A Single Phase Dynamic Voltage Restorer (DVR) based on five-level ground point shifting multilevel inverter topology has been proposed in this paper. The proposed inverter has a floating ground point. Therefore, by shifting the ground point, it is observed that the inverter circuit gives five output voltage levels from single DC voltage source. This configuration uses less number of switches compared to the existing multilevel inverter topologies. A fast sag swell identification technique using d-q reference frame is also discussed in this paper. This proposed topology of the DVR can compensate voltage sag, swell, flicker and maintain the required voltage at the load bus. The detailed simulation study is carried out using MATLAB/Simulink to validate the result.
- Voltage sag
- Ground Point Shifting Multilevel Inverter (GPSMI)
Fig. 1. General structure of the proposed DVR.
EXPECTED SIMULATION RESULTS
Fig. 2. (a) Grid terminal voltage (vt) and (b) load voltage (vl) during sag
Fig. 3. direct axis value of the d-q reference frame which is used to detect
sag in the system.
Fig. 4. During voltage sag (a) grid terminal voltage (vt), (b) series injected
voltage (vinj) and (c) inverter terminal voltage (vinv).
Fig. 5. FFT analysis of the series injected voltage (vinj).
Fig. 6. (a) Grid terminal voltage and (b) load voltage during Voltage flicker
This paper proposes dynamic voltage restorer based on the ground point shifting multilevel Inverter topology (GPSMI). The operation of the multilevel inverter and the power circuit diagram is explained. The inverter topology requires less number of switches than conventional multi-level inverter. In this inverter topology, only two switches are active at any instant of time that reduce switch conduction loss. The passive filter requirement in the DVR topology is reduced by using this multi-level inverter. Proper PWM for this proposed inverter has been explained. Instantaneous sag identification technique using d-q reference frame has also been explained. This proposed DVR can mitigate the power quality problem like sag/swell and voltage flicker.
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