Micro-grid island detection method

Abstract

The invention relates to the field of protection and control of micro-grids of electric power systems and particularly relates to a micro-grid island fast detection method. The method is sued for an inverter-based distributed generation (IBDG) with a PQ (power quest) decoupling control strategy; a corresponding reactive power control strategy is adopted in the method on the basis of measuring a voltage effective value UPCC and the load reactive power of a common coupling point PCC in real time through comparing the voltage effective value UPCC with the voltage effective value under a normal condition; when island determination is performed, firstly, a voltage threshold value and a frequency threshold value are predetermined, the voltage effective value UPCC is compared with the voltage threshold value, if the voltage effective value UPCC exceeds the threshold value, the PCC is directly determined be in an island state and the island detection is finished, and if the voltage effective value UPCC does not exceed the threshold value, the voltage frequency f of the PCC is compared with the frequency threshold value, the PCC is determined to be in the island state if the voltage frequency f of the PCC exceeds the threshold value. With the adoption of the detection method, the micro-grid island detection can be realized fast, and the effectiveness of the island detection can be ensured even under the existence of a plurality of inverter-based distributed generations.

Description

technical field [0001] The invention relates to the field of micro-grid protection and control in power systems, and relates to a micro-grid island detection method. Background technique [0002] Microgrid island detection is the prerequisite for the microgrid to change from an unplanned island to an island operation, and it plays an important role in changing the control strategy and protection configuration in the microgrid. Regarding the possible islanding effect, the relevant standards formulated by the Institute of Electrical and Electronics Engineers (IEEE) no longer specifically require the islanding detection method used, but focus on the performance index of the islanding detection method in the process of islanding detection, thus guiding the islanding The development trend of testing standards. The existing islanding detection methods can be divided into three categories: passive detection method, active detection method and switch state monitoring method. Among...

AI Technical Summary

Problems solved by technology

Among them, the passive detection method will not affect the power quality of the system, but when an unplanned island occurs, if the output power of the distributed generation (DG) is not much different from the power consumed by the load, the voltage at the point of common coupling (PCC) , frequency, etc. are within the allowable range of variation, this method will not be able to detect islands, and has a large detection blind area, and is usually used in combination with the active detection method

The active detection method introduces a disturbance signal into the control signal of the inverter DG, and monitors the response of electrical quantities such as voltage and frequency at the PCC to determine whether unplanned islanding occurs. This method reduces the detection blind area, but at the same time Power quality has a certain impact

In addition, when the active detection method is applied to multiple DGs, the effectiveness of the method will be reduced if the system response generated by the perturbation signal is not synchronized

The switch state monitoring method is to detect the on-off state of the circuit breaker on the side of the distribution network, and send this signal to the DG based on communication technology to judge the operation mode of the micro-grid. This method does not have detection blind spots and does not affect power quality, but Complicated to implement and less economical

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