Power grid reactive power compensation method and device and grid-connected inverter

Abstract

The invention discloses a power grid reactive power compensation method and device and a grid-connected inverter. The power grid reactive compensation method comprises the following steps of detecting the voltage of a power grid, when the voltage magnitude of the detected voltage is lower than the preset normal voltage magnitude, determining the electric reference parameters corresponding to the voltage; determining the current pulse width modulation (PWM) mode according to the electric reference parameters corresponding to the voltage, wherein the PWM mode comprises a unipolar modulation mode and a bipolar modulation mode; and outputting reactive power by utilizing the current PWM mode, so as to realize reactive compensation for the power grid. In the scheme provided by the invention, when the voltage of the power grid drops, the current PWM way is determined by the electric reference parameters corresponding to the detected voltage, thus, the unipolar modulation way and the bipolar modulation way are effectively combined in a current period; when the voltage of the power grid drops, the reactive power compensation can be effectively carried out for the power grid, and the switching losses and inductance losses can also be reduced.

Description

technical field [0001] The invention relates to the field of electrical technology, in particular to a grid reactive power compensation method, device and grid-connected inverter. Background technique [0002] As an environmentally friendly and renewable new energy, solar energy is increasingly favored by people. Among them, the conversion of solar energy into electrical energy has received particular attention. In order to convert the direct current generated by the solar panels into alternating current for feeding into the grid, a solar grid-connected inverter is required. [0003] Among them, when there is a power grid failure due to voltage drop, the solar inverter is required to be able to output reactive power to achieve reactive power compensation, thereby supporting the recovery of the power grid. Among them, the so-called voltage drop specifically refers to the decrease of the voltage amplitude of the power grid; the so-called reactive power refers to the electric...

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Problems solved by technology

Among them, when the bipolar modulation method is used to realize reactive power compensation, there is no special requirement for the current grid voltage value, but the switching loss and inductance loss are relatively large compared with the unipolar modulation method; while the unipolar modulation method is used to realize reactive power compensation , it can have small switching loss and inductance loss, but it is difficult to achieve soft switching when the grid voltage is low (such as near zero crossing of the grid voltage), so that reactive power compensation cannot be realized

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