Control Technique with Fast Response For Power Factor Correction Rectifiers MIRCEA BĂBĂIŢĂ, VIOREL POPESCU, ADRIAN POPOVICI, DAN LASCU, DAN NEGOIŢESCU Applied Electronics Department Politehnica University of Timisoara Address Bd. Vasile Parvan No.2 ROMANIA Abstract: - This paper proposes a new control technique for single-phase boost power-factor-correction rectifiers. The proposed circuit improves the dynamic response of the converter to load steps without the need of a high crossover frequency of the voltage loop. So a low distortion of the input current is easily achieved. A 200W power-factor correction rectifier with the proposed control scheme has been designed, simulated and implemented, validating the concept. Key-Words: - Power factor correction, average current control, rectifiers, power conversion 1 Introduction Low harmonic distortion is achieved by using average current-mode control (ACC) [1], [2] with bandwidth of the voltage loop limited to about 20 Hz in order to properly attenuate the second line harmonic that appears at the output voltage of the converter [3]. As a result, the dynamic response of the output voltage to load changes is slow. This paper proposes a new robust model-following ACC scheme (RMACC) with a high disturbance rejection and an analog implementation applied to boost PFC rectifiers. In case of a PFC rectifier, the amplification of the output voltage ripple would be especially disturbing, because the second line harmonic present at the control signals would be amplified [4]. Reference models are also used by other robust control techniques, like internal model control [5]. The advantages of the proposed control loop applied to PFC rectifiers are: • RMACC uses a reference model that has a low- pass nature, so that the output voltage ripple is not amplified. Therefore the contents of the second line harmonic present at the control signals is similar to that of conventional ACC, so that a low input current distortion can be achieved. • RMACC decreases significantly the closed-loop output impedance of the PFC rectifier at low frequencies. Hence, the dynamic response of the output voltage to load steps is faster. • The improvement of the closed-loop output impedance is achieved without the need of a high crossover frequency of the voltage control loop. Therefore, it is easy to sufficiently attenuate the second line harmonic at the control signals to achieve a low distortion of the output current. • RMACC does not add significant complexity to the control circuits when compared with the second harmonic elimination techniques. The proposed control method for PFC converters is useful in those applications that request fast response of the output voltage to load steps. A 200-W PFC rectifier based on a boost converter with RMACC has been designed, simulated and implemented, validating the concept. 2 Description of the RMACC 2.1 Small-Signal Model of on ACC Rectifier The ACC scheme of a typical boost PFC rectifier with feedforward of the rectifier input voltage is shows in Fig.1. A linear small-signal model [2] of the ACC- controlled boost PFC rectifier is shown in Fig.2, where: Fig.1 Typical Boost rectifier with ACC. Filter Voltage Controller Ziv Zfv Vref Multiplier Divider Rac Vc Current Controller βVo βVo R R1 R2 C Vg Rm iL L d iac Vac Zfs IM Zis fs Igm Vff PWM 2005 WSEAS Int. Conf. on DYNAMICAL SYSTEMS and CONTROL, Venice, Italy, November 2-4, 2005 (pp421-426)