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Control method for improving power grid frequency stability of flexible DC system converter

A stability control and flexible DC technology, which is applied in the direction of power transmission AC network, reducing/preventing power oscillation, etc., can solve the problem that the equivalent parameters of the system are difficult to obtain, the power controllability of the DC transmission system cannot be realized, and the equivalent rigidity of the AC side system Coefficient sensitivity and other issues, to achieve the effect of power support improvement

Active Publication Date: 2019-07-09
ELECTRIC POWER RESEARCH INSTITUTE, CHINA SOUTHERN POWER GRID CO LTD +1
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Problems solved by technology

Although VSG technology can increase the system inertia and provide frequency support, it is sensitive to the equivalent rigidity coefficient of the AC side system. The equivalent rigidity coefficient of the AC system will affect the output distribution relationship between the DC system and the synchronous motor unit. In actual situations, the system, etc. It is difficult to obtain the efficiency parameters, so the power controllability of the DC transmission system cannot be realized

Method used

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  • Control method for improving power grid frequency stability of flexible DC system converter
  • Control method for improving power grid frequency stability of flexible DC system converter
  • Control method for improving power grid frequency stability of flexible DC system converter

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Embodiment Construction

[0045] The present invention will be described in detail below in conjunction with the accompanying drawings and embodiments.

[0046] A novel dynamic frequency support control method based on the combination of FLC and improved virtual synchronous control proposed by the present invention, such as figure 2 As shown, among them, the FLC control link is as follows image 3 shown. Considering the characteristics of the rotor of the equivalent unit, the characteristics of the governor and the characteristics of the steam turbine unit, the frequency dynamics of the AC power grid at the receiving end can be expressed as:

[0047]

[0048] In the formula, Δω, ΔP m , ΔP L and ΔP mmc are the output frequency, mechanical power, load, and MMC injection power of the receiving end of the equivalent unit, respectively; H and D are the equivalent inertia and damping of the equivalent unit, respectively; 1 / R is the primary frequency modulation characteristic of the equivalent unit; G...

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Abstract

The invention relates to a control method for improving power grid frequency stability of a flexible DC system converter. The method is implemented according to FLC control and virtual synchronous control of a DC frequency limiter, in FLC control link, active power adjustment increment Delta PFLC required by frequency support of an MMC is obtained by detecting AC power grid frequency changing quantity and additive frequency feedback control loop. The method is characterized in that a frequency reference and a phase reference of an MMC output voltage are obtained by a virtual synchronous control-based active power control loop, a voltage amplitude reference of the MMC output voltage is obtained by a reactive power or AC voltage control loop, and AC voltage closed-loop tracing control is achieved by a voltage-current dual-loop control strategy after the phase reference and the amplitude reference of the output voltage are obtained.

Description

technical field [0001] The invention relates to a control method for improving the frequency stability of a power grid. Background technique [0002] As a new generation of DC transmission technology, voltage source converter based high-voltage DC (VSC-HVDC) has been widely developed and accepted worldwide because of its high power factor, flexible control, and low impact on the environment. application [1-3] . The voltage source converters commonly used in flexible DC transmission technology mainly consist of the following forms: two-level converters, diode-clamped three-level converters, and modular multilevel converters (MMCs). ). Compared with two-level and three-level converter topologies, MMC has the advantages of low switching frequency, good harmonic characteristics and easy expansion, so it is widely used in flexible DC transmission [4-6] . [0003] The asynchronous interconnection of two-region or even multi-region AC systems through flexible DC transmission t...

Claims

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Application Information

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IPC IPC(8): H02J3/24H02J3/36
CPCH02J3/24H02J3/36Y02E60/60
Inventor 陈雁洪潮李鹏飞李霞林郭力
Owner ELECTRIC POWER RESEARCH INSTITUTE, CHINA SOUTHERN POWER GRID CO LTD
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