Full-band conductance compensation method for improving MMC-HVDC stability under weak power grid

Abstract

The invention provides a full-band conductance compensation method for improving MMC-HVDC stability under a weak power grid. The method comprises the following steps: establishing a system grid-connected parallel form equivalent model through electrical parameters and control parameters of MMC-HVDC; deriving according to the equivalent model to obtain an MMC output admittance expression, and obtaining an output conductivity expression according to the MMC output admittance expression; and solving a first-order derivative about the angular frequency for the output conductance expression to obtain a minimum extreme point and a full-band conductance minimum value. Therefore, the negative conductance frequency band range and the full-frequency-band conductance compensation value of the MMC-HVDC control system are given, a full-frequency-band conductance compensation strategy is proposed based on the negative conductance frequency band range and the full-frequency-band conductance compensation value, and the stability of the MMC-HVDC control system under the weak power grid is remarkably improved.

Description

Technical field [0001] The present invention relates to the field of MMC control technology, and more particularly to a full-band conductance compensation method for improving MMC-HVDC stability under weak griding. Background technique [0002] Thanks to the urgent needs of the application scenarios, new energy is island sent out, new energy island sent, regional power grid asynchronous internet, and dozens of MMC-HVDC projects have been put into operation. With the increase in distributed power supply and network power and the extensive distribution of access grid positions, the grid is increasingly presenting weak grid characteristics, that is, the grid impedance is large and the mesh grid voltage contains rich background harmonics. The change in the operating mode of the grid also has led to a wide range of power grid impedance, when the weak AC system is short-circuited, the phase-locked loop cannot be accurately locked, and the traditional double-closed loop control strategy...

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Problems solved by technology

The change of the power grid operation mode also leads to the characteristics of the grid impedance showing a wide range of changes. When the short circuit of the weak AC system is relatively small, the phase-locked loop cannot lock the phase accurately, and the traditional double closed-loop decoupling control strategy cannot accurately and stably control the system. control, which brings serious challenges to the stable and efficient operation of MMC

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