Neighboring Power Systems Research Articles

The impact of events in the Slovene high – voltage network on the power quality in the distribution networks

This work analyses the impact of different events in Slovene high-voltage network on power quality in the 20 kV and 0.4 kV distribution networks. In order to perform the analysis a simplified dynamic model of the Slovene power system was build in the program package Matlab/Simulink, using toolbox PowerSys. The obtained model is appropriate for simulation of electromagnetic transients in duration up to a few seconds. It contains simplified dynamic models of all main generators and power transformers installed in the Slovene power system, detailed models of 400 kV, 220 kV and 110 kV networks, simplified models of the neighboring power systems and models of important consumers. The 20 kV and 0.4 kV distribution networks are modeled in the details only in the area of interests. Everywhere else, they are represented as constant loads connected to the 110 kV network. The aforementioned dynamic model was applied to analyze the impact of different events in the Slovene power system on power quality in the 0.4 kV distribution network during transients and in steady states. The power quality in distribution network was analyzed on 0.4 kV busbars in five substations (Cerkno, Škofja Loka, Vevče, Šentjur, Rače) for the following set of events: a switch-off of a 300 MVA (400 kV/110 kV) power transformer in the substation Okroglo; a three-phase short circuit on 110 kV busbars in the substation Kleče; a three-phase short circuit on 20 kV busbars in the substation Rogaška Slatina and a switch-on in a pumping regime of pump-turbine plants Avče and Kozjak which are currently at the design stage. The results obtained show that aforementioned events in some points of Slovene distribution network can cause power quality distortion over that allowed by the power quality standards.

Assessing new block order options of the EUPHEMIA algorithm: An optimization model for the economic dispatch problem in power exchanges

To implement the process of European power markets’ integration, a market-clearing algorithm has been developed among European power exchanges under the title EUPHEMIA (Pan-European Hybrid Electricity Market Integration Algorithm), being a strictly economic dispatch algorithm and providing several options and products to market participants. This paper proposes an optimization-based methodological framework for the optimal economic dispatch problem in power exchanges, further enhancing the EUPHEMIA algorithm’s block order module. More specifically, through the development of a mixed-integer linear programming (MILP) model and utilizing an iterative process, it quantifies the impacts of the proposed new options to the optimal energy mix, the wholesale prices, and on the market players’ economic performance. The model considers all the current market products of the EUPHEMIA algorithm, as well as introduces new market products such as the flexibility provision of the main aspects of block orders (minimum acceptance ratio, price offer, and block time limits), the modification of existing block orders (exclusive groups), the development of new linkage structure (linked block orders with parallel relationship), as well as the activation of mixed schemes combining existing types of block orders into new integrated forms. The developed optimization framework has been assessed in the Greek interconnected power system, including its interconnections with neighboring power systems. The proposed methodological approach suggests a robust and systematic methodological formation to provide useful insights on policy issues and ongoing debate regarding the shaping of more efficient market designs and structures to deal with the new operational challenges of low-carbon flexible power systems.

A low-carbon market-based multi-area power system expansion planning model

This paper proposes a low-carbon coordinated linear generation and transmission expansion planning (G&TEP) model for multi-area power systems (MAPS)s, wherein energy transactions are determined considering the power market environment. The proposed model presents an interesting decarbonization alternative for power systems with low renewable resources potential, by allowing them to meet their environmental targets through an increase in their energy transactions with neighboring power systems. In order to allow for more energy transactions with neighboring power systems, the proposed model aims at ensuring an advantageous collaboration from the perspective of all the areas participating in the MAPS. To this end, a preprocessing stage is carried out first to study the expansion planning of each area individually when no investments are to be made in inter-area transmission infrastructure. Subsequently, the MAPS expansion planning problem is solved bounded by the emissions levels and the profits realized by the market players in the preprocessing stage. Numerical simulations were carried out in GAMS environment and the results indicate the effectiveness of the proposed model in developing advantageous expansion plans for all the areas participating in the MAPS.

Korišćenje alata za tržišno modelovanje pri analizi benefita po elektroenergetski sistem izgradnjom novog interkonektivnog dalekovoda

The goal of this paper is to introduce the market modeling tool Antares and to point out possibilities of its utilisation in cost-benefit analysis of energy projects. Market modeling of power systems represents a detailed modeling of generating units, consumption and cross-border connections with neighboring systems in order to find economically optimal dispatching of power plants by which the total consumption will be satisfied. In this paper, two power systems connected by cross-border transmission lines will be modeled (in one of them there is a large amount of installed capacity of renewable energy sources). The benefits of reinforcing cross-border connection embodied in avoiding curtailment of available renewable energy due to low energy consumption and lack of energy storage systems will be analyzed, along with corresponding benefits of reduced CO2 emissions due to the ability to transfer green energy into neighboring power systems through increased cross-border capacity.

An optimization model for integrated portfolio management in wholesale and retail power markets

Abstract: The increasing interactions and interdependences of the wholesale and retail markets in the power sector have created the need for development of integrated approaches for the optimal portfolio management of vertically integrated utilities, aiming at drastically limiting their risk exposure. This work presents a generic mixed integer linear programming (MILP) model for the optimal clearing of a wholesale power market including market products widely used in power exchanges such as block and hourly orders. Based on the market clearing results, it then calculates the economic balance of vertically integrated utilities participating in retail markets, covering the whole value chain in the power sector. By considering a wide range of technology options in the wholesale market, including fossil fuel-based thermal units with or without carbon capture and sequestration capability (CCS), nuclear power, renewable energy, electricity trading and storage options, as well as different types of consumers in the retail market (low, medium and high voltage), the model determines the optimal electricity generation mix, the system’s marginal price and its environmental performance, as well as the net economic position of each power utility in both wholesale and retail markets. A series of sensitivity analyses on the CO2 emission pricing, the renewables’ penetration, and the applied environmental policy has been conducted to investigate the influence of several economic, technical and policy parameters on the operational scheduling and financial planning of each utility. The model applicability has been assessed in an illustrative case study of a medium-sized power system considering also its interconnections with neighboring power systems. The model results quantify the risk facing electric utilities participating in both wholesale and retail markets under several market conditions and with different schemes on the generation side, as well as with different representation shares on the demand side. The proposed optimization framework can provide useful insights on the determination of the optimal integrated generation and retail portfolios that address the new market operating challenges of contemporary power systems, subject to several technical and economic constraints, enabling also the design of medium-term operational strategies for vertically integrated power utilities.

Structural-and-Parametric Optimization of Automatic Control System for Power Units of 300 MW in Wide Range of Load Variations

The structural-parametric optimization of the automatic control system for power units (ACSPU) of 300 MW of Lukoml’skaya GRES (Lukoml Local Condensing Power Plant) in the mode of both the permanent and the variable superheated steam pressure upstream of the turbine is under consideration. During 1974–1979, eight units of the Lukoml’skaya GRES implemented the ACSPU with a leading boiler power control. At the moment, these systems no longer meet all the frequency control quality requirements. In 2016, the daily schedule of electric loads of the Belarusian power system was as follows: the basic part of the schedule of electric loads was covered by combined heat and power plants (CHP) and by mini-CHP (which are the least maneuverable of the power plants), the semi-peak part of it–by local condensing power plants (Lukoml’skaya GRES and Berezovskaya GRES), the peak part–by import electric energy from neighboring power systems. However, this year the first unit of the Belorussian NPP will be put into operation, while the second one–in 2020. After the launch of the Belorussian NPP, it will cover basic part of load curve; CPPs will cover the semi-peak part, while the peak part of load curve will be covered by local condensing power plants. Correspondingly, due to the alteration of the structure of daily schedule of electric loads of the Belarusian power system, it is necessary to improve the efficiency of power units of Lukoml’skaya GRES as well as of the entire Lukoml’skaya GRES in general. This can be achieved with the help of the method of parametric optimization of the typical ACSPU proposed in the present paper. As a result, the quality of control of power and pressure upstream of the turbine will be improved; the flow of fuel will be reduced, as well as the turbine regulation valve displacement; environmental performance of entire power plant will be improved, too. The proposed technique has been confirmed by the results of computer simulation of transient processes in the automatic control system under external and internal disturbances.

A power system scheduling model with carbon intensity and ramping capacity constraints

The integration of European electricity markets aims at market coupling among interconnected power systems and the evolution of environmentally friendly technologies. This process is anticipated to utilize more efficiently the flexible generation and interconnections transmission capacity and provide environmental and economic benefits to final consumers. This paper presents a mixed integer linear programming model for the optimal scheduling of a power system (unit commitment problem) simulating the day-ahead electricity market. The model determines the optimal daily power generation mix, the electricity trade with neighboring countries, the evolution of the system's marginal price and the resulting environmental impact. The model incorporates CO2 emissions intensity constraints and introduces flexible ramping products, in addition to reserve requirements, aiming to identify their impacts on both operational and economic decisions. The model is applied on the Greek power system and its interconnections with neighboring power systems in Southeast Europe. The proposed approach can provide useful insights on the optimal generation and interconnections portfolio that meets the real electricity market operating needs of contemporary power systems with environmental and ramping capacity constraints.

Incorporating unit commitment aspects to the European electricity markets algorithm: An optimization model for the joint clearing of energy and reserve markets

The European electricity markets’ integration aims at the market coupling among interconnected power systems and the enhancement of market competitive forces. This process is facilitated by the adoption of a common clearing algorithm among European power exchanges, entitled EUPHEMIA (Pan-European Hybrid Electricity Market Integration Algorithm), which however lacks to capture critical technical aspects of power systems, as done by the unit commitment problem including start-up and shut-down decisions, time constraints (minimum on- and off-times), as well as the consideration of ancillary services. This paper presents an optimization-based framework for the optimal joint energy and reserves market clearing algorithm, further utilizing the hourly offers module of the EUPHEMIA algorithm. In particular, through the formulation of a mixed integer linear programming (MILP) model and employing an iterative approach, it determines the optimal energy and reserves mix, the resulting market clearing prices, and it calculates the welfares of the market participants. The model incorporates intra-hourly power reserve constraints, as well as introduces new market products such as the option of forming linked groups of power units, aiming at supplying additional flexibility in the decision-making of the market participants. The model applicability has been assessed in the Greek power system and its interconnections with neighboring power systems in Southeast Europe. The proposed optimization framework can provide useful insights on the determination of the optimal generation and interconnection portfolios that address the new market-based operational challenges of contemporary power systems subject to technical and economic constraints.

Impact of large PV and wind power plants on voltage and frequency stability of Jordan’s national grid

The impact of integrating large photo voltaic (PV) and wind power (WP) renewable energy plants (REPs) to the national grid of Jordan is presented. The capacity of the national grid to integrate REPs and upgrading of the transmission grid to increase the grid capacity is examined through computer simulations using load flow analysis. Congestion management based on line flow capacity constraints has also been carried out. It was found that the maximum penetration levels of the REPs should not increase beyond 10% of the Jordan’s annual peak demand. However, accommodation of penetration levels to up to 1600MW of REPs by 2020 is proposed by network upgrading. The effect of increasing the penetration levels of REPs, during normal conditions, on voltage and frequency stability has been analyzed. The maximum power generation of the REP that can be connected to the grid at a proposed location before voltage collapse occurs has been determined. It was found that by introducing voltage and reactive power support, the maximum power generation of REPs can be doubled. Frequency stability analysis shows that frequency stability of the grid can be maintained even when the penetration level of the REPs reaches up to 40% of the total generation. Furthermore, stability analysis has confirmed the importance of interconnection with neighboring power systems. All simulation studies have been implemented using the professional DIgSILENT software package.

대용량 유도전동기 기동 개선에 관한 연구

본 논문에서는 전력에너지를 사용하는 산업체의 전동기용량이 점차 증가하고 있다. 전동기는 기동시 기동전류로 전압강하가 발생한다. 이 기동전류가 전력계통에서 대형 전동기 기동 시 전압강하로 기동이 어려워 인접한 전력계통에 나쁜 영향을 미치게 된다. 또한 전동기는 부하의 크기에 따라 토크를 내는 것으로 토크의 크기에 따라 속도가 변하고 속도는 전동기 기동에 중요하다. 일반적으로 변압기나 비상발전기로부터 전동기까지의 거리가 짧으며 전동기용량이 작아 기동에 대한 어려움이 없으나 산업설비 등에 많이 이용되는 대용량 전동기의 기동특성에 대한 이론과 실제의 운전특성을 측정 분석하였다. 따라서 이번 연구는 전동기 기동 시 속도와 토크에 관계와 대용량 전동기 기동을 위한 분석과 전동기 기동 해석에 대해 연구하였다. The motor power of the industry to use the electric energy is gradually increased. The electric motor generates a voltage drop in the starting current during startup. The starting current is started it is difficult to have an adverse effect on neighboring power systems with large motor starting when the voltage drop across the power grid. In addition to that the motor torque according to the load depending on the size of the rotation speed is changed to a motor start-up speed is important. However, the distance to the emergency generator transformers or motors from the motor capacity is smaller but short and difficult to maneuver the theory and practice of the operating characteristics of the starting characteristics of the motor used a lot of large industrial plants were measured and analyzed. Therefore, this study investigated the motor starting Analysis and interpretation for the relationship with the large motor starting torque and speed during motor starting.

Versioning-based service-oriented model for multi-area power system online economic load dispatch

The main objective of this paper is to construct a distributed environment through which the economic load dispatch solutions of multi-area power systems can be monitored and controlled. A single-server/multi-client architecture which enables the neighboring power systems to access the remote economic load dispatch (ELD) server at any time with their respective data and to get the economic load dispatch solutions from the remote server has been proposed. A .NET remoting architectural model has been implemented in such a way that for every specific period of time, the remote server obtains the system data simultaneously from the neighboring power systems which are the clients registered with the remote ELD server and the optimized economic load dispatch solutions from the server have been sent back to the respective clients. The ELD server creates a new thread of control for every client’s request and hence complete distributed environment is exploited.

Analysis of system frequency and active power control functioning of Serbian power system

This paper is the result of the Master's final project 'Analysis of System Frequency and Active Power Control Functioning of Serbian Power System'. It contains theoretical basis and the basic principles of frequency and active power control. A partial analysis of parameters and simulation of power system of Serbia and neighboring power systems state in three characteristic cases is performed, using a computer program developed at the Electrical Engineering Institute 'Nikola Tesla'. Sensitivity analysis of the obtained results on variations in key parameters of the regulator is also performed. Power system of Serbia and neighboring power systems states are shown by observing the characteristic parameters such as: frequency, active power and regulation errors.

A Large Wind Power System in Almost Island Operation—A Danish Case Study

In Denmark, incorporation of wind power into the power system is increasing whereas power generation from the large conventional power plants is reducing. The common concern has become maintenance of reliable and stable operation of the Danish power system with a large amount of wind power - the large wind power system. At present, maintaining the voltage stability of such a large wind power system relies on strong ac connections to neighboring power systems with sufficient reactive power and voltage control and on control of central power plants in Denmark. This paper presents the results of a stability investigation carried out by the Danish transmission system operator (TSO), Energinet.dk, for the case of almost island operation of the Western Danish wind power system. The main ac lines connecting Western Denmark to the synchronous area of the Union for the Co-ordination of Transmission of Electricity (UCTE) were out of service and the wind power generation was high. The investigation has shown that the reactive power and voltage control of the domestic power plants is essential for maintaining short-term voltage stability of the Western Danish wind power system and becomes even more relevant when ac connections to the strong transmission system of the UCTE are out of service. The results presented in this paper may also be relevant for the operators of the power systems that are in island ac operation and with plans for significant commissioning of wind power - Great Britain, Ireland, Tasmania, etc.

Component Model for Multi- Area Power Systems On-Line Economic Load Dispatch

The main objective of this paper is to develop component model architecture for economic load dispatch of multi - area power systems. A component which is based on a single-server serving multiple clients has been proposed which enables all neighboring power systems to have simultaneous access to the remote economic load dispatch server for obtaining continuous load dispatch solutions. An EJB (Enterprise Java Beans) based, distributed environment has been implemented in such a way that each power system client can access the remote economic load dispatch EJB server through JNDI (Java Naming and Directory Interface) naming service with its power system data. The server computes the economic load dispatch and it provides the continuous automated load dispatch solutions to all the registered power system clients. Economic load dispatch EJB server inherently creates a new thread of control for every client request and hence complete component based distributed environment can be achieved.

Application of superconductive magnetic energy storage in an asynchronous link between power systems

The concept that superconductive magnetic energy storage (SMES) can be incorporated into a back-to-back DC link is introduced. With an SMES-DC link, an SMES system can be shared between several neighboring power systems. This results in better economics for SMES usage for each participating power system. In addition to SMES operation, an SMES-DC link also allows asynchronous connection and interchange of power between the interconnected systems. It is demonstrated that an SMES-DC link can achieve significant economic benefits over pure power interchange or SMES operation alone. The basic principle of an SMES-DC link, which is able to interconnect any number of neighboring power systems with a single SMES unit, and various interconnected system operation modes are presented. A battery-DC link is discussed and compared with the SMES-DC link.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

System requirements for dynamic performance and response of generating units

Starting from a discussion of the fundamental characteristics of modern interconnected power systems, this paper goes on to categorize requirements for dynamic performance and response imposed on the aggregate generation which supplies the system. Both normal and abnormal operating modes are considered. The performance and response requirements are shown to stem from basic needs to maintain voltage, frequency, time, and continuity of service as well as the secondary requirements of maintaining operating economies and controlling inadvertent interchange between neighboring power systems. Typical data taken from operating records are used to illustrate and quantify several of the response requirements.