Resonant-impedance type hybrid active electric filter and control method thereof

Abstract

The disclosed filter includes active power filter (APF) and passive filter (PF). Output of APF is connected to primary side of isolating transformer. Being connected to series resonance circuit in parallel, the isolating transformer is connected to PF in series, and then connected to electric network. Steady state error of APF is lowered through iterative control algorithm of improper integral. Result output from the control algorithm is as equivalent control in slipform variable structure control, realizing combination of two methods so as to form triplet variable control structure. Comparing with slipform variable structure control or iterative control of improper integral adopted in solely, the invention possesses features of quicker responsibility and smaller steady state error.

Description

technical field [0001] The invention relates to a hybrid active power filter, in particular to a resonant impedance type hybrid active power filter. Background technique [0002] Electric energy is the main and essential energy in the production of modern society and people's life. With the development of power electronics technology, a large number of nonlinear loads have been added to the power supply system. It is a nonlinear time-varying topological load, which cannot Avoidance will generate non-sinusoidal waveforms and inject harmonics into the grid, which has become a "public nuisance" in the grid. Harmonic suppression devices mainly include passive power filters or active power filters. [0003] Although the passive filter used alone is low in cost and simple in structure, the filtering effect is greatly affected by the grid impedance and its own parameter changes, and it is easy to resonate with the grid impedance. Although the active power filter used alone has go...

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Problems solved by technology

[0003] Although the passive filter used alone is low in cost and simple in structure, the filtering effect is greatly affected by the grid impedance and its own parameter changes, and it is easy to resonate with the grid impedance

Although the active power filter used alone has good filtering performance, the cost is relatively high, especially in high-voltage and high-power occasions such as substations, it is difficult to apply

[0004] In the existing hybrid active power filter which combines the active power filter APF and the passive filter PF, although these hybrid forms reduce the capacity of the active part, the parallel APF+parallel PF form still bears the basic Wave voltage, and there are multiple harmonic channels in the system, APF will inject harmonics into the grid branch; the connection transformer in the form of series APF+parallel PF flows through the fundamental wave current of the load, and the insulation and maintenance of the active part are difficult; Parallel resonance The injection type APF does not have reactive power compensation capability; it is difficult to obtain better harmonic compensation performance and smaller active part capacity at the same time for the series resonance injection type APF, and the capacitance at the upper end of the branch will be large; the APF and PF The form of series connection and then parallel connection to the power grid is called SCAP (Series Connected APF and PF). This form of insulation and maintenance is more convenient, and it is very suitable for high-voltage system applications, but generally in order to reduce the fundamental voltage borne by the active part and the fundamental wave current flowing through it, the fundamental wave impedance of PF is very large, so this system is not suitable for applications requiring reactive power compensation

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