ABSTRACT:
This paper proposes an advanced control strategy to
enhance performance of shunt active power filter (APF). The proposed control
scheme requires only two current sensors at the supply side and does not need a
harmonic detector. In order to make the supply currents sinusoidal, an
effective harmonic compensation method is developed with the aid of a
conventional proportional-integral (PI) and vector PI controllers. The absence of
the harmonic detector not only simplifies the control scheme but also
significantly improves the accuracy of the APF, since the control performance
is no longer affected by the performance of the harmonic tracking process.
Furthermore, the total cost to implement the proposed APF becomes lower, owing
to the minimized current sensors and the use of a four-switch three-phase inverter.
Despite the simplified hardware, the performance of the APF is improved
significantly compared to the traditional control scheme, thanks to the
effectiveness of the proposed compensation scheme. The proposed control scheme
is theoretically analyzed, and a 1.5-kVA APF is built in the laboratory to
validate the feasibility of the proposed control strategy.
KEYWORDS:
1.
Active power
filters (APFs)
2.
Harmonic current compensation
3.
Power quality
4.
Resonant controller
SOFTWARE: MATLAB/SIMULINK
BLOCK DIAGRAM:
Fig.
1. Typical control scheme of a shunt APF.
Fig.
3. Steady-state performance with PI current controller under RL load.
Fig.
4. Steady-state performance with proposed control scheme under RL load.
Fig.
5. Dynamic responses of proposed control scheme under RL load
variations:
(a) load applied (b) load changed.
Fig.
6. Steady-state performance with proposed control scheme under RLC load.
Fig.
7. Dynamic responses of proposed control scheme under RLC load
variations:
(a) load applied (b) load changed.
Fig.
8. Steady-state performance of the proposed control scheme under
distorted
supply voltage condition with (a) RL load and (b) RLC load.
Fig.
9. Steady-state performances of the four-switch APF with (a) RL load
and
(b) RLC load.
CONCLUSION:
In
this paper, an advanced control strategy for the three-phase shunt APF was
proposed. The effectiveness of the proposed control strategy was verified
through various experimental tests, where the proposed control strategy
presented good steady-state performance with nonlinear RL and RLC loads as well
as good dynamic response against load variations: the supply current is almost
perfect sinusoidal and in-phase with the supply voltage even under the
distorted voltage condition. The experimental results verified that the absence
of a harmonic detector results in faster transient responses as well as assures
notches free in steady-state performances of the supply current. Moreover, we also
confirmed that the FSTPI can be used to implement the APF without any
degradation in the APF performance. In all of the experiments, THD factor of
the supply current was reduced to less than 2%, which completely comply with
the IEEE-519 and IEC-61000-3-2 standards.
REFERENCES:
[1]
Recommended Practice for Harmonic Control in Electric Power Systems, IEEE
Std. 519-1992, 1992.
[2]
Limits for Harmonic Current Emission, IEC 61000-3-2, 2001.
[3]
H. Akagi, “New trends in active filters for power conditioning,” IEEE Trans.
Ind. Appl., vol. 32, no. 2, pp. 1312–1332, Nov./Dec. 1996.
[4]
F. Z. Peng, “Application issues of active power filters,” IEEE Ind. Appl. Mag.,
vol. 4, no. 5, pp. 21–30, Sep./Oct. 1998.
[5]
H. Akagi, E. H. Watanabe, and M. Aredes, Instantaneous Power Theory and Applications
to Power Conditioning, M. E. El-Hawari, Ed.New York: Wiley, 2007.
