In this paper, different voltage injection schemes for dynamic voltage restorers (DVRs) are analysed with particular focus on the methods used to minimize the rating of the voltage source converter (VSC) used in DVR. The control and operation of a DVR is demonstrated with reduced rating VSC. The reference load voltage is estimated using the unit vectors and the synchronous reference frame (SRF) theory is used for the control of DVR. The compensations of sag, swell and harmonics in supply voltage using the reduced rating DVR are demonstrated using MATLAB with its Simulink power system blockset (PSB) toolboxes.
- Dynamic Voltage Restorer
- Power Quality
- Unit Vector
- Voltage Harmonics
- Voltage Sag
- Voltage Swell
Fig. 1. Scematic diagram of the DVR connected system.
EXPECTED SIMULATION RESULTS:
Fig. 2. Dynamic performance ofDVR with inphase injection during voltage sag and swell applied to critical load.
Fig. 3. Voltages at PCC and Load terminal.
Fig. 4. Dynamic performance of DVR during harmonics in supply voltage
applied to critical load.
Fig. 5. PCC Voltage and harmonic spectrum.
Fig. 6. Supply current and harmonic spectrum.
Fig. 7. Load voltage and harmonic spectrum.
Fig. 8. Dynamic performance of capacitor supported DVR during (a) voltage sag and (b) voltage swell applied to critical load.
The operation of a DVR has been demonstrated under different voltage injection schemes. A comparison of the performance with different schemes has been performed with reduced rating VSC including capacitor supported DVR. The reference load voltage has been generated using the method of unit vetors. The control of DVR has been achieved which minimizes the error of voltage injection. The SRF (synchronous reference frame) theory has been used for the control of DVR. It is concluded that the voltage injection in phase with the PCC voltage results in minimum rating of DVR but at the cost of an energy source at the dc bus.
 Math H.J. Bollen, Understanding Power Quality Problems- Voltage Sags And Interruptions, IEEE Press, New York, 2000.
 A. Ghosh and G. Ledwich, Power Quality Enhancement using Custom Power devices, Kluwer Academic Publishers, London, 2002.
 Math H. J. Bollen and Irene Gu, Signal Processing of Power Quality disturbances, Wiley-IEEE Press, 2006.
 R. C. Dugan, M. F. McGranaghan and H. W. Beaty, Electric Power Systems Quality. 2nd Edition, New York, McGraw Hill, 2006.
 Antonio Moreno-Munoz, Power Quality: Mitigation Technologies in a Distributed Environment, Springer-Verlag London limited, London 2007.