Novel single-phase NPC non-isolated photovoltaic grid-connected inverter circuit and modulation method

Abstract

The invention discloses a novel single-phase NPC non-isolated photovoltaic grid-connected inverter circuit and a modulation method thereof. The collector of the first switch tube S1 is connected withthe positive electrode of the DC source and the positive electrode of the first voltage-dividing capacitor Cdc1. The emitter of the first switch tube S1 is connected with the cathode of the first fly-wheel diode D1 and one end of the first filter inductor L1. The emitter of the third switch tube S3 is connected with the anode of the first fly-wheel diode D1, and the collector of the third switch tube S3 is connected with the negative electrodeof the first voltage-dividing capacitor Cdc1, the positive electrodeof the second voltage-dividing capacitor Cdc2, the emitter of the fourth switch tubeS4 and the negative end of the power grid. According to the novel single-phase NPC non-isolated photovoltaic grid-connected inverter circuit and the modulation method thereof, the problem of current leakage can be effectively solved.

Description

technical field [0001] The invention relates to a non-isolated photovoltaic grid-connected inverter circuit based on single-phase NPC and its control method, belonging to the technical field of power electronic photovoltaic grid-connected power generation Background technique [0002] In recent years, with the increase in energy demand and the introduction of environmental protection policies, renewable energy has received more and more attention. Among various renewable energy sources, solar energy has developed rapidly due to its safety, cheapness and reliability. In the traditional isolated photovoltaic grid-connected system, there is a transformer to increase the voltage and isolate the grid from the photovoltaic side. Transformers have the disadvantages of large volume, high cost, and large losses. Therefore, non-isolated photovoltaic grid-connected inverters are more widely used due to their high efficiency, small size, and low weight. [0003] However, in the non-i...

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Problems solved by technology

[0003] However, in the non-isolated photovoltaic grid-connected inverter system, since there is no electrical isolation between the photovoltaic cells and the grid, the leakage current may generate an electrical loop through the parasitic capacitance of the photovoltaic array and the filter capacitor and filter inductor in the circuit

The leakage current is caused by the high-frequency fluctuation of the common-mode voltage, which will cause serious leakage current in the common-mode circuit, which will endanger the safety of the whole system and distort the output current

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