Unified High Voltage Direct Current Converter Control Dedicated for New Power Systems
The development of new power systems has put forward higher demands for flexible DC transmission technology.With the proposal of the heterogeneous series converter,the flexible DC converter has been unified at the topology level.However,at the control level,although the traditional control has the power decoupling ability,there is a close coupling between AC voltage,DC voltage,and submodule capacitor voltage,which makes it difficult to fully utilize the advantages of flexible operation of fully controlled devices based converters.This article first proposes the concept of control degree of freedom based on traditional DC converter control structures,and introduces a characterization method of modulation ratio to construct a multi-degree of freedom control system for MMC converters.By analyzing the voltage coupling mechanism inside MMC and its relationship with modulation ratio,the correlation between various MMC control strategies is systematically revealed,forming a 4-degree of freedom unified control structure for MMC converters with"unified function and unified structure".And the applications and potentials of the 4-degree of freedom control structure are analyzed for MMC converters with different control objectives in flexible DC transmission systems.Finally,the performances of MMC 4-degree of freedom control in typical application scenarios are verified in a single-end MMC physical dynamic simulation experimental system.
flexible DC transmission systemsmodular multilevel convertervoltage coupling4-degree of freedom controlmodulation ratiodynamic simulation experiment
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维普
