直流孤岛外送风电变电流控制策略

由于风电具有波动性,对于没有足够火电配比的风电系统,尤其是风电孤岛系统,无法采用以往的定功率控制输送风电。为此,提出可以跟踪风电变化、输送可控可变功率的变电流控制策略。根据风电功率的波动性,该策略利用变电流控制方式实时输送波动的风电功率,且可以保证系统的电压电流均在允许范围之内。推导了该策略的控制原理、运行区域,确定了控制模型结构,设计了变电流控制器,搭建了仿真模型。仿真结果验证了所提策略的有效性。

控制软抓取器的电流变阀门的设计与性能探究

针对电流变流体驱动的软体机器人目前存在的如软体易损坏、复杂的腔体更换成本高、电流变液难以制得等诸多问题,提出一种由电流变阀门控制的软抓取器。该软抓取器使用了模块化的思想,将控制系统集中在了电流变流体控制阀中,而软体手指则是标准件,具有便于装配更换、控制系统简单的优点。电流变效应是指在外加电场作用下,电流变流体会由自由流动状态瞬间变刚度,呈现出凝固状态,当外加电场消失,又能迅速复原。为利用电流变效应去设计控制阀门系统,进行了电流变流体变刚度性能试验,通过试验讨论了不同影响因素对电流变流体变刚度能力的影响。试验结果表明,电场强度、两电极板之间的距离、电极的长度、电极的宽度、硅油的黏度对电流变流体变刚度性能产生不同的影响。通过试验结果,可以筛选出电流变流体工作的最优环境条件。此外,由电流变阀门控制的软抓取器可以通过控制流体的流动方向来控制机械手的抓取模式。软抓取器样机试验验证了其对不同形状物品的抓取能力。

虚拟仪器技术在电流变转向控制机构中的应用

基于Labview的虚拟仪器技术,对圆盘式电流变转向控制机构的主动轴进行编程控制,使其能在步进电机的驱动下,实现多种波形的转动,进而实现对电流变转向控制机构的自动控制。

基于电流变结构控制的三相电压型PWM整流器的研究

对三相电压型PWM整流器采用电流变结构控制进行了研究,分析了PWM整流器的数学模型,详细设计了电流变结构控制器,并对其稳定性进行了分析.通过仿真对该控制方法进行了验证,结果表明,方案切实可行,系统具有良好的动静态性能.

柔性边界控制的微电网协调调度

针对微电网调度中微燃机和储能装置因功率分配导致频繁调节问题,提出了柔性边界控制的微电网协调调度方法。首先,微燃机根据蓄电池的调节能力柔性改变其输出功率的调整边界。然后,蓄电池采用变电流充放电方法快速捕集随机变化的可再生能源和最大限度地释放储存的能量。最后,案例仿真表明微燃机减少了调节次数,蓄电池更加合理地进行充放电控制,可再生能源的利用率也得到了提高。因此,所提出的调度方法能够避免微燃机频繁调节、延长蓄电池使用寿命、降低设备损耗和系统运行成本,提高了微电网调度灵活性并降低了其对配电网的依赖度。

配电变一体化STATCOM结构设计及其控制方法

提出了一种新颖的配电变压器一体化静止无功补偿装置(DT-STATCOM)的设计思想和方法:将STATCOM从变压器高压绕组抽头接入,选择合适的接入电压等级,从而有利于减少功率单元级联数量,降低功率器件电流水平和发热损耗。同时,将STATCOM与变压器一体化设计,利用变压器绕组部分漏抗代替滤波器网侧电感,减小了注入系统的谐波含量;实现了对负载无功与变压器消耗无功的集中补偿,避免了线路无功传输造成的损耗。针对DT-STATCOM系统的特点,提出了基于功率平衡原理的无功指令电流计算方法,研究并采用了变环宽准恒定频率的滞环电流控制方法。仿真结果验证了所提出的DT-STATCOM系统结构及其控制方法的正确性和优越性。

电流变技术在流体动力传输中的应用研究

介绍了一种电流变流体控制元件的结构和工作原理 ,并对其进行了实验研究。研究结果表明 ,负载流量的大小和方向可直接由电流变流体控制元件上所加电场的大小来控制 ,验证了电流变技术应用于流体动力传输的可行性 。

基于虚拟仪器的电流变传动机构的动态测控

采用虚拟仪器技术,将图形编程程序LabVIEW与电流变技术相结合,构建旋转及轴向往复运动圆盘式电流变传动机构的测控系统。该测控系统可方便对旋转及轴向往复运动圆盘式电流变传动机构的主轴进行程序控制,做到多种波形的输入,使其在步进电机的驱动下,实现对电机的准确控制及对数据的同步采集。实验表明当该传动机构在两原盘与中间盘间隙挤压到足够小时,剪切-挤压复合运动模式比纯剪切运动模式传递的力矩明显增大。

三态Boost PFC变换器的高功率因数和轻载效率提升方法研究

工作于伪连续导电模式(pseudo-continuous conduction mode,PCCM)的三态Boost功率因数校正(power factor correction,PFC)变换器采用传统解耦控制,在输入电压增大时,存在功率因数较低的问题。文中结合三态Boost PFC变换器具有两个控制自由度的特点,从变换器的输入电流表达式出发,提出一种三态Boost PFC变换器的变占空比正弦参考电流控制方法,采用变占空比控制变换器的主开关管,正弦参考电流控制续流开关管,并对变换器参数和控制环路进行设计。相比于传统解耦控制的,变占空比正弦参考电流控制的三态Boost PFC变换器具有更高的功率因数,同时也具有快速动态响应与宽负载范围的优点。在此基础上,针对三态Boost PFC变换器轻载效率低的问题,提出混合模式控制方法提升其轻载效率。最后,通过一台400W的实验样机验证理论分析。

电动助力转向系统滑模变控制技术研究

以电动助力转向系统中直流助力电机的控制器为研究对象,依据助力电机的数学模型,应用带观测器补偿的滑模变结构控制方法,设计了滑模变控制器,通过调节助力电机的电压,获得预期的输出电流。仿真结果表明,所设计的滑模变控制器使助力电机具有很好的动态性能,系统基本无抖动现象,实现了助力电机输出电流对目标电流的跟踪特性。

一种双余度无刷直流电机转矩脉动抑制控制策略研究

针对两套并联绕组互差30°电角度的双余度无刷直流电机换相转矩脉动问题展开研究.提出一种基于变结构电流前馈的转矩控制方法.该方法结合对应相绕组轴线互差30°的特点,在均流控制的前提下,使用变结构控制策略独立控制两套绕组的电流以保证电机在换相时刻输出稳定的转矩.为了增加电流的响应速度,采用电流前馈控制方法提高电流的变化率.在MATLAB/Simulink环境下搭建模型进行仿真.结果表明,与传统的双余度电机均流控制策略相比,基于变结构电流前馈的转矩控制策略能够有效地降低电机的换相转矩脉动.

A NEW SOFT-SWITCHING PUSH-PULL THREE-LEVEL CONVERTER

The application areas of conventional push pull converters are limited because of high voltage stress of switches (twice of input voltage). This paper presents a novel zero voltage and zero current switching (ZCS) PWM push pull three level converter in which the voltage stress of switches is input voltage. With phase shifted modulation strategy, the leading switches can only realize zero voltage switching (ZVS), and the lagging switches can realize ZCS when block capacitor and block diodes are added. Using the strategy, the converter overcomes the drawbacks presented by the conventional push pull converter, such as magnetic aberration, large switch loss, and voltage spike on switches, so it can get higher efficiency, and a wider application area. The operating principle of the new converter is analyzed and verified on a 600 W, 50 kHz experimental prototype. Several zero voltage and zero current switching PWM push pull three level converters are proposed.

Fault tolerant control of electric pitch control system based on single current detection

In view of the current sensors failure in electric pitch system,a variable universe fuzzy fault tolerant control method of electric pitch control system based on single current detection is proposed.When there is single or two-current sensor fault occurs,based on the proposed method the missing current information can be reconstructed by using direct current（DC）bus current sensor and the three-phase current can be updated in time within any two adjacent sampling periods,so as to ensure stability of the closed-loop system.And then the switchover and fault tolerant control of fault current sensor would be accomplished by fault diagnosis method based on adaptive threshold judgment.For the reconstructed signal error caused by the modulation method and the main control target of electric pitch system,a variable universe fuzzy control method is used in the speed loop,which can improve the anti-disturbance ability to load variation,and the robustness of fault tolerance system.The results show that the fault tolerant control method makes the variable pitch control system still has ideal control characteristics in case of sensor failure although part of the system performance is lost,thus the correctness of the proposed method is verified.

EFFECTIVE DOUBLE LOOP CONTROL FOR A SQUARE WAVE BRUSHLESS DC MOTOR

A new type of brushless DC motor has been developed by using a square wave rare earth permanent magnet synchronous motor with its double loop control circuit. The double loop control scheme of the drive system yields a combination of desired characteristics including simplified control structure, small ripple torque, high speed accuracy, wide operating speed range, and fast dynamic response. Experimental results confirm excellent characteristics of the motor.

Fault diagnosis and fault-tolerant control of photovoltaic micro-inverter

An observer-based fault diagnosis method and a fault tolerant control for open-switch fault and current sensor fault are proposed for interleaved flyback converters of a micro-inverter system. First, based on the topology of a grid-connected micro-inverter, a mathematical model of the flyback converters is established. Second, a state observer is applied to estimate the currents online and generate corresponding residuals. The fault is diagnosed by comparing the residuals with the thresholds. Finally, a fault-tolerant control that consists of a fault-tolerant topology for the faulty switch and a simple software redundancy control for the faulty current sensor, is proposed to achieve a fault-tolerant operation. The feasibility and effectiveness of the proposed method has been verified by simulation and experimental results.

Finite Set-Model Predictive Current Control of Three-Phase Voltage Source Inverter for RES （Renewable Energy Systems） Applications

This paper focuses on a combination of three-phase VSI （voltage source inverter） with a predictive current control to provide an optimized system for three-phase inverters that control the load current. A FS-MPC （finite set-model predictive control） strategy for a three-phase VSI for RES （renewable energy systems） applications is implemented. The renewable energy systems model is used in this paper to investigate the system performance when power is supplied to resistive-inductive load. With three different cases, the evaluation of the system is done. Firstly, the robustness of control strategy under variable DC-Link is done in terms of the THD （total harmonic distortion）. Secondly, with one prediction step, the system performance is tested using different sampling time, and lastly, the dynamic response of the system with step change in the amplitude of the reference is investigated. The simulations and result analyses are carried out using Matlab/Simulink to test the effectiveness and robustness of FS-MPC for two-level VSI with AC filter for resistive-inductive load supplied by a renewable energy system.

PRIMARY SIDE DETECTION AND PEAK CURRENT MODE CONTROL IN FLYBACK CONVERTER

A new cycle-by-cycle control flyback converter with primary side detection and peak current mode control is proposed and its dynamic characteristics are analyzed. The flyback converter is verified by the OrCAD simulator. The main advantages of this converter over the conventional one are simplicity, small size, rapid regulating and no sensing control signals over the isolation barrier. The circuit is suitable for digital control implementations.

A new controller for the semi-active suspension system with magnetorheological dampers

A new sliding mode controller for semi-active suspension system with magnetorheological (MR) damper is presented in this paper. In the proposed sliding mode controller, a semi-active suspension based on the skyhook damper system is chosen as the reference model to be followed, and the control law is so determined that the asymptotically stable error dynamics occurs between the controlled state and the reference model state. Numerical simulations are carried out to study the performance of the new sliding mode controller. The results show that the proposed controller yields almost perfect tracking to the reference model and has a high robustness against model parameter uncertainties and disturbances.

Experimental Studies on High-Frequency Performance of the Inverse Control Magneto-Rheological Damper

Severe vibration of underground structures may be induced under blast loads. According to the characteristics of the explosion-induced ground shock wave, a new-type damper, inverse control magneto-rheological（MR） damper was designed to control the vibration, The high-frequency performance test of the MR damper was carried out on the small shaking table. It is shown that the performance can be modeled by use of the modified Bouc-Wen model, and the Parameters of the model keep stable in the range of 15--50 Hz.

A Method to Obtain Complex Transfer Functions of Four Order DC-DC Converters

Two TFs （transfer functions） are needed to analyze switching DC-DC converters in control-voltage mode： the duty-cycle to output-voltage （control to output） and the input-voltage to output-voltage （line to output）. To obtain these TFs a small-signal analysis is required. The CCM （continuous conduction mode） and the DCM （discontinuous conduction mode） analysis are different. When a circuit includes the loss resistances of the components, the number of parameters increases considerably, making manual nodal-loop circuit analysis techniques impractical to obtain the TFs. Moreover, these circuits are bilinear （non-linear） and it is necessary to linearize the equations at a DC operating-point （approximate linearization）. Vorp6rian describes a PWM （pulse-width-modulated） switch model that includes all non-linear parts of the DC-DC switching converters. This model can be linearized and replaced on the switching converter schematic leading to a linear circuit. At this point it is possible to use symbolic analysis programs to obtain these TFs or to simply apply numerical values for either the Bode diagrams or the calculation of poles and zeros. Here we describe an application of Ekrem Cangeici＇s method on X DC-DC converter to obtain control to output and line to output TFs in CCM and DCM including loss resistances. The method presented in this paper is optimized to use in the online publishing platform OctaveRS. Also the control to output TF for PCC （peak current controlled） in CCM is obtained.