Artificial intelligence-based speed control of DTC induction motor drives—A comparative study

The design of the speed controller greatly affects the performance of an electric drive. A common strategy to control an induction machine is to use direct torque control combined with a PI speed controller. These schemes require proper and continuous tuning and therefore adaptive controllers are proposed to replace conventional PI controllers to improve the drive's performance. This paper presents a comparison between four different speed controller design strategies based on artificial intelligence techniques; two are based on tuning of conventional PI controllers, the third makes use of a fuzzy logic controller and the last is based on hybrid fuzzy sliding mode control theory. To provide a numerical comparison between different controllers, a performance index based on speed error is assigned. All methods are applied to the direct torque control scheme and each control strategy has been tested for its robustness and disturbance rejection ability.     

含风电的交直流互联电网AGC两级分层模型预测控制

随着大规模风电接入交直流互联电网,传统的自动发电控制(AGC)方法难以有效地抑制风功率波动带来的频率稳定问题。为此,提出基于两级分层模型预测的AGC策略。该两级分层控制方法在下层对多个区域电网采用分散式模型预测控制;在上层对下层分散的控制器采用动态协调控制方式。以含多电源的两区域交直流互联电网AGC模型为例,仿真结果表明:与集中式模型预测控制和分散式模型预测控制方法相比,文中所提控制策略不仅对频率和联络线功率等具有良好的控制效果,还兼具高可靠性。     

考虑控制区域间影响的二级电压控制

从系统分析的观点阐述了二级电压控制的基本原理，说明了在电力系统联系日趋紧密的情况下，相邻控制区域间的相互关联对二级电压控制效果的影响。文中考虑了区域间联络线的无功潮流的变化，对现有的二级电压控制系统的控制策略进行了改进。采用新的控制方案后，相邻区域的无功电压变化不会影响本区域的控制性能，从而较好地解决了不同区域间二级电压控制器的分散协调控制问题。以新英格兰系统为例进行了数字仿真，验证了改进的二级电压控制方案的有效性。     

Design and analysis of nonlinear digital controllers-based two-level hierarchy for electric utility industry

This paper suggests a control strategy of coordinating multiple dynamic-braking units during the transients ensuing major disturbances. The control strategy considered in this study is a two-level hierarchy. The proposed two-level structure results from the decomposition of the overall problem into parallel subproblems. This allows the retention of the closed-loop controls associated with each subsystem, which together constitute the lower level (Level I). The central coordinating controller forms the upper level (Level II). The coordination of the local controllers by the central controller accounts for nonlinear terms and interconnections and yields the global optimization of the overall system transient performance. The local controllers are not dependent on one another and are robust to any changes in the network configuration, due to the feedback or closed-loop control formulation inherent in the proposed strategy. To ensure physical realizability of the local controllers, the input was restricted to locally measurable signals. The methodology was implemented in a prototype software program, which was tested on a single machine connected to a very large network approximated by an infinite bus, and then on the IEEE four-generator test system. These studies considered fault-clearing times greater than the critical, assuring an unstable condition. The well-damped optimal state and control trajectories illustrate the successful solution of the problem, indicating that the technique is a valuable tool dealing with transient control problems for large-scale systems.     

Two-level optimal load–frequency control for multi-area power systems

In large-scale power systems, classical centralized control approaches may fail due to geographically distribution of information and decentralized controllers result in sub-optimal solution for load–frequency control (LFC) problems. In this paper, a two-level structure is presented to obtain optimal solution for LFC problems and also reduce the computational complexity of centralized controllers. In this approach, an interconnected multi-area power system is decomposed into several sub-systems (areas) at the first-level. Then an optimization problem in each area is solved separately, with respect to its local information and interaction signals coming from other areas. At the second-level, by updating the interaction signals and using an iterative procedure, the local controllers will converge to the overall optimal solution. By parallel solving of areas, the computational time of the algorithm is reduced in contrast to centralized controllers. This approach is applicable to any interconnected large-scale power system. However, for simulation purposes, a three-are power system is presented to show advantages and optimality of the proposed algorithm.     

Synthesis of excitation controllers for synchronous generators setting specified stability margins in the under-excited operating region

A design procedure of field controllers for synchronous machines is presented. A prescribed enlargement of the stable operating domain in the P-Q plane and an aperiodic type of instability for the system under steady-state instability conditions are assumed as performance specifications. The effectiveness of the proposed design procedure is validated by digital simulations on a single machine infinite bus-bar system.     

Modeling and Bumpless Switching Control of Symmetrical Dual Three-Phase PMSM in Two Operating Modes

Abstract

This paper presents a frequency-domain model of the symmetrical dual three-phase permanent magnet synchronous machine (PMSM) in two working modes. Compared with traditional time-domain model, the presented frequency-domain model has simple expression and can be easily used in control system design and compensation. Furthermore, a frequency-model-based field oriented control (FOC) scheme for this machine is proposed. In this control scheme, parameters of proportional-integral (PI) controllers are analytically designed which can flexibly adjust the steady and dynamic performance of the entire closed-loop system. Moreover, this control strategy allows the drive system to bumpless switch between two operating modes without stopping. Finally, the developed control scheme was verified via simulations and experiments.     

Nonlinear Decentralized Feedback Linearizing Controller Design for Islanded DC Microgrids

This paper aims to design decentralized controllers for different components in islanded DC microgrids. The major components in the DC microgrid as considered in this paper include a fuel cell, solar photovoltaic (PV) unit, and battery energy storage system (BESS) along with critical and non-critical loads. The main control objective is to maintain the power balance within the DC microgrid through the regulation of the common DC-bus voltage. The controllers are designed based on the dynamical models of the fuel cell, solar PV unit, and BESS. The feedback linearization technique is employed to obtain the control laws, which simplifies the original dynamical models and decouples different components in the form of several subsystems. In this way, the feedback linearization technique allows different components in DC microgrids to achieve the desired control objectives by using only the local information (i.e., in a decentralized manner). The performance of the proposed decentralized controllers for different components is evaluated on a test DC microgrid under different operating conditions. Simulation results demonstrate that the proposed control scheme performs in a much better way as compared to an existing proportional integral controller.     

Equivalent turbogenerator model for design of multivariable controllers in multimachine systems

The design of multivariable controllers for turbogenerators is usually based on single-machine infinite-bus representations, which are not valid for multimachine power systems. Alternatively, an overall control strategy may be sought for all the generators in the system, but this arrangement is not feasible in practice and involves major mathematical difficulties. The paper describes a method for designing physically-realizable multivariable controllers for individual turbogenerators in multimachine systems, without the assumption of an infinite bus. This employs an equivalent model for each generator, which includes the effects of interconnections with other units in the power system. The method has been used to design optimal state-space controllers for a three-machine system, and results obtained by nonlinear computer simulation show that good performance is achieved.     

Multilevel Operation and Input Power Balancing for a Dual Two-Level Inverter with Insulated DC Sources

A multilevel inverter topology feeding a three-phase open-end winding machine is analyzed in this paper. The scheme is based on the use of two insulated dc supplies, each one feeding a standard two-level three-phase inverter. The three-phase six-wire winding is connected across the output terminals of the two inverters. A new modulation technique that is able to regulate the sharing of the output power between the two dc sources in each switching cycle is presented. The performance of the whole system has been verified by both numerical and experimental tests.      

分散模糊负荷频率控制器的优化设计

本文针对多区域互联电力系统的特点，建立了一个考虑各区域扰动影响的综合性能指标，并对比例因子采用智能调整措施，提出了一种分散模糊负荷频率控制器的优化设计方法，对一个两区域互联电力系统的数字仿真结果表明，所设计的分散模糊负荷频率控制器具有良好的控制效果和较强的鲁棒性。     

Simple adaptive control of uncertain systems

This paper considers adaptive control of various systems with unknown time-varying or non-linear dynamics in an attempt to show that practical adaptive control can be simple and robust. The simplified adaptive control methodology used is based on the observation that most real-world systems, even non-stationary or non-linear, can be stabilized by simple controller configurations. More complex controllers may be needed only in order to improve the performance of the control systems. In the adaptive scheme, the stabilizability properties of the plants are used only to satisfy the necessary conditions that guarantee robustness of simple adaptive controllers. The desired performance is then imposed upon the plant by these adaptive controllers, which force the plant to follow the input-output behaviour of low-order reference models. Examples from the recent literature of control with uncertainty are used to illustrate the power of these adaptive techniques.     

负荷频率系统的LFC模糊监控器设计

应用在LFC控制中常规的模糊调整增益PI控制器和I控制器,只针对单一区域的负荷频率进行控制,并不考虑实际模型中的互相扰动.其中最突出的问题是由于不限制联络线上的功率流动,电能总是从频率高区域流向频率低区域,加剧了频率高区域的控制负担,再加上各区域控制动作的不协调,使得当扰动在不同的时间和幅值时引起系统调节过程的急剧恶化,导致整个系统不稳定.提出一种基于模糊MAMDANI推理算法的模糊监督控制器,采用各个区域的频率偏差作为控制器的输入,监督控制器作为一种前馈补偿,设计输出为一个ACE的倍数,加快调节过程,到达稳态.经过实验仿真数据对比,说明提出的监督控制器能有效提高系统的稳定性.     

Enhanced current control of high-speed PM machine drives throughthe use of flux controllers

This paper compares various types of current controllers, including a novel method based on flux control. A proportional integral (PI) control method is used initially, to control the current in a high-speed permanent-magnet synchronous machine. The performance of this simple PI loop is presented, Various improvements to the PI controller are investigated, and the change in performance examined. A new current control scheme based on a flux-linkage model of the machine is introduced. The performance of the model-based control is demonstrated and compared with the performance of the PI current controller. Factors affecting the accuracy of the model-based control are given. By incorporating these factors into the model, the performance of the flux controller is further enhanced     

开绕组无刷双馈风力发电机最大功率点跟踪直接转矩模糊控制研究

基于风力发电机最大功率点跟踪原理,结合无刷双馈电机无电刷和集电环的特殊结构及采用双定子磁场调制使得所需变流器容量更小的特点,提出了一种由双两电平变流器拓扑构造三电平馈电的开绕组策略,阐述了无刷双馈风力发电机最大功率点跟踪、开绕组策略及直接转矩控制、模糊控制等各部分工作原理,进而利用Matlab/Simulink仿真软件,搭建了无刷双馈风力发电机控制绕组采用双两电平SVPWM变流器馈电实现最大功率点跟踪的开绕组直接转矩模糊控制模型,并进行了详细的性能仿真,最后,通过无刷双馈电机半实物仿真实验平台,证实了所提开绕组策略的正确性和可行性,为进一步研发半实物仿真实验平台及相关控制策略提供了良好的参考与借鉴。     

基于多模糊控制器的感应电动机矢量控制系统实验研究

给出了一个完全基于模糊控制器的感应电动机间接转子磁场定向矢量控制系统.在控制系统中,三个精心设计的模糊控制器分别用于控制电机的转速、励磁电流分量和转矩电流分量,实现转速精确控制和感应电动机的励磁和转矩之间的解耦控制.最后,本文对该感应电动机矢量控制系统进行实验研究,验证其可行性.     

跟踪COI思想应用于多机系统励磁控制

针对多机电力系统,提出了发电机功角和频率以动态跟踪系统惯量中心（COI）为目标的励磁控制思想。在该思想下,各发电机的功角按一定距离动态追踪系统COI功角的变化,而各发电机的频率则动态追踪系统COI频率的变化。相比于当前绝大多数以原运行点为发电机调节目标的控制思想而言,文中所提出的思想的主要特点在于它是利用系统的动态COI信号来将各发电机拉向同步,系统将根据实际情况稳定于某一可接受的频率,而不是局限于工频。在相同的发电机模型基础上,建立了2种不同思想下的控制系统模型,并给出了采用相同方法设计的鲁棒控制器。最后采用2区4机系统进行了动态仿真,以比较这2种鲁棒控制器以及自动电压调节器＋电力系统稳定器（AVR＋PSS）励磁系统在提高电力系统暂态稳定性方面的控制功效。     

Fuzzy Self-Tuning Speed Control of an Indirect Field-Oriented Control Induction Motor Drive

The field-oriented control of induction machines is widely used in high-performance applications. However, detuning caused by parameter disturbances still limits the performance of these drives. In order to accomplish variable-speed operation, conventional PID-like controllers are commonly used. These controllers provide limited good performance over a wide range of operation, even under ideal field-oriented conditions. An alternate approach is to use the so-called “fuzzy” controller. In this paper, a self-tuning fuzzy controller is implemented. The proposed controller has the ability to adjust its parameters online according to the error between actual machine speed and a model reference. The scheme is compared to the conventional proportional-integral control and validated by simulation and experimental tests of both control techniques.      

基于多模糊控制器的感应电动机矢量控制系统

介绍了一个完全基于模糊控制器的感应电动机间接矢量控制系统.一个模糊控制器用于控制电动机的转速,实现转速精确控制.在同步坐标轴系下,另外两个模糊控制器用于控制电动机的励磁电流分量和转矩电流分量,实现励磁和转矩之间的完全解耦控制.最后给出了控制系统的仿真和实验结果.