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.

Research on AC Electronic Load with Energy Recovery Based on Finite Control Set Model Predictive Control

Nowadays,AC electronic loads with energy recovery are widely used in the testing of uninterruptible power supplies and power supply equipment.To tackle the problems of control difficulty,strategy complexity,and poor dynamic performance of AC electronic load with energy recovery of the conventional control strategy,a control strategy of AC electronic load with energy recovery based on Finite Control Set Model Predictive Control(FCSMPC)is developed.To further reduce the computation burden of the FCS-MPC,a simplified FCS-MPC with transforming the predicted variables and using sector to select expected state is proposed.Through simplified model and equivalent approximation analysis,the transfer function of the system is obtained,and the stability and robustness of the system are analyzed.The performance of the simplified FCS-MPC is compared with space vector control(SVPWM)and conventional FCS-MPC.The results show that the FCS-MPC method performs better dynamic response and this advantage is more obvious when simulating high power loads.The simplified FCS-MPC shows similar control performance to conventional FCS-MPC at less computation burden.The control performance of the system also shows better simulation results.

Hybrid Dynamic Variables-Dependent Event-Triggered Fuzzy Model Predictive Control

This article focuses on dynamic event-triggered mechanism(DETM)-based model predictive control(MPC) for T-S fuzzy systems.A hybrid dynamic variables-dependent DETM is carefully devised,which includes a multiplicative dynamic variable and an additive dynamic variable.The addressed DETM-based fuzzy MPC issue is described as a “min-max” optimization problem(OP).To facilitate the co-design of the MPC controller and the weighting matrix of the DETM,an auxiliary OP is proposed based on a new Lyapunov function and a new robust positive invariant(RPI) set that contain the membership functions and the hybrid dynamic variables.A dynamic event-triggered fuzzy MPC algorithm is developed accordingly,whose recursive feasibility is analysed by employing the RPI set.With the designed controller,the involved fuzzy system is ensured to be asymptotically stable.Two examples show that the new DETM and DETM-based MPC algorithm have the advantages of reducing resource consumption while yielding the anticipated performance.

Finite Control Set Model Predictive Current Control of a Five-Phase PMSM with Virtual Voltage Vectors and Adaptive Control Set

This paper presents an improved finite control set model predictive current control(FCS-MPCC)of a five-phase permanent magnet synchronous motor(PMSM).First,to avoid including all the 32 voltage vectors provided by a two-level five-phase inverter into the control set,virtual voltage vectors are adopted.As the third current harmonics can be much reduced by virtual voltage vectors automatically,the harmonic items in the cost function of conventional FCS-MPCC are not considered.Furthermore,an adaptive control set is proposed based on voltage prediction.Best control set with proper voltage vector amplitude corresponding to different rotor speed can be achieved by this method.Consequently,current ripples can be largely reduced and the system performs much better.At last,simulations are established to verify the steady and transient performance of the proposed FCS-MPCC,and experiments based on a 2 kW five-phase motor are carried out.The results have validated the performance improvement of the proposed control strategy.

基于FCS-MPC的分布式HESS功率协调控制

针对孤岛直流微电网中分布式混合储能系统(HESS)协调运行问题,提出一种基于有限控制集模型预测控制(FCSMPC)的功率协调控制策略。该策略采用小波包变换来分解分布式HESS的功率需求,由于分解后信号的特点和分布式HESS中蓄电池初始状态的不同,于是对分解后最低频信号基于蓄电池荷电状态(SOC)设计自适应因数来进一步再分解。由于DC/DC变换器开关状态组合数量较少,使得多步FCS-MPC的滚动优化计算量较少,于是采用FCS-MPC取代双闭环PI控制,提高系统动态响应。搭建含有分布式HESS的孤岛直流微电网模型,并做了3种方案的仿真对比,验证该策略有效平缓了直流母线波动并实现蓄电池SOC一致。该策略有利于提高电网运行的稳定性,并延长蓄电池使用寿命。

Finite-Control-Set Model Predictive Control of Permanent Magnet Synchronous Motor Drive Systems——An Overview

Permanent magnet synchronous motors(PMSMs)have been widely employed in the industry. Finite-control-set model predictive control(FCS-MPC), as an advanced control scheme, has been developed and applied to improve the performance and efficiency of the holistic PMSM drive systems. Based on the three elements of model predictive control, this paper provides an overview of the superiority of the FCS-MPC control scheme and its shortcomings in current applications. The problems of parameter mismatch, computational burden, and unfixed switching frequency are summarized. Moreover, other performance improvement schemes, such as the multi-vector application strategy, delay compensation scheme, and weight factor adjustment, are reviewed. Finally, future trends in this field is discussed, and several promising research topics are highlighted.

基于虚拟矢量优选的FCS-MPC稳定性策略研究

为了提高并网逆变器有限集模型预测控制(FCS-MPC)方法中的稳定性问题,研究了基于Lyaponov准则的并网逆变器有限集模型预测控制大信号稳定性方法。首先建立数学模型,分析参数变化对预测误差的影响和大扰动导致的稳定性问题,接着提出采用虚拟电压矢量的Lyapunov控制器的有限集模型预测控制稳定性策略。利用Lyapunov控制器并结合考虑稳定性约束的目标函数增强系统抗扰动能力,虚拟电压矢量满足Lyapunov稳定性需求,同时改善控制性能,并设计有限集选取策略减少计算量。仿真和实验验证了所提方法在扰动及参数变化情况下控制性能和抗干扰能力。

FCS-MPC Strategy for PV Grid-Connected Inverter Based on MLD Model

In the process of grid-connected photovoltaic power generation,there are high requirements for the quality of the power that the inverter breaks into the grid.In this work,to improve the power quality of the grid-connected inverter into the grid,and the output of the system can meet the grid-connected requirements more quickly and accurately,we exhibit an approach toward establishing a mixed logical dynamical(MLD)model where logic variables were introduced to switch dynamics of the single-phase photovoltaic inverters.Besides,based on the model,our recent efforts in studying the finite control set model predictive control(FCS-MPC)and devising the output current full state observer are exciting for several advantages,including effectively avoiding the problem of the mixed-integer quadratic programming(MIQP),lowering the THD value of the output current of the inverter circuit,improving the quality of the power that the inverter breaks into the grid,and realizing the current output and the grid voltage same frequency and phase to meet grid connection requirements.Finally,the effectiveness of the mentioned methods is verified by MATLAB/Simulink simulation.

A Dual-mode Nonlinear Model Predictive Control with the Enlarged Terminal Constraint Sets

Aiming at a class of nonlinear systems with multiple equilibrium points, we present a dual-mode model predictive control algorithm with extended terminal constraint set combined with control invariant set and gain schedule. Local LQR control laws and the corresponding maximum control invariant sets can be designed for finite equilibrium points. It is guaranteed that control invariant sets are overlapped each other. The union of the control invariant sets is treated as the terminal constraint set of predictive control. The feasibility and stability of the novel dual-mode model predictive control are investigated with both variable and fixed horizon. Because of the introduction of extended terminal constrained set, the feasibility of optimization can be guaranteed with short prediction horizon. In this way, the size of the optimization problem is reduced so it is computationally efficient. Finally, a simulation example illustrating the algorithm is presented.

Model Predictive Control-Based Direct Torque Control for Matrix Converter-Fed Induction Motor with Reduced Torque Ripple

To reduce the torque ripple in motors resulting from the use of conventional direct torque control(DTC),a model predictive control(MPC)-based DTC strategy for a direct matrix converter-fed induction motor is proposed in this paper.Two new look-up tables are proposed,these are derived on the basis of the control of the electromagnetic torque and stator flux using all the feasible voltage vectors and their associated switching states.Finite control set model predictive control(FCS-MPC)has then been adopted to select the optimal switching state that minimizes the cost function related to the electromagnetic torque.Finally,the experimental results are shown to verify the reduced torque ripple performance of the proposed MPC-based DTC method.

O-Z源逆变器驱动PMSM的改进型FCS-MPC策略

针对O-Z源逆变器驱动永磁同步电机(PMSM)控制系统,在两相旋转坐标系下,提出一种改进型的有限状态控制集模型预测电流控制(FCS-MPC)策略。首先,结合变压器特点和ZSI拓扑结构,设计一种新型O-Z源逆变器(O-ZSI),并利用状态空间平均法建立O-ZSI的动态数学模型;其次,根据O-ZSI侧电容电压闭环以及PMSM系统输出功率前补偿来获得变压器激磁电感电流参考值,其与激磁电感预测电流值构建代价目标函数用来判断是否选取直通(ST)工作状态模式,以实现对O-ZSI直流侧的升压控制;然后,在O-ZSI处于非直通(NST)工作状态模式下,通过PMSM系统的定子电流预测方程来获得O-ZSI交流侧定子电压参考值,并与逆变器的8种开关状态所对应基本定子电压构建含有激磁电感电流项的代价目标函数,选择最佳开关状态来控制PMSM,从而提高PMSM系统的控制性能以及降低在线运算量;最后,仿真结果表明,本文所提控制策略不仅能实现对O-Z源逆变器的升压,而且能使O-ZSI驱动PMSM可靠稳定运行,同时系统具有良好稳态、动态性能。

应用滑模控制的四开关逆变器PMSM系统FCS-MPC策略

为了提高三相四开关逆变器永磁同步电机(PMSM)控制系统的性能,采用滑模控制方法,提出一种有限控制集模型预测控制(FCS-MPC)策略,并设计可以无抖振、单调收敛的滑模转速调节器.所设计的控制系统能够保证PMSM系统可靠稳定地运行,可抑制PMSM的电磁转矩脉动,改善三相定子电流波形效果,具备良好的转速跟随性能.仿真结果表明,与常规FCS-MPC方法相比,滑模转速调节器可以使电机加载时的转速跌落更小,并且转速能够更快恢复至参考值.所提出的FCS-MPC策略可以明显减小PMSM转矩脉动,降低三相定子电流总谐波失真(THD)值.当系统参数发生变化时,PMSM系统仍可平稳运行,三相定子电流能够保持良好的平衡性.

基于改进FCS-MPC的APF电流跟踪控制方法研究

针对传统FCS-MPC电流跟踪精度低的问题,提出一种能够快速准确实现电流跟踪控制的改进FCS-MPC方法。将代价函数中补偿电流转换为输出电压快速获取最优开关状态,通过三矢量代替单矢量减小补偿电流脉动,同时加入两步预测对电流跟踪控制进行时滞补偿。仿真结果表明,改进FCS-MPC的电流跟踪控制精度提高,APF谐波抑制性能更好。

More relaxed conditions for model predictive control with guaranteed stability

For the model predictive controller, terminal state satisfying a certain inequality can guarantee the stability but it is somewhat conservative. In this paper, we give a more relaxed stability condition by considering the effect of the initial state. Based on that we propose an algorithm to guarantee that the closed loop system is asymptotically stable. Finally, the conclusions are verified by a simttlation.

Model predictive control synthesis algorithm based on polytopic terminal region for Hammerstein-Wiener nonlinear systems

An improved model predictive control algorithm is proposed for Hammerstein-Wiener nonlinear systems.The proposed synthesis algorithm contains two parts:offline design the polytopic invariant sets,and online solve the min-max optimization problem.The polytopic invariant set is adopted to replace the traditional ellipsoid invariant set.And the parameter-correlation nonlinear control law is designed to replace the traditional linear control law.Consequently,the terminal region is enlarged and the control effect is improved.Simulation and experiment are used to verify the validity of the wind tunnel flow field control algorithm.

FCS-MPC在HAPF无功补偿控制中抑制谐振的研究

针对有源滤波器(APF)在无功补偿过程出现谐振的问题,为提高动态无功补偿中使用的控制算法的动态响应能力,提出一种新的基于有限控制集模型预测控制(FCS-MPC)的动态无功补偿策略。该策略是基于LCL滤波器方程的模型来预测系统状态并优化控制,同时采用多变量结构控制和自适应陷波滤波器来抑制共振,跟踪负载无功功率的波动和突变,提升HAPF的动态响应能力。并通过仿真和实际结果证明了FCS-MPC在HAPF无功控制中的可行性,设备的动态响应明显提高。结果表明,FCS-MPC在HAPF无功控制中可以快速跟踪负载无功功率变化,有效抑制APF中出现的谐振且系统的动态响应能力明显提升。

三相四开关容错逆变器的PMSM驱动系统FCS-MPC策略

针对三相四开关容错逆变器的永磁同步电机(PMSM)驱动系统,基于模型参考自适应(MRAS)观测器,提出一种有限控制集模型预测控制(FCS-MPC)策略。考虑温度变化对永磁磁链影响,采用MRAS技术,实现了对永磁磁链的在线辨识;同时考虑降低逆变器开关频率的需求,设计开关频率可优化的FCS-MPC系统目标函数。与常规FCS-MPC方法比较,本方法可以有效减小系统控制过程的计算量,与此同时,本方法中的电流反馈特性可对四开关逆变器直流母线电容分压不平衡形成的不利影响实现自动抑制。仿真结果表明,本方法能够保证四开关容错逆变器驱动的PMSM系统持续稳定运行、具有良好运行性能,并能明显降低逆变器功率管的开关频率。

基于FCS-MPC的五桥臂UPQC电能质量补偿策略研究

针对容错模式下的统一电能质量调节器(Unified Power Quality Conditioner,UPQC),提出了一种五桥臂形式的新型拓扑结构,实现故障下的电能质量扰动综合补偿。在此基础上,对串联变流器和并联变流器进行统一建模,提出了一种基于有限集模型预测控制(Finite Control Set Model Predictive Control,FCS-MPC)的五桥臂UPQC控制策略。相比传统线性控制策略,所提算法构建了统一的预测模型以及整合优化的价值函数,实现串联变流器与并联变流器的协同控制,提高了两侧变流器的补偿精度、暂态性能以及响应速度,有效降低了控制算法的复杂度和参数调节难度,并具有较高的参数鲁棒性。仿真结果验证了所提算法的可行性和有效性。