Model Predictive Control Strategy of Multi-Port Interline DC Power Flow Controller

There are issues with flexible DC transmission system such as a lack of control freedom over power flow.In order to tackle these issues,a DC power flow controller(DCPFC)is incorporated into a multi-terminal,flexible DC power grid.In recent years,a multi-port DC power flow controller based on a modular multi-level converter has become a focal point of research due to its simple structure and robust scalability.This work proposes a model predictive control(MPC)strategy for multi-port interline DC power flow controllers in order to improve their steady-state dynamic performance.Initially,the mathematical model of a multi-terminal DC power grid with a multi-port interline DC power flow controller is developed,and the relationship between each regulated variable and control variable is determined;The power flow controller is then discretized,and the cost function and weight factor are built with numerous control objectives.Sub module sorting method and nearest level approximation modulation regulate the power flow controller;Lastly,theMATLAB/Simulink simulation platformis used to verify the correctness of the establishedmathematicalmodel and the control performance of the suggestedMPC strategy.Finally,it is demonstrated that the control strategy possesses the benefits of robust dynamic performance,multiobjective control,and a simple structure.

Simulation Study of the Control Strategy of a DC Inverter Heat Pump Using a DC Distribution Network

Photovoltaics,energy storage,direct current and flexibility(PEDF)are important pillars of achievement on the path to manufacturing nearly zero energy buildings(NZEBs).HVAC systems,which are an important part of public buildings,play a key role in adapting to PDEF systems.This research studied the basic principles and operational control strategies of a DC inverter heat pump using a DC distribution network with the aim of contributing to the development and application of small DC distribution systems.Along with the characteristics of a DC distribution network and different operating conditions,a DC inverter heat pump has the ability to adapt to changes in the DC bus voltage and adds flexibility to the system.Theoretical models of the DC inverter heat pump integrated with an ice storage unit were developed.The control strategies of the DC inverter heat pump system considered the influence of both room temperature and varied bus voltage.A simulation study was conducted using MATLAB&Simulink software with simulation results validated by experimental data.The results showed that:(1)The bus fluctuation under the rated working voltage had little effect on the operation of the unit;(2)When the bus voltage was fluctuating from 80%-90%or 105%-107%,the heat pump could still operate normally by reducing the frequency;(3)When the bus voltage was less than 80%or more than 107%,the unit needed to be shut down for the sake of equipment safety,so that the energy storage device could adjust to the sharp decrease or rise of voltage.

Research on Scheduling Strategy of Flexible Interconnection Distribution Network Considering Distributed Photovoltaic and Hydrogen Energy Storage

Distributed photovoltaic(PV)is one of the important power sources for building a new power system with new energy as the main body.The rapid development of distributed PV has brought new challenges to the operation of distribution networks.In order to improve the absorption ability of large-scale distributed PV access to the distribution network,the AC/DC hybrid distribution network is constructed based on flexible interconnection technology,and a coordinated scheduling strategy model of hydrogen energy storage(HS)and distributed PV is established.Firstly,the mathematical model of distributed PV and HS system is established,and a comprehensive energy storage system combining seasonal hydrogen energy storage(SHS)and battery(BT)is proposed.Then,a flexible interconnected distribution network scheduling optimization model is established to minimize the total active power loss,voltage deviation and system operating cost.Finally,simulation analysis is carried out on the improved IEEE33 node,the NSGA-II algorithm is used to solve specific examples,and the optimal scheduling results of the comprehensive economy and power quality of the distribution network are obtained.Compared with the method that does not consider HS and flexible interconnection technology,the network loss and voltage deviation of this method are lower,and the total system cost can be reduced by 3.55%,which verifies the effectiveness of the proposed method.

基于双向DC/DC变换器的超级电容控制策略研究

本研究采用双向DC/DC变换器控制超级电容充放电,在分析超级电容、双向DC/DC变换器的数学模型基础上,提出了充放电控制策略。为验证该策略,搭建了仿真模型。仿真结果表明:该控制策略能够控制超级电容直流母线电压,维持母线电压恒定。

基于DCS的热电厂烟气净化系统研究

该文以DCS控制系统作为切入点,简要叙述DCS系统的结构组成、配置方案与设计原则,为DCS系统大规模应用推广奠定坚实基础,也为DCS系统的实践应用指明方向。重点基于DCS技术搭建热电厂烟气净化控制系统的具体策略,重点解决控制系统在前期搭建与投运使用阶段面临的现实问题。旨在全方位改善烟气净化控制效果,保障烟气净化系统平稳运行,帮助热电厂实现绿色生产目标。

核电DCS系统故障分析与处理策略探讨

为有效解决核电DCS系统故障,提高核电机组运行稳定性和安全性,介绍了核电DCS系统的结构组成和运行特点,指出DCS系统常见故障及其处理策略,并结合实际案例阐述了DCS系统网络通信故障的分析过程和处理方法。分析结果表明,核电DCS系统故障主要集中在机柜、现场回路、计算机固件和系统软件4个方面,只有树立预防性维修观念,严格落实系统检测和故障诊断,才能降低DCS系统故障的发生率,保证核电机组的运行安全。

西门子DCS系统在水泥窑脱硫系统中的应用

基于某6000t/d水泥熟料生产线湿法脱硫系统的工艺特点和控制要求,介绍了西门子DCS系统在水泥窑脱硫系统中的应用,以及如何利用该DCS系统实现烟道系统、吸收塔系统、石灰石浆液制备系统、石膏脱水系统、事故浆液系统的全自动控制运行。该生产线脱硫系统自投运以来,烟气SO_(2)排放浓度<15mg/Nm^(3),达到国家A级排放限值标准。

一种面向储能系统的双向隔离型AC-DC矩阵变换器控制策略

为了满足网侧高电能质量以及储能元件安全可靠和长使用寿命的需求,本文针对双向隔离型AC-DC矩阵变换器提出了一套系统的控制策略,包括对系统的双闭环控制和变换器的后级单重移相调制方法。其中双闭环控制包含网侧电流内环控制和直流侧电流外环控制,调制方法中保持前后级电路间协调同步,前级电路采用双线电压调制方式,后级电路采用等比例移相调制方式。仿真和实验结果显示,变换器的网侧功率因数可达0.99,直流侧电压纹波在0.15%以内。直流侧电流指令突变时,电流跟踪速度快且无超调。因此,采用所提出的控制策略可以保证网侧电能质量高、直流侧具有良好的动静态特性。

基于双向DC-DC变换器的串联电池组主动均衡电路

针对单体电池串联成组使用时出现不一致性的问题,提出了一种基于双向DC-DC变换器的串联电池组主动均衡电路。使用双向DC-DC变换器将单体电池中的高能量输送到能量低的单体电池中,无需额外的存储组件来存储和传送能量,减少了能量损失,提高了均衡效率。根据电池开路电压(open circuit voltage,OCV)与荷电状态(state of charge,SOC)之间近似分段线性的关系,采用以电压和SOC双变量作为均衡策略,通过相互实时修正电压均衡和SOC均衡,使得电池组间能量动态趋于一致。最后通过搭建由4节单体电池组成的均衡电路实验平台,对提出的均衡电路和均衡控制策略进行有效性验证。

基于扩展移相的隔离型AC-DC变换器零矢量PWM调制策略

传统隔离型双向AC-DC变换器多为两级式结构,变换器效率低、控制系统复杂,现有的单级式解决方案通常依赖大量实时计算,难以兼具低电流应力、宽软开关范围和高功率传输能力特性。为此,该文设计基于双有源全桥的新型单级隔离型双向AC-DC谐振变换器,提出一种含有零矢量的复合频率调制策略。从高频开关周期入手,利用数学推导,证明所提方案在实现自动功率因数校正功能的同时,可降低开关器件的开关频率,免除附加吸收电路,实现交直流全桥的软开关,且几乎无功率回流,从而有效提升变换器的功率传输能力,所提单变量调节方法简化控制系统设计。最后,搭建额定功率为450W的仿真和实验平台,证明理论分析的正确性和调制策略的可行性。

Control Strategy of DC Link Voltage Flywheel Energy Storage for Non Grid Connected Wind Turbines Based on Fuzzy Control

The large-scale development of wind power is an important means to reduce greenhouse gas emissions, alleviate environmental pollution and improve the utilization rate of renewable energy. At the same time, large-scale non grid connected wind power generation theory avoids the technical difficulties of wind power integration [1]. However, due to the randomness and uncontrollability of wind energy, the output power of the wind power generation system will fluctuate accordingly [2]. Therefore, the corresponding energy storage devices are arranged in the non-grid-connected wind power generation system to ensure the power quality, and it has become the key to full utilization of renewable energy. In the case of wind speed fluctuation, the DC bus control strategy of the wind turbine is proposed in this paper. It can reduce the impact on the unit converter and the power load;this ensures safe and stable operation of non-grid connected wind turbines.

DC/DC变换器控制新方法探究

近年来,随着科技的迅猛发展,电子产业进入了快速发展期,极大地带动了开关电源的发展。DC/DC变换器在电路中实现主次级功率的控制转化和级间传递,这种控制因加速平稳、快速响应的特点被广泛应用于计算机、军事、数据通讯等领域。文章主要介绍DC/DC变换器的各种现代化控制方法,比较现代控制方法的优缺点,展望DC/DC变换器控制方法的发展。

基于PLECS的双向DC/DC变换器控制策略设计

用于连接不同电压直流微网间的双向DC/DC变换器,能够实现直流微网间能量双向流动,有利于直流微网内部能量的消纳利用。分析了用于连接不同电压直流微网间双向DC/DC变换器的工作原理,提出了一种改进PI控制新策略,并通过小信号建模分析了该控制策略的稳定性,利用PLECS仿真验证了该控制策略的有效性。

一种双向部分隔离型四端口DC-DC变换器的研究

为减少家庭直流微电网中变换器的数量,提出了一种双向部分隔离型四端口直流变换器及其控制策略。变换器原边采用两个双向Buck-Boost电路与全桥变换器的桥壁开关管复用,构成两输入的双向交错Buck-Boost电路,副边采用半桥整流电路与同步Buck电路结合,形成高、低压两输出端口,并采用控制器变量竞争的方式实现变换器控制策略的切换。该四端口变换器(four-port converter,FPC)可以同时满足多电压等级的输入/输出,且功率能够双向流动,对比其他FPC,具有较高的功率密度和拓扑结构对称等优点。最后,在Simulink软件中搭建了仿真模型,并进行详细的试验分析。结果验证了理论分析的正确性以及控制策略的有效性。

基于DCS自动化控制系统的合成氨工艺研究

旨在研究基于DCS自动化控制系统的合成氨工艺,并探讨其优势、挑战和应用案例。通过对合成氨的生产过程和原理进行概述,分析了合成氨工艺的基本流程和关键步骤。接着介绍了DCS系统的定义、特点、组成和工作原理,并探讨了DCS系统在化工工艺中的应用优势。针对合成氨工艺中的关键控制环节和参数,探讨了基于DCS的合成氨工艺控制策略,并给出了相关优化方案。此外,通过技术分析和实践验证,验证了DCS系统的优势,并提出了在合成氨工艺中可能遇到的挑战和解决方案。通过本研究,可以得出结论:基于DCS自动化控制系统的合成氨工艺具有优化控制、精细化管理和效率提升的潜力,可以进一步提高合成氨工艺的自动化水平和生产效益。

部分信息下带有保费返还条款的DC养老金时间一致性投资策略

本文研究了部分信息下带有保费返还条款的DC养老金的时间一致性投资策略.假设养老金管理者只拥有股票的部分信息,即只能观测到股票的价格,而不能观测到股票的收益率.养老金带有保费返还条款,在基金累积期死亡的参与者可以获得前期缴纳的所有保费.此外,本文还考虑了通胀风险以及随机工资.首先,利用卡尔曼滤波理论,将部分信息情形下的最优投资组合问题转化为一个完全信息情形下的问题.然后,通过求解一个扩展的HJB方程,得到时间一致性投资策略和最优值函数,并给出了均值–方差有效前沿的参数表达式.最后,用蒙特卡洛方法进行数值模拟,分析了部分信息和保费返还条款对股票投资比例和有效前沿的影响,并给出了相应的经济学解释.

低压直流微电网新型主动限流器及控制策略

低压直流微电网中直流母线发生短路故障后,现有的被动式保护措施难以有效保护电力电子装置,并且当计及直流线路电感与变流器直流母线侧电容时,常规主动限流器会出现限流电感电流振荡的特性。详细分析了该电流振荡特性产生的机理,探究了系统参数变化对限流电感电流振荡峰值的影响。并提出了一种新型主动限流器拓扑结构及控制策略,该拓扑结构通过增加能量耗散支路,在限流器直流母线侧电容电压产生负压时导通,以此耗散能量,解决了电感电流振荡的问题。通过仿真与实验,验证了所提新型主动限流器对电感电流振荡特性抑制的有效性,且在不同工况下具有良好的鲁棒性。

基于MMC闭锁与负直流电压无闭锁的综合直流故障限流策略

基于模块化多电平换流器(MMC)的柔性直流电网存在抗直流故障扰动能力弱的问题。为此,在无闭锁和闭锁限流的基础上,提出了一种适用于柔性直流电网的无闭锁与闭锁的综合直流故障限流策略。故障发生后,各换流站首先根据直流侧出口电流进行基于负直流电压控制的无闭锁限流,若某换流站由于无闭锁降压限流失效而发生过流,则主动将该换流站闭锁。故障消失或隔离后,无闭锁换流站第一时间恢复正常工作模式,而无须等待重启过程较长的闭锁换流站,以尽量减小系统功率损失。基于MATLAB/Simulink的仿真结果表明,所提综合直流故障限流策略可快速阻断故障电流,并兼顾限流过程的安全性和快速性,最大限度保证系统功率传输,提高了直流电网的抗故障扰动能力。

基于新型VLMZVM的ANPC型三电平并网逆变器环流抑制方法

为解决广泛应用在大功率分布式发电系统中的多机有源中点钳位(ANPC)型三电平并网逆变器间的低频零序环流问题,提出一种基于虚拟大矢量的新型十三矢量调制(VLMZVM)策略。通过建立多机ANPC型三电平并网逆变器零序环流模型,分析零序环流产生机理和影响因素,通过检测零序环流状态,实时选择虚拟大矢量或实际大矢量合成方法来抑制零序环流,并提出区分奇偶扇区的矢量分配方法快速选择合成矢量。实验结果验证了新型VLMZVM策略能在电流突变、参数不一致、全功率因数范围都具有很好的环流抑制效果。

MMC直流侧故障有源限流策略

为了避免直流短路故障威胁到模块化多电平换流器(modular multilevel converter,MMC)型柔性直流电网的安全可靠运行,该文提出了一种适用于半桥型MMC直流侧故障的有源限流策略,限制直流短路电流和桥臂电流的峰值及上升速率。首先,该文阐述了故障期间系统控制策略对故障电流的影响,然后通过反馈桥臂电流分别调整差、共模调制波,进而改变上、下桥臂中子模块的数量及分配,达到快速抑制交、直流侧故障电流的目的。其次,推导了考虑有源限流策略下的故障电流解析式,并分析了该限流策略对控制系统稳定性的影响,为有源阻尼参数选取提供理论依据。最后,在PSCAD/EMTDC中搭建四端柔性直流电网模型,仿真结果表明:有源限流策略不仅能够显著降低直流断路器开断故障电流,且能保证桥臂内器件的安全。