Method for controlling low-voltage ride through of cascaded photovoltaic grid-connected inverter

A low-voltage ride-through and control method technology, which is applied in photovoltaic power generation, irreversible DC power input conversion to AC power output, single-grid parallel feeding arrangement, etc. Realize the effect of low voltage ride-through control

Active Publication Date: 2016-03-02
NANJING INST OF TECH
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  • Claims
  • Application Information

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Problems solved by technology

The more classic method is vector control. The vector control method requires positive and negative sequence component extraction and coordinate transformation for the grid-connected point voltage and grid-connected current, and the control system is relatively complicated.

Method used

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  • Method for controlling low-voltage ride through of cascaded photovoltaic grid-connected inverter
  • Method for controlling low-voltage ride through of cascaded photovoltaic grid-connected inverter
  • Method for controlling low-voltage ride through of cascaded photovoltaic grid-connected inverter

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Embodiment

[0037] This control method for low-voltage ride-through of cascaded photovoltaic grid-connected inverters is based on the mathematical models of grid-side voltage under two common asymmetric grid fault conditions, and summarizes the three-phase grid-side voltage amplitude under different fault conditions The law between phase and phase.

[0038] Based on the above rules, the control methods of cascaded photovoltaic grid-connected inverters under different fault conditions are deduced: (1) When a single-phase ground short-circuit fault occurs, fault-tolerant control based on zero-sequence voltage injection is adopted; (2) Two-phase When a phase-to-phase short-circuit fault occurs, fault-tolerant control based on negative-sequence voltage injection is adopted.

[0039] The low voltage ride-through control of the cascaded photovoltaic grid-connected inverter is realized by setting the switching state of the H-bridge power device to bypass the power unit, recalculate the optimal m...

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Abstract

The invention provides a method for controlling low-voltage ride through of a cascaded photovoltaic grid-connected inverter. The method is based on two common mathematical models of grid-side voltage under the condition of an unbalanced grid fault, and the laws between the three-phase grid-side voltage amplitude and phase under different fault conditions are summarized. A method for controlling a cascaded photovoltaic grid-connected inverter under different fault conditions is derived based on the laws. By setting the on-off state of an H-bridge power device, a bypass power unit controls low-voltage ride through of a cascaded photovoltaic grid-connected inverter. When a bypass is generated, the optimal modulation ratio of a normal operation unit is recalculated, and a carrier phase shift module is adjusted to produce a new PWM pulse signal. The method can ensure that a photovoltaic grid-connected inverter outputs symmetrical three-phase current during grid-side voltage failure and enable the photovoltaic grid-connected inverter to run under unit power factor, and is of great significance to ensuring safe and stable operation of the power grid after large-scale photovoltaic power integration.

Description

technical field [0001] The invention relates to a low-voltage ride-through control method of a cascaded photovoltaic grid-connected inverter, and in particular provides a method for realizing flexible grid-connected cascaded photovoltaic inverters when an asymmetric fault occurs in the grid-side voltage , belongs to the technical field of photovoltaic grid-connected power generation. Background technique [0002] In recent years, photovoltaic power generation technology has developed rapidly in my country, and the installed capacity has increased significantly. The proportion of photovoltaic grid-connected power generation connected to the grid is increasing. The mutual influence between photovoltaic grid-connected power generation system and power system cannot be ignored. When the power grid fails and the voltage at the grid-connected point drops, once the photovoltaic power plant is disconnected from the grid on a large scale, it may cause the voltage and frequency of the...

Claims

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Application Information

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Patent Type & Authority Applications(China)
IPC IPC(8): H02J3/38H02M7/48
CPCY02E10/56
Inventor 王书征李先允
Owner NANJING INST OF TECH
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