A Calculation Method of Reverse DG Access Capacity Based on Particle Swarm Algorithm

Abstract

The present invention relates to the field of electric power systems, and proposes an inverter-type DG access capacity calculation method based on the particle swarm algorithm without changing the relay protection setting value of the original distribution network, which is used to solve the problem of small-capacity multi-DG Impact on grid protection after access. The specific steps of the method are as follows: first, according to the control strategy of the inverter DG, an equivalent calculation model of the DG with low voltage ride-through capability is established; then, the calculation model of the fault current after the inverter DG is connected to the grid is established; The capacity maximization is the goal, and the three-stage current setting value of each line is used as the optimization model of the admission capacity of the inequality constraints, and the particle swarm algorithm is used to obtain the DG access.

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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