Method for calculating inverse DG penetration level on basis of particle swarm optimization

Abstract

The invention relates to the field of electrical power systems, and discloses a method for calculating an inverse DG penetration level on the basis of particle swarm optimization in case of no changes on the relay protection setting value of the original power distribution network, for solving the influence on power grid protection after low-level multi-DG access. The method comprises the following specific steps of: establishing a DG equivalent calculation model with a low-voltage through capacity according to the control strategy of inverse DG at first; then establishing a calculation model for a fault current after the grid connection of the inverse DG; finally establishing an optimization model taking DG access level maximum as a target, and taking the three-section current setting value of each circuit as the penetration level of an inequality constraint condition, and evaluating DG access by virtue of particle swarm optimization.

Description

technical field [0001] The present invention relates to the field of power systems, and more specifically, to a method for calculating the access capacity of an inverter DG based on a particle swarm algorithm. Background technique [0002] Existing studies generally believe that due to the small capacity of inverter distributed power sources such as photovoltaics and fuel cells and the limiting effect of inverters on short-circuit current, when the grid fails, the short-circuit current fed to the grid will have a significant impact on the power grid. The influence of system fault current level is small, so more attention should be paid to the fault characteristics of rotating motors. However, with the large-scale access of distributed power sources and the continuous increase in the capacity of inverter units, it is necessary to have a more comprehensive understanding of the fault characteristics of inverter-based power sources. [0003] However, according to the existing l...

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Problems solved by technology

[0003] However, according to the existing literature, the distributed power supply is generally simplified as a constant current source without attenuation or a constant potential source with internal impedance. This method does not consider the characteristics of the short-circuit current provided by different distributed Consider the influence of the protection action of the distributed power supply itself on the short-circuit current

In fact, these simplified analysis results are quite different from the actual situation, and it is difficult to meet the application requirements of protection characteristic analysis and setting calculation

[0004] In addition, in the event of a fault, whether the equivalent calculation model of distributed power generation can achieve low voltage ride through and realize grid-connected operation is not considered by most literatures. If the equivalent calculation model of distributed power generation cannot realize low voltage ride through and grid connection operation, the following fault current analysis and the setting method for the protection of the distribution network will become meaningless

Even if the control strategy of the inverter-type distributed power equivalent calculation model under normal operation is not off-grid under fault conditions, negative-sequence components will be generated under asymmetric fault conditions, which will lead to the instability of the capacitor voltage on the DC side, making the inverter The output power of the inverter contains double frequency components, but in the case of asymmetric faults, the existing literature does not consider the negative sequence model of the distributed voltage equivalent calculation model when calculating the sequence components

Therefore, the admission capacity of distributed power generation will not match the actual admission capacity

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