New Configuration of Dynamic Voltage Restorer for Medium Voltage Application

One of the undesirable power quality phenomenon in the distribution systems is voltage sag which risks the operation of sensitive loads. Dynamic voltage restorer (DVR) is well-known and reliable solution to mitigate this phenomenon and protect the sensitive loads. This paper proposes new configuration of DVR for medium voltage applications. The proposed configuration contains diode rectifier to converter power grid voltage to medium voltage dc link which is split between capacitors working at low-voltage level. Next stage is couple of full bridge (FB) dc-dc converters which are stacked together and each is fed with low voltage. Each FB dc-dc converter contains high frequency (HF) transformer to make isolated dc link for each phase since DVR needs to inject isolated voltage in each phase individually. Last stage of proposed configuration is the cascaded multicell inverter (CMI) which works as series converter of DVR to inject required voltage. The output of each FB dc-dc converters are fed to one cell of CMI. CMI is controlled with phase shifted sinusoidal pulse width modulation to absorb the same power from each cell causing to split the voltage of main dc link equally between low-voltage capacitors. Simulation results of the proposed configuration are presented to show the performance and effectiveness of the circuit.