regulating transformer, this paper presents a hybrid capacity regulating transformer(HCRT) that uses anti-parallel thyristors instead of mechanical switches. Advantages of presented HCRT are there is no arc in such transformer, faster response speed and longer service life. Taking into account of the characteristics of the semi-controllable thyristor, this paper proposes a transient optimization control strategy to avoid internal short circuit and load voltage loss in HCRT. After receiving the capacity regulating command which is the delay time calculated by the parameters of transformer, the closing time of the switch group is controlled, therefore, the continuity of the magnetic flux and load voltage in each phase in the process of capacity regulating is ensured. Finally, the simulation results of comparative experiments are provided to illustrate the advantages and effectiveness of the proposed method. Meanwhile, the experimental results obtained on the prototype of HCRT are provided to verify the effectiveness of transient optimization control strategy for HCRT.