Sliding mode control of three-phase AC/DC converters using exponential rate reaching law

Sliding mode control(SMC) becomes a common tool in designing robust nonlinear control systems, due to its inherent characteristics such as insensitivity to system uncertainties and fast dynamic response.Two modes are involved in the SMC operation, namely reaching mode and sliding mode.In the reaching mode, the system state is forced to reach the sliding surface in a finite time.The major drawback of the SMC approach is the occurrence of chattering in the sliding mode, which is undesirable in most applications.Generally, the trade-off between chattering reduction and fast reaching time must be considered in the conventional SMC design.This paper proposes SMC design with a novel reaching law called the exponential rate reaching law(ERRL) to reduce chattering, and the control structure of the converter is designed based on the multiinput SMC that is applied to a three-phase AC/DC power converter.The simulation and experimental results show the effectiveness of the proposed technique.

FCS-MPC for four-switch three-phase AC-DC converters with DC-link capacitor voltage balancing

Due to the decrease in the number of switches for the four-switch three-phase alternating current-direct current(FSTP AC-DC)converter,it can easily lead to DC-link capacitor voltage imbalance and the system stability reduction.In order to solve these problems,a finite control set model predictive control(FCS-MPC)for FSTP AC-DC converters with DC-link capacitor voltage balancing is proposed.In this strategy,in order to facilitate calculation,theαβcoordinate system model is established and all voltage vectors are evaluated by establishing a cost function.During the whole process,phase locked loop(PLL)and complex modulation strategy are not required.In the new established cost function,the additional objective term of suppressing capacitor voltage fluctuation is to eliminate effectively the capacitor voltages oscillations and deviations and improve the system reliability.The simulation results show that the proposed strategy can keep the capacitor voltage balancing and has good dynamic and static performance.

Vector Control of Three-Phase Solar Farm Converters Based on Fictive-Axis Emulation

In this paper,a new method for adjusting the current of three-phase voltage source DC-AC converter in orthogonal(DQ)reference frame is presented.In the DQ reference system,AC variable appears in the constant form of DC,making the controller design the same as the DC-DC converter[1].It provides controllable gain benefits at the steady-state operating point,and finally realizes zero steady-state error[2].In addition,the creative analytical model is dedicated to building up a series of virtual quantities orthogonal to the actual single-phase system.In general,orthogonal imaginary numbers get the reference signal by delaying the real quantity by a quarter period.However,the introduction of such time delay makes the dynamic response of the system worse.In this paper,orthogonal quantities are generated from a virtual axis system parallel to the real axis,which can effectively improve the dynamic performance of traditional methods without increasing the complexity of controller structure.Through PSCAD simulation,the ideal experimental results are obtained.

Three-phase Voltage-fed Quasi-Z-Source AC-AC Converter

The paper proposes a novel three-phase voltage-fed quasi-Z-source ac-ac converter topology to overcome the shortcomings of the traditional three-phase AC-AC chopper.The quantitative relationship between the output voltage and duty-ratio is deduced by investigating the topology and operating principle.It can provide buck-boost function,and the output voltage of the circuit can keep stable in the case of voltage sagging.Simulation is performed using the MATLAB software,and the experimental circuit is built based on the simulation results,the simulation and experimental results verify the correctness and feasibility of the proposed ac-ac converter topology.

Finite control set model predictive control of three-port converter for interfacing a PV-battery energy storage system to a three-phase stand-alone AC system

This paper proposes a multiport bidirectional non-isolated converter topology that provides advantages in terms of simultaneous multiple operations,single-stage conversion,high power density and reduced power losses due to the lower number of switches.The proposed multiport converter uses a centralized non-linear controller known as a finite control set model predictive controller to manage the flow of power between different ports.It deals with the parallel operation of photovoltaic and battery energy storage systems for stand-alone alternating current(AC)systems.The converter connects the lower voltage battery to the photovoltaic port using a bidirectional buck/boost converter and the photovoltaic port is linked to the stand-alone AC load through a three-phase full-bridge inverter.Each leg of the three-phase converter will act as a bidirectional direct current(DC)/DC converter as well as an inverter simultaneously.Only six switches manage the power transfer between all the connected ports of photovoltaic-battery energy storage system linked to the stand-alone AC load.The proposed multiport converter is mathematically modelled and controlled by a finite control set model predictive controller.The system is validated in simulation(1-kW rating)and experimental environment(200-W rating).The hardware prototype is developed in the laboratory and the controller is implemented on the field-programmable gate array board.Two independent case studies are carried out to validate the efficacy of the system.The first scenario is for a change in solar irradiance,while the second scenario is for a change in the output load.

利用瑞利面波提高近地表横波速度精度的方法

二维油气地震勘探中,由于受野外施工条件、成本效益等诸多因素限制,地震记录的野外采集道间距往往较大,这种地震记录往往容易产生空间假频,降低其频率—速度谱信噪比。为此,提出利用小波变换良好的时频分析特性,对大时空采样记录进行基于小波基的道内插值,以提高P-SV转换波地震资料中的瑞利面波频散高频信息的精度,从而提高反演表层横波速度结构精度,提高P-SV转换波的横波静校正精度。对理论模型和实际数据进行的验证计算表明,基于小波基的道内插值方法具有抗假频性,瑞利面波基阶频散曲线拐点更清晰,高频段能量更加集中,反演的横波速度精度更高,取得了较好效果。

静止坐标系下无电网电压传感器虚拟同步机控制策略

针对采用虚拟磁链算法的无电网电压传感器存在的直流偏移等问题,提出基于一阶低通滤波器和高通滤波器串联结构的改进磁链观测器,利用改进的磁链观测器得出虚拟磁链,提高了观测的精度。在得到虚拟磁链的基础上,针对不同电网频率运行条件,利用锁相环思想提出电网角频率的计算结构,并由虚拟出的磁链与电压的关系来重构电网电压。此外,将所提无电网电压传感器策略应用于网侧变流器系统中,在两相静止坐标系下设计虚拟同步控制结构,相比于旋转坐标系,可省去控制内环的解耦环节,同时还能简化坐标变换环节,避免了因坐标变换中角度不准而引入的不稳定因素。最后,通过仿真与实验验证所提控制策略与磁链观测器的有效性与可靠性。

基于VHDL-AMS的模数转换器辐射效应建模与仿真方法

模数转换器(Analog-to-Digital Converter,ADC)是连接模拟信号域与数字信号域的关键器件,而现有研究缺乏ADC辐照效应建模的相关内容.为满足大型模数混合信号系统辐照效应建模仿真的需要,本文提出了建立具有辐照效应的ADC行为级模型的方法.首先根据ADC的工作原理将其拆解为不同的通用模块,使用模拟和混合信号硬件描述语言(Very High speed integrated circuit hardware Description Language for Analog and Mixed Signals,VHDL-AMS)建立了各模块的行为级模型.接着根据基本原理将各模块动态组合为未辐照情况下基本的ADC模型.对于ADC的辐照效应,通过开展辐照试验,测量了ADC芯片HWD7710和SAD9434受总剂量(Total Ionizing Dose,TID)效应和中子辐射(Neutron Radiation,NR)效应影响的工作参数,并利用最小二乘法拟合获得ADC的工作参数与辐照剂量的关系式.最后根据辐照关系式,在基本模型上添加辐照参数模块,并建立两种不同结构ADC的TID与NR模型.通过仿真结果与试验数据对比,验证了所建ADC辐射效应模型的普适性和精度.模型的静态参数仿真结果与试验结果的相对偏差在5%以内,证明该方法支持对不同ADC及不同辐射效应进行辐照效应模型建模.

多直流馈入受端电网的最大受电能力估计方法

为保证多直流馈入受端电网稳定运行,提出一种静态稳定约束下多直流馈入受端电网的最大受电能力估计方法。首先,基于奇异值理论推导出多直流馈入受端电网静态电压稳定约束;然后,在考虑静态电压稳定性约束的情况下,建立多直流馈入受端电网优化调度模型;接着,给出一种计及静态电压稳定约束的优化调度模型分段线性求解方法,并基于该方法给出最大受电能力估计方法;最后,通过修改的IEEE39节点系统验证本文所提方法的有效性。

集无功和谐波补偿功能于一体的构网型变流器研发

为了解决大规模风电并网面临的电压越限、谐波谐振、主动支撑能力变差等问题,充分利用电力电子变换装置灵活可控的优势,研发了一种集静止无功发生器(SVG)和有源滤波器(APF)功能于一体的构网型变流器。类比直流母线电容的充放电特性和同步发电机转子的加减速特性,设计有功控制环,在不引入锁相环的情况下实现电网相位跟随、谐振风险降低;基于无功-电压下垂控制原理,设计无功控制环,实现无功补偿和电压支撑;通过谐波电流检测和内环电流控制,实现负载谐波电流补偿。最后,搭建基于RT-Box的硬件在环实验平台,对所提构网型变流器的多重功能进行验证。结果表明,并联设计的集静止无功发生器和有源滤波器功能于一体的构网型变流器可大大改善电网谐波、功率因数,提高电力系统的电能质量。

虚拟同步机控制策略下的STATCOM相间电容电压平衡方法研究

针对基于直挂式级联H桥拓扑结构的静止同步补偿器在运行时产生的相间电容电压不平衡的问题,本文在虚拟同步机的控制策略基础上提出了一种平衡相间电容电压的方法。虚拟同步机具有响应速度快的优点,但用于静止同步补偿器来作无功补偿时会产生相间电容电压不平衡的问题。因此本文首先引入电容电压平均值来完成虚拟同步机的快速并网,其次将虚拟同步机算法的无功调节分为3部分来实现分相无功补偿,再在电压合成前引入电容电压平均值作反馈,以实现相间电容电压平衡。最后在Matlab/Simulink环境下搭建仿真模型,验证了所提控制策略能有效解决相间电容电压不平衡问题,并且仿真结果表明所提控制策略具有良好的动态响应特性。

Three-phase AC-DC Converter for Direct-drive PMSG-based Wind Energy Conversion System

In this paper,a wind energy conversion system(WECS)is presented for the electrification of rural areas with wind energy availability.A three-phase AC-DC converter based on a bridgeless Cuk converter is used for power extraction from the permanent magnet synchronous generator(PMSG).The bridgeless topology enables the elimination of the front-end diode bridge rectifier(DBR).Moreover,the converter has fewer components,simple control,and high efficiency,making it suitable for a small-scale WECS.A squirrel cage induction motor(SCIM)is used to emulate a MOD-2 wind turbine to implement the PMSG-based WECS.A direct-drive eight-pole PMSG is used in this study;thus,a low-input-voltage system is designed.The converter is designed to operate in the discontinuous inductor current mode(DICM)for inherent power factor correction(PFC)and the maximum power point tracking(MPPT)is achieved through the tip-speed ratio(TSR)following.The performance of the developed system is analyzed through simulation,and a 500 W hardware prototype is developed and tested in different wind speed conditions.

自主可控SFC控制器设计与研发

静止变频器(SFC)是大型同步电机变频启动的核心设备。基于自主可控的软硬件平台,研制了基于国产芯片的自主可控SFC控制器,介绍了该控制器的硬件和软件设计流程,并在实时数字仿真(RTDS)系统中建立同步电机、励磁、电力网络模型,搭建半实物仿真试验平台,测试并验证控制系统功能。测试结果表明:自主可控SFC控制器能够实现同步电机的启动功能,具备工程实施条件。

基于模型预测控制的全功率变速抽水蓄能与SVG功率协调控制

全功率变速抽水蓄能机组(FSC-VSPSU)通过背靠背变流器接入电网,具有功率快速可调、有功无功独立解耦的优点,在近年来得到了广泛关注。由于新能源场站具有波动性,通常配置静止无功发生器(SVG)来维持系统电压稳定。针对SVG易出现容量不足的状况,研究FSC-VSPSU与SVG功率协调控制。分析了FSC-VSPSU与SVG无功调节特性,提出了基于模型预测控制的功率协调控制策略。采用模型预测控制协调响应时间不同的FSC-VSPSU与SVG,通过电压灵敏度计算无功和电压的关系,建立以并网点电压、FSC-VSPSU电压偏差最小以及SVG无功储备最大为目标的模型预测控制(MPC)问题数学模型,求解得到FSC-VSPSU与SVG功率参考值。通过仿真验证了所提模型预测控制的可行性以及其相较于下垂控制的优越性。

同步电机静止变频软起动及其电枢电流谐波分析

同步电机软起动是由静止变频器(Static Frequency Converter,SFC)将同步电机从静止逐渐拖动至额定转速。但SFC短时和频繁起动会造成大量谐波,该谐波施加在同步电机电枢绕组对同步电机造成不可逆的危害。本文首先图解分析了同步电机软起动低速和高速阶段的换相过程,由此推导出各阶段电枢电流模型,从而分析得出电枢电流谐波特性。最后,搭建出同步电机软起动的Matlab/Simulink模型,验证本文推导的准确性。

可控电流源型换流器IGCT串联均压技术

高压大功率逆阻型集成门极换流晶闸管(integrated gate commutation thyristor,IGCT)串联是可控电流源型换流器的关键技术之一,主要面临开通和关断不一致将会引起击穿的问题,目前尚缺乏深入研究和实验测试。该文首先分析可控电流源型换流器均压问题产生的原因,提出串联器件均压电路。接着,对开通不一致影响因素进行分析,给出IGCT使用电压和保护电压的配合关系,以确保开通过程器件安全。然后,对IGCT的自然和主动关断2种特殊关断过程影响因素进行分析,给出缓冲电路参数选择方法。最后,研制8级串联的IGCT模块样机,搭建实验平台进行测试。结果表明,所提方法能够有效抑制IGCT关断电压过冲,均压不一致性控制在8%以内。

大型H级调峰燃机电站主接线优化设计

国内大型H级调峰燃机电站,一般都设置发电机出口断路器(generator circuit-breaker,GCB)。基于相关标准及实际运行需求,对燃机电站GCB设置方式进行分析研究,提出一种大型H级调峰燃机主接线优化设计方案,并通过技术经济分析论证此方案的技术可行性和经济性。

燃气轮机大功率静止变频启动装置的维护和保养研究

大功率静止变频启动装置SFC在燃气轮发电机组启动过程中有着重要的应用。为了进一步提高机组启动的可靠性和稳定性,针对大功率静止变频启动装置SFC常见的故障问题加强维护,以大功率燃气轮机静止启动变频器为研究对象,通过对其原理和结构的研究,结合大功率静止变频启动装置SFC的常见故障及维护要点,分析了大功率静止变频启动装置SFC的维护方法,保证大功率静止变频启动装置SFC的高效可靠运行。

航空静止变流器的仿真与分析

航空静止变流器是飞机上的重要电源设备,其功能是在飞机主电源失效时将低压直流电转变为交流电,以满足飞机应急状态下的交流用电需求,是飞机供电系统的最后一道“屏障”。通过分析航空静止变流器的结构及数学模型,建立了基于PSIM平台的仿真模型,并对DC/DC-DC/AC结构型的变流器进行了仿真分析。结果表明,该变流器在稳定性、抗冲击性和响应时间上都具有较大的优势,能满足飞机用电设备的电压要求。

国产50 MW重型燃机SFC起动及控制策略

介绍了首台全国产50 MW重型燃气轮机组的SFC起动控制回路、运行模式、起动及并网流程的设计思路。针对本机型在起动阶段的特殊工况,制定相应的SFC起动策略,给出包括转子初始位置检测、功率桥控制方式、转速及转矩调节器和励磁电流调节器等SFC关键技术的设计要点。通过真机验证表明,针对本型号燃机的SFC系统开发,能够实现对燃机各起动阶段的平稳控制,为后续类似项目实施提供了借鉴和参考。