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A photovoltaic grid-connected inverter low-voltage ride-through control system

A low-voltage ride-through and control system technology, applied in photovoltaic power generation, AC network voltage adjustment, AC network circuits, etc., can solve problems such as limiting the size of reactive power and the impact of reactive power, and prevent capacitor voltage fluctuations from exceeding the limit , Optimize the fluctuation range of sub-module capacitor voltage and increase the effect of output reactive power

Active Publication Date: 2018-05-08
NANJING INST OF TECH
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  • Abstract
  • Description
  • Claims
  • Application Information

AI Technical Summary

Problems solved by technology

At present, most researches are based on traditional VSC-based photovoltaic grid-connected inverter low-voltage ride-through technology, but with the emergence of new inverters, such as MMC (modular multi-level inverter), VSC-based When the voltage ride-through method is transferred, it will be somewhat inappropriate. For example, when the reactive power injection method is used in the MMC-based system, the sub-module capacitor voltage fluctuation will be affected by the reactive power. When the reactive power emitted by the MMC reaches a certain value, The voltage fluctuation of the sub-module capacitor may exceed the specified value, thus limiting the size of the reactive power output

Method used

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  • A photovoltaic grid-connected inverter low-voltage ride-through control system
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  • A photovoltaic grid-connected inverter low-voltage ride-through control system

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Embodiment Construction

[0041] Take the MMC modular multilevel inverter as an example: such as figure 1 As shown, the photovoltaic grid-connected inverter low-voltage ride-through control system of the present invention is as follows: on the basis of the traditional double-closed-loop vector control system of the current inner loop voltage outer loop, the low voltage ride-through control module and sub-module capacitors are added Voltage control module; when the grid-connected point voltage drop is detected, the low-voltage control module is used to inject reactive current and limit the active current, and the sub-module capacitor voltage control module is used to control the fluctuation range of the sub-module capacitor voltage when reactive power is emitted.

[0042] Such as figure 2 As shown, the low-voltage control module includes a reactive current injection unit and an active current limiting unit; when the grid-connected point voltage drop is detected, the reactive current injection unit is u...

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Abstract

The invention provides a photovoltaic grid-connected inverter low-voltage ride-through control system. On the basis of double closed-loop vector control of an inner current loop and an outer voltage loop, the system further comprises a low-voltage ride-through control module and a sub module capacitor voltage control module. When that the voltage at a grid connection point drops is detected, the low-voltage ride-through control module injects reactive current and limits active current, and the sub module capacitor voltage control module sends out a sub module capacitor voltage fluctuation range at reactive power under control of a bridge arm ring current optimization unit and / or a sub module capacitor reference voltage regulation unit. With the system, the problem that reactive power injection low-voltage ride-through is not smooth due to sub module capacitor voltage fluctuation is solved. Some inverters cannot achieve low-voltage ride-through properly. There is no need to arrange an additional power device. Low-voltage ride-through of a photovoltaic inverter system based on MMC is realized with low cost. Photovoltaic safe grid-connected operation is ensured.

Description

technical field [0001] The invention relates to the field of power electronics, in particular to the field of low-voltage ride-through control of photovoltaic grid-connected inverters Background technique [0002] With the rapid increase in the proportion of photovoltaic power generation, the grid connection of photovoltaic power stations will also bring security and stability problems to the operation of the power system, especially in the case of voltage drops due to failures at the grid connection points of the system, which will bring low voltage to the grid connection of photovoltaic power stations. Crossing the question. The low-voltage ride-through problem we are facing now has become a difficult point and research hotspot in new energy grid-connected technology. At present, most researches are based on traditional VSC-based photovoltaic grid-connected inverter low-voltage ride-through technology, but with the emergence of new inverters, such as MMC (modular multi-le...

Claims

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Application Information

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Patent Type & Authority Patents(China)
IPC IPC(8): H02J3/38H02J3/16
CPCH02J3/16H02J3/383Y02E10/56Y02E40/30
Inventor 李先允姜婷婷倪喜军王书征
Owner NANJING INST OF TECH
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