Research On Control System For Three-phase Three-wire Shunt Active Power Filter

With the rapid development of new power electronic equipment,Power quality faces serious challenges.The harmonic current is a common problem of power quality.Active power filters play an important role in eliminating harmonic current.APF can dynamically compensate for harmonic current.Also,it is applied flexibly.However,APF still has many shortcomings,such as precision in detection of harmonic and regulation of current.In view of the shortcomings,APF is fully discussed in dissertation.Improving the performance of harmonic estimation,dissertation constructs current model of load.Kalman filter is applied to estimate harmonics in real time.For optimising the dynamic performance,Dissertation presents a method that parameters of filter is adjusted according to operational state of system.The way satisfies the need of fast transition.Further,Phase-locked loop is a traditional way to measure angular frequency.However,it has many disadvantages.Therefore,Dissertation designs a estimator of angular frequency based on state observer.It can provide accurate parameters for harmonic and controller.With the help of Simulink,the algorithms of harmonic detection and angular frequency are fully verified.Based on deeply analysis of APF control system,dissertation establishes a certainly mathematical model of APF system.The current tracking controller is designed based on output regulation theory to compensate harmonic current.At the same time,in order to improve robustness of system and suppress influence of parameters,dissertation establishes mathematical model with unknown parameters based on certainly mathematical model.Adaptive backstepping current controller is designed and unknown parameters are estimated online.The results show that performance of controllers has high accuracy in tracking load current to fundamental current.On basis of theory and analysis of simulation,dissertation builds a hardware platform of hardware-in-loop.The performance of the control strategy is experimentally analyzed.The results illustrate that estimation of harmonic and angular frequency,as well as strategy of current compensation have a good performance.