Application Of Capacitive Split APF In Low Voltage Distribution Network

According to the problem of harmonic pollution,three-phase unbalance and low power factor in distribution network.Based on the idea of composite compensation,the theory and technology of three-phase four wire APF which can compensate harmonic,unbalance and reactive current is studied.On this basis,an improvedi_p-i_qdetection algorithm which verifies that the zero sequence component does not affect the application of thei_p-i_qdetection algorithm in the three-phase four-wire system is proposed under the condition of non-ideal voltage.The research in this paper shows that the application of the split-capacitance APF can effectively solve the problem of power quality.The main tasks of this paper include:(1)This paper present the whole system design of the split capacitor APF,illustrating the working principle of APF and establishing the mathematical model of the split capacitor APF.(2)The principle of common pq detection method andi_p-i_qdetection method and the applicable occasion are deduced in detail.The error caused by phase information of non sinusoidal and asymmetric voltage is analyzed by using PLL in the voltage of non-ideal power grid,and the influence of the accuracy ofi_p-i_qdetection algorithm is verified.The improvedi_p-i_qdetection algorithm is used to extract phase information of the fundamental positive sequence component of the non-sinusoidal and asymmetric voltage to eliminate the influence of the inaccurate voltage phase extraction on thei_p-i_qdetection algorithm.The application of mathematical deduction proves that thei_p-i_q detection algorithm can also be applied to three-phase four-wire system.(3)The reason of capacitor-splitting APF DC side capacitance voltage oscillation is analyzed by mathematical deduction.In this paper,the effect of the mean pressure control is introduced into the outer loop of the instruction current detection algorithm.The control method can not only solve the problem of DC side voltage instability caused by neutral line current,but also improve the compensation effect.(4)With the capacitor splitting structure of active filter,DC side voltage oscillation will make the system response time slows down and affect the compensation effect,so the DC side voltage control directly affect the performance of the entire compensation device.The control of DC side voltage is usually based on the traditional Pi control method,but it is influenced by the system parameters and external disturbances and the poor robustness in this paper,the DC side voltage is optimized by using the control method of auto disturbance rejection to improve the control effect.(5)This paper uses simulation software to verify the instruction current detection algorithm and the rationality and correctness of the control strategy,through the comparison and analysis of simulation.The experimental results show that the harmonic,reactive and unbalanced current can be compensated synthetically by the capacitance splitting APF.