This paper presents a utilization technique for enhancing the capabilities of dynamic voltage restorers (DVRs). This study aims to enhance the abilities of DVRs to maintain acceptable voltages and last longer during compensation. Both the magnitude and phase displacement angle of the synthesized DVR voltage are precisely adjusted to achieve lower power utilization. The real and reactive powers are calculated in real time in the tracking loop to achieve better conditions. This technique results in less energy being taken out of the DC-link capacitor, resulting in smaller size requirements. The results from both the simulation and experimental tests illustrate that the proposed technique clearly achieved superior performance. The DVR’s active action period was considerably longer, with nearly 5 times the energy left in the DC-link capacitor for further compensation compared to the traditional technique. This technical merit demonstrates that DVRs could cover a wider range of voltage sags; the practicality of this idea for better utilization is better than that of existing installed DVRs.
- DVR capability
- Energy optimized
- Energy source
- Series compensator
- Voltage stability
Fig 1: Single-line diagram of a power system with the DVR connected at PCC.
EXPECTED SIMULATION RESULTS:
Fig.2. D-axis voltages at the system (VSd), DVR (VDVRd), and load (VLd). during in-phase compensation (simulation).
Fig. 3. Q-axis voltages at the system (VSq), DVR (VDVRq), and load (VLq) during in-phase compensation (simulation).
Fig. 4. The overall three-phase voltage signals during in-phase compensation (simulation).
Fig.5 Real power at source (PS), the DVR (PDVR) and load (PL) during in- phase compensation (simulation).
Fig. 6 The DVR DC-side voltage (VDC) during in-phase compensation (simulation).
Fig. 7. D-axis voltages at the system(VSd), DVR (VDVRd), and load (VLd) during zero-real power tracking compensation (simulation).
Fig. 8.. Q-axis voltages at the system (VSq), DVR (VDVRq), and load (VLq) during zero-real power tracking compensation (simulation).
Fig. 9. The overall three-phase voltage signals during zero-real power tracking compensation (simulation).
Fig. 10. Real power at source (PS), the DVR (PDVR) and load (PL) zero-real power tracking compensation (simulation).
It is clear from both the simulation and experimental results illustrated in this paper that the proposed zero-real power tracking technique applied to DVR-based compensation can result in superior performance compared to the traditional in-phase technique. The experimental test results match those proposed using simulation, although some discrepancies due to the imperfect nature of the test circuit components were seen.
With the traditional in-phase technique, the compensation was performed and depended on the real power injected to the system. Then, more of the energy stored in the DC-link capacitor was utilized quickly, reaching its limitation within a shorter period. The compensation was eventually forced to stop before the entire voltage sag period was finished. When the compensation was conducted using the proposed technique, less energy was used for the converter basic switching process.
The clear advantage in terms of the voltage level at the DC-link capacitor indicates that with the proposed technique, more energy remains in the DVR (67% to 14% in the traditional in-phase technique), which guarantees the correct compensating voltage will be provided for longer periods of compensation. With this technique, none (or less) of the real power will be transferred to the system, which provides more for the DVR to cover a wider range of voltage sags, adding more flexible adaptive control to the solution of sag voltage disturbances.
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