Dynamic Voltage Regulator

Marudhar Engineering College, Bikaner
DYNAMIC VOLTAGE RESTORER
Saturday, 24 March 2018 1

CONTENTS
 INTRODUCTION
 REQUIREMENT OF DVR
 VOLTAGE SAGS AND SURGES
 STRUCTURE OF DVR
 THREE PHASE GREATZ BRIDGE
 NEUTRAL POINT CLAMPED INVERTER
 H BRIDGE INVERTER
 OPERATING STATUS OF DVR
 DVR COMPENSATION TECHNIQUES
 VOLTAGE SAG DETECTION TECHNIQUES
 FURTHER DEVEOPMENT
 CONCLUSION
 REFERENCES
Saturday, 24 March 2018 Marudhar Engineering College, Bikaner 2

INTRODUCTION
A DVR is a series-connected solid-state device that
injects voltage into the system in order to regulate the
load side voltage.
It is normally installed in a distribution system
between the supply and a critical load feeder at the so
called Point of Common Coupling (PCC) which is
defined as the point of the network changes.
 Its primary function is to rapidly boost up the load-
side voltage in the event of voltage sag in order to
avoid any power disruption to that load.

REQUIREMENT OF DVR
Power quality in the distribution system can be improved by
using a custom power device DVR for voltage disturbances such as
voltage sags, swells, harmonics, unbalanced voltage and etc.
The Dynamic Voltage Restorer (DVR) is a device that detects the
sag or swell and connects a voltage source in series with the
supply voltage in such a way that the load voltage is kept inside the
established tolerance limits.
It is normally installed in a distribution system between the
supply and the critical load feeder at the point of common coupling
(PCC).
Other than voltage sags and swells compensation, DVR also has
added other features like: line voltage harmonics compensation,
reduction of transients in voltage and fault current limitations.

VOLTAGE SAGS AND SURGES
Disturbance Voltage Duration
Voltage Sag 0.1 – 0.9 pu 0.5 – 30 cycle
Voltage Swell 1.1 – 1.8 pu 0.5 – 30 cycle

STRUCTURE OF DVR

THREE-PHASE GRAETZ BRIDGE

NEUTRAL POINT CLAMPED
INVERTER

H BRIDGE INVERTER

OPERATING STATUS OF DVR
During a short circuit or fault in the
downstream of the distribution line
During the normal operation
During a voltage sag/swell on the line

DVR COMPENSATION TECHNIQUES

Voltage tolerance method with minimum energy injection

VOLTAGE SAG DETECTION
TECHNIQUES
 Fourier transform
 Phase Locked Loop (PLL)
 Vector control (Software Phase Locked Loop –
SPLL)
 Peak value detection
 Applying the wavelet transform to each phase

FURTHER DEVELOPMENTS
 As a future work and a further development an additional
control can be added to neutralize the injected voltage
component during the normal operation, by generating a similar
sinusoidal waveform with a phase shift of 180˚, which is
basically the drop across the DVR internal impedance.
 The control circuit can be implemented using electronic
components and power electronic switches can be used to
generate DVR injected voltages. Then the simulation results
can be compared with that of the hardware and the
effectiveness of the simulated model can be ensured.
 By selecting the ratings of the components with worst case
analysis, the cost and the performance are optimized, better
results could be obtained.

3:20 AM R.K.Pradhan 17
CONCLUSION
Voltage sag compensation using Dynamic Voltage Restorer was considered.
Even though three phase DVR system and its control techniques are popular
among the researchers, very less consideration was given to single phase
DVRs and its control techniques. This describes a voltage sag compensation
technique for a single phase DVR. The control technique was designed by
combining both the in-phase and pre-sag compensation techniques to
minimize the requirement of real power and voltage ratings of the DVR when
the voltage sag prevails for a longer period of time .It uses a closed loop
control system to detect the phase angle and magnitude errors between the
voltages during and before the sag.
The system was simulated for several cases. To cover all possible voltage sags,
the sags were created with and without phase angle shift, and it was initiated
at different point of the supply voltage waveform. Finally the supply voltage
with harmonic content also checked in the simulation. In all results, the
developed control technique with the proposed single phase DVR circuit has
shown a very good level of voltage compensation.

REFERNECES
[1] http://en.wikipedia.org/wiki/Phase-locked_loop “Wikipedia the free
encyclopaedia”, accessed on January, 2007
[2] http://www.du.edu/~etuttle/electron/elect12.htm, “The phase locked loop”,
accessed on January, 2007
[3] http://perso.orange.fr/polyvalens/clemens/clemens.html, accessed on January,
2007
[4] http://www.w3.org “PI Controller” , accessed on January, 2007
[5] C. S. Chang, Zhemin Yu, “Distributed Mitigation of Voltage Sag by Optimal
Placement of Series Compensation Devices Based on Stochastic Assessment”,
IEEE transactions on Power Systems, Vol.19, No.2, May 2004, pg.788-795.
[6] Peradeniya University Annual Research Sessions (PURSE – 2006) held at
University of Peradeniya, Sri Lanka on November 30th 2006.
Topic of the Technical paper and presentation: Compensation techniques of the
Dynamic Voltage Restorer for single phase voltage sags.
[7] Second International Conference on Information and Automation 2006 (ICIA
2006)
held at Galadari Hotel, Colombo, Sri Lanka on 14-17th December 2006.
Topic of the Technical paper and presentation: Automated control technique for a
single phase Dynamic Voltage Restorer

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Dynamic Voltage Regulator

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