Design Of Power Circuit Of The Medium Voltage Wind Power Converter

Wind power generation is taking on some new trends at present. For example, the capacity of the single machine increases constantly, and the wind farm is gradually moving from land to sea. High power offshore wind turbine has become the focus of the world wind power industry. Converter is an important part of the wind power system. In the design of the medium voltage and high power wind power converter, the power circuit is usually designed as a power module for the advantages of compact structure and convenient maintenance. The design level of power module directly determines whether the converter performance is good or not. At present, the research on the control strategy of wind power converter has been relatively mature, but the engineering design of the main circuit and power circuit in high power offshore wind power converter is still lacking, especially in the design and research of heat dissipation as well as laminated busbars. Therefore, this thesis works on the heat dissipation and laminated busbars designing of the medium voltage converter, with respect to its main circuit topology and control strategy.The present development of the medium voltage high power converter is surveyed in several aspects, such as the multilevel converter topology structures, control strategies, heat dissipation and the laminated busbar designing.Then the NPC three-level converter’s working principle and control strategies of the machine side converter and the grid side converter are analysed, and some of the key components in the main circuit are optimizely selected for a 3MW wind power converter. The reasonability of control strategies and parameters selection are verified with MATLAB/Simulink simulationBased on the analysis of the power device loss calculation method, and heat flow path between internal heat source of power device and external environment, two types of water cooled plate are designed for medium voltage converter. The thermal performance of these two design schemes is campared using Icepak software. The correctness of heat dissipation design method for high power converter is verified by software thermal simulation and indirectly validated by temperature rise test of a low power converter..The laminated busbar low stray inductance characteristics and factors affecting the busbar stray inductance are analyzed. Four types of commutation circuits which lead toover voltage during the NPC three-level converter power devices turn-off process are summarized. Based on these work, two types of laminated busbar with different structure characteristics are designed for the power circuit of medium voltage converter, and the two busbars’stray inductance values are extracted using Ansoft Q3D. The correctness of the laminated busbar design for high power converter is verified with finite element simulation and indirectly validated by double pulse experiments of the low power converter.