A kind of photovoltaic inverter and its control method

Abstract

The invention discloses a photovoltaic inverter, comprising: a photovoltaic module, an intermediate capacitor, a first filter inductor, a second filter inductor, a third filter inductor, a first diode, a second diode, and a first switch tube , the second switch tube, the third switch tube, the fourth switch tube and the drive control circuit; the first filter inductor, the second filter inductor, and the third filter inductor only work in half the power frequency cycle, the first switch tube and the second switch tube The switch tubes are high-frequency switches for the negative half cycle and positive half cycle of the grid voltage respectively, and the third switch tube and the fourth switch tube are power frequency switches. The present invention controls the current value of the first filter inductance and the second filter inductance, thereby ensuring that the grid current and the grid voltage have the same frequency and phase, and realizes the unit power factor output, and at the same time, there is only one switch tube for each half power frequency cycle of the grid High-frequency switching reduces switching loss and improves system conversion efficiency. The photovoltaic inverter of the invention has no common-mode leakage current and has high reliability.

Description

technical field [0001] The invention relates to the field of photovoltaic technology, in particular to a photovoltaic inverter and a control method thereof. Background technique [0002] Since the non-isolated photovoltaic inverter has no isolation between the photovoltaic module and the grid, common mode leakage current may flow through the parasitic capacitance of the photovoltaic module to the ground. This common-mode leakage current will cause electromagnetic interference, increase system loss, and even pose a threat to personal safety in series. The German VDE012611 standard stipulates that the effective value of common-mode leakage current of non-isolated photovoltaic inverters should be less than 300mA. If the system detects that it exceeds this value, the non-isolated PV inverter will stop. [0003] Experts and scholars at home and abroad have conducted a series of fruitful research on how to suppress the common-mode leakage current of non-isolated photovoltaic inv...

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Problems solved by technology

However, the effect of the above method to suppress the common-mode leakage current is easily affected by the parasitic capacitance of the photovoltaic module to the ground and the change of circuit parameters. Therefore, it is necessary to study the inverter topology and its control method that can fundamentally eliminate the common-mode leakage current.

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