Three-phase load flow calculation method for ungrounded power distribution network

Abstract

The invention discloses a three-phase load flow calculation method for an ungrounded power distribution network. The structure data of the network, the parameter information, the control information of a balance end point and PV end points and the end point load information are acquired and are initialized, wire voltages of the balance end point are converted into phase voltages based on an equivalence neutral point, a nodal admittance matrix of the network based on the balance end point equivalence neutral point and a Jacobian matrix constant term are calculated, a node current imbalance equation of network imbalance end points, a constraint equation of which a zero sequence current is zero, a total active constraint equation of the PV end points and a wire voltage amplitude constraint equation are comprehensively considered, a real-virtual portion of each end point voltage, a real-virtual portion of a star-shaped connection wire load end point neutral point voltage and a real-virtual portion of a PV end point injection current are taken as state variables, a Newton-Ralfson's method algorithm based on an injection current mode is employed, corresponding imbalance amount and a Jacobian matrix are calculated, a state variable is finally updated, convergence determination is carried out, and three-phase load flow calculation of the ungrounded power distribution network is realized.

Description

technical field [0001] The invention belongs to the technical field of power system steady-state power flow calculation, and in particular relates to a three-phase power flow calculation method of an ungrounded distribution network. Background technique [0002] Distribution network power flow calculation is an important method to obtain the operating state of the distribution network, and it provides basic data for the relevant analysis and calculation of the distribution network, and is an important part of the distribution management system. At the same time, the distribution network directly faces power users, and its power quality and operation status directly affect people's production and life. Different from the three-phase symmetry of the transmission network, the three-phase asymmetry of the power flow in the distribution network is significant due to the asymmetry of network parameters and load asymmetry, so it is necessary to study the three-phase power flow calc...

AI Technical Summary

Problems solved by technology

2) The three-wire current at each terminal point of the grounding system is independently controllable; since there is no zero-sequence current path in the non-grounding system, its zero-sequence current is zero, that is, it cannot be independently controlled

However, this method has the following problems: 1) This method does not consider the unmeasurable characteristics of the terminal phase voltage of the ungrounded system, and still establishes the power terminal model with the phase voltage controllable; The concept of point power, but it is considered that the known quantity of constant power star load is the ground power of each node, and based on this, a three-phase steady-state model of constant power star load is established

In the prior art, the line-to-line voltage is used as the state variable, although the problem of non-unique reference point selection is avoided, but there are still the following deficiencies: 1) The neutral point voltage of the star-connected load cannot be calculated, so that the load bears cannot be known 2) Although this method takes the line voltage of the power supply terminal as the state variable, it does not consider the uncontrollable characteristics of the phase voltage of the power supply terminal, but simply converts the phase voltage into the line voltage on the basis of the three-phase voltage symmetry

Therefore, the existing methods cannot accurately calculate the power flow distribution and operating status of the ungrounded distribution network.

Images