Research On Improved Control Strategy And Application Of Active Power Filter

Due to social development and the improvement of residents’ living standards,a large number of loads are connected to the power system through the low-voltage distribution network,which greatly increases the load rate of some distribution lines.If the distribution network planning is unreasonable,it will lead to heavy overload,low voltage,three-phase imbalance and so on.In order to solve the problem of unbalanced load distribution of low-voltage power supply lines in rural areas,improve the power consumption satisfaction of power users and improve the health level of system operation,the application of active power filter(APF)to improve the three-phase load imbalance of distribution network is proposed,and the improved repetitive control strategy is studied.The effectiveness and feasibility of the proposed method are verified based on Tieling Power Grid.The specific work is as follows:By studying the research and application method and basic theory of APF,a method based on the difference between reactive and active current at a certain time of power system is obtained,which proves that the detection method is better than the detection method in theory.Because the method of detecting negative sequence current in APF system is similar to that of detecting harmonic current,taking the elimination of harmonic current as an example,the simulation experiment shows that both detection method and detection method can obtain reliable detection results under normal grid voltage.However,if there is external disturbance and serious uneven load distribution in the grid,the detection method can obtain better and more reliable results than the detection method.The mechanism,implementation method and performance of PI and standard repetitive control strategy are analyzed.Because these two methods have the disadvantages of slow response to input changes,poor ability to deal with disturbances and low accuracy,in order to realize three-phase load balancing regulation of power grid by using APF,an improved repetitive control strategy is proposed in this thesis.Simulation results show that the improved strategy has better performance and balance compensation effect.This thesis analyzes the causes of three-phase imbalance of a distribution network in Tieling rural area from multiple dimensions,uses Simulink to simulate the model under various load imbalance modes of Tieling rural distribution network,studies the compensation method formed by reasonably configuring APF in the simulation environment,and adopts the improved repetitive control strategy.It is concluded that the improved distribution network has good load balance and effectively improves the three-phase imbalance problem.This conclusion proves that the control strategy proposed in this thesis can effectively solve the problem of average load allocation of rural distribution network in Tieling area,and meet the expected technical requirements.