Research on Mixed Logic Dynamic Modeling and Finite Control Set Model Predictive Control of Multi-Inverter Parallel System

Parallel connection of multiple inverters is an important means to solve the expansion,reserve and protection of distributed power generation,such as photovoltaics.In view of the shortcomings of traditional droop control methods such as weak anti-interference ability,low tracking accuracy of inverter output voltage and serious circulation phenomenon,a finite control set model predictive control(FCS-MPC)strategy of microgrid multiinverter parallel system based on Mixed Logical Dynamical(MLD)modeling is proposed.Firstly,the MLD modeling method is introduced logical variables,combining discrete events and continuous events to form an overall differential equation,which makes the modeling more accurate.Then a predictive controller is designed based on the model,and constraints are added to the objective function,which can not only solve the real-time changes of the control system by online optimization,but also effectively obtain a higher tracking accuracy of the inverter output voltage and lower total harmonic distortion rate(Total Harmonics Distortion,THD);and suppress the circulating current between the inverters,to obtain a good dynamic response.Finally,the simulation is carried out onMATLAB/Simulink to verify the correctness of the model and the rationality of the proposed strategy.This paper aims to provide guidance for the design and optimal control of multi-inverter parallel systems.

Modeling and Control of a Continuous Stirred Tank Reactor Based on a Mixed Logical Dynamical Model

A novel control strategy for a continuous stirred tank reactor(CSTR)system,which has the typical characteristic of strongly pronounced nonlinearity,multiple operating points,and a wide operating range,is initiated from the point of hybrid systems.The proposed scheme makes full use of the modeling power of mixed logical dy- namical(MLD)systems to describe the highly nonlinear dynamics and multiple operating points in a unified framework as a hybrid system,and takes advantage of the good control quality of model predictive control(MPC) to design a controller.Thus,this approach avoids oscillation during switching between sub-systems,helps to relieve shaking in transition,and augments the stability robustness of the whole system,and finally achieves optimal(i.e. fast and smooth)transition between operating points.The simulation results demonstrate that the presented ap- proach has a satisfactory performance.

MLD-MPC Approach for Three-Tank Hybrid Benchmark Problem

The present paper aims at validating a Model Predictive Control(MPC),based on the Mixed Logical Dynamical(MLD)model,for Hybrid Dynamic Systems(HDSs)that explicitly involve continuous dynamics and discrete events.The proposed benchmark system is a three-tank process,which is a typical case study of HDSs.The MLD-MPC controller is applied to the level control of the considered tank system.The study is initially focused on the MLD approach that allows consideration of the interacting continuous dynamics with discrete events and includes the operating constraints.This feature of MLD modeling is very advantageous when an MPC controller synthesis for the HDSs is designed.Once the MLD model of the system is well-posed,then the MPC law synthesis can be developed based on the Mixed Integer Programming(MIP)optimization problem.For solving this MIP problem,a Branch and Bound(B&B)algorithm is proposed to determine the optimal control inputs.Then,a comparative study is carried out to illustrate the effectiveness of the proposed hybrid controller for the HDSs compared to the standard MPC approach.Performances results show that the MLD-MPC approach outperforms the standardMPCone that doesn’t consider the hybrid aspect of the system.The paper also shows a behavioral test of the MLDMPC controller against disturbances deemed as liquid leaks from the system.The results are very satisfactory and show that the tracking error is minimal less than 0.1%in nominal conditions and less than 0.6%in the presence of disturbances.Such results confirm the success of the MLD-MPC approach for the control of the HDSs.

应用混合逻辑动态模型预测控制器的磁轴承三电平调制策略

传统磁轴承三电平调制策略在数字控制系统中存在控制延迟问题,影响电流纹波抑制效果。针对上述问题,提出一种基于混合逻辑动态模型预测控制器的磁轴承三电平调制策略。基于混杂系统理论,建立混合逻辑动态模型,统一表征出驱动电路充电、放电和续流工作模态,实现三电平调制;结合模型预测控制理论,将所建立的混合逻辑动态模型作为预测模型,预测磁轴承的控制电流,实现对控制延迟的补偿,并将预测控制电流送入到代价函数中,得出驱动电路的最优控制信号;基于所提调制策略构建了磁轴承控制系统,并与传统调制策略进行对比。仿真结果表明:在轻载扰动工况下,所提调制策略相比于传统三电平滞环调制策略与传统三电平脉冲宽度调制(pulse width modulation,PWM)策略,电流纹波分别降低了49.90%和49.87%;在中载扰动工况下,所提调制策略相比于传统三电平滞环调制策略与传统三电平PWM策略,电流纹波分别降低了49.99%和49.84%;在重载扰动工况下,所提调制策略相比于传统三电平滞环调制策略与传统三电平PWM策略,电流纹波分别降低了50.08%和49.77%。在三电平调制机制的基础上,所提调制策略能够有效补偿一个采样周期的控制延迟,达到降低电流纹波的效果。

基于MLD-MPC的快速路出口与辅路协调控制

城市交通信号控制系统是典型的混杂控制系统。针对当前大中城市普遍存在的快速路出口匝道、辅路及下游交叉口的信号协调控制问题,研究了一种多信号自适应控制方法,以保证出口匝道排队长度较小且下游交叉口排队不溢流。首先,基于车道路段当量排队长度建立状态方程,分别选取出口匝道、辅路交叉口和下游交叉口排队长度为连续状态变量,信号灯切换信号为离散控制变量;其次,以有限排队长度为模型约束,建立了包含快速路出口匝道、辅路及下游交叉口排队长度和信号状态的混合逻辑动态MLD模型;然后,比较研究了快速路出口匝道有信号灯控、无信号灯控两种不同情况下的MPC模型预测控制方法。仿真结果表明,基于MLD-MPC的控制方法可解决快速路出口匝道与辅路及下游交叉口的多交叉口信号协调控制问题。

分段仿射模型在智能车辆混合控制的应用研究

针对智能车辆混合动力学控制问题,首先采用分段仿射模型(PWA)非线性逼近车辆主要部件的系统特性,将智能车辆纵向动力学转化为计算混合逻辑动力学(MLD)模型,在此基础上提出了混合模型预测控制(HMPC)策略。通过求解混合整数二次规划(MIQP)问题,设计了能够计算智能车辆纵向工作模式(二进制控制输入),以及节气门开口度和制动压力(连续控制输入)在自动调速过程中切换顺序的控制器。最后通过仿真对比模拟分析,验证了所设计的混合控制器在典型工况下具有良好的纵向速度调节控制性能。

基于MLD模型GTAW焊接熔透控制方法仿真研究

针对GTAW非线性焊接过程的混杂特性,给出混杂系统的建模方法,描述成混合逻辑动态(MLD)模型,并研究其GTAW焊接熔透控制策略.仿真的结果表明,该算法有效,能使系统输出稳定在设定点.为研究MLD建模在焊接过程控制中的实际应用起步研究奠定了基础.

MLD模型下逆变电路改进型直接功率预测控制

建立了新型逆变电路精确的混合逻辑动态(MLD)模型,并将其作为预测模型,研究了新型逆变电路基于预测直接功率控制(P-DPC)的模型预测控制方法。为了达到航空电源电压输出要求和降低开关损耗,在原来的3+3电压矢量控制序列法的基础上扩充了零矢量进行了改进,形成了一种新的对称的4+4电压矢量序列法,通过对下一时刻输出电压有功和无功分量的预测,在最小化目标函数值的基础上求出每一个电压矢量的作用时间,完成电路的控制。该方法减小了输出电压THD,具有良好动静态特性有一个较为稳定的开关频率,仿真和实验验证了所提方法的可行性和有效性。

基于MLD的微电网多逆变器并联组态的建模及优化控制

针对现有微网逆变器并联系统建模精度不高、控制方案复杂、控制效果不理想等问题,文中提出了一种基于混合逻辑动态(MLD)的光伏微网多并联逆变器的建模和优化控制方法。该方法将每个开关周期分为多个子周期,同时引入逻辑变量来判断系统运行的动态模式;然后用HYSDEL工具编程得到MLD模型;最后根据系统的自然约束及系统控制目标设计预测控制器,并通过求解相应的整数线性规划问题达到减少输出电压跟踪误差及各逆变器之间的环流的目标。相较传统的建模与控制方法,该方法具有模型精度高、控制方案简便、控制效果好的特点。仿真结果验证了模型的正确性和控制器性能的优越性。

基于ESO-MLD的逆变器开路故障快速诊断方法

为了减小电机驱动系统中未知干扰对逆变器开路故障诊断的影响,提出了一种基于扩展观测器ESO(extended state observer)和混合逻辑动态MLD(mixed logic dynamic)模型的逆变器开路故障快速诊断方法。通过分析开关管在正常工作和故障状态下的电流流向路径,建立了逆变器的混合逻辑动态模型,并设计了一种电压扩展观测器。根据观测器的观测电压和实际系统输出电压之间的相电压残差进行故障检测,通过故障相残差与正常两相残差之间的数值关系来定位故障相和故障管。该方法有效减小了系统中未知干扰和不确定因素对逆变器故障诊断的影响,提高了故障诊断率。最后,通过Matlab/Simulink仿真验证了该方法的正确性和有效性。

A Hybrid Approach to Modeling and Control of Vehicle Height for Electronically Controlled Air Suspension

The control problems associated with vehicle height adjustment of electronically controlled air suspension （ECAS） still pose theoretical challenges for researchers, which manifest themselves in the publications on this subject over the last years. This paper deals with modeling and control of a vehicle height adjustment system for ECAS, which is an example of a hybrid dynamical system due to the coexistence and coupling of continuous variables and discrete events. A mixed logical dynamical （MLD） modeling approach is chosen for capturing enough details of the vehicle height adjustment process. The hybrid dynamic model is constructed on the basis of some assumptions and piecewise linear approximation for components nonlinearities. Then, the on-off statuses of solenoid valves and the piecewise approximation process are described by propositional logic, and the hybrid system is transformed into the set of linear mixed-integer equalities and inequalities, denoted as MLD model, automatically by HYSDEL. Using this model, a hybrid model predictive controller （HMPC） is tuned based on online mixed-integer quadratic optimization （MIQP）. Two different scenarios are considered in the simulation, whose results verify the height adjustment effectiveness of the proposed approach. Explicit solutions of the controller are computed to control the vehicle height adjustment system in realtime using an offline multi-parametric programming technology （MPT）, thus convert the controller into an equivalent explicit piecewise affine form. Finally, bench experiments for vehicle height lifting, holding and lowering procedures are conducted, which demonstrate that the HMPC can adjust the vehicle height by controlling the on-off statuses of solenoid valves directly. This research proposes a new modeling and control method for vehicle height adjustment of ECAS, which leads to a closed-loop system with favorable dynamical properties.

基于MLD的加权区间预测控制

针对生产过程中某些被控变量并没有苛刻的设定值要求,只要满足在给定区间内即可的问题,提出了一种基于混合逻辑动态模型的加权区间预测控制算法,在控制器设计中引入逻辑变量,将基于逻辑命题的目标函数以约束条件的形式集成到预测控制器模型框架下。通过逻辑变量的取值检测被控变量预测值所处的偏差区域,设定相应的误差权重值,使预测控制根据输出在不同的偏差区域范围,采取不同的控制强度,从而保证快速控制的同时满足稳定控制的要求。通过对Shell塔的仿真,验证了算法的有效性。

A Hybrid Model Predictive Control for Handling Infeasibility and Constraint Prioritization

A hybrid approach using MLD (mixed logical dynamical) framework to handle infeasibility and constraint prioritization issues in MPC (model predictive control) based on input-output model is introduced. By expressing constraint priorities as propositional logics and by transforming the propositional logics into inequalities,the infeasibility and constraint prioritization issues are solved in the MPC. Constraints with higher priorities are met first, and then these with lower priorities are satisfied as much as possible. This new approach is illustrated in the control of a heavy oil fractionator-Shell column. The overall control performance has been significantly improved through the infeasibility and control priorities handling.

城市排水系统混合逻辑动态(MLD)建模方法及应用

传统的排水系统机理模型在城市排水系统精细化模拟和设计评估方面应用广泛,但是在以排水系统优化控制为主攻方向的实时控制模式中,机理模型的计算复杂性与低时效性不利于与优化系统结合,难以形成较为完善的模拟-预测-优化体系。混合逻辑动态法作为一种广泛应用在物理过程建模和自动控制领域的线性离散化模拟手段,通过研究其在排水系统中的建模原理与优化方式,并通过案例分析其模拟与优化的准确性与可靠性,展现了其在城市排水系统模拟领域的应用潜力和价值。

Multi-model predictive control with local constraints based on model switching

Because model switching system is a typical form of Takagi-Sugeno（T-S） model which is an universal approximator of continuous nonlinear systems, we describe the model switching system as mixed logical dynamical （MLD） system and use it in model predictive control （MPC） in this paper. Considering that each local model is only valid in each local region,we add local constraints to local models. The stability of proposed multi-model predictive control （MMPC） algorithm is analyzed, and the performance of MMPC is also demonstrated on an inulti-multi-output（MIMO） simulated pH neutralization process.

空气悬架混杂系统车身高度与可调阻尼分层控制

针对空气悬架车身高度调节控制过程中车身高度和阻尼器阻尼力难以进行协调控制的难题,提出一种基于混合逻辑动态(MLD)模型的空气悬架车身高度与可调阻尼分层控制策略。考虑空气悬架充放气过程中存在的混杂特性,应用MLD建模方法建立具有电磁阀和磁流变阻尼器的非线性空气悬架混杂系统模型,设计描述电磁阀开关状态的混杂自动机进行车高调节上层控制,基于混杂模型预测控制方法对磁流变阻尼器输入电流进行下层控制,进而通过改变电磁阀开关状态和磁流变阻尼器输入电流实现车身高度与可调阻尼分层控制。在随机路面激励工况下进行仿真验证,结果表明:所提控制方法在有效跟踪车身高度的同时,车身加速度相比于被动悬架和混杂模型预测控制分别降低了34.33%、34.34%,不仅能有效提高车辆乘坐舒适性,也能直接防止电磁阀频繁切换现象的发生,从而延长电磁阀的使用寿命。

基于混合逻辑动态模型的PMSM系统开路故障诊断方法

针对永磁同步电机驱动系统功率器件开路故障问题,提出了一种基于混合逻辑动态模型和剩余电流的开路故障诊断方法,以提高永磁同步电机驱动系统的安全性与可靠性。通过研究电机驱动系统离散开关信号和连续电流状态变量,建立永磁同步电机系统的混合逻辑动态模型对电机电流进行估计;然后,利用估计模型与实际电流的残差极性与残差间的差值极性作为诊断特征量,通过查找设计的故障状态表以实现故障器件定位。该方法利用控制策略中已使用的变量实现开路故障诊断,避免使用额外的传感器,并且可有效消除转速和负载变化对诊断结果准确性的影响。仿真与实验结果表明,该方法具有诊断时间短、准确度高、鲁棒性强等优点,且诊断时间均小于基本电流周期的60%。

ECAS车身高度与整车姿态控制混杂自动机研究

针对电子控制空气悬架(electronically controlled air suspension, ECAS)系统存在明显的混杂动态特征,不易于车身高度和整车姿态精确控制等问题,建立了考虑电磁阀气动特性的ECAS整车非线性机理模型,通过设置车身高度、侧倾角和俯仰角的变化范围设计了描述悬架系统各电磁阀开关切换状态的混杂自动机;利用混合逻辑动态(mixed logical dynamics, MLD)建模方法将所设计的混杂自动机编译为标准MLD模型,从而可直接调整电磁阀的开关状态实现车身高度与整车姿态之间的协调控制;最后对所设计的混杂自动机进行仿真验证。仿真结果表明,该混杂自动机通过对电磁阀开关进行逻辑控制,可以精确地控制车身高度并有效地改善整车姿态,在一定程度上提高了操纵稳定性和乘坐舒适性。

单相CHBR改进型无网压传感器直接功率控制

以降低单相级联H桥整流器(CHBR)系统硬件成本、改善控制系统性能为目的,提出一种改进型无网压传感器直接功率控制方法。首先,建立单相CHBR的数学模型,并通过混合逻辑动态方法估算出网侧输入电压。针对已有虚拟磁链观测器存在的缺点,提出改进型的虚拟磁链观测器,并给出详细的频域分析过程。所提观测器可以有效地解决幅、值相位误差和直流偏置问题,并且能够有效地抑制谐波。此外,提出一种基于比例积分(PI)控制器的CHBR改进型直接功率控制(DPC)方法。相较于传统DPC方法,改进型DPC取消了旋转坐标变换,不需要网压相位信息,改善了系统动态响应速度。最后,在实验样机上对已有的虚拟磁链观测器方法、直接功率控制方法以及所提改进型控制方法展开对比实验研究,结果验证了所提方法的可行性和有效性。

五相PMSM驱动系统开路故障混合诊断方法

为了进一步提高五相永磁同步电机驱动系统的可靠性与安全性能,针对逆变器系统功率器件开路故障问题,提出一种基于混合逻辑动态模型剩余电流的开路故障诊断方法。在分析电机驱动系统连续电流状态变量以及离散开关信号的基础上,建立电机驱动系统混合逻辑动态模型对电机实时电流状态进行估计,利用该模型与实际电流残差作为诊断特征,通过对不同故障状态下剩余电流极性的分析设计故障关系表,实现具体开路故障的检测与定位。实验证明,该方法能有效诊断五相永磁同步电机驱动系统中单个以及两个同相功率器件同时开路故障,且诊断时间小于基本电流周期的50%。