The Research Of Shunt Active Power Filter In Harmonic Detection And Control Technology

Electric is essential to our daily lift.With the increasing use of nonlinear loads and electric and electronic devices,the negative impact of harmonic waves on power grid becomes severe.The most efficient device to restrain harmonics is APF.However,the APF that we used nowadays work not as well as we expected from the view of control and design,which limits its application.The defection of traditional harmonic measurement algorithm is analyzed at the beginning of the thesis.Base on this,a non-phase locked loop(non-PLL)measurement algorithm for three-phase circuit harmonics and reactive current is proposed.Such an algorithm accurately measure the currents of each phase,even when the voltages of three phases are not symmetric and the frequency shifts.Compared with the algorithms with PLL,it eliminates the impact of PLL on the measurement precision,which improves the measurement precision.Finally,the algorithm is validated that it has a steady-state precision and a quick dynamic response,using MATLAB simulation.For the requirement of engineering,a non-PLL ip-iq measurement method for specific order harmonic is also proposed.It can measure the positive/negative-sequence component of specific order harmonic in three-phase three-wire non-symmetric system,which is added up to give the current of the harmonic of specific order.Theoretically,the shift of frequency does not affect the results in ip-iq transform.Such a method has been validated using simulation.In order to improve the accuracy of compensation for specific order harmonic of APF,a strategy for control harmonic currents based on multi-rotation synchronized coordinates is proposed.Adapting the rotation transform synchronized with the angular velocity of the harmonic of specific order,transform the harmonic to direct current,to compensate the current of the harmonic without static error.Finally,using TMS320F28335 as controller,design and implement a three-phase three-wire parallel APF prototype,both hardware and software.Finally,the simulation analysis of the control strategy mentioned above,and the results are given.The conclusion can be drawn that the current control strategy for specific order harmonic has a high precision and a quick dynamic response and it can also work along with the traditional control strategy.The goal has been achieved.Therefore,such a control strategy is promising in engineering.