In recent years, there are rapid development in the area of power electronics and electric drive systems. Although these power electronics devices have benefited the electrical and electronics industry, these devices being nonlinear loads are the principal cause of power harmonics in the power system. This leads to power quality problems and affects the operation of motors, control equipments and protection devices. Harmonics can also cause resonance in the electrical network.
Conventionally, passive filters were used to solve these problems but they have many problems such as the fixed compensation, the dependence on network impedance, possibility of causing resonance and the large size.
The development of active power filter (APF) has put an end to all these problems. With the development of power electronic technology, APF has found its wide application in the modern industry. As compared with conventional passive filters, APF has significant advantages such as good controllability, fast response and high control accuracy etc. Also, APFs have the advantage of dynamic compensation which is very important taking into account the dynamic nature of the network topology.
In this thesis, a three phase shunt APF based on a space vector modulation (SVM) and hysteresis current controller (HCC) technique is proposed. The proposed APF with a SVM based on HCC is implemented in a closed loop control system. The use of a SVM reduces the switching frequency and the use of HCC is to fast the dynamic performance. By implementing this control strategy, the APF manages to generate better compensated harmonic currents to the line.
A complete dynamic modeling of the proposed APF is implemented on Matlab/Simulink and power system tools to validate the dynamic performance of the drive system. The simulation results show that the proposed APF is able to improve the total harmonic distortion (THD) for the distorted line current caused by an uncontrolled rectifier as balanced nonlinear load and the unbalanced nonlinear loads. |
