M-series modulation and variance judgement based parallel network active alone island detection system and method

Abstract

The invention relates to a synchronization active type islanding detection system and a method based on M sequence modulation and variance estimation. The detection system comprises a synchronization inverter, a synchronization switch, a voltage Hall sensor arranged on a synchronization communal join point, a digital signal processor connected with the synchronization inverter, the synchronization switch and the voltage Hall sensor. The detection method is to utilize the pseudo-random signal M sequence of the communication technique, modulate the modulation wave of the inverter according to the distribution law of the M sequence, so as to make the output have the characteristics of the M sequence, and thus the output signals also have the characteristics of random signals. During synchronizing, the voltage of the synchronization communal join point is controlled by a power network and the randomness is small; therefore the obtained variance value of the random sequence is very small; when islanding, the voltage of the synchronization communal join point is determined by the output of the inverter, the output of the inverter is modulated through the digital signal processor and have the characteristics of the random signals, so the variance value is significantly increased. During detecting, a variance threshold value is set, and islanding can be determined when the detected variance is more than the threshold value. The synchronization active type islanding detection system and the method has the advantages of simple arithmetic, low cost, small effects to harmonic waves of the output power and small islanding detection blind zone.

Description

technical field [0001] The invention relates to a grid-connected active island detection system and method based on M-sequence modulation and variance judgment. Background technique [0002] The development and utilization of new energy such as photovoltaic power generation and wind power generation has been continuously developed, and more distributed power generation systems composed of renewable energy will appear in the future. Using these distributed generation systems in parallel on the grid can realize the power complementarity between the distributed generation system and the grid. However, the parallel connection of distributed generation systems on the grid brings many security risks to the grid, and island detection is one of them. important technology. The commonly used islanding detection methods include the power system end detection method and the power converter end detection method. The cost of power system end detection method is relatively high. There a...

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Problems solved by technology

The passive detection algorithm is simple and easy to implement, but there is a large detection blind area; the active detection method currently roughly includes detection methods such as active frequency interference, slip frequency drift, reactive power change, voltage unbalanced current harmonics, and related technologies. Active frequency interference detection leads to harmonic increase; slip frequency drift detection method fails to detect in purely resistive load or in resonance state; reactive power change detection method not only leads to harmonic increase, but also when there are multiple In a distributed power generation system, the changing reactive power interference will also cause detection failure; the detection method of voltage unbalanced current harmonics and the detection method of related technologies are too complicated and not suitable for practical application

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