Two-stage single phase three-level T-shaped asymmetric inverter as well as control method and device

Abstract

The invention discloses a two-stage single phase three-level T-shaped asymmetric inverter, comprising a three-level Boost converter a single phase T-shaped asymmetric inverter connected with the three-level Boost converter, due to adoption of the T-shaped circuit of the inverter disclosed by the invention, compared with an I-shaped circuit in the prior art, a clamping diode does not need to be added, cost is reduced, power loss is avoided, and a circuit structure is also simplified. The invention also discloses a control method used for the inverter, and by adopting the provided control method, a numerical value of the obtained common mode voltage is relatively single. Number of times that the common mode voltage transforms in a predetermined cycle is fewer, a produced leakage current alsocan be correspondingly relatively small, and normal operation of the inverter is guaranteed. Besides, the invention also discloses a control device used for the inverter, and the effects of the control device are as mentioned above.

Description

technical field [0001] The invention relates to the technical field of power electronics, in particular to a two-stage single-phase three-level T-shaped asymmetrical inverter, a control method and a device. Background technique [0002] With the rapid development of photovoltaic power generation, as the core equipment of photovoltaic system and grid interface, photovoltaic inverter has become a research hotspot in its topology and control mode. In the non-isolated photovoltaic grid-connected inverter, there is a large ground-to-ground parasitic capacitance between the photovoltaic array and the ground, forming a common-mode resonant circuit composed of parasitic capacitance, filter elements and grid impedance. At the same time, under the high-frequency switching action of the inverter, a common-mode current will be generated. When the common-mode current flows through the resonant circuit, the parasitic capacitance of the photovoltaic array to the ground will generate a leak...

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Problems solved by technology

At the same time, under the high-frequency switching action of the inverter, a common-mode current will be generated. When the common-mode current flows through the resonant circuit, the parasitic capacitance of the photovoltaic array to the ground will generate a leakage current. The leakage current will not only reduce the grid-connected current quality, causing current distortion, increasing harmonics and losses, and also bringing electromagnetic interference problems, reducing system safety and reliability, and even endangering equipment and personal safety

[0003] At present, the commonly used inverter is a two-stage single-phase three-level I-type asymmetrical inverter, please refer to figure 1 , figure 1 It is the post-stage structure of the post-stage I-type circuit in the two-stage single-phase three-level I-type asymmetrical inverter in the prior art, and the post-stage structure of the post-stage I-type circuit of the inverter adopting this structure need to add clamping diodes, such as figure 1 D in 3 and D 4 (i.e. the diode in the dotted box), and increase the clamping diode D 3 and D 4 Not only will it increase the cost, but the clamp diode will also have power loss

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