Non-isolated photovoltaic grid-connected inverter and control method thereof

Abstract

The invention discloses a non-isolated photovoltaic grid-connected inverter and a control method thereof and belongs to the technical field of power electronics converters. The inverter comprises a power supply circuit (10), a high-frequency chopper circuit (20) and a low frequency inverter circuit (30), wherein the power supply circuit (10) is formed by a photovoltaic array and an input filter capacitor, the high-frequency chopper circuit (20) is formed by a first to a second power switch tube, a first diode and a first to a second filter inductor, the low frequency inverter circuit comprises a third, a fourth, a fifth and a sixth power switch tube, the first power switch tube and the second power switch tube are high frequency switches, and the third power switch tube, the fourth power switch tube, the fifth power switch tube and the sixth power switch tube are low frequency switches. The non-isolated photovoltaic grid-connected inverter and the control method thereof have the advantages that leakage current of the grid-connected inverter can be eliminated, grid-connected current waveforms qualities are improved, simultaneously the efficiency is high, the controlling is simple, the reliability is high and the like.

Description

technical field [0001] The invention relates to the technical field of new energy power generation, in particular to a power converter and a corresponding control method. Background technique [0002] Photovoltaic grid-connected power generation is the most important way of solar power generation application. According to statistics, more than 90% of the installed capacity of photovoltaic power generation equipment in the world is for grid-connected applications. [0003] Photovoltaic grid-connected inverter is a bridge connecting solar photovoltaic power generation equipment to the grid, and is one of the most critical devices in photovoltaic grid-connected power generation systems. Classified according to the isolation method, photovoltaic grid-connected inverters can be divided into power frequency transformer isolation type, high frequency transformer isolation type and non-isolation type. Compared with the other two photovoltaic grid-connected inverters, the non-isolat...

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Problems solved by technology

The working mode of the full-bridge grid-connected inverter is completely symmetrical when it adopts bipolar modulation, so it can effectively eliminate the leakage current of the grid-connected inverter, but it will increase the loss and reduce the efficiency of the grid-connected inverter, and The harmonics of the grid-connected current are large, resulting in an increase in the size, weight, and cost of the filter inductor of the grid-connected inverter

The half-bridge grid-connected inverter can also eliminate the leakage current of the grid-connected inverter, but the voltage on the DC input side of the grid-connected inverter is more than twice the peak value of the grid voltage, resulting in an increase in the voltage stress of the power switch tube, thereby increasing the system cost, reduced system efficiency and reliability

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