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.
- Active power filters (APFs)
- Harmonic current compensation
- Power quality
- Resonant controller
Fig. 1. Typical control scheme of a shunt APF.
Fig. 2. Structure of the proposed control scheme for three-phase shunt APF.
EXPECTED SIMULATION RESULTS:
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.
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.
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