Determining method of maximum load in direct current support weak receiving system recovery procedure

Abstract

The invention discloses a maximum load determination method in the process of restoring a direct current support weak receiving system, which is simple, low in computation and easy to implement. The method comprises the following steps of: 1) determining an equivalent circuit of a high voltage direct current (HVDC)-containing transmission system under different control modes and linearizing the equivalent circuit; 2) solving a transfer function of a direct current control system, and respectively drawing root-locus diagrams when a frequency limitation link does not function or functions;3) analyzing a relationship between the stability and the direct current control mode of the direct current control system and short circuit capacity and moment of inertia of transmitting-end and receiving-end systems through the root-locus diagrams to obtain value ranges of the gain Kp at a constant current control link and the gain G at the frequency limitation link, and determining a practicable operating mode of the direct current system; and 4) determining one-time restorable maximal workload in the process of restoring an alternating current system according to frequency constraint conditions of the alternating current system and the direct current operating mode.

Description

technical field [0001] The invention relates to a method for determining the maximum load in the recovery process of a weak receiving end system supported by direct current, and belongs to the technical field of HVDC (high voltage direct current transmission) stability control. Background technique [0002] At present, the biggest problem facing the restoration process of the power grid after a large-scale blackout is that large-capacity generator sets cannot be quickly put into the power grid due to the influence of many factors such as unit characteristics and minimum start-up time constraints. Due to its good transmission stability and rapid adjustment, HVDC has the potential to support the recovery of the power system. It is used for emergency power support to stabilize the frequency of the AC system when the AC system is short-circuited or cut off due to a fault. The commonly used method is Using DC power boost function to compensate AC system active power shortage (Xie...

AI Technical Summary

Problems solved by technology

[0004] 1 The recovery process of the existing AC system is to drive the recovery of other units and loads in the system through the unit with black start capability in the AC system, and the recovery speed of the system is limited by the active output of the units that have been started

[0005] 2 Generator output adjustment rate is obviously slower than DC power adjustment rate (Liu Liangjun, Wang Xinming, Li Hongjuan, Zhao Wanjun. Fast power control of DC system with AC and DC parallel operation. China Electric Power, 1995, 2:2-8.), when the system is restored Poor ability to adjust system frequency during the process

[0006] 3 The most commonly used control method for DC control systems in HVDC transmission systems is constant current control on the rectifier side and constant voltage control on the inverter side (Xu Zheng. Dynamic Behavior Analysis of AC and DC Power Systems. Mechanical Industry Press, 2004), but in the affected This control method is less stable when the short-circuit capacity of the AC system at the end is small (S.Barsali, R.Salvati, R.Zaottini. Use of HVDC links for power system restoration. Electric Power Systems Research.79(2009):973–983. )

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