Suppression Method of Second Harmonic Current Input to Two-stage Single-phase Inverter

Abstract

Disclosed is an inhibition method for input second-harmonic current of a two-level single-phase inverter. The method is not only capable of inhibiting significantly the input second-harmonic current, but also capable of reducing dependence on a DC busbar filtering capacitor. The method multiplies output inductive current sampling signals of a preceding-stage DC-DC convertor and modulating signals of a DC-DC convertor through a multiplying unit. Output signals of the multiplying unit pass a band-pass filter, and then together with the inductive current sampling signals which pass a follower, are used as feedback signals of a current regulator. Output signals of a voltage regulator are used as a reference of the current regulator. The current regulator generates modulating signals and sends the modulating signals into a PWM modulator and at last through a driving circuit, driving signals which control main power tubes Q1-Qn of a Buck-class DC-DC convertor to work are obtained. The method has the advantages of being capable of directly inhibiting a second-harmonic component of input current of the two-level single-phase inverter, simple in structure of control circuit and convenient to realize and the like.

Description

Technical field: [0001] The invention relates to a method for suppressing the second harmonic current input by a two-stage single-phase inverter, which belongs to the control technology in electric energy conversion devices. Background technique: [0002] At present, distributed power generation systems such as new energy, aircraft and electric vehicles are usually compatible with traditional low-voltage DC power supply system specifications, such as 28V, 42V and other DC power supplies. In order to obtain the 115V or 220V AC required by the load, it is usually necessary to adopt a two-stage structure - the front-stage DC-DC converter completes the inverter input and output voltage matching and electrical isolation, and the rear-stage inverter completes the DC-to-AC conversion and supplies the terminal power supply to the load. [0003] In the two-stage single-phase inverter, since the instantaneous output power of the latter stage inverter contains pulsating power of twice...

AI Technical Summary

Problems solved by technology

The second harmonic current will not only increase the current stress of the switch tube, but also increase the conduction loss of the switch tube and the loss of magnetic components, and will affect the soft switching of the switch tube, which is not conducive to improving the efficiency of the converter

On the other hand, the double-frequency low-frequency pulsation in the input current will cause interference to the input source, affect the performance of the input source, and have a major impact on the life of new energy sources such as fuel cells. The standard stipulates that it must be controlled at a small value

[0004] Increasing the DC bus capacitance is the easiest way to suppress the pulsating current, but this will increase the volume of the system, which is not conducive to the improvement of the power density of the converter

The method of paralleling the bidirectional converter on the DC bus can achieve the effect of suppressing the pulsating current without increasing the bus capacitance, but this increases the complexity of the system and is not conducive to the improvement of reliability

For the direct-to-direct converter with double-loop control, methods such as adding a band-stop filter to the output of the voltage loop, adding a band-pass filter to the current sampling link, and virtual impedance can effectively suppress the input current ripple, but the essence is to suppress the inductance The current pulsation is realized indirectly, and its suppression effect depends entirely on the size of the DC bus capacitor, and the suppression effect is limited

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