Inverter positive and negative sequence impedance measurement method based on sampling signal disturbance superposition

Abstract

The invention discloses an inverter positive and negative sequence impedance measurement method based on sampling signal disturbance superposition, and the method comprises the steps: S1, switching on a switch, superposing positive sequence disturbance current signals with different frequencies in current sampling signals of grid-connected points, and measuring and recording a group of three-phase voltages and three-phase currents of the corresponding grid-connected points; s2, disconnecting a switch, connecting an inductor in series into an inverter positive and negative sequence impedance measurement circuit, superposing a positive sequence disturbance current signal which is the same as S1 in a current sampling signal of a grid-connected point, keeping the amplitude and the frequency consistent with those in S1, and measuring and recording a group of three-phase voltage and three-phase current of the corresponding grid-connected point; s3, calculating the positive sequence impedance of the three-phase grid-connected inverter through the three-phase voltage and the three-phase current of the two groups of grid-connected points obtained in S1 and S2; and S4, changing the superposed positive-sequence disturbance current signal into a negative-sequence disturbance current signal, and repeating the steps S1 to S3 to obtain the negative-sequence impedance of the three-phase grid-connected inverter. According to the invention, a large power supply for generating a disturbance signal in a main loop is saved, and the cost is greatly reduced.

Description

technical field [0001] The invention relates to the technical field of impedance measurement, in particular to a method for measuring the positive and negative sequence impedance of an inverter based on the disturbance superposition of sampling signals, and in particular to a positive and negative sequence impedance measurement method of a three-phase grid-connected inverter based on the superposition of disturbance signals by resampling signals. Sequence impedance measurement method. Background technique [0002] At this stage, my country is striving to build a clean, low-carbon, safe and efficient energy system, and build a new power system based on new energy. In the new energy power generation system, photovoltaic, wind power, energy storage and other units are mainly integrated into the power grid through power electronic conversion devices. Therefore, with the increasing penetration of new energy in the modern power grid, the power electronic characteristics of the pow...

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Problems solved by technology

[0004] Disturbance injection is the main method to realize inverter impedance measurement. The existing disturbance injection method mainly injects harmonic voltage or harmonic current into the high-voltage main circuit. The generation of harmonic signals depends on additional power electronic control devices. The waveform of the injected signal , amplitude and frequency are flexible and controllable, and the impedance measurement accuracy is high, but the disturbance injection of the primary side high-voltage main circuit is easy to change the operating conditions of the system, and additional equipment is required, which increases the cost and is not conducive to practical promotion

For this reason, a method of injecting small-signal disturbances into the control system of the secondary side of the inverter has been proposed, which does not require additional impedance measurement devices. The disturbance injection and detection are implemented inside the controller, which limits the practical application of this method to a certain extent

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