Method for calculating main circuit parameters of three-level active power filter

Abstract

The invention discloses a method for calculating main circuit parameters of a three-level active power filter. The method comprises the following steps: carrying out equal-amplitude PARK transformation on a mathematical model under a fundamental wave rotating coordinate system of a three-phase four-wire system APF to obtain a dq coordinate system function; substituting the output current componentvalue output by the APF after symmetrical harmonic is compensated for five times into the dq coordinate system function to obtaina maximum value range of the total filter inductance after the symmetrical harmonic is compensated for five times; calculating the vector relationship of the voltage and the current to obtain an inductance value range meeting the current output capability and ripple current limitation at the same time under different direct-current bus voltages and power grid voltages; obtaining a main filtering capacitor capacitance value according to relational expressions of theresonant frequency of the LCL filter and the switching frequency and the power grid frequency; and obtaining the resistance value of the damping resistor according to the relationship between the damping resistor loss and the harmonic current flowing through the damping resistor. Accurate parameters of each component of the main circuit can be obtained under the conditions of different limit compensation currents and different power grid voltages, and the obtained parameter values have obvious effects on compensation of harmonic current and suppression of the switching frequency.

Description

technical field [0001] The invention relates to the technical field of harmonic compensation of an active power filter, in particular to a method for calculating main circuit parameters of a three-level active power filter. Background technique [0002] The three-phase four-wire active power filter APF with three-level NPC structure is the most researched form of three-phase four-wire multi-level APF. Compared with the two-level structure, it has small ripple and low electromagnetic interference. Etc. The three-level active power filter adopts the diode-clamped three-level IGBT topology, the N line of the power grid is directly connected to the midpoint of the DC capacitor, the output filter adopts the LCL form, and a damping resistor is connected in series with the filter capacitor. To suppress the resonance of the LCL filter. Since the voltage stress of the IGBT in the three-level topology is half of the DC bus voltage, reducing the withstand voltage level of the IGBT ha...

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Problems solved by technology

[0004] If the parameter matching of the filter is unreasonable, when the compensation current increases, the inductance value will decrease rapidly, which will deteriorate the compensation effect and even amplify other harmonics

However, using simulation or other conventional calculation methods, it is difficult to obtain accurate calculation values

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