Research On Strategy Of New Hybrid Injection Type Active Power Filter

With the wide application of the power electronic device to industry, the harmonic current produced by it is injected into the grid and influences the normal work of the electric equipment. The problem of harmonic pollution has become an important issue of the quality of power supply. With the harmonic suppression as the research object, by using a new type of hybrid active filter injection HAPFIS (Hybrid Active Power Filter with Injection Structure), this paper studies in detail harmonic detection, harmonic filtering principle, steady-state compensation characteristics, and control algorithms of HAPFIS, etc., and forms a fairly complete system technology plan of HAPFIS.First, analyzes and compares the active power filter harmonic detection method commonly used at present. ip-iq detection which can be applied in the situation of the supply voltage distortion, but when applied to power three-phase voltage asymmetry, there are errors in the positive sequence reactive power components detection, based on which the traditional ip-iq method can be improved. This paper uses ip-iq detection method based on supply voltage filtering, and MATLAB software writing programs to make the simulation research.Second, the paper introduces HAPFIS topology. HAPFIS is a mixture of the series resonant injected active power filter and passive filter branch in parallel. The passive part of the compensation for reactive power, active part and the passive part co-suppress harmonic. Fundamental series resonant circuit generates series resonance in the places of fundamental frequency. With very small impedance, the inverter withstands only a small fundamental voltage, thus can further reduce their capacity. The paper analyses HAPFIS filtering principles:the active part of HAPFIS is equivalent to connecting a controllable in series with the power grid branches. When harmonic impedance is large enough, power network harmonic current will be reduced to very small or even zero, playing the role of suppressing harmonics currents and constraining the resonance between the passive part and the grid impedance at the same time. Additionally, the paper studies steady-state compensation characteristics and resonance features of the suppression system of HAPFIS.Third, the paper generalizes the research states of the active power filter control method. HAPFIS is different from the active filter used alone, so its control methods can not completely copy those of the active filter used alone. Considering HAPFIS the control reference signal as the amount of the cycle, recursive integral PI control algorithm is adopted to eliminate the system's steady-state error. After the use of active filter, the filtering effect of passive filter branch has been greatly affected, based on which the recursive integral PI control algorithm has been improved by using sub-frequency control-based the recursive integral PI control algorithm, to free the passive filter slip from its impact after the input of active inverter.Fourth, the paper introduces fuzzy control to the control algorithm of HAPFIS, and combines the sub-frequency control-based recursive integral PI control algorithm with fuzzy control algorithm to form a fuzzy-recursive integral PI composite control algorithm, which combines the advantages of the two control methods. The parameter achieves online adjustments and solves the errors due to inaccurate parameter settings.Finally, the paper uses PSIM simulation software to make simulation analysis of the three control algorithms respectively to verify the effectiveness of various control methods.