Single-phase non-isolated photovoltaic grid-connected inverter and control method thereof

Abstract

The invention discloses a single-phase non-isolated photovoltaic grid-connected inverter and a control method thereof. The single-phase non-isolated photovoltaic grid-connected inverter comprises a photovoltaic cell array module, 6 controllable switch tubes, 2 diodes and 2 inductors. The control method of the single-phase non-isolated photovoltaic grid-connected inverter enables the common mode voltage of the inverter during the overall working period is equal to or is approximate to half of the cell voltage, so that the voltage at two ends of the photovoltaic system grounding stray capacitor has no high frequency components and then the leak current of the non-isolated grid-connected inverter can be eliminated. Only two of the 6 controllable switch tubes in the circuit works in the high frequency mode at any moment, so that the switch loss can be effectively reduced and the conversion frequency can be improved. The single-phase non-isolated photovoltaic grid-connected inverter and the control method thereof are suitable for the photovoltaic grid-connected occasion without isolation of transformers.

Description

technical field [0001] The invention relates to inverter control technology in the field of power electronic conversion, in particular to a single-phase non-isolated photovoltaic grid-connected inverter and a control method thereof. Background technique [0002] Non-isolated photovoltaic grid-connected inverters have the absolute advantages of high efficiency, small size, light weight and low cost. However, due to the existence of the parasitic capacitance of the photovoltaic panel to the ground, the switching action of the switching device of the grid-connected inverter may generate a high-frequency time-varying voltage to act on the parasitic capacitance, and the resulting leakage current may exceed the allowable range. The generation of high-frequency leakage current will also bring conduction and radiation interference, increase the harmonics and loss of network current, and even threaten equipment and personal safety. [0003] Single-phase full-bridge inverter SPWM mod...

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Problems solved by technology

[0006] The patent EP1369985A2 proposes to add a bidirectional controllable switch group between the midpoints of the bridge arms of the full bridge circuit to construct a new freewheeling circuit; the patent US7411802B2 only introduces a high-frequency switch at the positive terminal of the photovoltaic cell side, which can also realize the photovoltaic cell terminal in the freewheeling stage. Separated from the grid, but there are always three switching devices in the current path, and the on-state loss is large

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