Power grid unit scheduling method based on transient overvoltage constraint after extra-high voltage direct current fault

Abstract

The invention relates to a power grid unit scheduling method based on transient overvoltage constraint after an extra-high voltage direct current fault, and belongs to the technical field of power grid scheduling. According to the method, a high-proportion new energy direct current sending-out power grid is considered; after the short-circuit capacity is reduced, the transient overvoltage level isincreased; for ensuring that the transient overvoltage of the system meets the requirements under a certain direct-current transmission limit and ensuring that the short-circuit capacity of each direct-current bus of the system meets the minimum constraint, the startup mode is arranged on the basis of ensuring the minimum constraint of the short-circuit capacity, and the method has important significance for stabilizing voltage fluctuation and reducing the transient overvoltage level of a sending end.

Description

technical field [0001] The invention relates to a dispatching method of power grid units based on transient overvoltage constraints after UHV DC faults, and belongs to the technical field of power grid dispatching. Background technique [0002] With the rapid development of ultra-high voltage direct current and new energy, large-scale new energy is connected to the direct current transmission system, and a large number of conventional water and thermal power units are replaced by new energy. New energy units are asynchronously isolated from the grid through inverters. operation, resulting in a lower disturbance response capability of the new energy system than conventional units. Due to the large disturbance during DC faults and the poor ability of new energy units to withstand voltage disturbances, the transient overvoltage problem of the DC busbar and nearby new energy sources is prominent after the DC fault. A further increase in voltage will easily lead to the cascading...

AI Technical Summary

Problems solved by technology

[0002]With the rapid development of UHV DC and new energy, large-scale new energy is connected to the DC transmission system, and a large number of conventional water and thermal power units are replaced by new energy .The new energy unit realizes asynchronous isolation operation with the grid through the inverter grid connection, resulting in a lower disturbance response capability of the new energy system than the conventional unit

Due to the large disturbance during DC faults and the poor ability of new energy units to withstand voltage disturbances, the transient overvoltage problem of the DC busbar and nearby new energy sources is prominent after the DC fault. A further increase in voltage may easily lead to the cascading disconnection of surrounding wind turbines. The above problems have become the main constraints restricting the increase of DC power

[0003] At present, there have been relatively in-depth research on the problem of transient overvoltage after DC faults, mainly focusing on the following two aspects. With the rapid development of new energy, large-scale new energy is centrally connected to the DC external transmission system, and a large number of conventional water and thermal power units are replaced by new energy. New energy units are connected to the grid through inverters to achieve asynchronous and isolated operation, resulting in new energy systems. Disturbance response capability is lower than that of conventional units

Due to the large disturbance during DC faults and the poor ability of new energy units to resist voltage disturbances, the transient overvoltage problem of DC busbars and new energy sources in the vicinity is prominent after DC faults [1-4]. And the reduction of the power flow will lead to a further increase of the voltage, which will easily lead to the cascading disconnection of the surrounding wind turbines. The above problems have become the main constraints restricting the increase of DC power.

[0004] In the actual operation of the power grid, for a specific DC line, in order to ensure that the DC bus has sufficient short-circuit capacity to support the transient overvoltage after a DC fault, it is necessary to rely on a large number of The simulation calculation determines the operation mode of the unit. Since the current combination of unit modes and simulation analysis based on offline data cannot enumerate all possible operation modes of the system, we can only focus on the start-up mode of new energy sources and conventional units in the near area, and through the operation control plan. The DC transmission power is related to the number of conventional units in the near area. Under a certain DC transmission power, it is necessary to arrange the start-up combination of the conventional units in the near area to meet the requirements.

However, this method of strongly associating the DC power with the start-up mode of the near-area unit has stricter requirements on the arrangement of the DC near-area unit to a certain extent. When there are two or more DC sending points, the most serious way is usually used when formulating the plan, that is, to ensure that the transient overvoltage level does not exceed the standard after a single DC fault is considered as the goal and the start-up method of the nearby unit is not considered. The start-up mode of conventional units and other DC supporting units in the near area leads to the need to maintain a relatively large number of conventional units in the DC group transmission system. During the period of new energy consumption, the space for new energy consumption is reduced.

The research on unit combination and operation mode in the academic circle is also relatively in-depth, and generally focuses on the optimization and solution algorithms of various unit combinations and the research on multi-objective, multi-constraint, and multi-decision variable unit combinations. Considering DC group transient overvoltage and short-circuit current capacity There are relatively few studies on the start-up mode of the unit with support constraints

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