低频输电技术原理之二——M^(3)C的稳态特性与主回路参数设计

Principles of Low Frequency Power Transmission Technology:Part 2-The Steady-state Characteristics of M^(3)C and the Design of Main Circuit Parameters

低频海底电缆输电技术在远海风电送出和海上风电场构网方面具有竞争优势,而M^(3)C(模块化多电平矩阵变流器)是低频输电技术的核心元件。针对M^(3)C的稳态特性与主回路参数设计展开研究,基于M^(3)C在αβ坐标系中的数学模型并依据控制器将M^(3)C环流抑制到零的条件,推导出各桥臂电流的表达式;基于开关函数法和逐次逼近法,推导出子模块电容电流集合平均值以及子模块电容电压集合平均值的解析表达式。并在此基础上,给出确定桥臂子模块数目的算法和设计子模块电容器电容值的公式。

Low-frequency submarine cable power transmission technology has competitive advantage in offshore wind power transmission and offshore wind farm network construction,and the modular multilevel matrix converter(M^(3)C)is the core component of low-frequency power transmission technology.This paper focuses on the steady-state characteristics and the design of main circuit parameters of the M^(3)C.Based on the mathematical model of the M^(3)C in theαβcoordinate system and the condition that the controller suppresses the M^(3)C circulating current to zero,this paper derives the expression of the arm current of the M^(3)C.Based on the switching function(SF)approach and the successive approximations method(SAM),this paper derives the analytical expressions of the set average value of the sub-module capacitor current and the set average value of the sub-module capacitor voltage of the M^(3)C.On this basis,the algorithm for determining the number of sub-modules of the arm and the formula for designing the capacitance value of the sub-module are given.