Parallel APF Time Optimal Resistance Research On Control Algorithm Of Starting Impact

With the rapid development of modern controllable transformation power electronics technology,people's quality of life has been mentioned and benefited from it.However,due to the harmonic pollution caused by nonlinear dynamic loads,the utilization of power quality will be reduced.The active power filter(APF)can not only improve the use of power quality,but also have significant effect on reactive power compensation and dynamic harmonic suppression.In view of the instantaneous impact of the DC side capacitance voltage and the inductance current of the AC side,the inductance and capacitance of the AC and DC side are damaged and the action error of the switch protection device is caused by the APF input voltage and the inductance current of the AC side.This paper analyzes and studies the problems.Through the traditional method of starting current limiting resistor plus PI control,there is a long start time and high hardware cost,so a more advanced and effective control strategy is needed to control the start process.Aiming at the shortcomings of traditional PI control,this paper proposes a variety of control algorithms to improve.By comparing the simulation results of different control algorithms,the effectiveness of each control algorithm in restraining impact on the AC and DC side grid is illustrated.The main contents are below:(1)Firstly,the three-phase parallel APF is selected as the system template,and the basic principle and general classification of the system are described,and several harmonic detection methods based on the instantaneous reactive power theory are emphasized.Then the mathematical model of APF is designed and established,laying the groundwork for the next research on control algorithm of grid connection to suppress impact.For some important system parameters,such as DC side capacitance and voltage,AC side inductance is analyzed.(2)Based on the theoretical derivation of symmetrical component method and instantaneous energy method,the maximum fluctuation amplitude and wave distortion rate of DC capacitor voltage are analyzed.For the problem of excessive voltage shock at the instant of grid starting,a time optimal Bang-Bang control algorithm is proposed to suppress the impact,and the ripple voltage after stability is eliminated by switching to the fuzzy PI through the deviation threshold and fuzzy rules.Through the comparison and analysis of the simulation experiments,compared with the traditional methods such as precharging resistance or PI control,the new improved algorithm is adopted,and the impact effect is better and the optimal control in time is realized.(3)For the problem that the instantaneous impact of the AC side inductance current is too large,the objective function is established through the detailed analysis of the active and reactive current,and then the analysis of the double ring starting analysis based on the external voltage loop and the inner loop of the current is analyzed.The results show that the optimal control of the time can not be achieved.There is a delay and a shortcoming.Finally,a new control algorithm based on the three-phase current feedforward decoupling step by step is used to reduce the instantaneous impact of the grid connected current,and the effect of the impact current is best,and there is no burr,and the stability time is less.Finally,the validity is verified in the simulation.(4)Several kinds of grid-connected soft-start methods for power electronics are introduced.Finally,the effect of different capacitance and inductance value on the starting of the system is simulated and verified,and the appropriate parameters are determined.