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Self-adaptive virtual inertia frequency modulation control method for flexible direct-current power transmission system

A technology of virtual inertia and power transmission system, which is applied in the direction of AC network circuits, electrical components, circuit devices, etc., and can solve the problems of high reliability requirements of the main converter station, difficulty in parameter setting, and high requirements for inter-station communication. , to achieve the effect of facilitating frequency recovery, preventing DC voltage from exceeding the limit, and enhancing inertial frequency stability

Active Publication Date: 2021-03-23
NORTH CHINA ELECTRIC POWER UNIV (BAODING)
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  • Abstract
  • Description
  • Claims
  • Application Information

AI Technical Summary

Problems solved by technology

[0005] (1) The master-slave control method has higher requirements for inter-station communication and higher requirements for the reliability of the main converter station
[0006] (2) The control method of the virtual synchronous machine has a complex structure, and it is difficult to set parameters
[0007] (3) The droop control with additional frequency adjustment has the advantages of simple control structure, flexible terminal number expansion, and no dependence on communication, and has high engineering practicability; but the frequency modulation effect is relatively general, the transient fluctuation is large during the frequency modulation process, and the DC voltage may also be Overrun occurs

Method used

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  • Self-adaptive virtual inertia frequency modulation control method for flexible direct-current power transmission system
  • Self-adaptive virtual inertia frequency modulation control method for flexible direct-current power transmission system
  • Self-adaptive virtual inertia frequency modulation control method for flexible direct-current power transmission system

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Embodiment

[0079] In order to verify the effect of the proposed control method, based on the PSCAD / EMTDC electromagnetic transient simulation environment, the five-terminal flexible DC transmission system shown above is built to simulate the no-inertia control, fixed inertia control and adaptive virtual inertia control respectively. The frequency modulation effect of the method is compared. Four different working conditions are set at the AC grid G3, such as sudden input of large load, sudden removal of small load, instantaneous three-phase short-circuit fault of AC grid, and random fluctuating load access, to intuitively analyze the effect of the proposed control method under different working conditions. see Figure 4-7 The effect of each control strategy under different working conditions can be visually compared.

[0080] Depend on Figure 4 It can be seen that when the load increases greatly, in order to maintain the frequency stability of the AC side, the DC voltage changes great...

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Abstract

The invention provides a self-adaptive virtual inertia frequency modulation control method for a flexible direct-current power transmission system. The control method comprises the following steps of:firstly, realizing secondary frequency modulation of an alternating-current side system by controlling a reference value of active power in droop control; secondly, enabling virtual inertia power tobe equal to capacitor charging and discharging power, and establishing a coupling relationship between a direct-current voltage reference value and the active power; adopting self-adaptive virtual inertia control adjusted according to a fitting hyperbolic tangent function, reducing an inertia coefficient when a direct-current voltage is close to a limit value, thereby preventing the direct-currentvoltage from exceeding the limit value; and increasing the inertia coefficient when the direct-current voltage is far away from the limit value, thereby making the frequency more stable. With the method adopted, the overshoot in the secondary frequency modulation process is reduced, the frequency recovery of an instantaneous fault is facilitated, the frequency stability of an AC system is improved, and the stability of an interconnection system is improved.

Description

technical field [0001] The invention relates to the technical field of direct current transmission, in particular to a frequency modulation control method in a flexible direct current transmission system. Background technique [0002] At the end of the 20th century, flexible DC transmission technology has been greatly developed. Due to the advantages of flexible DC transmission technology in centralized transmission of new energy, asynchronous grid interconnection, weak grid and island power supply, so far, there have been a large number of flexible DC transmission projects. successively put into operation. At the same time, the flexible direct current transmission system can easily form a multi-terminal flexible direct current transmission system (MTDC) to realize multi-point interconnection. [0003] Although the flexible DC transmission system has many advantages, as the proportion of the flexible DC transmission system in the power grid is increasing, there are also som...

Claims

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Application Information

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Patent Type & Authority Applications(China)
IPC IPC(8): H02J3/36H02J3/24
CPCH02J3/36H02J3/24H02J2003/365Y02E60/60
Inventor 刘英培谢乾梁海平
Owner NORTH CHINA ELECTRIC POWER UNIV (BAODING)
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