IEEE Transactions on Power Delivery, 2015
ABSTRACT:
An interline dynamic voltage restorer (IDVR) is a
new device for sag mitigation which is made of several dynamic voltage
restorers (DVRs) with a common DC link, where each DVR is connected in series
with a distribution feeder. During sag period, active power can be transferred
from a feeder to another one and voltage sags with long durations can be
mitigated. IDVR compensation capacity, however, depends greatly on the load
power factor and a higher load power factor causes lower performance of IDVR.
To overcome this limitation, a new idea is presented in this paper which allows
to reduce the load power factor under sag condition, and therefore, the
compensation capacity is increased. The proposed IDVR employs two cascaded
H-bridge multilevel converters to inject AC voltage with lower THD and
eliminates necessity to low-frequency isolation transformers in one side. The
validity of the proposed configuration is verified by simulations in the
PSCAD/EMTDC environment. Then, experimental results on a scaled-down IDVR are
presented to confirm the theoretical and simulation results.
KEYWORDS:
1. Back-to-back converter
2. Cascaded H-bridge
3. Interline dynamic voltage restorer
SOFTWARE: MATLAB/SIMULINK
BLOCK DIAGRAM:
Fig.
1. Power circuit schematic of the IDVR with active power exchanging capability.
EXPECTED SIMULATION RESULTS:
Fig. 2. Investigating the IDVR
performance when the proposed method is applied for a sag with depth of 0.4p.u.
Fig.3. Investigating the IDVR
performance when the proposed method is applied for a sag with depth of 0.6p.u.
CONCLUSION:
In
this paper, a new configuration has been proposed which not only improves the
compensation capacity of the IDVR at high power factors, but also increases the
performance of the compensator to mitigate deep sags at fairly moderate power
factors. These advantages were achieved by decreasing the load power factor
during sag condition. In this technique, the source voltages are sensed
continuously and when the voltage sag is detected, the shunt reactances are
switched into the circuit and decrease the load power factors to improve IDVR
performance. Finally, the simulation and practical results on the CHB based
IDVR confirmed the effectiveness of the proposed configuration and control
scheme.
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