Maximum load supply capability evaluation method of medium-voltage power distribution network for loop power supply

Abstract

The invention provides a maximum load supply capability evaluation method of a medium-voltage power distribution network for loop power supply. The method comprises determining the regression model of a multivariable nonlinear regression curve representing the quantitative relationship between the output power flow of a substation and a leading switching station based on a power flow tracing theory; establishing a maximum load supply capability target function of the medium-voltage power distribution network; and resolving of the target function by sequential quadratic programming method while considering the requirement of N-1 criterion of power supply security for urban power grid and selecting the network power balance, the circuit thermal stability limit, the bus voltage, and the power of a power output node and a load node as the constraint conditions to obtain the optimum solution, i.e. the maximum load supply capability of the medium-voltage power distribution network for loop power supply.

Description

technical field [0001] The invention belongs to the field of calculating the maximum power supply capacity of a power distribution system, in particular to a method for evaluating the maximum power supply capacity of a ring-type power supply medium-voltage distribution network. Background technique [0002] The urban power grid is the main component of the power system. It is responsible for ensuring reliable and continuous power supply for users and providing good power quality. It is an important infrastructure and a necessary energy supply system for urban construction and economic development. In the past, the phenomenon of "heavy power generation, light supply, and no use" in power construction led to a long-term lack of reasonable planning and capital investment in the distribution network, and weak infrastructure. With the rapid development of urban economy and the rapid increase of electricity load, the distribution network has shown the contradiction of "can't send ...

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Problems solved by technology

However, this method ignores the change of bus voltage amplitude and the resistance of the line, and only solves the active power part of the line flow. Although it can greatly reduce the calculation amount and improve the calculation speed, for the distribution network, especially for the 10kV grid structure, Since the resistance of the line is often not much smaller than the reactance, the DC power flow method is used for calculation, and the error of the result will be large

Literature [6] proposes a method based on the trust region method for the maximum power supply capacity of urban power grids. This method solves the power flow equation based on AC power flow. The basic constraints are power generation capacity, line thermal stability, transformer capacity, and bus voltage. The power supply capacity is the objective function, but this method needs to use the parameter perturbation method at each search point to perform the second-order equivalent of the objective function. The accuracy of the equivalent model has a great influence on the result, and the computational complexity is greatly increased

Documents [7-9] stipulate that urban power grid planning should consider the planning principle of ensuring continuous power supply to users when any line is out of service or a main transformer in a substation is out of operation. Documents [10-11] propose to take into account "N- 1" criterion, although this method can directly calculate the power supply capacity of the distribution network without iteration and has the advantage of fast calculation speed, the solution obtained by using the direct method is not optimal under the existing constraints In some cases, the error is relatively large. The root cause is that when calculating the load rate of each main transformer in the process of solving the power supply capacity, it is considered that the load rate of all the main transformers in the same tie line unit is the same, which is not realistic. of

[0005] The existing distribution network power supply capacity calculation models and methods are generally aimed at the open-loop distribution network, and there are few reports on the model for the maximum power supply capacity of the ring power distribution network.

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