Control and test of dynamic voltage restorer on the medium voltage grid

Power quality problems like voltage dips and sags are presently important issues in the utilities. Major economic losses might appear at the customers due to those failures. This paper presents a power electronic device, which keeps voltage sags away from sensitive loads. It is a dynamic voltage restorer (DVR), which creates a series injection of voltage into the medium voltage grid. Energy storage is keeping the sensitive load running in a limited time. The design and a new control method of a DVR are explained in this paper. The DVR is also tested at medium voltage level (10 kV) and methods to initiate voltage dips are described and implemented. Different test results at 10 kV level show that the DVR keep the voltage to a sensitive load fixed in the case of voltage dips. Furthermore, it is also demonstrated that in the case of a transformer failure the system also works very fine.