H6 one-phase non-isolated photovoltaic grid-connected inverter and modulation method thereof

Abstract

The invention provides an H6 one-phase non-isolated photovoltaic grid-connected inverter, comprising six switch tubes, a filtration module and a modulation circuit module, wherein a source of the first switch tube is connected with the drain of the second switch tube and one end of an alternating current side; the source of the second switch tube is connected with the source of the fourth switch tube and the drain of the six switch tube; the drain of the fourth switch tube is connected with the source of the third switch tube and the other side of the alternating current side; the drain of the third switch tube is connected with the drain of the first switch tube and the source of the fifth switch tube; the drain of the fifth switch tube is connected with the positive electrode end of a direct current side; the source of the six switch tube is connected with the negative electrode end of the direct current side. By using the inverter, the common mode current harm is effectively eliminated, and the modulation method has a three-level modulation effect; in addition, only two switch tubes work at high frequency, the other four switch tubes work at a half of the frequency, the total harmonic distortion of grid-connected current is reduced, and the efficiency is improved. The invention also provides a modulation method of the H6 one-phase non-isolated photovoltaic grid-connected inverter.

Description

Technical field [0001] The present invention relates to the technical field of power electronic power conversion, in particular to a H6 single-phase non-isolated photovoltaic grid-connected inverter and a modulation method of the H6 single-phase non-isolated photovoltaic grid-connected inverter. Background technique [0002] In the distributed power generation system with solar energy as input, the grid-connected inverter has the function of converting DC power into AC power that meets the requirements of the city power and connecting it to the grid. Traditional grid-connected systems often use isolated grid-connected inverters with output transformers to produce electrical isolation between the grid and the DC side to ensure personal safety. It can also provide voltage matching and grid-connected current DC component suppression, but power frequency transformers The volume, weight and cost are increased, and the high-frequency transformer complicates the control and reduces the ...

AI Technical Summary

Problems solved by technology

[0005] For ordinary full-bridge grid-connected inverters, such as figure 2 As shown, when using bipolar SPWM modulation, this method has very good common mode characteristics, but has relatively low conversion efficiency and poor grid-connected current quality

When the unipolar SPWM modulation method is used, it has the advantages of small grid-connected current ripple and easy filtering, etc., but at the same time it produces a high-frequency pulsating common-mode voltage, which has poor common-mode characteristics, making it suitable for use in non-isolated full-scale Direct application in bridge-connected inverters is limited

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