Photovoltaic grid-connected inverter and grid-connected control method thereof

Abstract

The invention discloses a photovoltaic grid-connected inverter, which comprises a direct current (DC) signal detection module, an inversion module, a transformer, an alternating current (AC) contactor, an AC signal detection module and a control circuit, wherein the control circuit comprises a current loop PI regulator consisting of a d-axis current regulator and a q-axis current regulator, a space vector pulse width modulation (SVPWM) space vector module, a Clark / Park conversion module, a Clark / Park inverse transform module and an excitation command operating module; and the excitation command operating module can output an output quantity serving as a reference signal of the q-axis current regulator and control the inversion module to output a reactive component to pre-excite the transformer. The invention also discloses a grid-connected control method for the photovoltaic grid-connected inverter. Compared with the prior art, the invention has the advantages that: an inverter can be connected to a grid seamlessly, overcurrent impact is prevented, the system loss is reduced, and the reliability and stability of the system are improved.

Description

technical field [0001] The invention relates to a photovoltaic grid-connected inverter, in particular to a photovoltaic grid-connected inverter with an isolation transformer on an AC output side and a grid-connected control method thereof. Background technique [0002] Photovoltaic power generation has two working modes: off-grid and grid-connected. The grid-connected type puts forward higher requirements for the inverter. On the one hand, the safety of grid-connected needs to be met. The power grid causes harmonic pollution, so generally domestic grid-connected inverters are equipped with isolation transformers on the AC output side. Therefore, it also brings the following two problems: on the one hand, the direct connection of the output side of the photovoltaic grid-connected inverter transformer to the grid will cause problems such as overcurrent and shock oscillation. The traditional control method for this problem is: first connect to the power grid through a closed s...

AI Technical Summary

Problems solved by technology

Therefore, it also brings the following two problems: On the one hand, the output side of the photovoltaic grid-connected inverter transformer is directly connected to the grid, which will cause problems such as overcurrent, shock oscillation, etc.

This control method can prevent the shock during the process of connecting to the grid to a certain extent, but there will be a certain current shock in the process of switching to the power grid and increase the system cost, and the output side of the inverter cannot be ideal. Connect to the grid

On the other hand, when the DC input energy is insufficient, especially in the morning and rainy weather, this direct grid-connected control method will easily cause the system to switch on and off frequently, and the output side switch or contactor to be switched on and off repeatedly. Reduced switch or contactor life, reducing system reliability

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