ABSTRACT:
In this paper,
a new hybrid power conditioner is proposed for suppressing harmonic currents
and neutral-line current in three-phase four-wire distribution power systems.
The proposed hybrid power conditioner is composed of a neutral-line current
attenuator and a hybrid power filter. The hybrid power filter, configured by a
three-phase power converter and a three-phase tuned power filter, is utilized
to filter the nonzero-sequence harmonic currents in the three-phase four-wire
distribution power system. The three-phase power converter is connected to the
inductors of the three-phase tuned power filter in parallel, and its power
rating can thus be reduced effectively. The tuned frequency of the three-phase tuned
power filter is set at the fifth harmonic frequency. The neutral- line current
suppressor is connected between the power capacitors of the three-phase tuned
power filter and the neutral line to suppress the neutral-line current in the
three-phase four-wire distribution power system. With the major fundamental
voltage of the utility dropping across the power capacitors of the three-phase tuned
power filter, the power rating of the neutral-line current suppressor can thus
be reduced. Hence, the proposed hybrid power conditioner can effectively reduce
the power rating of passive and active elements. A hardware prototype is
developed to verify the performance of the proposed hybrid power conditioner.
Experimental results show that the proposed hybrid power conditioner achieves
expected performance.
KEYWORDS:
1. Harmonic
2. Neutral-line
current
3. Power converter
SOFTWARE: MATLAB/SIMULINK
CIRCUIT DIAGRAM:
Fig. 1. Configuration of the advanced hybrid
power filter.
Fig. 2. System configuration of the proposed
hybrid power conditioner.
EXPECTED SIMULATION RESULTS:
Fig. 3. Experimental results of the balanced
three-phase load: (a) phase a load
current, (b) phase b load current, (c) phase
c load current, and (d) neutral line current of load.
Fig. 4. Experimental results of the hybrid
power conditioner under the balanced three-phase load: (a) phase a utility
current, (b) phase b utility current, (c) phase c utility current, and (d)
neutral line current of the utility.
Fig.
5. Experimental results of the three-phase four-wire hybrid power conditioner under
the transient of applying the neutral-line current attenuator: (a) phase a
utility voltage, (b) phase a utility current, (c) phase a load current, and (d)
neutral line current of the utility.
Fig.
6. Experimental results of the unbalanced three-phase load, (a) phase a load
current, (b) phase b load current, (c) phase c load current, and (d) neutral line
current of the load.
Fig. 7. Experimental results of the hybrid
power conditioner under the unbalanced three-phase load: (a) phase a utility
current, (b) phase b utility current, (c) phase c utility current, and (d)
neutral line current of the utility.
Fig.
8. Experimental results of the hybrid power conditioner under the transient of
increasing load: (a) phase a utility voltage, (b) phase a utility current, (c) phase
a load current, and (d) neutral line current of the utility.
CONCLUSION:
Three-phase four-wire distribution power
systems have been widely applied to low-voltage applications; however, they encounter
serious problems of harmonic current pollution and large neutral-line current.
In this paper, a new hybrid power conditioner, composed of a hybrid power
filter and a neutral- line current attenuator, is proposed. In the proposed
hybrid power conditioner, the power capacity of power converters in the hybrid
power filter and neutral-line current attenuator can be effectively reduced,
thus increasing its use in high-power applications and enhancing the operation
efficiency. A prototype is developed and tested. Experimental results verify that
the proposed hybrid power conditioner can suppress the harmonic currents and
attenuate the neutral-line current effectively whether the loads are balanced
or not. Hence, the proposed hybrid power conditioner is an effective solution
to the problems of harmonic currents and neutral-line current in three-phase
four-wire distribution power systems. Besides, the output current of the three-phase
power converter is much smaller than the conventional hybrid power filter, and
the power rating of the zig-zag transformer is smaller than the rating of the
conventional neutral-line current attenuator.
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