AC chopper and chopping method thereof

Abstract

The invention provides an AC chopper and a chopping method thereof. The chopper is connected between an AC power source and a load, and comprises a switch group, an inductor, a current polarity detector and a switch-control logic unit, wherein the switch group comprises a plurality of switches and is connected with the AC power source; one end of the inductor is connected with the switch group, and the other end of the inductor is connected with the load; the current polarity detector is connected between the inductor and the load and is used to detect the direction of current output to the load by the chopper at the moment of switching switch states; and the switch-control logic unit receives current-direction signals sent by the current polarity detector and sends different control time-sequence signals to a plurality of switches according to the current-direction signals so as to control the turn-on sequence of the switches and convert the inductor mutually between a follow-current state and a charged state. As the method is based on current polarity but not voltage polarity to perform detection, input-voltage short circuit does not exist at any moment. In addition, the method detects current polarity only at the moment of switching switch states, and is a non-continuous detection method, thus systems are not easy to oscillate.

Description

technical field [0001] The invention relates to an AC converter, in particular to an AC chopper and a chopping method for realizing power conversion by using a switch mode. Background technique [0002] As a relatively mature AC voltage regulation technology, phase-controlled rectification technology has replaced electromagnetic voltage regulation technology in many occasions and has been widely used. However, the phase-controlled rectification technology has many insurmountable defects, such as low power factor affected by the firing angle, slow dynamic response speed, rich output low-order harmonics, and serious grid harmonic current pollution. In recent years, the AC chopper based on the simple topology of the DC chopper has become a new research hotspot. The AC chopper control voltage regulation technology has the advantages of only depending on the power factor of the load, fast dynamic response speed, wide linear voltage regulation range, easy filtering of input and o...

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Problems solved by technology

Moreover, in the above-mentioned AC chopper topology based on input voltage polarity detection, the state of the switch at any time is related to the polarity of the input voltage, which requires continuous feedback of the input voltage polarity into the non-linear block of the circuit , the fluctuation of the voltage at the zero-crossing point can easily cause the oscillation of the system

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