Study Of The Shunt Active Power Filter

Nowadays, harmonics contamination become more and more severe problems in power distribution system because of the ever-increasing nonlinear loads. Improving the power quality is very important to the safe and economic operation of the power system and the electrical facility, to guarantee the product's quality and the people's normal living. Active power filter, as one of the most effective solution, has been widely researched and developed in the recent years.In this paper, the main research area is shunt active power filer. As a result, the topology of shunt APF, detection methods of compensation reference, control strategies and design of physical circuit are systemically analyzed and discussed.Four widely used detecting methods of compensating components are demonstrated in detail. Compared under ideal supply voltage conditions, they are equivalent to each other. The four detection methods can be realized with recursive approach in real-time. The detection method based on the Park transform calculates the compensating current reference accurately even under the unsymmetrical and non-sinusoidal supply voltage conditions. Further, used in 3-phase 3-wire network, it can determine arbitrary single order harmonic current. Simulation results show the precision of the proposed approach.The crucial research and development activity in this thesis is the investigation of control strategies of shunt active power filter. In the paper, we make a general introduction of sinusoidal pulse wide modulation and hysteresis control. Based on analyzing the basic principle of voltage space vector pulse width modulation (SVPWM), the realization of SVPWM is discussed and a simpler method to calculate the operating time of each vector is offered. Compared with conventional SPWM, this one can improve the precision of the active power filter, reduce the switching losses and improve the utilization of DC voltage. This paper presents recursive integral PI algorithm applied for APF to improve its steady-state and dynamic performance. The characteristics of the proposed algorithm are small computation capacity and easy for engineering application.In order to achieve quick current response in transient state and eliminate harmonic current in stable state, this paper presents a novel double hysteresis current control method for active power filter with voltage space vector. The control is directly executed on a - β coordinates. This new method, which utilizes output voltage of the inverter and its effect on current error to determine the locations of the reference voltage vector, is accurate, simple and reliable. Meanwhile, voltage space vector is introduced into the control system to ensure the optimal behavior of the vector control with minimal ripple content and maximum utilization of the dc bus voltage. Therefore the proposed control strategy could efficiently suppress the error current and harmonic contents. Finally, simulation results show good agreement with the anticipated performance.Based on the theoretical deduction, an experimental prototype of 3-phase 3-wire shunt APF with 50kVA is designed and built consequently. According to the experimental results, it verified the validity of the proposed detection method and control strategies. This thesis provides the basic and important background for the development of the shunt APF.