This paper presents a novel dynamic voltage restorer (DVR) capable of handling deep sags including outage on a low voltage distribution system. The DVR recovers sags up to 10% of nominal voltage; otherwise, it will operate as an uninterruptible power supply (UPS). A transformer is connected in series with the load when restoring sags, and is reconfigured into parallel connection using switches when handling outages. The controller uses a Fuzzy Logic with 3 inputs to maintain the load voltage through d-q transformation. Preliminary results from laboratory tests are also presented in this paper.
Fig. 1. Block diagram of the proposed DVR
EXPECTED SIMULATION RESULTS:
(a) Grid Voltage
(b) Load Voltage
(c) Inverter Voltage
Figure 2. The grid, load and inverter voltages under 3-phase fault
Figure 3. Grid and load voltages during 1-phase to ground fault
A dynamic voltage restorer using Fuzzy Logic controller was demonstrated to remedy sags and outage voltages. Phase jumps and unbalanced conditions due to single phase-to-ground fault can also be compensated by the DVR. In the event of outage, where the voltage drops below 10%, the DVR restore the voltage into the normal. Thus, the load voltage is unaffected by the disturbances including sags and outages.
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