Power converter control based on neural and fuzzy methods

The new power converter control approaches based on neural network techniques and fuzzy logic theorems are briefly reviewed and discussed in this paper. Current-controlled voltage source inverters offer substantial advantages in improving motor system dynamics for high-performance AC drive systems. The controller switches follow a set of reference current waveforms. Fixed-band and sinusoidal-band hysteresis current controllers have been studied. The first part of this paper develops neural network and fuzzy logic based current-controlled voltage source inverters. The models and learning techniques have been investigated by simulation. The implementation of neural networks is described and simulation results are presented. In the second part of this paper, the new UPS (uninterruptible power supply) with fuzzy logic compensator is proposed. The proposed fuzzy logic compensator is used to prevent voltage drop from nonlinear loads. The total harmonic distortion (THD) of the proposed scheme is better than that of conventional deadbeat control methods for linear and nonlinear loads. The applications of fuzzy and neural network control to DC-DC converters operating at finite switching frequency are studied in the third part of this paper. The fuzzy logic and neural network controller for unity power factor rectifiers, half-bridge DC-DC ZVZCS converters, DC motor drives, induction motor drives and permanent-magnet motor drives are also discussed. Some simulations are presented in this paper.     

永磁同步电动机逆系统解耦控制

提出了一种永磁同步电动机（PMSM）的逆系统线性化解耦控制方法。首先,通过非线性状态反馈获得PMSM的逆系统,将多变量、非线性、强耦合的PMSM动态解耦成转速与定子电流两个低阶的线性子系统,然后,分别设计线性控制器对转速与定子电流子系统进行闭环控制。仿真结果表明：提出的控制方案具有优良的动态和静态性能,且对负载变化具有较强鲁棒性。     

Demonstration of the internal model principle by digital repetitive control of an educational laboratory plant

A key topic in classical control theory is the Internal Model Principle (IMP). A particular case of the IMP for tracking periodic references or attenuating periodic disturbances in closed-loop control systems is a technique called repetitive control. This work proposes and describes an educational laboratory plant to show the students the advantages of repetitive controllers in systems with periodic references or disturbances. The plant has been designed to be low cost, easy to build, and subject to periodic disturbances with a clear physical explanation. More specifically, it consists of a pulsewidth modulation (PWM) electronic amplifier, a small dc motor, and a magnetic setup that generates a periodic load torque under constant mechanical speed operation. The control objective for the closed-loop control system is to regulate the mechanical speed to a constant value in spite of the periodic load torque disturbance. In order to accomplish this performance specification, a detailed design of a digital repetitive controller is presented, and some basic experimental results are provided to prove its good behavior. The paper also includes some repetitive control concepts and facts that teaching experience shows as essential to understand the design process.     

A closed-loop selective harmonic compensation for active filters

This paper proposes a control algorithm for parallel active power filters, based on current-controlled pulsewidth-modulated converters, which allows precise compensation of selected harmonic currents produced by distorting loads. The approach is based on the measurement of line currents and performs the compensation of the selected harmonics using closed-loop synchronous frame controllers. Thanks to the closed-loop operation, full compensation of the desired harmonics is achieved even in the presence of a significant delay in the current control. Thanks to the selective approach, active filter interactions with possible dynamic components of the load are minimized. Moreover, the complexity of the synchronous frame controllers is overcome using equivalent stationary frame controllers. Experimental results confirm the theoretical expectations     

磁悬浮开关磁阻电机悬浮力与旋转力的神经网络逆解耦控制

为了实现磁悬浮开关磁阻电机径向二自由度悬浮力与旋转力三者之间的完全解耦,首先对系统的数学模型进行了可逆性分析,证明该系统在一定条件下可逆,在此基础上应用神经网络逆系统方法,将非线性、强耦合的多变量系统转变成3个彼此无耦合的伪线性子系统,最后应用线性系统控制原理和智能控制理论,对这3个子系统设计了闭环专家PID控制器。仿真结果表明,系统具有良好的动静态性能。     

An Energy Conversion Laboratory Using Industrial-Grade Equipment

Laboratory experiences are an important component of the education of engineering students. Rotating machinery laboratories assist with the visualization of the three-dimensional and rotating equipment. Contemporary use of rotating machines in industry often includes adjustable speed drives and digital controllers. Additionally, instrumentation is used to feedback electrical and mechanical variables to the drives and controls. Using an equipment grant from an industrial automation manufacturer, cost-effective laboratory workstations have been developed. Industrial-grade equipment is not designed for student experimentation but was adapted for this use. The workstations described in this paper incorporate modern power electronic-based drives and motors, electrical and mechanical sensors, and a computer-based control system with data acquisition. The advantages of these workstations include cost-effectiveness and the use of actual industrial devices that students might encounter in industry. Additionally, the workstations can be accessed by remote users, enabling off-campus students to also perform experiments on the workstations. The paper includes details of the workstation and its components, the data acquisition and control system, and sample experimental results.     

基于免疫优化的机炉协调系统模糊增益调度H∞鲁棒控制

针对非线性锅炉-汽轮机系统在负荷点大范围变动情况下的协调控制,提出了一种新的免疫优化模糊增益调度 鲁棒控制方法。该方法首先利用 /混合灵敏度方法设计出多个 局部鲁棒控制器以覆盖机炉系统的负荷变化区间;然后采用模糊推理生成增益调度准则以实现各局部控制器间的软切换;最后利用免疫遗传算法对模糊增益调度准则的结构参数进行优化设计,从而保证闭环系统具有良好的全局控制性能。仿真研究表明：基于该方法设计出的协调控制系统在大工况范围内具有优良的调节品质。     

Electronic line-shafting control for paper machine drives

The current synchronized motion control methods used in paper machine drives are not designed to possess the inter-shaft stiffness properties which were responsible for the coordinating force inherent in classical, mechanically coupled paper machines. Consequently, these controllers cannot easily maintain coordination for all operating conditions. This paper presents the application of an “electronic line-shafting” control technique which serves to replicate and even improve on the historical, mechanical line-shafted properties. This technique was tested on a four-shaft experimental setup to evaluate such control during periods of drive-limited torque as well as sectional drive load disturbances. The experimental results demonstrate that the “electronic line-shafting” technique significantly improves the coordination, robustness, and overall stability of paper machine drives subjected to realistic physical limitations     

Using power measurements to diagnose degradations in motordrivepower systems: a case study of oilfield pump jacks

A study of diagnostics of faults in motor drive-power systems is reported. The study focuses on oil-field pump jacks and includes basic analysis, computer simulation, full-scale laboratory emulation and measurements in the oil fields. Spectrum analysis of instantaneous power and current delivered to the electric motor is used for diagnosis. An original electronic system for conditioning the input instantaneous power and current is explained. A model for the pump jack and its common degradations is given. A full-scale load control system emulates measured pump-jack loads in the laboratory     

Passivity based control for induction motor drives with voltage-fed and current-fed inverters

In recent years, passivity based control (PBC) scheme has gained wide attention among various nonlinear control methods. Based on Euler–Lagrange equations of motion, controllers are designed from an energy point of view. In this paper, the PBC is applied to induction motor (IM) speed drives with voltage-fed and current-fed inverters, respectively. The stability of the overall system for the voltage-fed IM drive has been verified rigorously, but it lacks for the current-fed IM drive. However, the controller structure of the latter is simpler than that of the former. Experimental results show that the PBC scheme is successful in speed control application for both IM drives. There is no significant differences between two IM drives. The overall system exhibits good robust performances in presence of motor parameter variations and load disturbances.     

Comparative evaluation of sliding mode fuzzy controller and PID controller for a boost converter

Nonlinear controllers such as fuzzy controllers and sliding mode controllers have been applied to boost converters because of their nonlinear properties. Although both fuzzy and sliding mode controllers have desirable characteristics, they have disadvantages in practice when applied individually. A sliding mode fuzzy controller is proposed to control boost converters. The sliding mode fuzzy controller combines the advantages of both fuzzy controllers and sliding mode controllers. It also has advantages of its own that are well suited for digital control design and implementation. A sliding mode fuzzy controller is designed and verified with experimental results using a prototype boost converter with a DSP-based digital controller. Experimental results of the boost converter using sliding mode fuzzy control are evaluated in comparison with experimental results using a linear PID and PI controller. The comparison indicates that the sliding mode fuzzy controller is able to obtain the desired transient response under varying operating points without chattering. The startup response using sliding mode fuzzy control is superior to the response using PID and PI control, while the load transient response shows no obvious advantage.     

Example applications of the linear adaptive design technique

Adaptive controllers can be designed by a variety of different methodologies that have been developed over the past 35 years. However, all these methodologies have one thing in common; they lead to adaptive controllers that are intriniscatly non-linear in structure. Recently a new, unorthodox approach to the adaptive control problem has been developed. This new methodology leads to a new class of adaptive controllers that, in many cases, are entirely linear and have all-constant parameters (constant gains). In the present paper this new approach to adaptive control is used to design‘linear adaptive controllers’for two example applications, and the closed-loop adaptive performance obtained in each case is illustrated by digital simulation tests. These results demonstrate that the new linear adaptive controllers are able to produce a surprisingly high-degree of adaptation over significant ranges of plant parameter variations and disturbances.     

基于速度跟踪算法的机械负载动态模拟

提出并介绍了用两台同轴直流电动机建立对机器人关节机械负载进行模拟的实验系统,建立了此系统模型.采用基于速度跟踪的控制算法,对建立的数学模型就此控制算法在Matlab/Simulink下进行仿真.最后对实验系统进行了性能测试和负载模拟的实验,证明了基于速度跟踪的算法和此实验系统对机器人关节的非线性机械负载进行模拟是可行有效的,但系统动态性能和精度尚待进一步提高.     

BUCK型开关变换器最优PID控制器设计

针对开关电源的复杂性和时变性,传统PID控制器整定方法无法很好满足其控制性能要求的问题,提出一种面向性能指标的最优PID控制器参数整定方法。基于DP算法,计算保证闭环系统稳定的PID控制器参数范围;利用具有全局寻优能力的遗传算法,按照ITAE性能指标在该范围内进行参数寻优。以BUCK变换器为利的仿真研究表明,该方法在指定的性能指标上取得了满意的控制效果,在负载发生摄动时,较传统PID控制器,具有较好的鲁棒性,且计算相对简单、实用性强,可推广到非线性PID控制器的参数整定和相关工程实践中。     

高压直流输电系统换流站鲁棒自适应输出反馈控制

针对高压直流输电系统,设计了一种鲁棒自适应输出反馈控制器.首先,将高压直流输电系统换流站动态模型转换成用输入输出表示的非线性系统.然后,利用自适应非线性阻尼项来抑制系统的非线性动态不确定性和未知有界扰动,应用Lyapunov稳定性理论构造出控制器和自适应参数的表达式.Lyapunov稳定性分析结果表明,文中所提出的控制器保证了闭环系统的稳定性.最后,将设计的控制器应用到一个3机直流输电系统中,仿真结果表明,与传统的PI控制器相比较,文中控制器可大大提高系统的稳定性和鲁棒性.     

ANALYSIS OF POWER CONVERTER CONTROL USING NEURAL NETWORK AND RULE-BASED METHODS

ABSTRACT

Current-controlled voltage source inverters offer substantial advantages in improving motor system dynamics for high-performance ac drive systems. The controller switches follow a set of reference current waveforms. Fixed-band hysteresis and sinusoidal-band hysteresis controllers have been studied. The first part of this paper develops neural network and fuzzy logic based current-controlled voltage source inverters. The models and learning techniques have been investigated by simulation. The implementation of neural networks is described and simulation results are presented. In the second part of this paper, the new UPS (uninterruptible power supply) with fuzzy logic compensator is proposed. Proposed fuzzy logic compensator is used to prevent voltage drop from nonlinear load. The total harmonic distortion (THD) of proposed scheme is better than that of conventional deadbeat control method for linear and nonlinear load. In the third part of this paper, the application of fuzzy control to DC-DC converters operating at finite switching frequency is studied. Several control methods currently used for buck, boost and buck/boost converters are compared to the fuzzy converter control. Simulation results for several control methods are presented. The simulations show that the fuzzy control method has better dynamic performance and less steady state error.     

AP1000核电站仿真分析平台的研发

介绍了AP1000核电站仿真分析平台的结构及设计方案。基于RELAP5程序开发了热工水力模型,采用Matlab/Simulink仿真建模软件和工业组态软件构建了控制系统模型和人机界面,构成了AP1000核电站仿真分析平台。机组线性降负荷和阶跃降负荷仿真测试结果表明,该平台能够较好地模拟系统变功率瞬态工况,可进行相关技术培训和核电站仪表控制系统的验证、参数优化等。     

多机系统中励磁与SVC的协调控制

主要研究基于结构保持模型的多机电力系统的暂态稳定性。将连接与阻尼分配?无源控制方法进行从常微分方程到微分代数方程的拓展,求解一类仿射非线性微分代数系统的调节问题。并用所提方法设计多机系统中的发电机励磁与静止无功补偿器的协调控制器,不再拘泥于单机系统的协调控制研究。该方法充分利用整个系统的物理结构,通过引入电气与机械动态之间的耦合项进行能量整形,加强两者之间的联系,保证闭环系统的渐近稳定性。仿真结果说明了协调控制器在阻尼振荡和增强电压稳定性上的有效性。     

Nonlinear excitation control of a synchronous generator with implicit terminal voltage regulation

The objective of this paper is to design nonlinear excitation controllers for single-machine infinite-bus power systems. Because of the nonlinear nature of such systems, nonlinear controllers are more effective in providing larger stability margins than their linear counterparts. To take advantage of well-developed linear control techniques, the concept of feedback linearization is used. A characterization of the region over which the linearizing state transformation is guaranteed to be diffeomorphic is provided. Also, a new formulation for the linear controller design is provided to solve the problem of the terminal voltage regulation. Simulation results of a single-machine infinite-bus power system indicate that in the presence of major disturbances the proposed controller outperforms existing linear and nonlinear controllers in maintaining the system's stability, in damping the rotor angle oscillations, and in reaching the desired performance during postfault operations.