Transformer-free unilateral inductor grid-connected inverter circuit

Abstract

The invention relates to a transformer-free unilateral inductor grid-connected inverter circuit which comprises a high-frequency bridge arm, a low-frequency bridge arm, an output module and a control switching tube speed unit, wherein the high-frequency bridge arm and the low-frequency bridge arm are respectively connected to a direct current input power supply and the output module; the output module is connected to a mains supply; the high-frequency bridge arm is provided with two high-frequency switching tubes; the low-frequency bridge arm is provided with two low-frequency switching tubes; the output module is in the form of a unilateral inductor; an inductor in the output module is connected to the null line end or power line end of the mains supply; the end, which is not connected to the inductor, of the output module is connected to the low-frequency bridge arm; and the end, which is connected to the inductor, of the output module is connected to the high-frequency bridge arm. The transformer-free unilateral inductor grid-connected inverter circuit provided by the invention is used for greatly reducing the common mode current of the direct current input power supply to the ground and improving the working efficiency of a whole machine. The amplitude value of the common mode current can be reduced under the condition of controlling a switching speed, thereby achieving an effect of controlling the electromagnetic interference and improving the efficiency of the whole machine. Besides, the transformer-free unilateral inductor grid-connected inverter circuit has the advantages that the adopted elements are small and the cost is lower.

Description

technical field [0001] The invention relates to a single-side inductance grid-connected inverter circuit without a transformer. Background technique [0002] In the photovoltaic grid-connected system, due to the parasitic capacitance between the photovoltaic panel and the ground, common-mode current will be generated during the process of photovoltaic grid-connected power generation, which increases electromagnetic radiation and potential safety hazards. In order to try to suppress the generation of this common-mode current, There are two main solutions: 1. Use an isolated photovoltaic grid-connected inverter with a power frequency or high frequency transformer, so that the mains and the solar panel system can be electrically isolated, and the impact of the panel on the ground can be avoided. leakage current. 2. Adopt a non-isolated grid-connected topology that can effectively suppress the magnitude of common-mode current. [0003] However, the inverter circuit using trans...

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Problems solved by technology

[0003]However, the inverter circuit using transformer isolation has the following disadvantages: If a power frequency transformer is used, it will be bulky, heavy and expensive

[0004]The general non-isolated inverter topology has several defects:

[0005] 1. If the traditional single-phase full-bridge inverter adopts bipolar modulation, although the electromagnetic interference is small, the conversion efficiency of the inverter is low.

[0006] 2. If the traditional single-phase full-bridge inverter adopts unipolar modulation, the electromagnetic interference will be serious and the common-mode current will be large

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