针对人工神经元网络应用中最主要的问题之一——"黑箱"特性进行文献综述.增加人工神经元网络系统的透明度是解决该问题必不可少的手段.为了便于理解各种已有方法的应用特点及其局限性,提出"透明度"研究中的方法分...针对人工神经元网络应用中最主要的问题之一——"黑箱"特性进行文献综述.增加人工神经元网络系统的透明度是解决该问题必不可少的手段.为了便于理解各种已有方法的应用特点及其局限性,提出"透明度"研究中的方法分类框架.首先将"透明度"研究划分为两种基本策略:1)将先验信息引入系统设计;2)从模型中提取系统相关规则或知识.在此基础上,对各种主要方法进一步分类并进行应用特点介绍.最后对机器学习多目标研究进行讨论.提出基于"性能价格比"与基于提高系统"透明度"的目标函数.指出提高"透明度"是神经元网络研究中最为基本而又直接的解决方案.为此提出"反馈知识增长(Knowledge Increasing via Feedback)"型机器学习方法.展开更多
Static synchronous compensators(STATCOM)can be used as a reactive power compensation for induction motor(IM)loads due to its effective control and good compensation.Terminal voltage control(TVC)in a STATCOM has a grea...Static synchronous compensators(STATCOM)can be used as a reactive power compensation for induction motor(IM)loads due to its effective control and good compensation.Terminal voltage control(TVC)in a STATCOM has a great influence on voltage dynamics which is a significant concern in a system with many IM loads.This paper investigates the interaction between IM loads and TVC in a STATCOM under weak grid conditions from the viewpoint of active and reactive power flow.A corresponding induction machine model is proposed,based on which the interaction mechanism between IM loads and TVC in a STATCOM can be intuitively understood.It is shown that the negative damping component provided by TVC in a STATCOM can lead to system oscillation instability.Grid strength and the inertia constant of the induction machine affect the extent of such interaction.Time-domain simulation results of IM loads connected to an infinite system through a long transmission line,with STATCOM compensation implemented in MATLAB/Simulink,validate the correctness of the analyses.展开更多
Diode clamped multi-level inverter （DCMLI） has a wide application prospect in high-voltage and adjustable speed drive systems due to its low stress on switching devices, low harmonic output, and simple structure. Ho...Diode clamped multi-level inverter （DCMLI） has a wide application prospect in high-voltage and adjustable speed drive systems due to its low stress on switching devices, low harmonic output, and simple structure. However, the problem of complexity of selecting vectors and capacitor voltage unbalance needs to be solved when the algorithm of direct torque control （DTC） is implemented on DCMLI. In this paper, a fuzzy DTC system of an induction machine fed by a three-level neutral-point-clamped （NPC） inverter is proposed. After introducing fuzzy logic, optimal selecting switching state is realized by applying various strategies which can distinguish the grade of the errors of stator flux linkage, torque, the neutral-point potential, and the position of stator flux linkage. Consequently, the neutral-point potential unbalance, the dr/dr of output voltage and the switching loss are restrained effectively, and desirable dynamic and steady-state performances of induction machines can be obtained for the DTC scheme. A design method of the fuzzy controller is introduced in detail, and the relevant simulation and experimental results have verified the feasibility of the proposed control algorithm.展开更多
文摘针对人工神经元网络应用中最主要的问题之一——"黑箱"特性进行文献综述.增加人工神经元网络系统的透明度是解决该问题必不可少的手段.为了便于理解各种已有方法的应用特点及其局限性,提出"透明度"研究中的方法分类框架.首先将"透明度"研究划分为两种基本策略:1)将先验信息引入系统设计;2)从模型中提取系统相关规则或知识.在此基础上,对各种主要方法进一步分类并进行应用特点介绍.最后对机器学习多目标研究进行讨论.提出基于"性能价格比"与基于提高系统"透明度"的目标函数.指出提高"透明度"是神经元网络研究中最为基本而又直接的解决方案.为此提出"反馈知识增长(Knowledge Increasing via Feedback)"型机器学习方法.
基金supported in part by National Basic Research Program of China (973 Program) (No.2012CB215100)Major Program of National Natural Science Foundation of China (No.51190104)National Natural Science Fund for Excellent Young Scholars (No.51322704)
文摘Static synchronous compensators(STATCOM)can be used as a reactive power compensation for induction motor(IM)loads due to its effective control and good compensation.Terminal voltage control(TVC)in a STATCOM has a great influence on voltage dynamics which is a significant concern in a system with many IM loads.This paper investigates the interaction between IM loads and TVC in a STATCOM under weak grid conditions from the viewpoint of active and reactive power flow.A corresponding induction machine model is proposed,based on which the interaction mechanism between IM loads and TVC in a STATCOM can be intuitively understood.It is shown that the negative damping component provided by TVC in a STATCOM can lead to system oscillation instability.Grid strength and the inertia constant of the induction machine affect the extent of such interaction.Time-domain simulation results of IM loads connected to an infinite system through a long transmission line,with STATCOM compensation implemented in MATLAB/Simulink,validate the correctness of the analyses.
文摘Diode clamped multi-level inverter （DCMLI） has a wide application prospect in high-voltage and adjustable speed drive systems due to its low stress on switching devices, low harmonic output, and simple structure. However, the problem of complexity of selecting vectors and capacitor voltage unbalance needs to be solved when the algorithm of direct torque control （DTC） is implemented on DCMLI. In this paper, a fuzzy DTC system of an induction machine fed by a three-level neutral-point-clamped （NPC） inverter is proposed. After introducing fuzzy logic, optimal selecting switching state is realized by applying various strategies which can distinguish the grade of the errors of stator flux linkage, torque, the neutral-point potential, and the position of stator flux linkage. Consequently, the neutral-point potential unbalance, the dr/dr of output voltage and the switching loss are restrained effectively, and desirable dynamic and steady-state performances of induction machines can be obtained for the DTC scheme. A design method of the fuzzy controller is introduced in detail, and the relevant simulation and experimental results have verified the feasibility of the proposed control algorithm.
