A frequency conversion control method of photovoltaic grid-connected inverter based on lcl filter

Abstract

The invention provides a variable frequency control method of a photovoltaic grid-connected inverter based on LCL filtering. The method comprises the following steps that a power grid voltage eabc anda grid-connected current iabc are collected, the collected signals are converted to a synchronous rotation dq axis coordinate system, a current loop is subjected to feedforward decoupling under the dq axis, and reference signals are obtained and output, wherein details of the reference signals are shown in the description; a sampled output current ia passes through a frequency controller, a suitable current carrier frequency fsw is obtained, and finally the reference signals and the carrier frequency fsw are sent to an SVPWM generator, wherein the details of the reference signals are shown inthe description. The variable frequency control method is not only suitable for a voltage current double closed loop control method, but also suitable for other various grid-connected control strategies, and is different from a common SVPWM modulation method. According to the variable frequency control method, the current carrier frequency of SVPWM waves can be selected according to the current output power of the inverter, the grid-connected electricity quality can be improved to the maximum content, especially when the generated power of a photovoltaic component does not reach to the ratedpower, the photovoltaic component can adapt to fixed parameters of an LCL through frequency conversion, and finally the harmonic content of the output current is remarkably lowered.

Description

technical field [0001] The invention belongs to the technical field of photovoltaic inverters, and in particular relates to a frequency conversion control method of a photovoltaic grid-connected inverter based on LCL filtering. Background technique [0002] In the photovoltaic grid-connected inverter based on LCL filtering, its filter parameters are usually designed according to the rated power of the grid-connected inverter. However, the power generation of photovoltaic modules is closely related to the intensity of solar radiation. Since the intensity of solar radiation changes with time and seasons, the inverter will not always work at the rated power. When the output power of photovoltaic modules gradually decreases, the filter performance of the LCL filter circuit designed according to the rated output power will decrease when the output current decreases, and the output harmonics will increase, resulting in a significant decrease in output power quality. [0003] The ...

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Problems solved by technology

[0005] At present, complex algorithms are mostly used to compensate for grid-connected power quality problems, but this also puts forward higher requirements for the controller

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