Z source reverser and soft start method

Abstract

The present invention provides a z-source inverter and its soft starting method, belonging to power electronic converter. The inverter main circuit is composed of a DC voltage source, a three-phase inverter bridge, a z-source network, a power diode, characterized in that the positive end of the three-phase inverter bridge is connected to the cathode of the DC voltage source, the negative end of the three-phase inverter bridge is connected to the Z source network. Compared with the voltage source type and the current source type inverter, the Z source inverter realizes pressure raising change function, and the upper and the lower switch tubes of the same bridge arm are directly passing, so the dead zone does not need, the circuit structure is simple, having high credibility. Compared with the traditional Z source inverter, the capacitor voltage of the Z source network in the Z source inverter has small stress, and realizing the soft start of the transformer, avoiding the problems of large voltage and current when the traditional Z source inverter starts, the work of the transformer is safe and credible, and having light volume and weight.

Description

1. Technical field [0001] The Z-source inverter and its soft-start method involved in the present invention belong to power electronic converters. 2. Background technology [0002] Inverters are widely used in motor drives, uninterruptible power supplies, induction heating, static var generators and compensators, and active filtering. Traditional inverter circuit topologies include voltage source inverters and current source inverters. [0003] attached figure 1 It is the main circuit of the voltage source inverter. The circuit is composed of a DC voltage source and a three-phase inverter bridge. The inverter bridge is composed of six power switches. Each power switch is connected in parallel with a body diode to provide bidirectional current flow and unidirectional voltage blocking capability. The voltage source inverter has the following defects: 1) The output AC voltage is lower than the DC bus voltage, so the voltage source inverter is essentially a step-down inverter...

AI Technical Summary

Problems solved by technology

The voltage source inverter has the following defects: 1) The output AC voltage is lower than the DC bus voltage, so the voltage source inverter is essentially a step-down inverter. In order to realize the function of boost conversion, it is necessary to add an additional 2) The upper and lower switching tubes of the same bridge arm cannot be turned on at the same time, otherwise it will cause a short circuit of the input voltage source, causing damage to the circuit, and the switching caused by electromagnetic interference Turning on the tube by mistake will also damage the circuit; 3) Dead time needs to be added between the upper and lower switching tubes of the same bridge arm, but this will cause distortion of the output waveform

The current source inverter has the following defects: 1) The output AC voltage is higher than the DC bus voltage, so the voltage source inverter is essentially a step-up inverter. In order to realize the function of step-down conversion, an additional 2) At any time, at least one of the three switches at the upper end of the bridge arm must be turned on, and at least one of the lower switch tubes must be turned on at the same time, otherwise the input current source will be blocked. Open circuit will cause damage to the circuit, and the wrong turn-off of the switch tube caused by electromagnetic interference will also damage the circuit; 3) The commutation overlap time must be added when the switch tube is switched, but this will cause distortion of the output waveform

However, the traditional Z-source inverter also has the following disadvantages: 1) The capacitor voltage in the Z-source network is not less than the input voltage, which leads to a large voltage stress, requiring high-voltage capacitors, and the volume and cost of the converter are relatively high; 2) The start-up of the converter The inrush current is very large, and the resonance between the capacitor and the inductor in the Z source network, the stress on the components is large, and the soft start of the converter cannot be realized, all of which may damage the converter

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