Robust Nonlinear Current Sensorless Control of the Boost Converter with Constant Power Load

The boost converter feeding a constant power load (CPL) is a non-minimum phase system that is prone to the destabilizing effects of the negative incremental resistance of the CPL and presents a major challenge in the design of stabilizing controllers. A PWM-based current-sensorless robust sliding mode controller is developed that requires only the measurement of the output voltage. An extended state observer is developed to estimate a lumped uncertainty signal that comprises the uncertain load power and the input voltage, the converter parasitics, the component uncertainties and the estimation of the derivative of the output voltage needed in the implementation of the controller. A linear sliding surface is used to derive the controller, which is simple in its design and yet exhibits excellent features in terms of robustness to external disturbances, parameter uncertainties, and parasitics despite the absence of the inductor’s current feedback. The robustness of the controller is validated by computer simulations.

A Model Predictive Scheduling Algorithm inReal-Time Control Systems

Abstract-The ineffective utilization of power resources has attracted much attention in current years. This paper proposes a real-time distributed load scheduling algorithm considering constraints of power supply. Firstly, an objective function is designed based on the constraint, and a base load forecasting model is established when aggregating renewable generation and non-deferrable load into a power system, which aims to transform the problem of deferrable loads scheduling into a distributed optimal control problem. Then, to optimize the objective function, a real-time scheduling algorithm is presented to solve the proposed control problem. At every time step, the purpose is to minimize the variance of differences between power supply and aggregate load, which can thus ensure the effective utilization of power resources. Finally, simulation examples are provided to illustrate the effectiveness of the proposed algorithm.

Distributed Model Predictive Load Frequency Control of Multi-area Power System with DFIGs

Reliable load frequency control LFC is crucial to the operation and design of modern electric power systems. Considering the LFC problem of a four-Area interconnected power system with wind turbines, this paper presents a distributed model predictive control DMPC based on coordination scheme. The proposed algorithm solves a series of local optimization problems to minimize a performance objective for each control area. The generation rate constraints GRCs, load disturbance changes, and the wind speed constraints are considered. Furthermore, the DMPC algorithm may reduce the impact of the randomness and intermittence of wind turbine effectively. A performance comparison between the proposed controller with and without the participation of the wind turbines is carried out. Analysis and simulation results show possible improvements on closed-loop performance, and computational burden with the physical constraints. © 2014 Chinese Association of Automation.

Real-Time Operation of Microgrids

Microgrid (MG) systems effectively integrate a generation mix of solar, wind, and other renewable energy resources. The intermittent nature of renewable resources and the unpredictable weather conditions contribute largely to the unreliability of microgrid real-time operation. This paper investigates the behavior of microgrid for different intermittent scenarios of photovoltaic generation in real-time. Reactive power coordination control and load shedding mechanisms are used for reliable operation and are implemented using OPAL-RT simulator integrated with Matlab. In an islanded MG, load shedding can be an effective mechanism to maintain generation-load balance. The microgrid of the German Jordanian University (GJU) is used for illustration. The results show that reactive power coordination control not only stabilizes the MG operation in real-time but also reduces power losses on transmission lines. The results also show that the power losses at some substations are reduced by a range of 6% - 9.8%.

Improved Control in Single Phase Inverter Grid-Tied PV System Using Modified PQ Theory

Grid-connected reactive-load compensation and harmonic control are becoming a central topic as photovoltaic(PV)grid-connected systems diversified.This research aims to produce a high-performance inverter with a fast dynamic response for accurate reference tracking and a low total har-monic distortion(THD)even under nonlinear load applications by improving its control scheme.The proposed system is expected to operate in both stand-alone mode and grid-connected mode.In stand-alone mode,the proposed controller supplies power to critical loads,alternatively during grid-connected mode provide excess energy to the utility.A modified variable step incremental conductance(VS-InCond)algorithm is designed to extract maximum power from PV.Whereas the proposed inverter controller is achieved by using a modified PQ theory with double-band hysteresis current controller(PQ-DBHCC)to produce a reference current based on a decomposition of a single-phase load current.The nonlinear rectifier loads often create significant distortion in the output voltage of single-phase inverters,due to excessive current harmonics in the grid.Therefore,the proposed method generates a close-loop reference current for the switching scheme,hence,minimizing the inverter voltage distortion caused by the excessive grid current harmonics.The simulation findings suggest the proposed control technique can effectively yield more than 97%of power conversion efficiency while suppressing the grid current THD by less than 2%and maintaining the unity power factor at the grid side.The efficacy of the proposed controller is simulated using MATLAB/Simulink.

一种应用于探测的可预测电流模式FSBB电路

探测器的能源供给离不开DC-DC变换器,先进的控制方法能提高工作效率。预测电流模式控制相比于传统的PI控制具有动态响应快、易于进行过流保护等优点,因此被广泛应用到电力电子控制领域。由于控制回路的问题,不能通过计算开环增益的方式对负载波动与输出电压变化的闭环传递函数进行有效地设计。因此,提出了一种在不加前馈控制的情况下,基于预测电流模式控制四开关Buck-Boost(four-switch Buck-Boost,FSBB)变换器补偿器的设计方案,该方法能提升负载动态响应,通过实验数据,证明了该方法的有效性。

舰船脉冲功率负载Buck变换器自适应阻尼比控制方法

针对脉冲功率负载的周期性功率突变造成接口变换器输出电压瞬时跌落和持续扰动的问题,提出一种Buck变换器的自适应阻尼比控制方法,使得输出电压的响应性能能够直接通过阻尼比实现精确调节,不依赖于控制参数,且对输入电压扰动具有抑制作用。该方法通过引入类电压环消除了时变的输入和占空比的非线性饱和,建立输出电压与其参考值的单输入单输出二阶系统,将不确定负载扰动的控制问题转化为二阶系统的阻尼比控制问题。此外,在不影响电压调节性能的前提下,通过附加占空比调节实现并联变换器供电结构的均流控制。仿真和硬件在环实验结果表明,在脉冲功率负载的不同暂态过程,并联变换器均能够实现快速平滑的电压调节和输出电流均衡。

永磁无刷轮毂电机轮对系统同步工况下的协调控制策略

针对双轮毂电机在负载不平衡工况下转速同步精度不够及同步响应速度不快的问题,该文提出速度环补偿PID交叉耦合同步控制和电流环补偿PID交叉耦合同步控制策略。首先,建立双轮毂电机的数学模型,采用双闭环六步方波控制。基于该模型,采用速度环补偿PID交叉耦合同步控制代替单增益交叉耦合控制器,使转速同步调节精度提升。在两侧电机负载不平衡工况下,用电流环补偿PID交叉耦合控制方法进一步提升转速同步精度,同时加快同步响应速度,并兼顾了转矩精度。仿真和实验验证了所提控制策略的正确性和有效性。

基于滑模理论的轧机异步电机模型预测电流控制

小型热连轧机异步传动电机具有生产效率高、操作简单等特点,但由于其经常处于高温、高压、粉尘等恶劣的工作环境中,对控制器的抗干扰性要求较高。针对小型热连轧机异步传动电机,结合滑模控制理论和模型预测控制,运用自适应滑模控制器(ASMC)作为转速外环控制器,且运用全阶滑模磁链观测器(SMRFO)观测并计算转子磁链,设计控制系统。仿真结果表明:该系统能够有效地控制小型热连轧机异步传动电机,相较于传统的模型预测电流控制系统,其响应速度和精度得到显著提升;当电机负载转矩突变时,该系统能够快速重新追踪给定速度,进一步提升抗干扰能力。

三相多负载无线电能传输系统建模与特性分析

为了提高无线电能传输系统单体容量和整体传输能力,提出采用基于三相逆变器的多负载无线电能传输系统,发射端采用电压型双极性正弦脉冲宽度调制(SPWM)控制桥式逆变器,接收端为3个采用并联谐振电路的独立单元。通过耦合电路理论推导了系统传输效率公式,分析了传输效率与负载、互感系数的关系。在此基础上,提出了传输系统恒流输出自适应PID控制方案和负载切入切出控制方法。最后通过MATLAB仿真和实物实验平台验证了所提及拓扑和控制方案的有效性和可行性。三相传输系统每相的输出功率达到60 W左右,传输效率分别达到90%以上,与单相无线系统输出功率和传输效率相当,有效提高了传输系统的单体容量和传输能力。

考虑动态三相不平衡度的输电线路线损控制方法

为了精准计算线路三相不平衡度并降低线路损耗,治理三相电流不平衡度,研究考虑动态三相不平衡度的输电线路线损控制方法。估算输电线路的三相电压不平衡度,并以其为参考计算输电线路三相电流不平衡度,结合等值电阻法与不平衡度因素计算输电线路的线损,当线路损耗过高时,通过在线路中接入基于电压控制的统一潮流控制器,降低输电线路中的电阻功率值与阻抗,实现输电线路线损控制。实验结果证明,该方法可以有效分析三相不平衡负载下输电线路两端电压、电流波形变化,并准确计算输电线路中三相电流不平衡度,且线损率计算结果准确,控制后线损率呈明显下降趋势。

基于关联特性矩阵的电网安全控制系统设计

在当前的电网安全控制系统中,控制因素为发电功率、负荷、交流母线电压。但由于控制过程未考虑三者的关联性,在只能以其中一个因素为控制目标时的控制效果较差。为此,设计一种基于关联特性矩阵的电网安全控制系统。首先,设计电网运行因素控制软件,并在软件数据库内构造关联特性矩阵,明确电网安全控制系统中发电功率、负荷、交流母线电压的关联关系,以实现多因素协同控制。然后,设计系统功能部分控制与预警模块,将关联特性矩阵与设计的系统功能模块相结合。最后,对电压、发电功率、负荷进行协同控制,以实现电网安全控制系统设计。试验结果表明,所设计的系统能够将电网的发电功率、负荷及交流母线电压控制在设定范围内。所设计的系统具有较高的可靠性,可提升电力系统的安全性和稳定性。

图腾柱功率因数校正器的二自由度控制分析

TPFC一般采用一自由度输出电压控制,在负载变化时输出电压动态特性较差,且启动过程存在明显超调。本文在推导TPFC双闭环控制结构基础上,引用了负载电流前馈控制和输出电压反馈补偿控制,构成两种二自由度(2DOF)控制结构。仿真分析表明,负载电流前馈型2DOF控制可以有效抑制负载变化引起的输出电压波动,但启动过程超调明显;输出电压反馈补偿型2DOF控制可以实现输出电压无超调启动,但是抑制负载变化的能力较差;综合负载电流前馈型和输出电压反馈补偿型的2DOF控制获得满意的输出电压控制效果,表现为启动过程无超调和变载过程无波动。

机械传动系统电加载技术研究

文章主要研究电加载试验台设计方案、控制方式及试验验证技术,采用驱动电机与加载电机进行电功率封闭,通过整流、逆变单元以及可编程逻辑控制器(Programmable Logic Controller,PLC)实现转速和加载功率的无级控制与加载精度要求,并与润滑系统、机械系统实现关联互锁,保证系统运行稳定可靠。通过共直流母线控制方案技术研究,实现能源的回收再利用,降低试验成本。

基于固定时间滑模的直流微电网一致性控制

针对含多组蓄电池储能单元的直流微电网系统,为抑制负载波动以及恒功率负载造成的母线电压振荡问题,提出了一种基于固定时间滑模的直流微电网系统的一致性控制方法。首先,建立直流微电网系统储能的数学模型,其中包含恒功率负载和储能单元;其次,根据一致性算法获得平均母线电压;然后,构造固定时间滑模控制器,同时分析系统稳定性;最后,以含有恒功率负载和多组蓄电池储能单元的直流微电网系统为例进行仿真。结果表明:所提出的控制方法相较于传统方法在应对负载波动导致母线电压失稳的问题上,具有更好的鲁棒性和可靠性。

车载用燃料电池直流变换器全状态双环控制方法

研究车载用燃料电池直流变换器全状态双环控制方法,以获得更稳定的输出电压,满足车载电源需求。分析燃料电池输出特性,揭示燃料电池输出电压、电流关系,将其作为依据并结合汽车动力系统结构,设计二次型Boost变换器,在分析其主电路结构以及工作原理的前提下,提出基于输入电压前馈的全状态双环控制策略,电流内环控制通过比较实际输出电流和期望输出电流的差值调节开关操作,以完成负载变化时燃料电池输出电流控制;电压外环控制器根据输出电压和期望电压值之间的差异调整开关状态,实现对燃料电池输出电压控制。实验结果表明:该方法可实现直流变换器控制,控制后的输出电压波形稳定、电压纹波较小、超调量低、控制效率高。

A Dedicated MAC Protocol Package for Real-Time Ocean Current Field Estimation Using Distributed Underwater Acoustic Sensor Networks

Distributed underwater acoustic sensor networks(UASNs)are envisioned in real-time ocean current velocity estimation.However,UASNs at present are still dominated by post-processing partially due to the complexity of on-line detection for travel times and lack of dedicated medium access control(MAC)protocols.In this study,we propose a dedicated MAC protocol package for real-time ocean current velocity estimation using distributed UASNs.First,we introduce the process and requirements of ocean current velocity estimation.Then,we present a series of spatial reuse time division multiple access(TDMA)protocols for each phase of real-time ocean current field estimation using distributed UASNs,followed by numerical analysis.We divide UASNs into two categories according to their computing ability:feature-complete and feature-incomplete systems.The feature-complete systems that have abundant computing ability carry out the presented MAC protocol package in three phases,whereas the feature-incomplete ones do not have enough computing ability and the presented MAC protocol package is reduced to two phases plus an additional downloading phase.Numerical analysis shows that feature-complete systems using mini-slot TDMA have the best real-time performance,in comparison with feature-incomplete systems and other feature-complete counterparts.Feature-incomplete systems are more energy-saving than feature-complete ones,owing to the absence of in-network data exchange.

基于扰动观测器的电压源型逆变器负载电流前馈控制方法研究

传统的电压源型逆变器负载电流前馈控制方法主要依赖前馈控制环路,虽然逆变器电流局部控制效果更佳,但很难满足前馈控制的需求。为此,设计了一种基于扰动观测器的电压源型逆变器负载电流前馈控制方法。该方法通过提取逆变器负载扰动电流的前馈特征,引入扰动电流作为前馈信号,将前馈点作为输出电压,得到了逆变器负载电流的动态变化规律。同时,基于扰动观测器控制电压源型逆变器的电流偏差量,将负载电流作为外部扰动信号来抑制非线性负载的干扰,以满足对负载电流的前馈控制需求。通过仿真实验验证了该方法具有较好的前馈控制效果。

数据中心中压负荷逐级投切解决方案简析

根据数据中心负荷逐级投切装置的控制要求,对目前应用比较多的专用负荷逐级投切装置、带有负荷逐级投切功能的10kV双电源转换开关控制器、采用分立元器件自行搭建和编程的PLC控制器、基于IEC61850光纤环网GOOSE传输技术的数字通信自动控制几种负荷逐级投切解决方案进行比较分析,并提出选择建议。

使用平均电流控制的逆变器并联系统

研究了基于平均电流控制的逆变器并联系统。通过分布在各模块中的平均电路,对各模块的电流给定信号进行平均后产生共享的电流基准信号,由此实现负载均分。推导了带负载电流前馈补偿的并联系统的数学模型,其等效传递函数与单台逆变器相似;通过理论分析、仿真和实验对有、无负载电流补偿两种控制方式下的并联系统外特性和均流性能进行了对比分析。实验结果表明并联系统具有动态响应快速,均流性能好的特点。