Optimum design method for extra-high voltage multi-level flexible direct-current power transmission operation interval

Abstract

The invention relates to an optimum design method for an extra-high voltage multi-level flexible direct-current power transmission operation interval, and belongs to the field of high-voltage direct-current power transmission converter control strategies. The method comprises the following steps: obtaining upper and lower bridge arm currents of a converter through current transformer measurement, and averaging to obtain a current error generated by bridge arm alternating ring current; integrating the current error to obtain ring current voltage drop generated by the bridge arm alternating ring current; calculating direct-current voltage, internal phase electromotive force of the converter and the ring current voltage drop to obtain upper and lower bridge arm voltage reference values, and participating modulation. The method has the advantages that internal components of the converter do not need to be modified, and system parameters do not need to be changed, so that the original performances of the converter are guaranteed; the power operation interval of the converter is optimized on the basis of original equipment, and the original construction occupied area and relatively low investment cost are guaranteed. The power operation interval of the converter is optimized, and simultaneously the capacitor voltage fluctuation of sub-modules is reduced, so that the bridge arm ring current is inhibited.

Description

technical field [0001] The invention relates to the field of control strategies for high-voltage direct current transmission converters, in particular to a control method for optimizing the operating range of the converter, especially a method for optimizing the operating range of UHV modular multi-level flexible direct current transmission. Background technique [0002] Applying the flexible DC transmission system to overhead lines can greatly reduce construction costs and increase line transmission capacity. However, for MMC, the sub-module capacitor voltage presents low-frequency periodic fluctuations during actual operation, which is limited by the voltage of the sub-module IGBT devices. To ensure the breaking capacity, the fluctuation amplitude of the capacitor voltage of the sub-module must be within the specified range, and the capacitor voltage of the sub-module is directly related to the operating point of the system power, so the operating range of the system power ...

AI Technical Summary

Problems solved by technology

[0004] 1) Increasing the parameters of the internal components of the converter will inevitably increase the volume of the components themselves, thereby increasing the construction area of ​​the converter station

[0005] 2) To modify the structure and components inside the converter, the project is complicated and the investment is high, and the original performance of the converter will change

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