Frequency Regulation of Alternating Current Microgrid Based on Hierarchical Control Using Fuzzy Logic

An alternating current(AC)microgrid is a system that integrates renewable power,power converters,controllers and loads.Hierarchical control can manage the frequency of the microgrid to prevent imbalance and collapse of the system.The existing frequency control methods use traditional proportion integration(PI)controllers,which cannot adjust PI parameters in real-time to respond to the status changes of the system.Hierarchical control driven by fuzzy logic allows real-time adjustment of the PI parameters and the method used a two-layer control structure.The primary control used droop control to adjust power distribution,and fuzzy logic was used in the voltage loop of the primary control.The secondary control was added to make up for frequency deviation caused by droop control,and fuzzy logic was used in the secondary frequency control to deal with the dynamic change of frequency caused by the disturbances of loads.The proposed method was simulated in Matlab/Simulink.In the primary control,the proposed method reduced the total harmonic distortion(THD)of two cycles of the output voltage from 4.19%to 3.89%;in the secondary control,the proposed method reduced the frequency fluctuation of the system by about 0.03 Hz and 0.04 Hz when the load was increased and decreased,respectively.The results show that the proposed methods have a better effect on frequency maintenance and voltage control of the AC microgrid.

A Fuzzy Logic Based Supervisory Hierarchical Control Scheme for Real Time Pressure Control

This paper describes a supervisory hierarchical fuzzy controller （SHFC） for regulating pressure in a real-time pilot pressure control system. The input scaling factor tuning of a direct expert controller is made using the error and process input parameters in a closed loop system in order to obtain better controller performance for set-point change and load disturbances. This on-line tuning method reduces operator involvement and enhances the controller performance to a wide operating range. The hierarchical control scheme consists of an intelligent upper level supervisory fuzzy controller and a lower level direct fuzzy controller. The upper level controller provides a mechanism to the main goal of the system and the lower level controller delivers the solutions to a particular situation. The control algorithm for the proposed scheme has been developed and tested using an ARM7 microcontroller-based embedded target board for a nonlinear pressure process having dead time. To demonstrate the effectiveness, the results of the proposed hierarchical controller, fuzzy controller and conventional proportional-integral （PI） controller are analyzed. The results prove that the SHFC performance is better in terms of stability and robustness than the conventional control methods.

Movability of the tracked pipeline-robot based on hierarchical fuzzy control

The turning motion of a tracked pipeline-robot implemented by skid steering is a nonholonomic dynamic problem with intrinsic nonlinearity, to which the classical control method is inappropriate and cannot be applied. This paper presents a novel path tracking control method based on hierarchical fuzzy structure. The controller consists of three sub-level low dimensional fuzzy control systems： fuzzy supervisory control, fuzzy steering and fuzzy velocity control. As a result, establishing the bases of rules for the fuzzy control becomes feasible and simplified, and the related controller can be adapted to complicated ground and environment. Using this method, the number of fuzzy controt rules is greatly decreased so that the curse of dimensionality causing the multivariable problem does not occur. Simulation and experimental results validate the effectiveness of the proposed method with satisfied performance on path tracking. Autonomous navigation of the caterpillar-inspired pipeline-robot is also implemented based on the sensor feedbacks.

Intelligent Control Scheme of Engineering Machinery of Cluster Hybrid System

In a hybrid system, the subsystems with discrete dynamics play a central role in a hybrid system. In the course of engineering machinery of cluster construction, the discrete control law is hard to obtain because the construction environment is complex and there exist many affecting factors. In this paper, hierarchically intelligent control, expert control and fuzzy control are introduced into the discrete subsystems of engineering machinery of cluster hybrid system, so as to rebuild the hybrid system and make the discrete control law easily and effectively obtained. The structures, reasoning mechanism and arithmetic of intelligent control are replanted to discrete dynamic, conti- nuous process and the interface of the hybrid system. The structures of three types of intelligent hybrid system are presented and the human experiences summarized from engineering machinery of cluster are taken into account.

分布式电驱动汽车横摆稳定性控制

针对分布式电驱动汽车在转向变道、高速和低附着系数路面等极限工况下容易失去稳定的情况,提出一种分层控制策略.对车辆进行了稳定性分析,判断控制器开启条件.上层控制器采用模糊滑模控制,积分滑模控制得到附加横摆力矩,为了削减积分滑模控制器的抖振,采用模糊控制器进行优化.下层控制器采用基于轮胎负荷率的纵向力分配和基于轴载比例的纵向力分配,并对两种力矩分配进行对比,通过Carsim和MATLAB/Simulink联合仿真,分别在高速高附着系数路面和低速低附着系数路面进行验证.结果表明:提出的稳定控制策略能有效提升车辆的稳定性,且两种力矩分配器都有较好的控制效果,其中基于轴载比例的纵向力分配效果更好.

基于模糊控制的锂电池组分层均衡研究

传统的电感式均衡电路中要实现电池组均衡,能量只能通过相邻电池慢慢传递而不能在任意电池间转移。这种均衡方式效率低,均衡路径、时间长。为此,提出一种Buck-Boost电路与反激式电路相结合的新型分层拓扑。组内均衡采用双向Buck-Boost电路,使能量仅在相邻两节电池之间转移,因而均衡路径短。组间均衡采用双向反激式电路,通过控制原副边绕组开关管状态,使能量在模组与电池组间相互转移,从而达到电池组均衡。在均衡过程中加入模糊控制策略,动态调节开关管的占空比,以输出合适的均衡电流、提高均衡效率。搭建Matlab仿真模型进行分析。仿真结果表明,所提出的均衡电路相较于传统的Buck-Boost电路在静置和充、放电状态下均衡时间分别缩短约18%、17%和20%。均衡效率的提高对未来电动汽车等多锂电池串联设备的发展有着重要意义。

红外干燥箱变论域模糊PID复合温控设计

烘干失重法粮食水分测定过程中,干燥箱温度的精准控制是检测结果准确性的重要保障。针对干燥箱温度变化过程非线性、时滞性和温控精度高的特点,提出一种基于粒子群模型参数辨识的变论域模糊PID复合温度控制策略。基于红外辐射干燥机理及能量守恒方程建立温控系统非线性模型,并利用粒子群优化算法完成参数辨识,通过设定二级偏差阈值,将变论域模糊PID算法结合Bang-Bang控制方法构成自适应分级复合控制策略。系统仿真实验表明:相较于常规PID控制和传统模糊PID控制方法,改进后的复合控制策略在超调量、调节时间和控制进度方面明显改善,在不同工作点温度下,控制误差均小于0.4℃,且具有较好的抗干扰能力。

跷跷板系统干扰补偿的分层滑模控制策略研究

为提高跷跷板系统在外部干扰下的平衡控制性能,提出一种基于指数收敛干扰观测器与切换增益模糊自适应分层滑模控制相结合的复合控制策略。首先,设计一种指数收敛干扰观测器,对系统受到的外部扰动等不确定因素进行估计补偿,以改善控制器鲁棒性。该观测器不需要状态变量二阶导的信息,可以应对实际工程中难以通过求导的方式获取加速度信号的问题。然后,针对跷跷板这类强耦合欠驱动系统提出一种分层滑模控制算法,并进一步针对滑模控制算法在未知大干扰下切换增益过大的问题,通过模糊规则的设计将切换增益模糊化,以降低系统抖振。最后,仿真和试验结果表明,相较于传统的滑模控制算法,该分层滑模控制算法抗干扰能力更强、切换增益更低。该策略可应用于类跷跷板平衡控制的实际系统。

基于分布式驱动汽车的分层式控制系统设计

目前汽车之所以没有广泛采用轮毂电机驱动车轮,其一是考虑成本,其二是轮毂电机的搭载大大增加了簧下质量,对车辆行驶过程中的操纵稳定性有较大影响。以分布式驱动汽车为研究对象,设计分层式控制系统:上层控制器对车辆总横向运动进行解耦控制,其中纵向采用PID控制跟踪纵向车速,横向设计滑模控制器计算所需方向盘转角;中间层采用模糊控制计算维持车辆行驶稳定性所需附加横摆力矩;底层以轮胎附着利用率为优化目标对力矩进行最优分配。对比仿真试验表明:分层式控制系统可有效降低车辆行驶过程中的横摆角速度16%~48%,质心侧偏角62%~67%,抑制了实际值与理想值之间的偏差,提高了车辆在行驶过程中的安全性和舒适性。

价值工程在绿道项目成本控制中的应用

运用模糊德尔菲法,建立绿道功能评价模型,采用层次分析法确定绿道功能指标的权重值,运用价值工程理论对绿道建设方案进行优化和完善。将价值工程应用于DH绿道GC段的建设,该项目证明了在绿道景观项目中应用价值工程进行成本控制的可行性,并为其他类似的政府项目引入价值工程提供参考。

Dynamic stability enhancement of interconnected multi-source power systems using hierarchical ANFIS controller-TCSC based on multi-objective PSO

Suppression of the dynamic oscillations of tie-line power exchanges and frequency in the affected interconnected power systems due to loading-condition changes has been assigned as a prominent duty of automatic generation control(AGC). To alleviate the system oscillation resulting from such load changes, implementation of flexible AC transmission systems(FACTSs) can be considered as one of the practical and effective solutions. In this paper, a thyristor-controlled series compensator(TCSC), which is one series type of the FACTS family, is used to augment the overall dynamic performance of a multi-area multi-source interconnected power system. To this end, we have used a hierarchical adaptive neuro-fuzzy inference system controller-TCSC(HANFISC-TCSC) to abate the two important issues in multi-area interconnected power systems, i.e., low-frequency oscillations and tie-line power exchange deviations. For this purpose, a multi-objective optimization technique is inevitable. Multi-objective particle swarm optimization(MOPSO) has been chosen for this optimization problem, owing to its high performance in untangling non-linear objectives. The efficiency of the suggested HANFISC-TCSC has been precisely evaluated and compared with that of the conventional MOPSO-TCSC in two different multi-area interconnected power systems, i.e., two-area hydro-thermal-diesel and three-area hydro-thermal power systems. The simulation results obtained from both power systems have transparently certified the high performance of HANFISC-TCSC compared to the conventional MOPSO-TCSC.

基于磁流变减振器的汽车悬架振动控制

分析了磁流变减振器特性,为了抑制汽车磁流变悬架的振动,提出了一种含有控制级和协调级的分级模糊控制。在控制级,把天棚、地棚混合控制策略与模糊智能控制策略相结合,设计了1/4车辆垂直振动的半主动模糊智能控制器;在协调级,设计了整车控制的协调器,根据反馈变量对整车4个独立模糊智能控制器输出参数进行调整。把某微型汽车的4只被动减振器改装成磁流变减振器,搭建了磁流变悬架全车测控系统,运用设计的分级模糊控制器,进行了平顺性随机输入实车道路试验。试验结果表明对汽车磁流变悬架的垂直振动进行分级模糊控制是可行的,能有效提高汽车的乘坐舒适性和操纵稳定性。

过热汽温系统的自适应递阶模糊PID参数控制

为了克服在锅炉过热汽温控制中对象参数变化对系统控制带来的困难 ,根据对锅炉动态特性影响较大的工况参数 ,提出了一种新的分层递阶模糊控制方法。对分层递阶模糊PID控制方法进行了理论分析 ,给出了自适应递阶模糊控制系统的结构设计和控制算法。该算法可根据误差e和误差变化Δe,对动态过程中的PID控制参数进行实时在线调节 ,从而使控制系统获得理想的性能指标。同时 ,根据目标参数和操作参数的变化 ,基于操作人员对实际过程的分析和模糊控制规则的非线性映射建立规划策略 ,从而获得PID控制参数的模糊调整。控制级、监督级和规划级组成了分级递阶结构的动态校正策略。设计实例与仿真结果表明 ,分层递阶模糊控制在火电厂过热汽温控制中是十分有效的 ,较好地克服了对象参数变化的影响 ,控制系统响应速度快 ,超调小 ,鲁棒性强。

城市交通干线递阶模糊控制

用递阶结构和模糊理论来解决交通干线的实时协调控制问题。仿真研究表明本文提出的方法能够有效地缩小排队长度，从而达到减少车辆延误的目的。

钢球磨煤机制粉系统的递阶模糊控制

针对火电厂球磨机制粉系统特性 ,提出了一种新的递阶模糊控制算法 ,该算法可显著地减少模糊控制规则数。使模糊控制算法能够方便地用于实际生产。文中给出的磨入口负压、出口温度、磨负荷的模糊控制查询表及协调级的模糊控制查询表 ,已在实际生产中得到验证 ,可有效地解决球磨机制粉系统存在的大时滞、强耦合问题。图 6表 3参

城市主干道交通信号灯模糊线控制的探讨

本文首先提出城市交通系统线控制的两级递阶结构：第一级，用模糊逻辑控制器确定单路口交通信号灯的周期和绿信比；第二级，用模糊相位控制器确定相邻两路口的相位差；两级间用模糊转换开关协调；然后，提出具体的实现方法。

核动力装置蒸汽发生器水位的分层模糊自适应控制

针对压水堆核动力装置蒸汽发生器的水位控制提出一种分层模糊自适应控制方案。该方案中 2个模糊控制器分层连接 ,每个模糊控制器均采用典型模糊控制单元 ,使得模糊规则个数和可调参数个数大大减少 ,便于在线学习和实时控制。给出了分层模糊控制器的解析表达式及可调参数的在线学习方法。在快速加负荷和突然甩负荷的仿真实验中 ,该方案的控制效果明显优于已有的变参数 PID控制 ,验证了该方案的有效性。

基于dSPACE的车辆起步控制策略硬件在回路仿真

基于dSPACE软硬件,应用matlab/simulink系统建模方法,搭建了车辆起步控制的硬件在回路仿真平台;针对车辆起步控制系统存在的非线性、时变、多参数等特性,提出了对离合器和油门进行协调控制的分级模糊控制方法;利用推理法编写了单片机的模糊控制程序;基于上述平台,详细调整了各级模糊控制规则,并进行了起步控制的硬件在回路仿真实验;结果表明,该方法能够满足实时性要求,并具有良好的控制效果。

基于FPGA的模糊自整定PID控制器的研究

提出了一种基于VHDL描述、FPGA实现的模糊自整定PID控制器设计方法。首先,借助Matlab系统仿真工具,优化得出模糊自整定PID参数的模糊推理规则和控制器算法结构。然后,进行控制器的VHDL分层设计,作为单一控制器芯片,重点编程实现和时序仿真:模糊逻辑推理、模糊自整定PID算法、数据缓存和I/O接口控制。最后,在一个具体的FPGA芯片上实现该控制器,并在此基础上进行系统实验。实验结果表明:FPGA作为单一控制器实现模糊自整定PID控制编程规范、时序验证方便、系统修改灵活,且基本无须改动硬件,是实现单片或小系统智能控制策略的一种新的有效途径。

电动汽车驱动力分层控制策略

为了提高两后轮独立驱动电动汽车的操纵稳定性,提出一种驱动力分层控制策略.该分层控制策略包括车辆动力学模型设计层、补偿横摆力矩制定层和驱动力分配层,将车辆横摆角速度和质心侧偏角的实际值与理想值的偏差作为控制量,利用模糊算法计算得出两侧车轮的驱动力矩.在前期仿真验证的基础上进行实车快速控制原型试验,验证控制策略的实车控制效果.试验结果表明,设计的驱动力分层控制策略在过弯时能够对驱动轮转矩进行合理分配,在不影响车辆动力性的同时,提高车辆的操纵稳定性.