Active Frequency Offset Island Detection Method Based on Synchronous Rotating Coordinate System

A technology of active frequency offset and synchronous rotation, applied in the direction of photovoltaic power generation, electrical components, fault location, etc., can solve the problems of DC bus voltage fluctuation, misjudgment, high total harmonic distortion rate, etc.

Active Publication Date: 2011-12-21
HARBIN INST OF TECH
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Problems solved by technology

Its advantage is that there is no detection blind zone when the grid-connected inverter matches the local load power. However, nonlinear factors in the actual system may cause the total harmonic distortion rate of the access point voltage to be higher than the current standard under normal grid conditions. It may be misjudged when the power grid is normal because the detection threshold is too small
The second is over-undervoltage, over-underfrequency detection method. This method judges whether an i

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  • Active Frequency Offset Island Detection Method Based on Synchronous Rotating Coordinate System
  • Active Frequency Offset Island Detection Method Based on Synchronous Rotating Coordinate System
  • Active Frequency Offset Island Detection Method Based on Synchronous Rotating Coordinate System

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[0032] Combine figure 1 To illustrate the specific implementation of the present invention, based on the active frequency offset islanding detection method under the synchronous rotating coordinate system, it is realized by the following steps:

[0033] Step 1: Use a three-phase phase-locked loop to phase-lock the AC grid voltage to obtain the vector angle θ of the AC grid voltage in the synchronous rotating coordinate system;

[0034] Step 2: Determine the current vector angle θ according to the vector angle θ of the AC grid voltage obtained in step 1. i ;

[0035] Step 3: According to the vector angle θ of the AC grid voltage obtained in step one and the current vector angle θ obtained in step two i And the given value of active current i d_ref Determine the given value of reactive current i q_ref , And use the current controller to obtain the control voltage;

[0036] Step 4: Collect the frequency and amplitude of the output voltage of the photovoltaic inverter, judge whether isla...

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Abstract

The invention provides an island detection method of AFD (active frequency drift) based on a synchronous rotation coordinate system, relating to an island detection method of AFD. The method can be used to meet access requirements of a distributed power supply in a middle or low pressure power distribution network. An island detection algorithm of the AFD based on the synchronous rotation coordinate system is compared with a passive island detection algorithm, and when the load power is matched with the power output of an inverter, detection dead zones do not exist; and the island detection algorithm of the AFD based on the synchronous rotation coordinate system is compared with a traditional AFD algorithm, a distortion position does not generate at a current zero-crossing position, and active currents do not fluctuate, thus DC (direct current) busbar voltages do not fluctuate consequently. The method is applied to the island detection.

Description

technical field [0001] The invention relates to an active frequency offset island detection method. Background technique [0002] Since the photovoltaic grid-connected power generation system is directly connected to the grid, it is necessary to consider the protection measures of the system in the event of a grid failure. When the grid is disconnected, the photovoltaic power generation system continues to supply power to the local load as an isolated power source, which forms an "island effect". . The islanding effect may cause huge damage to electrical loads and grid maintenance personnel. Therefore, the corresponding international standards clearly state that photovoltaic grid-connected inverters must have anti-islanding functions that meet their standards, that is, after the islanding phenomenon occurs, within the specified Within a short period of time, the photovoltaic system can detect the occurrence of the island phenomenon and stop power generation in time to elimi...

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Application Information

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IPC IPC(8): H02H7/26H02J3/38G01R31/08
CPCY02E10/563Y02E10/56
Inventor 张学广徐殿国王瑞刘义成
Owner HARBIN INST OF TECH
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