Study Of Digital Control Of Series Hybrid APF Basing On Fundamental Magnetic Flux Compensation

The wide use of power electronic equipments makes harmonic problem deteriorated increasingly in the power system. Harmonic badly influences power quality of the electric network. Active power filter (APF) which is a new electrical electronic device can suppress harmonic and compensate reactive power. Because APF conquers many disadvantages of the LC filter, it received widely attention.Firstly the thesis introduces the development of suppression of the harmonic and compensation of the reactive power, then analyses the operational principle and structure of the different APF according to the classifications.Based on the magnetic flux compensation theory, the thesis proposes a new structure of series hybrid APF and analyses its operational principle. The mathematical model of the system and theoretical analysis of the stability are provided. To increase the capacity of the active power filter, a novel transformer structure with multiple compensation winding is proposed.The thesis introduces the mathematical model of the active power filter, in which the PWM inverter is the core, is established. Then, the filtering characteristic of the active power filter is analyzed. Three measures which can improve the filtering effect are gained: augmenting the filtering inductance properly; increasing the transformation ratio of the series transformer reasonably; or adopting the voltage feed forward control.The thesis introduces the real time harmonic and reactive current detection method based on the instantaneous reactive power theory. Based on that, a new fundamental current detection method used for single-phase power system is proposed. Active power filter's control strategy and inverter's output control are analyzed in detail. The thesis adopts triangle wave compare control and monopole frequency doubling PWM mode.The thesis introduces the realization of the active power filter by two parts: the detection of the reference current and the control of compensated current.Many experiments are done on the experimental equipment of series hybrid active power filter under various work conditions. The validity of the new principle is verified by the experiment results.