The design scheme for a dynamic voltage restorer applicable to compensating for regional voltage sags in 10 kV distribution systems is carried out

in which the cascaded H-bridge based main circuit

the devices for energizing the dynamic voltage restorer (DVR) and the transformer-free coupled circuit are presented in detail. In order to solve the voltage sag problem in an isolated neutral distribution system

a reference voltage calculation method for restoring the line voltage on the load side is put forward. In the end

a simulation model for a substation including the designed DVR devices is built in PSCAD

and the compensation results under different fault types are simulated and analyzed while the influence of energizing devices on the distribution system is studied. The correctness and effectiveness of both the DVR hardware design and reference voltage calculation method is verified by simulation results. This work is supported by National Natural Science Foundation of China (No. 51007065).