Fault-tolerant Control Of Active Power Filter Based On Feedback Linearization

With the rapid development of power electronic technology and its application, a large number of harmonic current and reactive power have been injected into the power system. The Active Power Filter(APF) is a kind of device which can dynamic control harmonic current and compensate reactive power, because of the fragility of the power electronic switch devices in the APF, prone to short circuit and open circuit fault, affecting the reliability of itself. APF fault-tolerant control can make the system still normal operate within a certain range of performance indicators after the fault by reconstructing topology structure and control algorithm, which will increase the reliability of the system. This paper mainly studies on the control strategy of three-phase four-switch APF.This thesis sets forth the fault-tolerant control strategy which can reconstruct a three-phase six-switch APF to a three-phase four-switch APF. A three-phase four-switch APF mathematical model in d-q rotating coordinate system is established. Multiple Input multiple Output (MIMO) nonlinear feedback linearization algorithm is used on the system for linearizing the nonlinear system. A diffeomorphism coordinate transformation for control inputs is derived. The active current and reactive current of the three-phase four-switch APF decoupling control is realized. On the basis a controller is design by using linearization control methods, Zero steady-state error tracking is realized.A Space Vector Pulse Width Modulation (SVPWM) optimization algorithm is posed. The existence of the potential fluctuation in the middle of the three-phase four-switch APF’s DC bus. The change of four basic space voltage vectors is analyzed in details. Present a sector judgment and duty cycle calculation method in three-phase four-switch SVPWM. Effectively improve the accuracy of the synthetic instruction voltage. A capacitance balance control method is proposed to ensure the two series capacitor voltage balance when capacitance parameter changes.This paper designed and built a low voltage three-phase four-switch APF Physical experiment platform with the capacity of lkVA. The product design and implementation methods of three-phase four-switch APF is discussed. Simulation experiment and Physical experiments have proved the correctness and validity of the methods in the paper.