MMC capacitor voltage equalization control method based on driving signal logic processing

Abstract

The present invention discloses an MMC capacitor voltage equalization control method based on driving signal logic processing. The method comprises: (1) collecting the current capacitor voltage values of submodules; (2) ranking the current capacitor voltage values of the submodules; (3) grouping and calculating the capacitor voltage difference values according to the ranking of the submodules.; and (4) performing logic processing of the original driving signals and distributing driving signals again for the submodules according to the grouping and the voltage difference values. The MMC capacitor voltage equalization control method based on a driving signal logic processing is low in real-time requirement, saved in the calculation resource of a controller and easy to be applied to a large-scale MMC system, does not need the detection of the leg current so as to reduce the communication complexity of the system and reduce the cost of partial current sensors, and does not need the addition of the hardware circuit so as to avoid extra system cost. Under the control of the MMC capacitor voltage equalization control method based on the driving signal logic processing, all the submodules share the same switch frequency and the switch stress, and the switch frequency is low so as to facilitate system thermal design, effectively recover from the capacitor voltage unbalance and improve the system reliability.

Description

technical field [0001] The invention belongs to the technical field of electric power systems, and in particular relates to an equalization control method of MMC capacitor voltage based on logical processing of driving signals. Background technique [0002] With the increasing contradiction between environmental pollution and energy supply and demand, a large number of policies have been introduced by governments to support the development of the renewable energy industry. The flexible DC transmission system based on the voltage source converter has the characteristics of independent control of active and reactive power, fast and convenient power flow reversal, etc., making it widely used in the fields of new energy grid connection, island and weak grid power supply. Compared with the traditional multilevel voltage source converter, the modular multilevel converter (MMC) has the advantages of high modularity, less output harmonic content and a common DC bus. Modular system ...

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Problems solved by technology

[0007] The present invention provides a balanced control method of MMC capacitor voltage based on drive signal logic processing, which can solve the problem of high sorting frequency, inconsistent switching frequency of power devices and power frequency of capacitor voltage increment under high-frequency carrier phase-shift modulation in the prior art. Problem with sorting algorithms not recovering from capacitance imbalance

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