Three-level half-bridge photovoltaic grid connected inverter

Abstract

The invention provides a three-level half-bridge photovoltaic grid connected inverter, which comprises a power frequency switching circuit and a half bridge inverter circuit; the input side of the inverter is connected with a solar photovoltaic battery board, while the output side of the inverter is connected with a power grid through a grid connected inductor; two power switch tubes in the power frequency switching circuit are switched by zero-crossing triggering of a power frequency power grid voltage, and the two power switch tubes work in a low frequency mode and alternately connect the voltage of a solar battery board into the two ends of a corresponding voltage-sharing capacitor on a direct current bus so as to realize the aim of reducing a direct current voltage input by the inverter and increasing the utilization rate of the direct current voltage; and therefore, the switch loss is reduced, and the system efficiency is improved.

Description

technical field [0001] The invention relates to an inverter, in particular to a three-level half-bridge photovoltaic grid-connected inverter. Background technique [0002] Today, with the gradual shortage of fossil energy and the increasingly serious environmental pollution problems, solar photovoltaic grid-connected power generation, which is a clean and air-free energy source, is more and more popular among people. Undoubtedly, the photovoltaic grid-connected inverter is the core of the energy conversion and control of the entire grid-connected photovoltaic system. Power Point Tracking (MPPT). [0003] In the medium-high-voltage and high-power occasions, multilevel inverters have become a research hotspot in the current power electronics technology. The three-level half-bridge inverter is a kind of multi-level inverter that appeared earlier. On the one hand, because its bridge arm has three output levels of +1, 0, and -1, the same output voltage harmonic Under standard ...

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Problems solved by technology

However, due to the addition of an additional stage of conversion circuit, it will definitely reduce the efficiency of the entire system, and the technical threshold of the isolated high-frequency chain DC / DC converter is high, and it is not easy to realize

In addition, the traditional three-level half-bridge inverter has fluctuations in the midpoint potential (O) of the DC capacitor during actual implementation, and the midpoint potential fluctuation will cause distortion of the output voltage of the three-level half-bridge inverter. At this time, the original intention of improving the output waveform by increasing the number of output voltage levels will be greatly compromised.

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