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.

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.

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.

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。

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。

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。

DC Traction Power Supply System Based on Modular Multilevel Converter Suitable for Energy Feeding and De-icing

A novel DC traction power supply system suitable for energy feeding and de-icing is proposed in this paper for an urban rail transit catenary on the basis of the full bridge submodule (FBSM) modular multilevel converter (MMC). The FBSM-MMC is a novel type of voltage source converter (VSC) and can directly control the output DC voltage and conduct bipolar currents, thus flexibly controlling the power flow of the urban rail transit catenary. The proposed topology can overcome the inherent disadvantages of the output voltage drop in the diode rectifier units, increase the power supply distance and reduce the number of traction substations. The flexible DC technology can coordinate multiple FBSM-MMCs in a wide area and jointly complete the bidirectional control of catenary power flow during the operation of the electric locomotive, so as to realize the local consumption and optimal utilization of the recovered braking energy of the train. In addition, the FBSM-MMCs can also adjust the output current when the locomotive is out of service to prevent the catenary from icing in winter. The working modes of the proposed topology are illustrated in detail and the control strategy is specially designed for normal locomotive operations and catenary de-icing. Simulation cases conducted by PSCAD/EMTDC validate the proposed topology and its control strategy.

Flexible control strategy for HVDC transmission system adapted to intermittent new energy delivery

Intermittent new energy delivery requires increasing the flexibility of ultra-high voltage direct current(DC)power adjustment.Based on a converter steady-state model and a DC power model,the control angle constraints of a converter valve are relaxed for power regulation.In this paper,a flexible DC power control method based on a fixed tap changer position is proposed.The initial ratio of the converter transformer is optimized.The effects of the fixed-tap changer position control on the control angle,reactive power compensation,and commutation failure are analyzed.The new control method allows a DC system to operate at a large angle and increase the additional reactive power loss while improving the commutation security margin.Steady-state and electromagnetic transient simulations in the CIGRE test system verify the validity of the method proposed in this paper and the correctness of the analysis conclusions.

Technology and engineering application of cross area HVDC interconnection system high-precision simulation modeling based on ADPSS

In recent years, a large number of high voltage direct current(HVDC) transmission projects have been connected to AC systems. This has started to have an impact on AC/DC hybrid power grids, particularly receiving terminal power grids. An HVDC system is a large-scale power electronic integrated nonlinear system, and it includes a primary system and a control and protection system. Hence, the precision and degree of detail of HVDC systems directly affect the actual effect of simulation. In recent years, in the case of the normal operation and failure of AC power grids, the abnormal fluctuation and even locking of HVDC systems caused by the inappropriate strategies of the control and protection system component have strongly affected power grids. This has significantly affected the safety and stability of receiving power grids and normal operation. In this study, the actual engineering HVDC control logic provided by a manufacturer is analyzed and simulated based on the user defined component library of the ADPSS electromagnetic transient calculation program, and an HVDC control model based on an actual system is established. The accuracy of the DC control custom model based on ADPSS is verified through the simulation of an actual power grid.

Diagnosis of gas phase near the substrate surface in diamond film deposition by high-power DC arc plasma jet CVD

Optical emission spectroscopy （OES） was used to study the gas phase composition near the substrate surface during diamond deposition by high-power DC arc plasma jet chemical vapor deposition （CVD）. C2 radical was determined as the main carbon radical in this plasma atmosphere. The deposition parameters, such as substrate temperature, anode-substrate distance, methane concentration, and gas flow rate, were inspected to find out the influence on the gas phase. A strong dependence of the concentrations and distribution of radicals on substrate temperature was confirmed by the design of experiments （DOE）. An explanation for this dependence could be that radicals near the substrate surface may have additional ionization or dissociation and also have recombination, or are consumed on the substrate surface where chemical reactions occur.

应用Power Perfecter实现DCS的锅炉优化控制

介绍了Maxl000DCS系统和PowerPerfecter锅炉优化控制技术;针对锅炉现有主要监测参数,提出了对炉膛负压、送风量、氧量、煤量等过程变量的优化控制方案;通过分析网络数据交换的特点。

Low Power Passive Photovoltaic System Development to Assist Inconvenient Grid Connection Locations

Sun radiation is known as one of the cleanest energy available and free maintenance on the earth to support the extensive demand for electrical power requirement for large and small scale. This energy is known as most promising renewable energy available during the whole year. This fact has shown a very strong interest among the researchers, industries and consumers to develop technology and system that can harvest solar energy to electrical energy. A lot of researches have been done to explore the capability of sun as natural energy source which is capable to provide huge alternative support to the increasing demand of electrical power in society. All the research findings have been adaptively combined to design, develop and structure as a reliable finished product for end users implementation. The fast improving research in photovoltaic application has proven that photovoltaic renewable energy is considered as one of the most promising source to support the increasing demand in electrical utilization. Advantages implementing the photovoltaic technology will benefit during the fuel price increment and be insufficient of the non-renewable energy to support the increasing demand from the society. Looking into this factor, many industries have developed the electrical photovoltaic system in large, medium and small scale for implementation. Electricity is becoming an essential requirement because of the increasing demand for electrical power from the society. Due to the increasing demand for electrical power, many researches are conducted to support the conventional way of generating electricity. This research has explored many other available abundant renewable energy resources such as solar, wind and thermal which are largely available to support the increasing demand. In this research, researchers discovered that the solar energy is the main contributor to support the increasing demand for electricity. The research outcome has helped the industries to develop solar power photovoltaic systems. This paper discusses the approaches to design and develop a real-time 500 Watt DC to AC Solar Power System. The system capability to store the harvested energy is discussed in this paper.