Transformer-free type low-leakage-current photovoltaic grid-connected inverter circuit with active clamp and modulation method thereof

Abstract

The invention discloses a transformer-free type low-leakage-current photovoltaic grid-connected inverter circuit with an active clamp and a modulation method thereof. The transformer-free type low-leakage-current photovoltaic grid-connected inverter circuit with the active clamp comprises two filter capacitors Cdc1, Cdc2, eight switch tubes S1, S2, S3, S4, S5, S6, S7, S8 and two filter inductors L1, L2, and is characterized in that an active switch tube is additionally arranged in the circuit so as to form a clamping unit, common-mode voltage in a grid-connected inductance follow current stage is clamped to the midpoint of a bus capacitor by being matched with an appropriate switching sequence, common-mode voltage disturbance of the system is removed, and thus a suspension problem of common-mode voltage of a decoupling inverter in zero level output is solved; and parasitic oscillation of a common-mode circuit is removed at the same time, and a phenomenon of common-mode resonance is suppressed. The photovoltaic grid-connected inverter circuit disclosed by the invention has the advantages of simple circuit structure, high efficiency, simple modulation method and the like. The photovoltaic grid-connected inverter circuit can ensure an inverter not to be affected by a current zero crossing point in unit power factor running, and can avoid current waveform distortion caused by influences of grid power fluctuations or operations at a non unit power factor.

Description

technical field [0001] The invention belongs to the technical field of photovoltaic grid-connected power generation of power electronics technology, and specifically relates to an active-clamp transformerless low-leakage current photovoltaic grid-connected inverter circuit and a modulation method thereof. Background technique [0002] In recent years, with the continuous reduction of the cost of photovoltaic grid-connected power generation systems, distributed photovoltaic grid-connected power generation has been widely used and developed rapidly. However, photovoltaic grid-connected systems have high initial investment and long cost recovery period, so how to further reduce system power generation costs and improve system power generation efficiency and system reliability has become a hot spot of concern. [0003] As an important interface for electric energy conversion, the choice of photovoltaic grid-connected inverter scheme is directly related to the efficiency, reliabi...

AI Technical Summary

Problems solved by technology

However, since the common-mode voltage of the system is in a suspended state during the freewheeling phase of the grid-connected inductor, it is affected by the circuit parasitic parameters of the common-mode loop and the zero-crossing distortion of the grid voltage, which inevitably causes high-frequency common-mode leakage current, that is, suppresses The leakage current is not thorough, and the problem is not fundamentally solved, which will still cause the above hidden dangers

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