Method for Measuring Equivalent Admittance of Grid-connected Inverter in the Condition of Unknown Grid Impedance
A technology of grid impedance and equivalent admittance, applied in the field of effective admittance, can solve problems such as the unknown state of the target grid, and achieve the effects of avoiding measurement errors, accurate impedance information, and improving accuracy
Active Publication Date: 2021-07-20
CHONGQING UNIV
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Problems solved by technology
In order to analyze the stability of the inverter grid-connected system, it is particularly important to obtain the impedance of the inverter, but in the process of measuring the impedance of the grid-connected inverter, the impedance of the target grid is often in an unknown state
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[0069] Below in conjunction with accompanying drawing, the present invention is further described:
[0070] The present invention provides a method for measuring the equivalent admittance of the grid-connected inverter when the impedance of the grid is unknown, which is characterized in that it includes: the equivalent admittance Y of the grid-connected inverter INV Determined as follows:
[0071]
[0072] Among them, Y INV (f P ) represents the equivalent admittance of the inverter in the inverter grid-connected system, Y SA (f p ) means the frequency is f P mutual admittance, Indicates that the frequency is 2f 0 -f P The conjugated transadmittance of , Represents the product of the self-admittance and its conjugate at different frequencies, Indicates that the frequency is 2f 0 -f P The grid impedance after the conjugate;
[0073] Among them, Y SA (f p ), and Determined by simultaneous formula (2) to formula (4),
[0074]
[0075] Among them, Y SA (...
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The invention provides a method for measuring the equivalent admittance of a grid-connected inverter under the condition that the grid impedance is unknown, and belongs to the field of new energy grid-connected. In a real measurement scenario, the impedance of the inverter is affected by the grid impedance. The traditional measurement method obtains the impedance of the inverter when the grid impedance is known, but in the actual measurement scenario, the grid impedance is often unknown. Therefore, the present invention provides that when the grid impedance is unknown, a mathematical model is established through six sets of measurement information, and the characteristic admittance Y of the grid-connected inverter itself is solved. SA , and use the characteristic admittance to determine the equivalent admittance of the inverter. The invention considers the interaction between the grid impedance and the inverter impedance, avoids the introduction of synchronous phase angle, and has high measurement accuracy.
Description
technical field [0001] The invention relates to the field of grid-connected new energy sources, in particular to a method for measuring the equivalent admittance of a grid-connected inverter when the impedance of the grid is unknown. Background technique [0002] In recent years, environmental degradation, climate warming, and the depletion of fossil fuels have prompted governments around the world to vigorously develop renewable new energy sources. At present, new energy represented by wind power and photovoltaics has been vigorously developed. As of the end of 2018, the installed capacity of wind power in my country was 184 million kilowatts, and the installed capacity of photovoltaic power generation was 174 million kilowatts. The newly added and accumulated installed capacity both continue to rank first in the world. The grid connection of new energy can easily impact the stability of the power grid. For example, in 2015, harmonic oscillations of 25 Hz and 75 Hz occurr...
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IPC IPC(8): G01R27/08G01R27/16G01R27/04
CPCG01R27/04G01R27/08G01R27/16
Inventor 杜雄刘俊良张博杜程茂孙鹏菊罗全明
Owner CHONGQING UNIV