Hybrid-paralleled power-factor-correction system for high-power equipment harmonic suppression

This paper proposes a novel power-factor-correction system for the harmonic suppression of high-power equipment. It connects a PWM (pulse width modulation) rectifier and several uncontrolled diode rectifier units in parallel. The PWM rectifier is not connected to the load, and the power of the IGBT device is lower than that of the traditional PWM rectifier. The diode rectifier unit is connected in parallel without the loop current, which is convenient for expansion. The diode rectifier unit can still work when the IGBT fails, which enables high reliability. When compared to conventional APFs (active power filters), the proposed system only controls the grid current as a sinusoidal wave at the power frequency, without tracking harmonics, which makes the control simpler and the current THD (total harmonic distortion) lower. In this paper, the operating modes of the proposed parallel system are analyzed and the mathematical model of the circuit is derived. In addition, the corresponding control strategy is proposed and the parameters of the LCL are designed. Finally, simulations were carried out to demonstrate the superiority of the proposed parallel system when compared with the traditional APF, and a 60 kW experimental platform was built to demonstrate the feasibility of the proposed scheme.