A method for controlling a photovoltaic grid-connected inverter

Abstract

The invention discloses a method for controlling a photovoltaic grid-connected inverter. The method includes the steps that a connecting switch of a photovoltaic array and the grid-connected inverter is controlled to be switched on or off by judging the relation between the output voltage of the photovoltaic array and a preset range, according to working conditions of the photovoltaic array, the active current instruction value and the corresponding reactive current instruction value of the grid-connected inverter are acquired, the acquired active current instruction value and the acquired corresponding reactive current instruction value of the grid-connected inverter are correspondingly converted, adjusted and calculated, and PWM signals for controlling the switch of the grid-connected inverter to be switched on or off are acquired. According to the different working conditions of the photovoltaic array, the grid-connected inverter is switched and operated among three different modes that only the active power of the photovoltaic array is output, the active power of the photovoltaic array and part of reactive power needed for an alternating current bus side are output and the grid-connected inverter only serves as a reactive power compensator, the situation that the grid-connected inverter cannot be fully loaded and even unloaded is avoided, the utilization rate of the inverter is increased, and stability of the alternating current side voltage is improved.

Description

technical field [0001] The invention relates to the field of electrical technology, in particular to a control method for a photovoltaic grid-connected inverter. Background technique [0002] With the increasing depletion of traditional energy sources, distributed photovoltaic power generation systems have become an important part of electric energy. In the grid-connected photovoltaic power generation system, the grid-connected inverter is used to convert the DC power of the photovoltaic array into AC power with the same frequency as the grid voltage. The rated capacity of the photovoltaic grid-connected inverter matches the nominal power of the photovoltaic module. In order to output the nominal power of the photovoltaic module to the load, in the controller of the grid-connected inverter, the reactive current is usually given The fixed value is set to zero, that is, the output current and voltage are in the same phase, and the power factor is 1. [0003] However, the pho...

AI Technical Summary

Problems solved by technology

This seriously affects the operating efficiency of the grid-connected inverter

In addition, the photovoltaic power generation system only provides active power to the load, and the insufficient part is provided by the grid. At the same time, the grid also provides the reactive power required by the load. If the reactive power provided by the grid is insufficient, the AC bus voltage will drop. bus voltage rise

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