Method for controlling output current peak values of photovoltaic inverter during temporary asymmetric voltage drop

A photovoltaic inverter, voltage asymmetry technology, applied in photovoltaic power generation, single grid parallel feeding arrangement, etc., can solve problems such as safety hazards and inverter over-power

Active Publication Date: 2014-07-30
NORTH CHINA ELECTRIC POWER UNIV (BAODING)
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Problems solved by technology

At this time, the peak value of the inverter output current can reach several times that of the symmetrical grid voltage, which brings great safety hazards to the power electronic switches in the inverter and the entire photovoltaic system, and even causes the inverter to operate over-current protection.

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  • Method for controlling output current peak values of photovoltaic inverter during temporary asymmetric voltage drop
  • Method for controlling output current peak values of photovoltaic inverter during temporary asymmetric voltage drop
  • Method for controlling output current peak values of photovoltaic inverter during temporary asymmetric voltage drop

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[0034] In order to make the purpose, technical scheme and advantages of the present invention clearer, the following will be combined with the attached figure 1 , 2 , 3, describe it in detail.

[0035] The photovoltaic grid-connected system when the grid voltage is asymmetrically sags, such as figure 1 As shown, the topological structure of the photovoltaic inverter is as follows figure 2 shown. At this time, the control strategy of the photovoltaic inverter has a decisive impact on the output of the photovoltaic system. In the case of asymmetric grid voltage sag, due to the existence of negative sequence components, photovoltaic inverters will have problems such as output active power fluctuations, output reactive power fluctuations, and output currents containing more harmonics and negative sequence components.

[0036] Step 1: In order to suppress the fluctuation of the active power output of the inverter, calculate the reference value of the output current of the ph...

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Abstract

The invention discloses a method for controlling output current peak values of a photovoltaic inverter during temporary asymmetric voltage drop, and belongs to the field of photovoltaic power generation control technology. The method comprises the steps of calculating the reference value of the output current of the photovoltaic inverter under the condition of temporary asymmetric voltage drop on the basis of an instantaneous power theory; calculating the output current peak values of the photovoltaic inverter and the possible maximum current peak value; putting forward the restrictive measures for the output current peak values according to a current peak value expression; designing an output current control structure of the photovoltaic inverter under the condition of the temporary asymmetric voltage drop. The method for controlling the output current peak values of the photovoltaic inverter during the temporary asymmetric voltage drop has the advantages that grid connection current control of the photovoltaic inverter during the temporary asymmetric voltage drop can be achieved effectively, the fact that the output currents of the photovoltaic inverter under the condition of the temporary asymmetric voltage drop cannot exceed the maximum current limiting value is guaranteed, and therefore the potential safety hazards brought to operation of a photovoltaic system by enlargement of the current peak values are eliminated.

Description

technical field [0001] The invention belongs to the technical field of photovoltaic power generation control, and in particular provides a method for controlling the output current peak value of a photovoltaic inverter when voltage asymmetry sags. Background technique [0002] In the actual operation of the power grid, there will always be a certain degree of asymmetry in the voltage, especially when a fault occurs, there may be a voltage sag with a more serious asymmetry. At this time, the negative sequence component is twice the frequency pulsation in the positive synchronous rotating coordinate system , if the control algorithm of voltage symmetry is still used, due to the lack of control of the negative sequence component, the photovoltaic inverter will have problems such as DC side voltage fluctuations and output power fluctuations, which will seriously affect the stability of the photovoltaic inverter. The research on inverter control under the condition of voltage asy...

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Application Information

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Patent Type & Authority Applications(China)
IPC IPC(8): H02J3/38
CPCY02E10/56
Inventor 徐永海黄浩
Owner NORTH CHINA ELECTRIC POWER UNIV (BAODING)
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