Control method suitable for universal input voltage buck-boost grid-connected inverter

Abstract

The invention discloses a control method suitable for a universal input voltage buck-boost grid-connected inverter and belongs to an inverter control method. According to the method, an input voltage feedback signal is subjected to given comparison with switching voltage to output a gating switch control signal, when the gating switch control signal is at a low level, the universal input voltage buck-boost grid-connected inverter works in a buck-boost mode, a first power switching tube, a second power switching tube, a fifth power switching tube and a sixth power switching tube are turned on and off at high frequency within a half power frequency period, and a third power switching tube and a fourth power switching tube are turned on and off at high frequency within the whole power frequency period; and when the gating switch control signal is at a high level, the universal input voltage buck-boost grid-connected inverter works in a step-down mode, the first power switching tube, the second power switching tube, the third power switching tube and the fourth power switching tube are turned on and off at the power frequency, and the fifth power switching tube and the sixth power switching tube are turned on and off at high frequency within the half power frequency period. The method is suitable for the grid-connected inverter with universal input voltage and buck-boost conversion, the weight and the size of a filter inductor are reduced, the voltage and current stresses of the power switching tubes are reduced, the conversion efficiency is improved, the cost is reduced, the problem of direct connection of the power switching tubes of the bridge-type inverter bridge arm is solved, and the reliability is improved.

Description

technical field [0001] The invention relates to a control method of an inverter, in particular to a control method suitable for a wide input voltage buck-boost grid-connected inverter. Background technique [0002] In recent years, with the increasing environmental pollution and the continuous shortage of fossil energy, renewable energy has attracted more and more attention due to its advantages of cleanness, safety, pollution-free, and renewable. The output of solar cells and fuel cells is direct current, while the grid voltage is alternating current. Therefore, grid-connected inverters become an important part of distributed power generation systems. Since the output voltage range of solar cells and fuel cells is wide, such as 200-500V, sometimes it is lower than the grid voltage, sometimes it is higher than the grid voltage. Adding a pre-stage DC-DC converter increases the complexity of the system, reduces the reliability and increases the cost of the system. The disclo...

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Problems solved by technology

However, the proposed control method can only work in the buck-boost mode; there are 2 power switch tubes that switch at high frequency in the entire power frequency cycle, and 4 power switch tubes that switch at high frequency in half the power frequency cycle, and the switching loss is relatively low. High; the voltage stress of two power switch tubes is the sum of the input voltage and the output voltage of the inverter itself. If the input voltage is 500V and the peak output voltage of the inverter itself is 311V, the voltage that the power switch tubes withstand is 811V. It is difficult to select high-frequency switching MOS transistors with such high voltage stress

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