Parallel capacitor switching control method of sending-end converter station during high-power fluctuation

Abstract

The invention discloses a parallel capacitor switching control method of a sending-end converter station during high-power fluctuation. Dual criteria are employed, a first criterion is a reactive support capability criterion of a DC matching power supply, reactive power Q<ac-dc> provided by a DC sending-end power supply and needed by the convertor station is enabled not to exceed maximum reactivepower support capability Q<Gmax> of the DC sending-end power supply, otherwise a SC-type parallel capacitor group is directly switched; and a second criterion is a conversion bus voltage criterion, anSC group is switched if an AC voltage U<bus> of a conversion bus is still smaller than difference between a voltage reference value U<ref> and a voltage dead-zone value U<band> on the basis of conforming to the first criterion after delay t<ref> is passed, the SC group is removed if the U<bus> is larger than the sum of the U<ref> and the U<band>, otherwise the current SC groups in the station ismaintained. According to the control method proposed by the invention, the dual criteria are employed, the reactive power support capability of the DC matching power supply is fully utilized, the SC switching frequency during high-power stable running of a high-voltage DC convertor station and frequent fluctuation of a DC transmission power is reduced, the service lifetime of an SC circuit breakeris prolonged, and the control method has important significance to safe and economic running of a DC system.

Description

technical field [0001] The invention belongs to the field of electric power systems, relates to the technical field of reactive power control of high-voltage direct current converter stations, and in particular relates to a method for controlling switching of shunt capacitors when high power fluctuations occur in a sending-end converter station. Background technique [0002] During the operation of the HVDC system, the reactive power balance of the AC-DC system is mainly achieved by controlling the input sequence and quantity of reactive power units mainly including AC filters and shunt capacitors (SC) in the converter station. In order to prevent the AC filter from being overloaded and meet its filtering performance, the order of putting in reactive units is generally as follows: first put in all the AC filters except the standby group, and then put in the SC according to the need. When HVDC runs at high power, the reactive power consumption in the station is relatively lar...

AI Technical Summary

Problems solved by technology

[0005] In order to solve the problem of frequent switching of shunt capacitors, the present invention proposes a switching control method for shunt capacitors in high power fluctuations of the converter station at the sending end, using a DC matching power supply reactive power supporting capacity criterion unit (the first criterion unit) Coordinated with the converter bus voltage criterion unit (the second criterion unit), the sending-end converter station shunt capacitor switching control optimization scheme; the present invention aims at the operating scene characteristics of the DC sending-end power supply with dense electrical distance and makes full use of the On the basis of the reactive power compensation capability of the DC supporting power supply, combined with the two typical reactive power control schemes, the existing reactive power control scheme and the AC voltage control scheme, the reactive power support capability and commutation capacity of the target rectification station are controlled by the DC supporting power supply. The AC voltage of the busbar is the control quantity, and an optimization scheme for switching control of shunt capacitors is constructed when the operating power fluctuates under high-voltage DC heavy loads; the dual-criteria unit of the scheme improves the defect of single control quantity in the existing shunt capacitor control scheme, and the delay link Fully consider the reactive power support capacity of the DC sending end power supply, the purpose is to reduce the number of frequent switching of parallel capacitors when the high-voltage DC large-load operating power fluctuates, which can effectively prolong the service life of the parallel capacitor circuit breaker, which is of great importance to the safe and economic operation of the DC system. important meaning

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