scholarly journals Modified Voltage Control Law for Low Frequency Railway Power Systems

2017 ◽  
Author(s):  
John Laury ◽  
Lars Abrahamsson ◽  
Math Bollen
Keyword(s):  
Power Systems ◽  
Reactive Power ◽  
Low Frequency ◽  
Voltage Control ◽  
Load Sharing ◽  
Alternative Methods ◽  
Control Law ◽  
Public Power ◽  
Negative Impacts ◽  
Railway Power Systems

In today’s Swedish and Norwegian low frequency railway power system the voltage at a converter is controlled such that its voltage will drop with increased reactive power output. However, for low frequency railways the influence of active power on voltage is larger compared to public power systems and alternative methods are interesting to investigate. This paper presents a modified voltage control law for increased load sharing between converter stations and reduce the risk for converter overload in low frequency railways power systems. The modified voltage control law is derived mathematically and tested with different droops for two case studies. The results confirms the increased load sharing between the converter stations. The results are analysed and discussed; ideas are presented to counteract some of the negative impacts of the modified voltage control law.

Preliminary Study on the Influence of Wind Power on Low-Frequency Oscillation under Outward Transmitting Thermal Generated Power Bundled with Wind Power Typical Scene

2013 ◽  
Vol 391 ◽  
pp. 271-276
Author(s):  
Peng Li ◽  
Ning Bo Wang ◽  
De Zhi Chen ◽  
Xiao Rong Zhu ◽  
Yun Ting Song
Keyword(s):  
Power Systems ◽  
Power System ◽  
Wind Power ◽  
Wind Farm ◽  
Reactive Power ◽  
Simulation Analysis ◽  
Low Frequency ◽  
Simulation Software ◽  
Frequency Oscillation ◽  
Low Frequency Oscillation

Increasing penetration level of wind power integration has a significant impact on low-frequency oscillations of power systems. Based on PSD-BPA simulation software, time domain simulation analysis and eigenvalue analysis are employed to investigate its effect on power system low-frequency oscillation characteristic in an outward transmitting thermal generated power bundled with wind power illustrative power system. System damping enhances markedly and the risk of low-frequency oscillation reduce when the generation of wind farm increase. In addition, dynamic reactive power compensations apply to wind farm, and the simulation result indicates that it can improve dynamic stability and enhance the system damping.

A Method of Automatic Voltage Optimization Control Based on Real Time Digital Simulation

2013 ◽  
Vol 336-338 ◽  
pp. 653-658
Author(s):  
Yu De Yang ◽  
Yu Sheng Qiu
Keyword(s):  
Power Systems ◽  
Real Time ◽  
Reactive Power ◽  
Digital Simulation ◽  
Voltage Control ◽  
Test Method ◽  
Control Effectiveness ◽  
Advantages And Disadvantages ◽  
The Status ◽  
Optimal Control Scheme

With the development of smart grid, regional grid automatic voltage control (AVC) system has been widely used in power systems, but the effect is uneven, and there are not relating tools to evaluate its performance. The paper proposes a Closed-loop test method combining Real Time Digital Simulation system (RTDS) with reactive optimization procedures to simulate and optimization the status of actual grid. An optimal control scheme of the actual grid from the new method can be used to judge the advantages and disadvantages of actual AVC system. Simulation tests show online RTDS-based power system reactive power and voltage control simulation is good. It can be regard as reference to evaluate the control effectiveness of the actual AVC system.

scholarly journals Secondary voltage regulation based on average voltage control

TecnoLógicas ◽  
2018 ◽  
Vol 21 (42) ◽  
pp. 63-78
Author(s):  
Edwin H. Lopera-Mazo ◽  
Jairo Espinosa
Keyword(s):  
Control System ◽  
Power Systems ◽  
Reactive Power ◽  
Voltage Control ◽  
Voltage Regulation ◽  
Voltage Profile ◽  
Real Power ◽  
Power Resources ◽  
Control Actions ◽  
Secondary Voltage

This paper compares a conventional Secondary Voltage Regulation (SVR) scheme based on pilot nodes with a proposed SVR that takes into account average voltages of control zones. Voltage control significance for the operation of power systems has promoted several strategies in order to deal with this problem. However, the Hierarchical Voltage Control System (HVCS) is the only scheme effectively implemented with some relevant applications into real power systems.The HVCS divides the voltage control problem into three recognized stages. Among them, the SVR is responsible for managing reactive power resources to improve network voltage profile. Conventional SVR is based on dividing the system into some electrically distant zones and controlling the voltage levels of some specific nodes in the system named pilot nodes, whose voltage levels are accepted as appropriate indicators of network voltage profile.The SVR approach proposed in this work does not only consider the voltage on pilot nodes, but it also takes the average voltages of the defined zones to carry out their respective control actions. Additionally, this innovative approach allows to integrate more reactive power resources into each zone according to some previously defined participation factors.The comparison between these strategies shows that the proposed SVR achieves a better allocation of reactive power in the system than conventional SVR, and it is able to keep the desired voltage profile, which has been expressed in terms of network average voltage.

scholarly journals Application of Artificial Intelligence Techniques in Reactive Power/Voltage Control of Power System

2014 ◽  
Vol 1 (1) ◽  
pp. 5
Author(s):  
Gehao Sheng ◽  
Guangyu Tu ◽  
Yi Luo
Keyword(s):  
Artificial Intelligence ◽  
Power Systems ◽  
Power System ◽  
Reactive Power ◽  
Fuzzy Theory ◽  
Voltage Control ◽  
Control Methods ◽  
Multi Agent System ◽  
Multi Agent ◽  
Artificial Neural Network Ann

<p>As one of the important constituents of power system automation, reactive power/voltage control possesses inherent characteristics of complexity, nonlinearity, inaccuracy and high requirement for control speed, parts of which are hard to be described by the traditional mathematical models or to be realized by routine control methods. The artificial intelligence (AI) techniques have intelligence feature which traditional method does not bear, so special attentions are paid to the application of AI techniques in reactive voltage control and a lot of results in this field are obtained. In this paper the main results and methods of applying the AI techniques, such as Expert System (ES), Artificial Neural Network (ANN), Fuzzy Theory (FT), Genetic Algorithm (GA) and Multi-Agent System (MAS), etc., to reactive voltage control in power systems are summarized, the respective application features of these techniques are analyzed and compared and some problems to be solved are pointed out.</p>

scholarly journals Development of an Intelligent Voltage Control System for Bulk Power Systems

2021 ◽  
Vol 11 (19) ◽  
pp. 9233
Author(s):  
Heungjae Lee ◽  
Wonkun Yu ◽  
Junghyun Oh ◽  
Hyungsuk Kim ◽  
Jinyoung Kim
Keyword(s):  
Control System ◽  
Expert System ◽  
Power Systems ◽  
Power System ◽  
Performance Index ◽  
Reactive Power ◽  
Voltage Control ◽  
Searching Strategy ◽  
Space Modeling ◽  
Bulk Power

As modern power systems become large and complicated, an automated voltage and reactive power control system is required in most developed countries due to the remarkable recent progress in computer networks and information technology. To date, voltage control has depended on human operators in the Korean power system. Accordingly, this paper proposes a universal intelligent voltage control system for bulk power systems based on sensitivity analysis and a main expert system. A detailed state space modeling technique is discussed, and an effective performance index is proposed to accelerate the searching performance of the expert system. As the searching strategy is an important factor for the speed of the expert system, the least-first search algorithm is applied using this performance index. The proposed system has been applied to the Korean power system, showing promising results.

AC Cables Strengthening Railway Low Frequency AC Power Supply Systems

2017 ◽  
Author(s):  
Lars Abrahamsson ◽  
Daniel Serrano Jimenez ◽  
John Laury ◽  
Math Bollen
Keyword(s):  
Power Systems ◽  
Power System ◽  
High Voltage ◽  
Transmission Lines ◽  
Power Supply ◽  
Low Frequency ◽  
Hvdc Transmission ◽  
Reactive Compensation ◽  
Ac Transmission ◽  
Railway Power Systems

In present-day railway power supply systems using an AC frequency lower than the one in the public power system of 50/60 Hz, high voltage overhead transmission lines are used as one measure of strengthening the railway power supply system grids. This option may be economically beneficial, compared to strengthening the grid purely by increasing the density of converter stations or increasing the cross section areas of the overhead catenary wires. High voltage AC transmission lines in the railway power supply system allow larger distances between converter stations than would otherwise be possible for a given amount of train traffic. Moreover, the introduction of AC transmission lines implies reduced line losses and reduced voltage level fluctuations at the catenary for a given amount of train traffic. However, due to the increased public and government resistance for additional overhead high voltage AC transmission lines in general, different alternatives will be needed for the future improvements and strengthening of railway power systems. For a more sustainable transport sector, the share and amount of railway traffic needs to increase, in which case such a strengthening becomes inevitable. Earlier, usage of VSC-HVDC transmission cables has been proposed as one alternative to overhead AC transmission lines. One of the main benefits with VSC-HVDC transmission is that control of power flows in the railway power systems is easier and that less converter capacity may be needed. Technically, VSC-HVDC transmission for railway power systems is a competitive solution as it offers a large variety of control options. However, there might be other more economical alternatives reducing the overall impedance in the railway power system. In public power systems with the frequency of 50/60 Hz, an excess of reactive power production in lowly utilized cables imposes an obstacle in replacing overhead transmission lines with cables. In low frequency AC railway power system, the capacitive properties are less significant allowing longer cables compared to 50/60 Hz power systems. Moreover, in converter-fed railways, some kind of reactive compensation will automatically be applied during low-load. At each converter station, voltage control is already present following the railway operation tradition. Therefore, in this paper, we propose AC cables as a measure of strengthening low-frequency AC railway power systems. The paper compares the electrical performances of two alternative reinforcement cable solutions with the base case of no reinforcement. The options of disconnecting or toggling the cables at low load as well as the automatic reactive compensation by converter voltage control are considered. Losses and voltage levels are compared for the different solutions. Investment costs and other relevant issues are discussed.

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