A Control Method of Active Harmonic Resistance Applied to Parallel Capacitors

Abstract

The invention discloses a control method for an active harmonic resistor applied to a shunt capacitor. The control method includes the steps that (1) the optimal harmonic resistance ru is obtained according to power grid impedance Zs and reactive power compensation network impedance Zf; (2) a reactive power compensation branch current If is detected, a harmonic current Ifh is obtained through a detecting algorithm according to the reactive power compensation branch current If, and then a harmonic voltage instruction is obtained according to the optimal harmonic resistance ru and the harmonic current Ifh; (3) converter direct-current side voltage is detected, and a fundamental wave voltage instruction is obtained by multiplying the difference value between the converter direct-current side voltage and a preset voltage value by the phase of a converter alternating-current side current; (4) the result obtained by adding the fundamental wave voltage instruction and the harmonic voltage instruction is subtracted from a converter alternating-current side voltage feedback signal, error accumulation is conducted on the subtracted result, harmonic voltage is generated according to the error accumulation result, and the active harmonic resistor is controlled according to the harmonic voltage to suppress harmonic vibration. The active harmonic resistor is controlled so that harmonic vibration can be suppressed, and operation is simple.

Description

technical field [0001] The invention belongs to the technical field of power quality control of electric power systems, and relates to a control method for active harmonic resistance applied to parallel capacitors. Background technique [0002] In power systems, shunt capacitors are often used for reactive power compensation. However, with the wide application of non-linear loads in power systems, harmonic currents and voltages will be generated, plus background harmonics of the power grid, which will cause resonance between reactive power compensation capacitors and grid line inductance, triggering harmonics of shunt capacitors Protection and trip, affecting the normal reactive power compensation. [0003] Usually, a series reactor is connected to the capacitor to suppress resonance. The design method of the series reactor is as follows: when the lowest harmonic content of the grid is 3rd, the capacity of the series reactor is 12% of the parallel capacitor; when the lowes...

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Problems solved by technology

However, this method has certain limitations. When the harmonic spectrum of the power grid changes, the series reactor cannot guarantee that the reactive power branch is always inductive in all harmonic bands, and the harmonics may still be amplified.

Frequently changing the capacity of the series reactor will bring great trouble to the actual operation.

Another method is to use a hybrid active power filter for resonance suppression, but the hybrid filter is very sensitive to system parameters, and changes in system parameters will make its control effect worse

In addition, in the high-voltage system, voltage and current sensors will be added, and the corresponding cost will increase, which is not conducive to the promotion of hybrid filters

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