不对称规则采样CPS-PWM的基波近似模型及其频率特性  

Fundamental Approximation Model and Frequency Characteristics of CPS-PWM with Asymmetric Regular Sampling

作　　者：张雪垠 徐永海 徐少博 肖湘宁 ZHANG Xueyin;XU Yonghai;XU Shaobo;XIAO Xiangning(State Key Laboratory of Alternate Eleclrical Power System with Renewable Energy Sources(North China Electric Power University),Beijing 102206,China)

机构地区：[1]新能源电力系统国家重点实验室(华北电力大学),北京市102206

出　　处：《电力系统自动化》2020年第6期91-97,共7页Automation of Electric Power Systems

基　　金：北京市自然科学基金资助项目(3172036)。

摘　　要：中压多电平换流器常采用模块化结构,可应用于交/直流配电网。配电网电压较低,换流器子模块数较少,因此常采用载波移相脉宽调制(CPS-PWM)提升等效开关频率。建立CPS-PWM模型是换流器系统级建模的基础之一。调制环节非线性,因此常分析其基波。现有CPS-PWM基波近似模型以桥臂等效开关频率为准,在不对称规则采样下模型延时偏低、误差较大。以子模块为基础,通过子模块输出叠加建立了零阶保持器(ZOH)经纯延时近似、不近似以及纯延时环节经Padé近似的3种形式CPS-PWM基波近似模型,更准确地反映了CPS-PWM的频率特性。仿真研究验证了理论分析的正确性。Medium-voltage multilevel converters usually adopt modular structures. They can be used in AC/DC distribution networks. As a result of the relatively low voltage in distribution networks, the number of converter sub-modules is small.Therefore, the carrier phase shift pulse width modulation(CPS-PWM) is usually adopted to increase the equivalent switching frequency. The modeling of CPS-PWM is one of the fundamentals of converter system modeling. The modulation stage is nonlinear, and thus, only the fundamental frequency component is usually considered. The existing fundamental approximation model of CPS-PWM is based on equivalent switching frequency, hence the low time delay and large errors exist when asymmetric regular sampling is adopted. In this work, the following three forms of fundamental approximation models of CPS-PWM are established, i. e. zero order holder(ZOH) delay approximation, ZOH no approximation, and delay Padé approximation. These models are developed by combining the outputs of sub-models on the basis of a sub-module. The proposed models reflect the frequency characteristics of CPS-PWM more accurately than the traditional one. A simulation study verifies the correctness of the theoretical analysis.

关 键 词：多电平换流器 载波移相脉宽调制(CPS-PWM) 不对称规则采样 基波近似模型 频率特性 

分 类 号：TM46[电气工程—电器]