High power-factor 3-phase PWM rectifier

Abstract

The low harmonic currents in input side is required by the legislation of regulations for controlling harmonics. The power conversion system which has a 3-phase AC power source and isolated DC output power is widely applied for the telecommunication system over several kVa. The conventional DC 48 V output power supply for the telecommunication system have the 3-phase PWM rectifier in the first step in order to obtain the sinusoidal input current waveforms. In addition to this, the conventional power supply has the DC-DC converter which is isolated between input side and output one in a second step to obtain 48 V DC. As described above, the conventional power supply is composed of two power converters; 3-phase PWM rectifier and DC-DC converter. For this reason, the conventional power supply causes the low power efficiency and high cost. To solve this problem, the power conversion system which has a flyback converter has been already proposed. Using the flyback converter, this power conversion system can convert 3-phase AC input power into the isolated DC output power. However, the high voltage and the enlargement of turn off current across the power semiconductor devices does not allow the higher efficiency and larger capacity in this power conversion system to be obtained. This paper presents a novel forward rectifier which can directly convert 3-phase AC input into the isolated 48 V DC. The proposed rectifier consists of a power converter which is connected in 3-phase line to line. By controlling the duty factor of each active switch, the proposed rectifier has sinusoidal waveforms with unity power factor. The benefit of the proposed rectifier is lower peak current in each power semiconductor device because this rectifier is a forward type power converter system. For this reason, the proposed forward rectifier is suitable for the high power applications such as telecommunication power supply. In this paper, the design concept and the feasible performance evaluations of the novel forward rectifier is proposed and discussed. In the experimental result performed by using 1.4 kW experimental set-up, the power efficiency of 92.1% and the input current meeting the requirement of harmonic current regulations of EEC 6100-3-2 class A are obtained.