Bipolar Y-typed Modular Multilevel DC/DC Converter With Bidirectional Fault Locking
The isolated high-voltage high-power converters,commonly used in the interconnection of HVDC power networks,have the disadvantanges of large volume,high cost and low transmission efficiency.This paper presents a bipolar Y-typed modular multilevel DC/DC converter which achieves the bidirectional transmission of DC power and effectively locks the bidirectional DC faults without using the intermediate transformers.Firstly,the topology of the converter and the working principle of the fault blocking are analyzed,and a mathematical model is established according to the principle of potential equivalence in the bridge arm.Based on the energy balance constraints of the inter-arm and inter-phases,the bridge arm current compensation control is then introduced under the closed-loop control to improve the transient performance of the transformer.Finally,a DC-MMC simulation model is built in the Matlab/Simulink.The feasibility and validity of the proposed DC-MMC bidirectional power transmission control and the bidirectional fault blocking capability are verified by analyzing the dynamic parameters such as the port current,the arm current and the arm capacitance voltage.
modular multilevel DC/DC converterDC power networksbridge arm energy balancebidirectional DC power transmissionbidirectional DC fault blocking
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