Modular multi-level converter-based reactive power compensation device

Abstract

The present invention provides a modular multi-level converter-based reactive power compensation device. According to the device, new strategies of capacitor voltage balance control between sub-modules are adopted; the difference value Ndiff of the number of sub-modules of a bridge arm which are required to be switched on in the current period and the number of sub-modules of the bridge arm which are required to be switched on in the last current period is obtained through a modulation strategy; whether the difference value Ndiff is 0 is judged; if the difference value Ndiff is 0, the switching states of the sub-modules in the current period and the sub-modules in the last period are identical; if the difference value Ndiff is not 0, an optimization strategy according to which stabilization coefficient is introduced is adopted, so that sub-modules of which the capacitor voltages do not exceed limits can have ability for maintaining original switching states, and therefore, the switching frequency of a device can be decreased; the sub-modules are grouped according to the maximum value and minimum value of the capacitor voltages which are processed based on the introduced stabilization coefficient, and therefore, a large amount of execution time and complex calculation required by a traditional sorting algorithm can be avoided; and corresponding sub-modules are switched on according to the current direction of the bridge arm.

Description

technical field [0001] The invention relates to the field of electric power technology, in particular to a reactive power compensation device based on a modular multilevel converter. Background technique [0002] With the rapid development of the power system, the requirements for the voltage level and capacity of reactive power compensation are getting higher and higher, and a series of reactive power compensation devices with cascaded multi-level topology have emerged as the times require. The application of MMC (Modular Multilevel Converter, Modular Multilevel Converter) reactive power compensation device in high-voltage and high-power occasions is increasing day by day. The traditional MMC-STATCOM (Modular Multilevel Converter-Static Synchronous Compensator, based on Modular Multilevel Converter-Static Synchronous The voltage balance control method among the various sub-modules of the inverter (static synchronous compensator) device has the disadvantages of frequent swit...

AI Technical Summary

Problems solved by technology

The application of MMC (Modular Multilevel Converter, Modular Multilevel Converter) reactive power compensation device in high-voltage and high-power occasions is increasing day by day. The traditional MMC-STATCOM (Modular Multilevel Converter-Static Synchronous Compensator, based on Modular Multilevel Converter-Static Synchronous The voltage balance control method between the various sub-modules of the inverter (static synchronous compensator) device has the disadvantages of frequent switching of sub-modules, which causes the switching device frequency to be too high, and the sorting algorithm is complicated and the execution time increases rapidly with the increase of the number of sub-modules.

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