Islanding detection method for sinusoidal low-frequency phase disturbance of three-phase photovoltaic grid-connected inverter
A Technology of Phase Disturbance and Island Detection
Inactive Publication Date: 2017-07-14
XI'AN POLYTECHNIC UNIVERSITY
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It is characterized by the introduction of disturbances in the grid-connected output current of the inverter, and there is also a detection blind zone under certain conditions
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[0200] take f 2 = 5Hz, θ m =π / 15, the local load parameters are taken as R=15Ω, L=19.108mH, C=530.785μF, at this time, the local load quality factor Q=2.5, assuming the grid-connected voltage peak value is 380V, under the condition of active power matching, the grid will be disconnected When the amplitude of the front and rear load voltage remains unchanged, the amplitude of the inverter output current I m =380V / 15Ω=25.33A;
[0201] The grid-connected current command at this time is:
[0202]
[0203] Put the obtained current command i d * and i q * , with the feedback current i d and i q After comparison, the error Δe is obtained d * and Δe q * , the Δe d * and Δe q * After being adjusted by the regulator, the corresponding d and q axis voltage v d and v q , v d and v q After Park inverse transformation, the α and β axis voltage v α and v β , and then get the three-phase modulation wave v after Clarke inverse transformation A , v B and v C ; v A ,...
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The invention discloses an island detection method for sine low-frequency phase disturbance of a three-phase grid-connected photovoltaic inverter. The island detection method comprises the following steps that low-frequency phase disturbance deltatheta which changes according to a sine principle is applied between an inverter output current vector I with phase disturbance and a power grid voltage vector E; during normal grid connection, detected voltage of a public connection point is power grid voltage; after the power grid is switched off, the voltage of the public connection point is determined by inverter output current and a local load commonly; a voltage frequency is changed along with the change of the frequency of the inverter output current so that the frequency exceeds a regulated frequency range and an island phenomenon is detected. According to the island detection method for the sine low-frequency phase disturbance of the three-phase grid-connected photovoltaic inverter, hardware does not need to be additionally arranged; compared with a traditional active type detection method, the island detection method has the advantage of no detection blind region; the applied disturbance is periodically changed, so that the island detection method has the advantage of small grid-connected current distortion when being compared with a traditional fixed disturbance frequency detection method.
Description
technical field [0001] The invention belongs to the technical field of grid-connected inverter control methods, and in particular relates to an island detection method for sinusoidal low-frequency phase disturbance of a three-phase photovoltaic grid-connected inverter. Background technique [0002] With the rapid development of solar power generation technology, more and more photovoltaic systems are connected to the public grid in parallel. When the grid is normal, the photovoltaic system and the public grid supply power to the load; after the grid is disconnected, only the photovoltaic system supplies power to the load. , so higher requirements are put forward for the safe and stable operation of the power grid, and the problem that must be solved is the islanding detection of grid-connected inverters. [0003] Islanding effect may cause serious harm to circuit maintenance personnel and electrical equipment, so it is of great significance to study islanding detection. At ...
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IPC IPC(8): G01R31/00
Inventor 陈增禄高洁管瑞欣王宁孟新新
Owner XI'AN POLYTECHNIC UNIVERSITY