VSC-MTDC (Voltage source converter-multi-terminal high voltage direct current) voltage control method for offshore wind farm integration

Abstract

The invention provides a VSC-MTDC (Voltage source converter-multi-terminal high voltage direct current) voltage control method for offshore wind farm integration. The method comprises steps: voltage outer-loop control in a control system for a grid-side converter station is put to an integrated control center; an active power distribution ratio Ki is set according to power requirements, the power distribution ratio Ki is overlapped to a current given value for ith converter station inner-loop control, the Ki is sent to a corresponding converter station in a communication mode, and thus through adjusting a power distribution coefficient of the integrated control center, adjustment on active power distribution ratios of different converter stations can be realized, and stability and accuracy of DC voltage are barely influenced. When the strategy is compared with the traditional voltage droop control strategy in three conditions in which a wind speed varies, three-phase short circuit fault happens to the power grid and the converter station quits operation, better control effects are realized in aspects of DC voltage control precision and flexible active power distribution.

Description

technical field [0001] The invention relates to the field of high-voltage direct current transmission, in particular to a VSC-MTDC (voltage source converter multi-terminal high voltage direct current) direct current voltage control method for grid-connected offshore wind farms. Background technique [0002] More and more offshore wind farms will be put into construction in Europe, Asia and North America. In order to realize the grid connection of these large-scale and long-distance fluctuating wind power, the VSC-MTDC system has many technical advantages, such as reducing transmission Loss, increase control flexibility and improve power quality, etc. For the control of multi-terminal flexible DC transmission system, it is very important to stabilize the DC voltage and allocate active power flexibly. At the same time, in order to ensure the safe operation of the multi-terminal DC transmission system, it is also necessary to satisfy the N-1 rule, that is, when one of the conv...

AI Technical Summary

Problems solved by technology

But this will inevitably introduce DC voltage deviation, and the active power distribution ratio based on line impedance is difficult to adjust accurately, especially when the topology of the multi-terminal DC transmission system becomes more complex

There are also literatures that propose some methods that combine the above several control strategies to achieve the required control effect through the switching of control modes, but the complexity of switching instructions is unavoidable.

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