低载波比调制下的MMC-UPFC电容电压减频效应
Frequency-Decrease Effect in the Capacitor Voltage under the Low Modulation Frequency Ratio in an MMC-UPFC
陈志军 1王骏 1郁超 1张珂 1赵云龙 2王楚扬2
作者信息
- 1. 国网江苏省电力有限公司苏州供电分公司,江苏苏州 215000
- 2. 河海大学能源与电气学院,江苏南京 211106
- 折叠
摘要
低载波比(载波频率与基波频率之比)的载波移相调制策略可有效降低MMC-UPFC的开关损耗,但会导致"减频效应"造成电容电压谐波频率明显降低,严重削弱电容电压均衡策略的控制效果.根据电容电压谐波频率随载波比降低的规律,定量分析了低载波比调制下MMC-UPFC电容电压的减频效应,明确了低载波比与电容电压低频波动、子模块电容不稳定充放电状态和子模块间电容电压不均衡间的内在联系及其发生机理;在此基础上,提出一种基于RBF神经网络的减频效应抑制策略,通过检测电容电压的谐波分量进行最优载波比选择和电容电压控制.最后以苏州南部500kV UPFC示范工程为参考进行仿真,证明了MMC-UPFC电容电压的减频效应的存在性以及抑制方法的有效性.
Abstract
The carrier phase-shifting modulation strategy with a low carrier ratio(the ratio of carrier frequency to fundamental frequency)can effectively reduce the switching loss of MMC-UPFC but is prone to lead to a"frequency-decrease effect",resulting in a significant reduction in the harmonic frequency of the capacitor voltage,which severely weakens the control effectiveness of the capacitor voltage balancing strategy.Based on the rule that the harmonic frequency of the capacitor voltage decreases with the carrier ratio,this paper quantitatively analyzes the frequency reduction effect of MMC-UPFC capacitor voltage under low carrier ratio modulation.It clarifies the intrinsic relationship and occurrence mechanism between the low carrier ratio,low-frequency fluctuation of capacitor voltage,unstable charging and discharging state of sub-module capacitors,and imbalance of capacitor voltage among sub-modules.On this basis,a frequency reduction effect suppression strategy based on RBF neural networks is proposed,which optimizes carrier ratio selection and capacitor voltage control by detecting the harmonic components of the capacitor voltage.Finally,simulations were conducted using the 500kV UPFC demonstration project in southern Suzhou as a reference,demonstrating the existence of the frequency reduction effect of MMC-UPFC capacitor voltage and the effectiveness of the suppression method.
关键词
模块化多电平换流器/统一潮流控制器/减频效应/载波移相调制/RBF神经网络Key words
modular multilevel converter/unified power flow controller/frequency-decrease effect/carrier phase-shift PWM/RBF neural network引用本文复制引用
基金项目
江苏省电力有限公司科技项目(J2023001)
出版年
2024
NETL
NSTL
万方数据