The Study Of H-bridge Cascaded APF Based On Carrier Phase Shift Modulation Technology

With the development of modern industrial technology, A large number of non-linear loads increase in power system, causing serious harmonic pollution to the grid.Active Power Filter (Active Power Filter, APF) as a new harmonic and reactive power compensation device,which can realize dynamic compensation to improve power quality. Currently researches on the APF focused on the low-pressure areas, many of the key issues in the field of APF used in high pressure applications need to be resolved. Such as in the case of power electronic devices can not withstand high voltage level, how to make APF device withstand high voltages. Power electronics switching frequency increases as APF capacity decreases, lower switching frequency has a direct impact on the APF compensation effect. How to solve the contradiction between the switching frequency and devices capacity in the high-pressure area is another problem.For solving the problem of APF applied in the high-pressure environment, cascaded H-bridge topology is selected in this paper by series H bridge unit to improve the APF voltage level.Combining the characteristics of cascaded H-bridge structure basic operating modes, the multiplier carrier phase shift modulation technology is used to improve device equivalent switching frequency. For APF general detection and control issues,ip-iq harmonic detection method based on instantaneous reactive power theory is used in this paper.This method can extract the harmonic current quickly, provided reference target for the control of APF compensation current.In order to control the output current of the AC side effectively, direct current control method based on triangular carrier is used.In order to control discrete DC capacitor voltage stability and balance, the paper uses a double control method by superimposing DC active component and active voltage vector.Finally, this paper set up H-bridge cascaded APF system simulation model in simulink environment.The experiments of functional modules and systems overall function are carried out. The simulation results show that the modulation, detection and control strategies proposed is correct and feasible.