The influencing factor of the arc welding inverter power supply is the filtering interference. Filter interference not only affects work efficiency, but can even lead to dangerous situations. Therefore, harmonic suppression in the arc welding inverter power supply is particularly important. This article will detail the active and passive filtering in the arc welding inverter power supply.
Passive filter
The traditional method of harmonic suppression and reactive power compensation is power passive filtering technology, also known as indirect filtering method, which uses passive components such as power capacitors to form a passive filter, which is connected in parallel with a nonlinear load that needs to be compensated. The wave provides a low impedance path while providing the reactive power required by the load. Specifically, the distorted 50 Hz sine wave is decomposed into the fundamental wave and the associated main harmonic components, and then the respective filtering branches composed of L, C (or also R) are tuned by using the series resonance principle (or Offset tuning) to the main harmonic frequencies to form a low resistance channel and filter it out. It passively defends against the harmonics that have caused harmonics to electrical equipment.
The passive filtering scheme is low in cost and mature in technology, but it also has the following disadvantages:
(1) The filtering effect is affected by the impedance of the system;
(2) Due to the fixed resonant frequency, the effect on the frequency offset is not good;
(3) It may occur in series or parallel resonance with the system impedance, causing overload.
In the case of small and medium power, it is gradually being replaced by an active filter.
Active filter (AcTIveFi1ter, AF for short)
As early as the early 1970s, some scholars proposed the basic principle of active power filters. However, due to the lack of high-power switching elements and corresponding control techniques at that time, only linear amplifiers and other methods can be used to generate compensation currents. The Achilles heel, such as high cost and difficulty in increasing capacity, has not been put into practical use. With the improvement of the performance of power semiconductor switching components and the development of corresponding PWM technology, it is possible to develop a large-capacity and low-loss harmonic current generator, which makes the active filtering technology practical, when harmonics occur in the system. When the source is generated, a compensation current having the same magnitude and opposite phase as the harmonic current is generated by a method, and is connected in parallel with the circuit which is the source of the harmonic generation to cancel the harmonic of the harmonic generation source, so that the current on the DC side is only The fundamental component does not contain harmonic components.
When the harmonic generated by the harmonic generation source cannot be predicted as the high-order harmonic current and changes at any time, the harmonic current ih signal must be detected from the load current il, and the detected harmonic current The ih signal is modulated by the modulator and converted into a switching mode to control the current inverter operating mode according to the established method, so that the current inverter generates a compensation current ifm and injects into the circuit to cancel the harmonic current ih. The circuit generally adopts a DC/AC full-bridge inverter circuit, in which the switching element can be a high-power controllable power semiconductor component such as GTO, GTR, SIT or IGBT, and the output current waveform is controlled by the switching element switching. The required compensation current.
The active power filter is the most promising power device for suppressing the harmonics of the power grid and compensating for reactive power and improving the power quality of the power grid. Compared with the passive power filter, the power active filter has the following advantages:
(1) Dynamic compensation is realized, which can compensate for harmonics with varying frequency and size and varying reactive power, and has an extremely fast response to changes in the compensation object.
(2) The harmonic and reactive power can be compensated at the same time, and the magnitude of the compensated reactive power can be continuously adjusted.
(3) There is no need for energy storage components when compensating for reactive power, and the capacity of energy storage components required for compensating harmonics is not large.
(4) Even if the compensation target current is too large, the power active filter will not be overloaded and the compensation function can be performed normally.
(5) It is not affected by the impedance of the grid, and it is not easy to resonate with the impedance of the grid.
(6) The change of the grid frequency can be tracked, so the compensation performance is not affected by the frequency change.
(7) It can compensate for one harmonic and reactive power separately, and can also compensate for multiple harmonics and reactive power.
This paper mainly explains the harmonic suppression measures in the arc welding inverter power supply. Through the introduction of the two filtering methods of the edgeless filtering and the active filtering, it helps everyone to understand how to effectively realize the harmonics in the arc welding inverter power supply. Suppression, in the following article, Xiaobian will introduce the soft-switching technology for suppressing harmonics. I hope everyone can continue to pay attention.
Passive filter
The traditional method of harmonic suppression and reactive power compensation is power passive filtering technology, also known as indirect filtering method, which uses passive components such as power capacitors to form a passive filter, which is connected in parallel with a nonlinear load that needs to be compensated. The wave provides a low impedance path while providing the reactive power required by the load. Specifically, the distorted 50 Hz sine wave is decomposed into the fundamental wave and the associated main harmonic components, and then the respective filtering branches composed of L, C (or also R) are tuned by using the series resonance principle (or Offset tuning) to the main harmonic frequencies to form a low resistance channel and filter it out. It passively defends against the harmonics that have caused harmonics to electrical equipment.
The passive filtering scheme is low in cost and mature in technology, but it also has the following disadvantages:
(1) The filtering effect is affected by the impedance of the system;
(2) Due to the fixed resonant frequency, the effect on the frequency offset is not good;
(3) It may occur in series or parallel resonance with the system impedance, causing overload.
In the case of small and medium power, it is gradually being replaced by an active filter.
Active filter (AcTIveFi1ter, AF for short)
As early as the early 1970s, some scholars proposed the basic principle of active power filters. However, due to the lack of high-power switching elements and corresponding control techniques at that time, only linear amplifiers and other methods can be used to generate compensation currents. The Achilles heel, such as high cost and difficulty in increasing capacity, has not been put into practical use. With the improvement of the performance of power semiconductor switching components and the development of corresponding PWM technology, it is possible to develop a large-capacity and low-loss harmonic current generator, which makes the active filtering technology practical, when harmonics occur in the system. When the source is generated, a compensation current having the same magnitude and opposite phase as the harmonic current is generated by a method, and is connected in parallel with the circuit which is the source of the harmonic generation to cancel the harmonic of the harmonic generation source, so that the current on the DC side is only The fundamental component does not contain harmonic components.
When the harmonic generated by the harmonic generation source cannot be predicted as the high-order harmonic current and changes at any time, the harmonic current ih signal must be detected from the load current il, and the detected harmonic current The ih signal is modulated by the modulator and converted into a switching mode to control the current inverter operating mode according to the established method, so that the current inverter generates a compensation current ifm and injects into the circuit to cancel the harmonic current ih. The circuit generally adopts a DC/AC full-bridge inverter circuit, in which the switching element can be a high-power controllable power semiconductor component such as GTO, GTR, SIT or IGBT, and the output current waveform is controlled by the switching element switching. The required compensation current.
The active power filter is the most promising power device for suppressing the harmonics of the power grid and compensating for reactive power and improving the power quality of the power grid. Compared with the passive power filter, the power active filter has the following advantages:
(1) Dynamic compensation is realized, which can compensate for harmonics with varying frequency and size and varying reactive power, and has an extremely fast response to changes in the compensation object.
(2) The harmonic and reactive power can be compensated at the same time, and the magnitude of the compensated reactive power can be continuously adjusted.
(3) There is no need for energy storage components when compensating for reactive power, and the capacity of energy storage components required for compensating harmonics is not large.
(4) Even if the compensation target current is too large, the power active filter will not be overloaded and the compensation function can be performed normally.
(5) It is not affected by the impedance of the grid, and it is not easy to resonate with the impedance of the grid.
(6) The change of the grid frequency can be tracked, so the compensation performance is not affected by the frequency change.
(7) It can compensate for one harmonic and reactive power separately, and can also compensate for multiple harmonics and reactive power.
This paper mainly explains the harmonic suppression measures in the arc welding inverter power supply. Through the introduction of the two filtering methods of the edgeless filtering and the active filtering, it helps everyone to understand how to effectively realize the harmonics in the arc welding inverter power supply. Suppression, in the following article, Xiaobian will introduce the soft-switching technology for suppressing harmonics. I hope everyone can continue to pay attention.
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