Optimal Dynamic Voltage Restorer Using Water Cycle Optimization Algorithm

This paper proposes a low complexity control scheme for voltage control of a dynamic voltage restorer(DVR)in a three-phase system.The control scheme employs the fractional order,proportional-integral-derivative(FOPID)controller to improve on the DVR performance in order to enhance the power quality in terms of the response time,steady-state error and total harmonic distortion(THD).The result obtained was compared with fractional order,proportionalintegral(FOPI),proportional-integral-derivative(PID)and proportional-integral(PI)controllers in order to show the effectiveness of the proposed DVR control scheme.A water cycle optimization algorithm(WCA)was utilized to find the optimal set for all the controller gains.They were used to solve four power quality issues;balanced voltage sag,balanced voltage swell,unbalanced voltage sag,and unbalanced voltage swell.It showed that one set of controller gain obtained from the WCA could solve all the power quality issues while the others in the literature needed an individual set of optimal gain for each power quality problem.To prove the concept,the proposed DVR algorithm was simulated in the MATLAB/Simulink software and the results revealed that the four optimal controllers can compensate for all the power quality problems.A comparative analysis of the results in various aspects of their dynamic response and%THD was discussed and analyzed.It was found that PID controller yields the most rapid performance in terms of average response time while FOPID controller yields the best performance in term of average%steady-state error.FOPI controller was found to provide the lowest THD percentage in the average%THD.FOPID did not differ much in average response from the PID and average%THD from FOPI;however,FOPID provided the most outstanding average steady-state error.According to the CBMA curve,the dynamic responses of all controllers fall in the acceptable power quality area.The total harmonic distortion(THD)of the compensated load voltage from all the controllers were within the 8%limit in accordance to the IEEE std.519-2014.

An Equivalent Fundamental and Odd Harmonic Resonators Controller for a Single-phase Dynamic Voltage Restorer

为提高单相动态电压恢复器（dynamic voltage restorer,DVR）的补偿性能,提出一种基于等效基波及奇次谐波谐振器组的数字控制方法。采用可等效为一组谐振器的延时模块,能够有效抑制电网基波和谐波扰动。给出一种包含两个控制参数和一组零相移陷波滤波器的结构及其设计方法,使系统在保证稳定性的同时,获得较大的谐振增益。其中,延时环节衰减系数可增加谐振器组鲁棒性;控制器比例增益可解决零相移陷波器中使用延时带来的问题;零相移陷波器组既能对消LC谐振峰,也能解决等效谐振器组高增益在高频处的稳定性问题。同时,引入电源电压和负载电流双前馈来保证响应速度,增加了对扰动的抑制能力。所提控制策略结构简单,谐波补偿能力强,动态响应快,易于实现。在2kW单相DVR实验装置上的实验结果验证了该控制方法的正确性。

New Control Algorithm for Capacitor Supported Dynamic Voltage Restorer

In this paper, a simple control algorithm for the dynamic voltage restorer (DVR) is proposed to mitigate the power quality problems in terminal voltage such as sag, swell, harmonics, unbalance etc. Two PI (proportional-integral) controllers are used each to regulate the dc bus voltage of DVR and the load terminal voltage respectively. The fundamental component of the terminal voltage is extracted using the synchronous reference frame theory. The control signal for the series connected DVR is obtained indirectly from the extracted reference load terminal voltage. The proposed DVR control strategy is validated through extensive simulation studies using MATLAB software with its Simulink and Sim-power system (SPS) block set tool boxes.

Novel Control Method for Dynamic Voltage Regulator

Control strategy affects directly the working performances of dynamic voltage regulator （DVR）. One-cycle control is an effective nonlinear signal modulation control method. In this paper, a new one-cycle control scheme for DVR was proposed in single phase supply system. On the basis of principle analysis, the corresponding one-cycle control model for DVR was built up, which is characterized by simple control circuits, good control performance, and high control precision. As an example, a control model for single-phase DVR was simulated by using Matlab/Simulink and SimPowerSystem. The results show that the load voltage could be compensated quickly at the points of supply voltage stepping down and up, and the relative error was less than 4% in the whole voltage sag process. Both theory analysis and simulation results show that the new one-cycle control scheme for DVR is effective.

Neuro-Fuzzy Based Interline Power Flow Controller for Real Time Power Flow Control in Multiline Power System

This article investigates the power quality enhancement in power system using one of the most famous series converter based FACTS controller like IPFC (Interline Power Flow Controller) in Power Injection Model (PIM). The parameters of PIM are derived with help of the Newton-Raphson power flow algorithm. In general, a sample test power system without FACTs devices has generated more reactive power, decreased real power, more harmonics, small power factor and poor dynamic performance under line and load variations. In order to improve the real power, compensating the reactive power, proficient power factor and excellent load voltage regulation in the sample test power system, an IPFC is designed. The D-Q technique is utilized here to derive the reference current of the converter and its D.C link capacitor voltage is regulated. Also, the reference voltage of the inverter is arrived by park transformation technique and its load voltage is controlled. Here, a sample 230 KV test power system is taken for study. Further as the conventional PI controllers are designed at one nominal operating point they are not competent to respond satisfactorily in dynamic operating conditions. This can be circumvented by a Fuzzy and Neural network based IPFC and its detailed Simulink model is developed using MATLAB and the overall performance analysis is carried out under different operating state of affairs.

Fuzzy Controlled Ultra-Capacitor Based DVR (UCAP-DVR) for Power Quality Enhancement

In recent years, a rapid decrease in the cost of various energy storage technologies and their integration into grid becomes a reality with the advent of smart grid. The Dynamic Voltage Restorer (DVR) is a custom power device that has an excellent dynamic capability used to provide voltage sag, swell compensation in distribution systems. Among the energy storage devices, Ultra-Capacitors (UCAP) have ideal characteristics such as high power and low energy density essential for the compensation of voltage sag and swell, which require high power for short interval of time. This paper presents an integration of rechargeable UCAP with DVR. This UCAP-DVR presents a modular, flexible system configuration that will have an active power capability and also provide deep, extended mitigation for power quality problems. The DVR is integrated into UCAP via bidirectional DC-DC converter which supports a rigid dc-link voltage for DVR and also helps in compensating temporary voltage sag and swell. FUZZY LOGIC Controller is used to enhance the performance of UCAP-DVR. The simulation model for the proposed system has been developed in MAT-LAB and the performance over conventional DVR is compared with the results obtained.

Low-voltage ride-through capability improvement of Type-3 wind turbine through active disturbance rejection feedback control-based dynamic voltage restorer

Disconnections due to voltage drops in the grid cannot be permitted if wind turbines(WTs)contribute significantly to electricity pro-duction,as this increases the risk of production loss and destabilizes the grid.To mitigate the negative effects of these occurrences,WTs must be able to ride through the low-voltage conditions and inject reactive current to provide dynamic voltage support.This paper investigates the low-voltage ride-through(LVRT)capability enhancement of a Type-3 WT utilizing a dynamic voltage restorer(DVR).During the grid voltage drop,the DVR quickly injects a compensating voltage to keep the stator voltage constant.This paper proposes an active disturbance rejection control(ADRC)scheme to control the rotor-side,grid-side and DVR-side converters in a wind–DVR integrated network.The performance of the Type-3 WT with DVR topology is evaluated under various test conditions using MATLAB®/Simulink®.These simulation results are also compared with the experimental results for the LVRT capability performed on a WT emulator equipped with a crowbar and direct current(DC)chopper.The simulation results demonstrate a favourable transient and steady-state response of the Type-3 wind turbine quantities defined by the LVRT codes,as well as improved reactive power support under balanced fault conditions.Under the most severe voltage drop of 95%,the stator currents,rotor currents and DC bus voltage are 1.25 pu,1.40 pu and 1.09 UDC,respectively,conforming to the values of the LVRT codes.DVR controlled by the ADRC technique significantly increases the LVRT capabilities of a Type-3 doubly-fed induction generator-based WT under symmetrical voltage dip events.Although setting up ADRC controllers might be challenging,the proposed method has been shown to be extremely effective in reducing all kinds of internal and external disturbances.

食品协作机器人动态目标抓取控制方法研究

目的:解决目前协作机器人在食品动态目标抓取中存在的准确性较低问题。方法:基于协作机器人体系结构,提出将模糊自整定PID控制和鲁棒自适应补偿器相结合用于协作机器人食品动态目标抓取。PID结合模糊控制完成参数自整定,鲁棒算法与自适应算法相结合用于系统不确定性补偿。通过试验分析了所提方法的性能,验证了该方法的可行性。结果:所提方法在协作机器人动态目标抓取中具有较好的效果,提高了协作机器人动态抓取的准确性,在传送带速度100 mm/s时,动态抓取成功率达到99.50%,对食品动态目标抓取具有一定的应用价值。结论:通过优化现有目标抓取控制方法,可有效提高协作机器人的抓持精度。

单侧并联储能变流器并网谐振机理分析及抑制方法

为解决单侧并联储能变流器并网谐振问题,对谐振机理进行分析,设计抑制方法。通过研究系统待机与运行工况下的幅相参数,获取谐振特性。将谐振成因分为内因与外因,内因为并联系统输出电流随并机叠加,在并网阻抗上产生谐波压降,导致的电压谐波放大。外因为网侧所含背景电压谐波与并联系统阻抗频率在某些频段重叠。随并机数量增加,系统谐振点频率将降低。采用设计的电压谐波补偿单元进行功率解耦及动态多比例谐振控制器进行控制解耦两种方法,实现谐振抑制。通过仿真验证了谐振成因机理及抑制方法有效性。

丝杠进给系统运动控制研究

丝杠进给系统在运行过程中具有非线性、强耦合和参数时变等特点,由于传统PID控制器的参数固定,无法很好地适应系统变化,从而导致系统响应速度缓慢及跟踪性能较差。针对此类问题,将复杂的丝杠进给系统简化处理并建立二质量系统模型;对传统的模糊规则加以优化和改进,设计了一种模糊PI控制与加速度前馈补偿相结合的复合控制器。模糊PI控制器根据实际系统特性调整模糊规则,使得控制器参数自适应变化,提高控制效果;加速度前馈补偿控制器根据输入信号预先补偿系统,提升了系统带宽。在Simulink中搭建系统模型,在阶跃输入和干扰输入下对比观察2种控制器作用的系统响应曲线。经仿真验证,丝杠进给系统的动态特性、稳态特性和抗干扰能力都得到了明显地提升。

基于PSASP的低压用电设备无功动态补偿系统设计

为了解决低压用电设备功率因数与实际结果不一致,导致补偿误差较大的问题,基于PSASP设计一种新的低压用电设备无功动态补偿系统。分别设计电压/电流电路、保护电路和采集电路,计算限流电阻和输入电阻,分析电压值,利用六路串口进行补偿。计算无功功率和电能因数,对数据进行调整,将比较补偿、积分补偿、微分补偿三者相结合得出PASAP控制结果,获得动态功率因数,实现低压用电设备无功动态补偿。实验结果表明,该系统功率因数与实际结果基本一致,补偿误差低于0.01%。

构网型无功补偿抑制新能源送端暂态过电压

电网换相换流器型高压直流输电(line commutated converter based high voltage direct current,LCC-HVDC)是新能源大规模并网、远距离外送的关键。而直流闭锁、换相失败等故障可能导致送端短时无功过剩并引发暂态过电压,危及运行安全。文中突破传统基于电压-电流级联控制的电流源外特性快速无功补偿装置的技术原理,提出一种应用构网型无功补偿装置(grid-forming based reactive power compensation device,GFM-RPC)抑制新能源送端暂态过电压的方法,构建基于微分-代数关系的电压动态分析模型,阐明GFM-RPC抑制暂态过电压机理,并分析GFM-RPC相比现有基于静止同步补偿器(static synchronous compensator,STATCOM)抑制暂态过电压方法的优势。利用仿真验证GFM-RPC抑制新能源送端暂态过电压的效果,并分析主要参数对过电压抑制效果的影响。研究表明,STATCOM这类电流源外特性的无功补偿装置在直流输电系统故障瞬间呈现出恶化电压动态的“反调”特性,而GFM-RPC能够克服这种“反调”特性,并且通过合理的参数配置可以进一步抑制电压幅值的超调量。

基于前馈自抗扰控制的动态电压恢复器

针对动态电压恢复器(DVR)在传统比例-积分(PI)控制中补偿速度与补偿超调量之间的矛盾,提出了一种基于前馈补偿的自抗扰控制(FC-ADRC)策略。通过ADRC策略改进传统PI控制所存在的补偿超调问题,并引入LC滤波器的电压电流作为前馈量对DVR控制器进行补偿,实现对用户侧电压暂降进行快速电压补偿,保证用户侧电压的安全稳定。仿真实验结果表明,所提策略既保持DVR装置的高动态响应性,又保证装置应对不确定扰动的适应性。

基于交交变换的动态电压恢复器及其控制策略

传统的动态电压恢复器(DVR)中直流储能环节体积重量大,不易集成,交交变换技术省去实现动态电压补偿,更加经济节约。虚拟整流逆变拓扑作为主电路拓扑,结构简洁,并且能够实现自然换流;单周期控制精度高,动态跟踪性能佳,控制鲁棒性好,应用于DVR可以更好地满足其特殊的快速性要求。在理论分析基础上,研制了实验样机进行实验验证,实验结果验证了变换器的可行性及单周期控制良好的动态特性。

基于动态虚拟电抗的虚拟同步机系统有功环电压动态补偿策略

为解决新型电力系统中的虚拟同步机(Virtual synchronous generator,VSG)在电网电压跌落时出现的功角暂态失稳和过电流问题,对采用VSG控制的并网换流器暂态控制策略进行了改进。为降低故障期间有功功率的参考值进而实现VSG的功角暂态稳定控制,根据VSG的功角特性、有功功率参考值与功角稳定性之间的关系,引入电压动态补偿,并利用相图曲线理论分析了控制策略参数选取对暂态稳定的影响。为限制故障发生瞬间和故障切除瞬间的冲击电流、保证故障期间VSG系统的暂态功角稳定、实现故障限流,提出了一种以指数形式变化的虚拟电抗模型,确定了虚拟电抗的投切参数。仿真实验结果验证了改进策略的有效性。

动态电压恢复器的Fuzzy-PID控制策略的研究

针对电网电压跌落问题,主要研究了单相动态电压恢复器的Fuzzy-PID控制策略。首先对动态电压恢复器的原理和构成进行了简单介绍,并推导出系统方程。然后对电压环反馈控制和二维模糊控制器分别进行了设计,搭建仿真模型。应用Fuzzy-PID自调节控制实现了对负载电压的快速补偿,并对补偿电压进行FFT分析。仿真结果验证了方法的正确性与有效性。

基于嵌入式技术的轻小型落地抱杆自动控制系统研究

该文在分析轻小型落地抱杆结构的基础上,设计基于嵌入式技术的轻小型落地抱杆自动控制系统框架,由基础数据单元采集轻小型落地抱杆运行数据后,控制单元的嵌入式主控制器调用变频调速控制程序实现起升电机运行速度的控制,通过模糊PID控制器实现吊钩负载转矩补偿控制,并利用粒子群算法对控制器参数作在线实时整定,通过CAN总线将控制指令下达给各工作机构,并利用以太网实现与远程控制中心的信息交互。实验结果表明,该系统可实现轻小型落地抱杆自动控制,控制后的阶跃响应曲线平滑、超调量低,控制时间短,输出的模拟电压曲线走势稳定、平滑度高,不存在振荡问题。

动态电压恢复器精准相控整流方法研究

动态电压恢复器是一种新型的电力电子装置,串联于电源和敏感负载之间,主要功能是治理电网电压扰动。动态电压恢复器主要由储能元件、双向变流器、静态转换开关和控制单元组成,电网电压处于稳定状态时,静态转换开关导通,电网通过此回路向负载供电;电网电压异常时,静态转换开关切换至由变流器为负载供电。在研制小容量动态电压恢复器过程中发现,储能元件(超级电容)相控整流充电过程中,出现交流侧充电电流突然急剧增大的现象,导致变流器IGBT模块损坏。针对出现的充电电流突增现象进行理论分析和仿真验证,根据分析验证结果更改设备控制策略和参数设置,解决了储能元件(超级电容)相控整流充电过程中电流激增的问题。

Real-time multi-step prediction control for BP network with delay

Real time multi step prediction of BP network based on dynamical compensation of system characteristics is suggested by introducing the first and second derivatives of the system and network outputs into the network input layer, and real time multi step prediction control is proposed for the BP network with delay on the basis of the results of real time multi step prediction, to achieve the simulation of real time fuzzy control of the delayed time system.

Double-loop Control Structure Using Proportional Resonant and Sequence-decoupled Resonant Controllers in Static Coordinates for Dynamic Voltage Restorer

Among incidents on grids,the sag/swell voltage is considered as the most frequent incident.To solve this problem,custom power devices are used.In particular,the dynamic voltage restorer(DVR)is a modern and efficient customer device.DVRs are used to mitigate voltage sag/swells and harmonics on the load bus,thus protecting the sensitive loads.The DVR is a serial compensator that applies a voltage to the point of common coupling to maintain the voltage of sensitive load at the nominal value.To improve the performance of DVRs,in this study,the control strategy of the two-stage loop circuit is implemented.The external voltage control loop uses a sequence-decoupled resonant(SDR)controller,and the inner current-control loop uses the proportional resonant(PR)controller implemented in the stationary frameαβ.