This paper proposes an improved modulated carrier control with on-time doubler for the single-phase shunt active power filter, which eliminates harmonic and reactive currents drawn by nonlinear loads. This control method directly shapes the line current to be sinusoidal and in phase with the grid voltage by generating a modulated carrier signal with a resettable integrator, comparing the carrier signal to the average line current and making duty ratio doubled. Since the line current compared to the carrier signal is not the peak, but the average value, dc-offset appeared at the conventional control methods based on one-cycle control is effectively addressed. The proposed control technique extirpates the harmonic and reactive currents and solves the dc-offset problem. The operation principle and stability characteristic of the single-phase shunt active power filter with the proposed control method are discussed, and experimental results with laboratory prototype under various load conditions verify its performance.
- Single-phase shunt active power filter
- Modulated carrier control
- Indirect control
- One-cycle control
- Harmonic and reactive currents elimination
- Nonlinear load.
Fig. 1. Single-phase shunt active power filter with nonlinear load.
Fig. 2. Overall control structure of the proposed control method with the shunt APF.
EXPECTED SIMULATION RESULTS
Fig. 3. Measured grid voltage, line current, APF current and load current waveforms of the shunt APF system based on the proposed control method at full load condition (vin : 200 V/div, iin : 20 A/div, if : 20 A/div, i- L : 20 A/div).
Fig. 4. Measured grid voltage, line current, APF current and load current waveforms of the shunt APF system based on the proposed control method at half load condition (vin : 200 V/div, iin : 20 A/div, if : 20 A/div, iL : 20 A/div).
Fig. 5. Current controller switching mechanism.
Fig. 6. Measured dc-link voltage, line current, APF current and load current waveforms of the shunt APF system in load transient from 800 W to 1600 W (vo : 100 V/div, iin : 20 A/div, if : 20 A/div, iL : 20 A/div).
Fig. 7. Measured grid voltage, line current, APF current and load current waveforms of the shunt APF system at 110 Vrms grid voltage. (vin : 100 V/div, iin : 10 A/div, if : 10 A/div, iL : 10 A/div) Under (a) 200 W, (b) 270 W, (c) 340 W, (d) 400 W load condition
Fig. 8. Power factors of the nonlinear load system with and without the APF under various load conditions.
An improved modulated carrier control for single-phase active power filter has been proposed. The shunt APF with the proposed control method fulfills harmonic and reactive current elimination at the line current by comparing the carrier signal to the average line current and having the duty ratio doubled. On top of that, the control method totally gets rid of the dc-offset problem arisen at the conventional one based on one-cycle control and ameliorates the current control loop stability without additional ramp signal. The operation principle of power stage, the main control mechanism, and the stability characteristic of the current control loop are analyzed in detail. Experimental results with the shunt APF system under assorted conditions verify the performance of the proposed control method in steady and transient states.
- Elham B. Makram, E.V. Subramaniam, Adly A. Girgis, and Ray Catoe, “Hamonic filter design using actual recorded data,” IEEE Transaction on Industrial Application, vol. 29, no. 6, pp. 1176-1183, Nov. 1993.
- Z. Peng, “Harmonic sources and filtering approaches,” IEEE Transaction on Industrial Application Magazine, vol. 7, no. 4, pp. 18-25, Jul. /Aug. 2001.
- Czarnecki, L. S., Ginn, H. L., “The effect of the design method on efficiency of resonant harmonic filters,” IEEE Transactions on Power Delivery, vol. 20, no. 1, pp. 286-291, Jan. 2005.
- Fakhralden A. Huliehel, Fred C. Lee, and Bo H. Cho, “Small-signal modeling of the single-phase boost high power factor converter with constant frequency control,” PESC’92 Record. 23rd annual IEEE Power electronics Specialists Conference, 1992, vol.1, pp. 475 – 482.
- Martinez, P. N. Enjeti, “A high-performance single-phase rectifier with input power factor correction,” IEEE Transactions on Power Electronics, vol. 11, no. 2, pp. 311–317, Mar. 1996.