Three-Phase Four-Wire Shunt Active Power Filter For Selective Harmonic Compensation

On the one hand, the quality of power grid is seriously contaminated because of the use of mass power electronic facilities and increasing nonlinear loads. On the other hand, these power electronic facilities and various loads normal, stable, efficient operation requires the power grid to provide high quality power. Therefore, the researches on the harmonics suppression and the reactive power compensation for the power grid, improvement of public power grid quality are growing concerned. Active Power Filter (APF) is an efficient, stable and flexible advanced mean for optimizing power's quality, its application will play a significant role in improving the quality of power grid.Firstly, this paper presents a simple introduction to the public power grid quality, leads to the research direction of APF. Then, this thesis detailed introduces the APF system constitutes, operation principle, history, classification and development trends. Furthermore, this paper gives a detailed presentation of the three-phase four-wire APF research background and key technologies.One of the key technologies of three-phase four-wire shunt APF is to obtain the current order. The compensation performance of the APF fine or not depends on the current order accurate or not. Then this paper presents a simple overview to several current detection methods, focus on three current detection methods used in the three-phase four-wire systems. What's more, this paper analyses and study selective harmonic filtering technology for improving the flexibility function of APF. Finally, this paper proposes a realization of three-dimensional vector space PWM used for the main circuit of split-capacitor inverter for three-phase four-wire APF.APF mathematical model is a crucial theoretical basis to analyze and research active power filter, meantime it provides solid theoretical evidence for computer simulation and real experiment. Consequently, we establish a precise mathematical model for the split-capacitor inverter. Taking into account the digital control, we discrete the model with zero order holder.Based on the precise mathematical model, we proposed an initial control strategy for the control system of APF. Given the different conditions, we researched and studied the DC voltage control external loop and the current control internal loop, provided simulation model and results, verified the control strategy's correctness and availability, eventually, offered an effective simulation platform for effective analysis of the actual device operation.Finally, based on above analysis and research, we have built a three-phase four-wire active power filter experimental device. Making use of the experimental device, experiments have been carried out in different conditions, results proved that the current detection method and the control strategies are fully adapt to the three-phase four-wire shunt active power filter, ensure the APF operation with high compensation performance.