Now showing 1 - 8 of 8
  • Publication
    Minimising transmission reactive support required by high penetration of distributed wind power generation
    Wind power generation is the fastest growing renewable technology worldwide with large on- and off-shore wind farms being connected to the transmission networks. A significant share of it is, however, still being deployed at distribution levels. While distributed wind generation presents traditionally passive distribution networks with well-established technical challenges, reactive support needed by high penetrations of such new generation capacity might also have an impact on the weak areas of the transmission grid. In this work, a multi-period AC optimal power flow-based technique is proposed to find power factor and substation settings that minimise the transmission reactive support required by variable distributed generation while also considering N-1 contingencies. A section of Irish distribution network is analysed. Results show the significant benefits that a passive approach such as the use of optimal power factor and substation settings can achieve.
      305
  • Publication
    Capacity value of wind power: summary
    The capacity value of a generator is the contribution that a given generator makes to generation system adequacy. Due to the variable and stochastic nature of wind, the modeling of wind generation in the same manner as conventional generation for capacity value calculation is inappropriate. In this paper a short summary of the issue is given. This summary is largely based on IEA task 25 activities and the output of an IEEE task force. A preferred method for calculating capacity value along with approximate methods for the calculation are also described with their limitations outlined.
      390
  • Publication
    Application of wind generation capacity credits in the Great Britain and Irish systems
    The concept of capacity credit is widely used to quantify the contribution of renewable technologies to securing demand. This may be quantified in a number of ways; this paper recommends the use of Effective Load Carrying Capability (ELCC, the additional demand which the new generation can support without increasing system risk), with system risk being measured using Loss of Load Expectation (LOLE, this is calculated through direct use of historic time series for demand and wind load factor). The key benefit of this approach is that it automatically incorporates the available statistical information on the relationship between wind availability and demand during the hours of very high demand which are most relevant in assessing system adequacy risk. The underlying assumptions are discussed in detail, and a comparison is made with alternative calculation approaches; a theme running through the paper is the need to consider the assumptions carefully when presenting or interpreting risk assessment results. A range of applications of capacity credits from Great Britain and Ireland are presented; this includes presentation of effective plant margin, ensuring that the optimal plant mix secures peak demand in economic projection models, and the Irish capacity payments system. Finally, new results comparing capacity credit results from the Great Britain and Irish systems using the same wind data are presented. This allows the various factors which influence capacity credit results to be identified clearly. It is well known that increasing the wind load factor or demand level typically increases the calculated capacity credit, while increasing the installed wind capacity typically decreases its capacity credit (as a percentage of rated capacity). The new results also show that the width of the probability distribution for available conventional generating capacity, relative to the peak demand level, also has a strong influence on the results. This emphasises further that detailed understanding of risk model structures is vitally important in practical application.
      826
  • Publication
    Enhanced utilization of voltage control resources with distributed generation
    Distributed Generation (DG) is increasing in penetration on power systems across the world. In rural areas, voltage rise limits the permissible penetration levels of DG. Another increasingly important issue is the impact on transmission system voltages of DG reactive power demand. Here, a passive solution is proposed to reduce the impact on the transmission system voltages and overcome the distribution voltage rise barrier such that more DG can connect. The fixed power factors of the generators and the tap setting of the transmission transformer are determined by a linear programming formulation. The method is tested on a sample section of radial distribution network and on a model of the all island Irish transmission system illustrating that enhanced passive utilisation of voltage control resources can deliver many of the benefits of active management without any of the expense or perceived risk, while also satisfying the conflicting objectives of the transmission system operator.
      1284Scopus© Citations 170
  • Publication
    Optimal voltage control settings for wind power
    (Institution of Engineering and Technology, 2009) ; ; ;
    High penetrations of wind power on distribution networks are causing voltage rise on many networks. This voltage rise is limiting the permissible penetration levels of wind. Numerous active control schemes have been proposed to solve this issue, but widespread adoption of active management by network operators has yet to occur. Here, the fixed power factors of the generators' and the tap setting of the transmission transformer are optimally determined such that the voltage rise barrier is overcome and more wind can connect. The impact on the transmission system is becoming increasingly important and is also taken account of in the method. The method is tested on a sample section of distribution network illustrating that the optimal selection of voltage control settings can deliver some of the benefits of active management without any of the expense or perceived risk.
      487Scopus© Citations 5
  • Publication
    Simplified methods for renewable generation capacity credit calculation: A critical review
    Capacity credits are widely used to quantify the ability of different generating technologies to support demand. Most practical capacity credit calculations are based on detailed risk modelling, however a wide range of simplified approaches are also in use. This paper presents a critical review of these simplified approaches, ranging from annual peak calculations and probabilistic representations of wind, to closed-form expressions derived for small installed wind capacities. The principal themes are that simplified methods must retain the key features of the problem at hand, and that to be of interest simplified methods must either bring substantial computational advantages, or provide additional insight beyond that from a more detailed risk calculation.
      2088Scopus© Citations 31
  • Publication
    Minimising transmission reactive support required by high penetration of distributed wind power distribution
    Wind power generation is the fastest growing renewable technology worldwide with large on- and off-shore wind farms being connected to the transmission networks. A significant share of it, however is still being deployed at distribution levels. While distributed wind generation presents traditionally passive distribution networks with well-established technical challenges, reactive support needed by high penetrations of such new generation capacity might also have an impact on the week areas of the transmission grid. In this work, a multi-period AC optimal power flow-based technique is proposed to find power factor and substation settings that minimise the transmission reactive support required by variable distributed generation while also considering N-1 contingencies. A section of Irish distribution network is analysed. Results show the significant benefits that a passive approach such as the use of optimal power factor and substation settings can achieve.
      270Scopus© Citations 72
  • Publication
    Capacity value of wind power
    Power systems are planned such that they have adequate generation capacity to meet the load, according to a defined reliability target. The increase in the penetration of wind generation in recent years has led to a number of challenges for the planning and operation of power systems. A key metric for generation system adequacy is the capacity value of generation. The capacity value of a generator is the contribution that a given generator makes to generation system adequacy. The variable and stochastic nature of wind sets it apart from conventional energy sources. As a result, the modeling of wind generation in the same manner as conventional generation for capacity value calculations is inappropriate. In this paper a preferred method for calculation of the capacity value of wind is described and a discussion of the pertinent issues surrounding it is given. Approximate methods for the calculation are also described with their limitations highlighted. The outcome of recent wind capacity value analyses in Europe and North America, along with some new analysis are highlighted with a discussion of relevant issues also given.
      1937Scopus© Citations 268