Developed Of The Three-phase Four-wire Active Power Filter

With the proliferation of nonlinear loads such as power electronic equipments or arc furnaces, the amount of current harmonics has increased. This causes the power quality beyond acceptable level in many situations. Therefore, the active power filter (APF) as an efficient solution to improve the power quality has been brought as an increasing concern. Compared with passive power filters, active power filters can dynamically compensate harmonics, reactive power and unbalance produced by varying loads. In addition, resonance phenomena and several other serious problems caused by passive filters can also be avoidedThe ordinary countermeasure is to compensate the respective load attribute on the spot of the loads, but it is hard to avoid attending one thing and losing sight of another, when the compensation is not made by unitizing math mode. Now the use of Active Power Filter (APF) is an important trend for harmonic restraint and reactive power compensation. The countermeasure we adopt is to regard harmonic, reactive power and negative power as a kind of distorted wave, so we can compensate together. Our work is adopting some algorithm to integrate the distorted wave in the load current and controlling the compensation equipment according to some control technique, so that the compensation equipment can produce the distorted wave and achieve the compensation purpose.Three-phase four-wire systems are widely used in actual power network.Especially in a low-voltage distribution system, the three-phase four-wire system is the commonest supply mode and is widely used in industry and residential area .Recent years, harmonic and unbalance in three-phase four-wire system has been paid more and more concern for the increasing ratio. Therefore it is very important to compensate harmonic and reactive power in three-phase four-wire systems.The present APF uses PWM converter with power electronics switches...