Performance of PSS to Damp Power Oscillations Caused by an HVDC Link in AC-DC Power System

HVDC (High Voltage Direct Current) systems are increasingly being applied to improve power system operation and controllability. However, inappropriate setting of HVDC controller may have a detriment effect on the system performance. Generally, PSS (Power System Stabilizer) is known as a simple concept, easy to perform, and computationally effective to enhance damping of power system oscillations through excitation control of synchronous generator. This paper examines the effectiveness of the PSS to enhance the dynamic performance of AC-DC power systems and to compensate the negative damping of HVDC system. The dynamic performance is evaluated by examining the system response to various disturbances. In order to ensure the reliability of the simulation test results as well as the performance of the PSS, detailed HVDC modeling is adopted using SimPowerSystems toolbox in the MATLAB, and some important conclusions are drawn.

Identification of the Worst-case Static Voltage Stability Margin Interval of AC/DC Power System Considering Uncertainty of Renewables

Calculation of static voltage stability margin(SVSM)of AC/DC power systems with lots of renewable energy sources(RESs)integration requires consideration of uncertain load growth and renewable energy generation output.This paper presents a bi-level optimal power flow(BLOPF)model to identify the worst-case SVSM of an AC/DC power system with line commutation converter-based HVDC and multi-terminal voltage sourced converter-based HVDC transmission lines.Constraints of uncertain load growth’s hypercone model and control mode switching of DC converter stations are considered in the BLOPF model.Moreover,uncertain RES output fluctuations are described as intervals,and two three-level optimal power flow(TLOPF)models are established to identify interval bounds of the system worst-case SVSM.The two TLOPF models are both transformed into max–min bi-level optimization models according to independent characteristics of different uncertain variables.Then,transforming the inner level model into its dual form,max–min BLOPF models are simplified to single-level optimization models for direct solution.Calculation results on the modified IEEE-39 bus AC/DC case and an actual large-scale AC/DC case in China indicate correctness and efficiency of the proposed identification method.

Reliability of DC-link capacitor in pulsed power supply for accelerator magnet

Capacitors are widely used in pulsed magnet power supplies to reduce ripple voltage,store energy,and decrease power variation.In this study,DC-link capacitors in pulsed power supplies were investigated.By deriving an analytical method for the capacitor current on the H-bridge topology side,the root-mean-square value of the capacitor current was calculated,which helps in selecting the DC-link capacitors.The proposed method solves this problem quickly and with high accuracy.The current reconstruction of the DC-link capacitor is proposed to avoid structural damage in the capacitor’s current measurement,and the capacitor’s hotspot temperature and temperature rise are calculated using the FFT transform.The test results showed that the error between the calculated and measured temperature increases was within 1.5℃.Finally,the lifetime of DC-link capacitors was predicted based on Monte Carlo analysis.The proposed method can evaluate the reliability of DC-link capacitors in a non-isolated switching pulsed power supply for accelerators and is also applicable to film capacitors.

Equivalent Hamiltonian Equations Modelling and Energy Function Construction for MMC-HVDC in Hybrid AC/DC Power Systems

This paper proposes an equivalent Hamiltonian equations model for the modular multilevel converter-based high-voltage direct-current(MMC-HVDC)transmission system,and constructs an energy function for multi-machine power systems with MMC-HVDC transmission lines.The equivalent Hamiltonian equations model is verified to be able to track the power output dynamics of the full model of an MMC-HVDC transmission system.Both theoretical and numerical studies have been undertaken to validate that the energy function proposed for hybrid AC/DC systems satisfies the conditions of an energy function.The work of this paper bridges the gap between the well-developed direct methods of transient stability analysis and power systems with MMC-HVDC transmission lines.

Coordinated Modulation Strategy Considering Multi-HVDC Emergency for Enhancing Transient Stability of Hybrid AC/DC Power Systems

This paper presents a multi-HVDC emergency coordinated modulating strategy to enhance the transient stability of hybrid AC/DC power systems.First,the main factors that affect the unbalanced energy distribution during a fault are analyzed,and the dominant generators are determined online.Next,considering the influence on both generators in the sending and receiving ends,the assessment index that evaluates the effects of DC power support is established.On the basis of this,a dynamic DC power support strategy is put forward,and the DC support sequence table is promptly updated by the changing dominant generators.The AC/DC hybrid power system with multi-DC lines is built and used as a test system.The simulation results of different scenarios demonstrate that the proposed method could follow the dominant generator dynamically and adjust the DC participating in modulation to enhance the transient stability effectively and quickly.

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.

Design and Simulation for the Pulse High-Voltage DC Power Supply (HVPS) of 1.2 MW/2.45 GHz HT-7U Lower Hybrid Current Drive System

The superconducting tokamak HT-7U [1] has been designed by the Institute of Plasma Physics since 1998 and will be set up before 2003. The 1.2 MW /2.45 GHz HT-7U LHCD (Lower hybrid current drive) system which being the most efficient non-induction device can heat the plasma and drive the plasma current has been efficiently in operation 'owl and a particular design of the 2.8 MW/-35 kV high-voltage DC power supply has been already completed and will apply to the klystron of LHCD on HT-7 and the future HT-7U, and the project of the power supply has been examined and approved professionally by an authorized group of high-level specialist in the institute of Plasma Physics. The detailed design of the power supply and the simulation results are referred in the paper.

OES study of the gas phase during diamond films deposition in high power DC arc plasma jet CVD system

This paper used optical emission spectroscopy （OES） to study the gas phase in high power DC arc plasma jet chemical vapour deposition （CVD） during diamond films growth processes. The results show that all the deposition parameters （methane concentration, substrate temperature, gas flow rate and ratio of H2/Ar） could strongly influence the gas phase. C2 is found to be the most sensitive radical to deposition parameters among the radicals in gas phase. Spatially resolved OES implies that a relative high concentration of atomic H exists near the substrate surface, which is beneficial for diamond film growth. The relatively high concentrations of C2 and CH are correlated with high deposition rate of diamond. In our high deposition rate system, C2 is presumed to be the main growth radical, and CH is also believed to contribute the diamond deposition.

Multi-converter Approach to Higher Power Density DC-DC Converter for 380 V DC Distribution System

Multi-converter approach based on the series and parallel connection topology of modular power converters has been proposed to realize higher power density DC-DC converter. The availability of the proposed approach has been verified through the design consideration and the experiment. The design consideration for two DC-DC converters has been carried out by utilizing the power converter exact loss simulator, and the design parameters to maximize their power densities have been extracted taking the trade-off between the conversion efficiency and the power density into account. The prototypes of a 2,400 W, 256-384 V boost chopper using SiC-MOSFETs and a 300 W, 32-48 V GaN-FETs boost chopper have been also developed based on the design. The SiC chopper achieved the efficiency of 97.8% and the power density of 12,8 W/cm3, and the GaN chopper accomplished 98.9% and 18.6 W/cm3 in the experiment. These results show the validity of the design and the availability of the proposed approach. The multi-converter approach enables the cost reduction of the modular power converters, and contributes to realizing the widespread use of power electronics converters in the future 380 V DC distribution system.

Influences of ±800 kV Yunnan-Guangdong HVDC System on Security and Stability of China Southern Power Grid

The interaction mechanism between AC and DC systems in a hybrid AC-DC transmission grid is discussed with PSS/E software. Analysis shows that receiving-end AC faults may cause much more damage on the HVDC system operation than the sending-end AC faults in a multi-infeed HVDC system, and the damage severity depends on the power recovering rate of the HVDC systems. For HVDC systems with slow power recovering rate, the receiving-end AC faults may probably be a critical factor to constrain power transfer limits. Larger capacity of HVDC system means not only higher power transfer-limit of the parallel connected AC-DC transmission grid, but also more expensive stabilizing cost.

新时期火电厂DCS控制系统故障的应急处理和预防策略

新时期,火电厂的工作内容比较复杂,需要借助分散控制系统(Distributed Control System,DCS)提供控制方面的支持,这也要求加强DCS故障处理和预防工作。首先,分析火电厂DCS常见故障;其次,分析其应急处理方法及预防策略,分别就共性处理原则和硬件故障应急处理方法,以及建设故障感知模式、运用大数据组织预防等进行具体论述,呈现火电厂DCS故障特点的同时,为后续处理和预防活动提供必要参考。

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。

660MW超临界机组DCS自主可控改造实践

本文对某660MW超临界发电机组的DCS自主可控改造案例进行了研究,并从DCS系统性能分析、组态设计、现场调试等几个方面,介绍了DCS自主可控改造的实施过程,总结了此次改造的技术要点和注意事项,为其他机组的DCS自主可控改造提供了借鉴和参考。

火电厂DCS仿真软件系统测试方法设计研究

火电厂DCS仿真软件以软件的形式实现了DCS功能的模拟,其测试方法在符合软件测试要求的基础上,还应结合软件自身的功能特点。针对软件测试中的系统测试环节,开展了设计方法的研究,将系统测试中接口测试、强度测试等测试项与DCS仿真软件的特点相结合,分析了适合火电厂DCS仿真软件的软件系统测试方法,并可为其它工控领域的仿真软件系统测试设计提供参考。

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。

核电厂安全级DCS缺省值设置策略研究

针对数字化仪控系统中无效信号的质量位随意蔓延使系统处于一种不确定状态的问题,结合核电厂运行工况和信号特性,对龙鳞平台故障诊断机制和信号质量位标识进行研究。考虑故障安全准则,系统性地提出缺省值设置原则。从信号执行功能和信号边界两个维度进行分析,确认缺省值的设置范围,并详细给出执行保护功能、报警功能、维护和试验功能信号的缺省值设置策略。同时,针对传统的缺省值验证方式无法全面、有效地进行缺省值验证的问题,提出一种利用全范围模拟机和虚拟数字化控制系统(DCS)进行缺省值验证的新方法。利用该方法可有效地对DCS内设置的缺省值进行系统性的验证。所提出的缺省值设置策略和验证方法可为后续核电厂安全级DCS的缺省值分析和设置提供全面的指导。

DCS网络安全维护在电力系统监控中的关键技术研究与应用

随着信息技术的不断发展和普及,电力系统监控与控制逐渐向数字化、自动化以及智能化方向发展。同时,网络安全面临的挑战日益严峻。电力系统作为关乎国家经济安全和民生福祉的重要基础设施,其安全稳定运行对于社会的正常运转至关重要。分布式控制系统(Distributed Control System,DCS)作为电力系统监控与控制的核心系统,承担着实时监测、数据采集以及远程控制等重要任务,其安全性直接关系到整个电力系统的安全和稳定运行。文章从DCS网络安全维护的角度出发,探讨在电力系统监控与控制中的关键技术和应用策略。

Ovation DCS控制系统在火电厂自动配煤掺烧中的应用

为增强火电厂自动配煤掺烧效果,提出在火电厂自动配煤掺烧中应用Ovation DCS控制系统。详细介绍了Ovation DCS控制系统的特点和组成,强调其在火电厂自动配煤掺烧中的关键作用,并深入探讨了控制原则以及优先配煤、顺序配煤、余煤配煤3种控制方式,阐述了它们的应用场景和优势。此外,详细描述了自动配煤流程,并进行了火电厂自动配煤控制逻辑设计,包括控制流程设计和控制宏编写,以实现DCS系统的高效运行,并利用时序图方式进行了效果验证,证明了Ovation DCS控制系统在火电厂自动配煤掺烧中的有效性和可行性。

混合级联型HVDC系统的后续换相失败预判方法

白鹤滩—江苏±800k V特高压直流输电工程于2022年7月1日在中国投运,在世界上首次创造性地研发应用了特高压混合级联直流输电新技术方案。基于此系统背景对逆变侧电网换相换流器(line commutated converter,LCC)进行具有一定时间裕度的后续换相失败预判。分析了LCC控制器对电气量的控制作用和模块化多电平换流器(modular multilevel converters,MMC)对LCC的电压支撑作用,明确了混合级联直流输电系统逆变侧LCC发生后续换相失败的机理。推导了逆变侧LCC在首次换相失败后恢复过程末期关断角与故障后线路传输功率最小值的关系,定义了阈值功率的概念。然后建立了关断角与阈值功率的定量关系,提出一种故障后直流传输功率最小值与功率阈值相比较的后续换相失败预判方法。最后在PSCAD/EMTDC中搭建了相应的仿真模型,验证了理论分析和预测方法的准确性。

基于ADACS_N平台的DCS二层系统服务器国产化替代与软件移植研究

针对核电厂DCS系统服务器硬件老化与停产共性问题,基于法国ADACS_N平台的DCS二层系统,研究一种服务器国产化替代与软件移植的可行方法,结合系统软硬件架构分析、国产化服务器硬件替代选型策略、源代码移植技术研究、最小化测试平台开发,为延长核电厂DCS系统生命周期、解决进口设备“卡脖子”问题、提升核电厂DCS关键设备自主能力提供一定参考。