Alternating current converter and conversion method thereof

Abstract

The alternating current converter comprises a control chip and a CPLD module which are connected with each other. The CPLD module is connected with an upper half-bridge driver and a lower half-bridgedriver, the upper half-bridge driver is connected to an upper half-bridge switch module, and the lower half-bridge driver is connected to a lower half-bridge switch module. The output ends of the upper half-bridge switch module and the lower half-bridge switch module are in differential connection and then are connected to the filtering module, the waveform amplitudes of two output voltages of theupper half-bridge switch module and the lower half-bridge switch module are equal, the phase difference is 180 degrees, and the control chip is used for outputting an upper half-bridge control signal, a lower half-bridge control signal and a waveform phase adjustment signal to the CPLD module; the CPLD module is used for correspondingly outputting an upper half-bridge SPWM signal and a lower half-bridge SPWM signal to the upper half-bridge driver and the lower half-bridge driver respectively, and the upper half-bridge SPWM signal and the lower half-bridge SPWM signal are symmetrical to each other. Compared with the prior art, the degree of distortion of output voltage waveforms can be reduced, no transformer is arranged in the alternating-current converter, and the alternating-current converter has the advantages of being small in size, light in weight and large in power density.

Description

technical field [0001] The invention relates to the technical field of power electronic conversion, in particular to an AC converter and a conversion method thereof. Background technique [0002] In the process of electrical testing, it is often necessary to provide a pure sinusoidal AC excitation signal from an AC sinusoidal voltage source, and in some test occasions, there are relatively strict requirements on the distortion and volume of the AC sinusoidal voltage source. For example, on-site testing of partial discharge and dielectric loss of high-voltage motors, due to safety and site reasons, large voltage sources cannot be placed, and most of the existing AC voltage sources are bulky and heavy, and they are not very convenient to carry and use. [0003] For laboratories and scientific research institutes, due to the small space and dense experimental equipment, it is not only impossible to place a large AC voltage source, but also the requirements for the distortion of...

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Problems solved by technology

[0005]However, the driving circuit of the full-bridge topology is complex, and due to reasons such as dead time and inconsistent characteristics of the switching tubes, the output voltage inevitably contains a DC component; the half-bridge topology The structure is simple, but the voltage obtained at both ends of the load is low, only half of the DC power supply voltage, and the DC side needs to use two capacitors in series to balance the voltage, the output power is low, the collector current of the power switch tube is large, and the half-bridge topology It can only be used in low-power devices below a few kilowatts; the push-pull topology is simple, the two power tubes can be driven by the same ground, and can output large-capacity power, but the power tube withstands a DC voltage that is twice the switching voltage. The voltage peak value is large, and it is only suitable for applications with low DC bus voltage. In addition, the utilization rate of the transformer is low, and it is difficult to drive inductive loads.

In order to eliminate the DC component and stabilize the voltage, the output terminals of the above three topologies must be connected to a transformer. The existence of the transformer will reduce the power density and frequency range on the one hand, and directly increase the volume, weight and cost on the other hand. Not easy to carry and use

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