Construction method of equivalent load current detection link of multifunctional photovoltaic grid-connected inverter

Abstract

The invention relates to a construction method of an equivalent load current detection link of a multifunctional photovoltaic grid-connected inverter. The construction method comprises the following steps of: selecting a detection quantity as a power grid side three-phase current Igabc; establishing a three-phase/two-phase current conversion link, and equivalently converting Igabc into two-phase currents Ig alpha and Ig beta under an alpha-beta coordinate system; establishing a phase-locked loop PLL; establishing an alpha beta/dq current equivalent transformation link T alpha beta/dq, establishing a dq-axis current low-pass filtering link LPF, establishing a dq-axis current delay link Gtran(s), and finally outputting detected dq-axis current harmonics, unbalanced current components Ihd andIhq and a reactive current q-axis component Icq. The design is reasonable, the transient fluctuation problem of the multifunctional photovoltaic grid-connected inverter can be effectively suppressed,the photovoltaic power generation and electric energy quality compensation functions are ensured, the influence of equivalent load current fluctuation on the output current of the inverter is greatlyreduced, direct-current voltage fluctuation is further reduced, and inverter protection maloperation caused by equivalent load current fluctuation is prevented.

Description

technical field [0001] The invention belongs to the technical field of distributed power generation control, in particular to a method for constructing an equivalent load current detection link of a multifunctional photovoltaic grid-connected inverter. Background technique [0002] With the intensification of the energy crisis, renewable energy represented by solar energy has received widespread attention from all over the world in recent years, and distributed photovoltaic power generation technology has also been greatly developed. As an interface for energy conversion between photovoltaic arrays and the grid, photovoltaic grid-connected inverters have similar topological structures with power quality control devices such as active power filters (APF) and static var generators (SVG). Therefore, some scholars put forward the concept of Multi-function Photovoltaic Grid-connected Inverter (MFGCI): by compounding a variety of control strategies with different functions, while ...

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Problems solved by technology

Therefore, when the start-stop of impact load in the micro-grid or low-voltage distribution network, large-capacity load switching, or the exit of other photovoltaic inverters on the same bus have a serious impact on the equivalent load current, the inverter output current and DC voltage There will be large transient fluctuations. When the transient fluctuations are severe, the output current of the inverter will exceed 150% of the rated current or the DC voltage deviation will exceed -15% to +20% of the rated DC voltage, which will cause the inverter to Misoperation of output current or input overvoltage and undervoltage protection reduces the efficiency of the inverter

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