Now showing 1 - 10 of 70
  • Publication
    Pumped Hydro and Compressed Air Energy Storage at High Wind Penetrations
    (Energynautics GmbH, 2013-10-24) ;
    Energy storage is a widely used tool for balancing power systems and for providing increased operational flexibility - as such it can assist with the integration of variable renewable electricity generation. Grid-scale energy storage provides potential solutions to some of the technical and economic challenges which arise in systems with high penetrations of variable renewables, particularly on isolated systems. However, capital costs per MW are high, which means that variable renewable penetrations must reach significant levels before the operating cost reductions justify the capital expenditure. Optimum levels of grid-scale storage are explored, considering capital costs and potential operational cost savings for two storage technologies - pumped hydroelectric storage and compressed air energy storage. Grid-scale installations are found to achieve significant cost savings, particularly at high levels of wind generation. While the potential for savings is eroded significantly at high levels of DC interconnection, they remain high when non-synchronous penetration limits are increased.
  • Publication
    Utilising time of use surveys to predict water demand profiles of residential building stocks: Irish case study for domestic hot water
    (The WATEF Network, University of Brighton, 2014-09-11) ; ; ;
    The prediction of water consumption patterns is a challenge, especially when water metering is not available at scale. The paper focuses on the prediction of analytical domestic hot water (DHW) demand profiles for detailed building archetype models, using an occupant focused approach based on time-of-use survey (TUS) data. Five dwelling types are considered over different construction periods, representative of the majority of the Irish residential stock, which is used here as a case study. They are modelled at room level using EnergyPlus and converted into archetype models. A bottom-up approach is utilised to develop the required operational data at high space and time resolution. That methodology applies Markov Chain Monte Carlo techniques to TUS activity data to develop activity-specific profiles for occupancy and domestic equipment electricity use. It is extended to DHW demand profiles by combining the probability distributions for particular TUS activities with average daily DHW consumptions, depending on the household size, day type and season. The archetype models are found to be 90% accurate with the Irish standard dwelling energy assessment procedure in estimating the annual energy requirements for DHW heating. Moreover, they capture variations in DHW consumption, heat demand and energy usage for DHW heating, on a national scale and a fifteen-minute basis.
  • Publication
    Quantifying the Aggregate Frequency Response from Wind Generation with Synthetic Inertial Response Capability
    (Energynautics GmbH, 2013-10-24) ;
    Modern variable-speed wind turbines, although decoupled from the system frequency, can respond to significant power imbalances through power electronic controls as synthetic inertial or governor-like droop responses. However, frequency response capabilities from wind power plant cannot be considered a direct replacement for traditional frequency responsive services. Before such capabilities should be in- corporated into systems, their most effective implementation should be considered and a methodology for system operation under high synthetic inertia technology penetration should be identified. This paper considers a possible system frequency response requirement from wind generation and investigates issues surrounding quantification and scheduling of the future system resource, taking the combined Ireland and Northern Ireland system as an example. The distribution of local wind speeds, the variation in the response provided by different control structures, as well as the uncertainty associated with the aggregated capability at any one time, and the implications for the development of ancillary service market incentives or grid code requirements are considered. The impact of uncertainty over the aggregate wind response available is assessed and a strategy for the forecasting, management and coordination of such a resource on future power systems is proposed.
  • Publication
    Stochastic analysis of the impact of electric vehicles on distribution networks
    Advances in the development of electric vehicles, along with policy incentives, will see a wider uptake of this technology in the transport sector in future years. However, large penetrations of EVs could lead to adverse effects on power system networks, especially at the residential distribution network level. These effects could include excessive voltage drop and thermal loading of network components. A stochastic method is developed to take account of the uncertainties associated with EV charging and the technique is implemented on a residential test network using power system simulation software. The results show how voltage levels, component loading network losses are impacted from EV charging, taking into account the probabilistic behaviour of the EV owners.
  • Publication
    Power balance provision through co-ordinated control of modern storage heater load
    (Energynautics GmbH, 2013-10-24) ;
    Operational inflexibility due to wind variability at high penetration levels can be mitigated through flexible demand. However, most flexible loads entail a subsequent short-term higher energy payback and aggregated load coincidence. Storage heaters operating on a dual tariff, that typically charge during a fixed time window, can be considered as distributed thermal storage without an associated energy payback period. Modern storage heaters have improved heat retention, the capability to estimate their required charge, two way communication and local frequency measurement. Storage heating load currently exists in the system, making it more eminently suitable as bulk energy source/sink. This paper presents the use of modern storage heaters to accommodate higher levels of wind integration. A technical assessment of the capability of such load to provide reserves is also presented. Two types of heaters, with different capabilities and associated communication infrastructure requirements are considered for analysis. The results are demonstrated on a detailed single bus model of the 2020 Irish power system.
  • Publication
    Transient Stability Enhancement with High Shares of Grid-Following Converters in a 100% Converter Grid
    (IEEE, 2020-10-28) ;
    With increasing shares of power electronics-based generation in power grids, grid-following converters may become unstable during faults, resulting from a loss of phase-locked loop (PLL) synchronism. Even when current grid code low voltage ride through (LVRT) requirements are met, PLLs may still become unstable under high shares of grid-following converters, due to much reduced reactive current support from (online) synchronous generators or grid-forming converters. Consequently, a readily implementable transient stability enhancement approach is developed for grid-following converters using a reactive current priority current limiting strategy for faults on a transmission network. The proportional gain for the reactive current injection is determined by formulating an optimization-based transient stability problem, which ensures a valid PLL equilibrium point, maximizes active power output, fully exploits converter current capacity, and, at least, satisfies existing grid code LVRT requirements. An additional PLL frequency-feedback PI term is used to enhance PLL dynamic stability, in recognition of parameter estimation errors and imperfect control. A case study (100% converter-based grid) verifies that the proposed solution enables grid robustness against faults and the permissible share of grid-following converters to be increased (especially in weak grids).
      33Scopus© Citations 5
  • Publication
    Unit Commitment With Dynamic Cycling Costs
    (Institute of Electrical and Electronics Engineers, 2012-11) ; ; ;
    Increased competition in the electricity sector and the integration of variable renewable energy sources is resulting in more frequent cycling of thermal plant. Thus, the wear-and-tear to generator components and the related costs are a growing concern for plant owners and system operators alike. This paper presents a formulation that can be implemented in a MIP dispatch model to dynamically model cycling costs based on unit operation. When implemented for a test system, the results show that dynamically modeling cycling costs reduces cycling operation and tends to change the merit order over time. This leads to the burden of cycling operation being more evenly distributed over the plant portfolio and reduces the total system costs relative to the case when cycling costs are not modeled.
      601Scopus© Citations 49
  • Publication
    Investigation of demand response strategies in a mixed use building
    (Department of Civil Engineering, Aalborg University, 2016-05-25) ; ; ;
    This paper investigates demand response measures, using an EnergyPlus simulation model, developed specifically for demand response analysis, in a mixed-used commercial building. The effectiveness of various building pre-conditioning strategies, which were considered for different durations, immediacy and activation time were assessed using the simulation model. Assessment was carried out for a representative summer day and the contribution of the building capacitance as a mechanism for shifting the building electric power demand was evaluated, recording a maximum load reduction of 6.6% of the baseload.
  • Publication
    Demand side management potential of domestic water heaters and space heaters
    (Elsevier - International Federation of Automatic Control (IFAC), 2012-09-02) ;
    Demand side management (DSM) is a viable strategy for facilitating integration of renewable energy into power systems. The demand resource from water and space heating can be used to reduce or delay system demand peaks, and in combination with other flexible loads, reshape the aggregate demand profile and manage system ramping. In this paper, the aggregate power draw profiles for heat pump based water heating and under floor space heating systems for the Irish domestic sector have been synthesized and the effects of daily and seasonal variations, the type of dwelling and control / usage patterns on demand are discussed. The results show a significant seasonal and daily variation of the demand profile for water and space heating, indicating its viability as a DSM resource on the Irish power system, but also the challenges of operation.
  • Publication
    Emulated Inertial Response from Wind Power: Ancillary Service Design and System Scheduling Considerations
    Worldwide, variable-speed wind turbine and solar photovoltaic generation are displacing conventional power plant in market schedules. Committing out-of-merit conventional units to redress system synchronous inertia or primary frequency response shortfalls incurs start-up and production costs, and may also engender additional greenhouse gas emissions and wind/solar curtailment. In order to ensure that future system frequency response requirements are met in a low carbon manner, new sources of frequency stability ancillary services will need to be incentivised or mandated via grid codes. Nonsynchronous devices (batteries, flywheels, variable-speed wind turbines), with appropriate control architectures, can provide a fast frequency response following a system disturbance, i.e. a temporary injection of active power, supplied faster than existing primary frequency response deployment times. Operational considerations relevant to transmission system operators when designing a fast frequency response ancillary service are presented, particularly if sourced from wind power emulated inertial response. It is shown that careful consideration regarding the design of fast frequency response characteristics is required in high wind power systems: the system frequency response behaviour may be degraded if a holistic approach to fast frequency response design is not taken. A method to characterise the system-wide (aggregate) emulated inertial response from wind power is presented, which can be integrated as a form of fast frequency response within unit commitment and economic dispatch. Endogenous incorporation in unit commitment and economic dispatch ensures that non-synchronous fast frequency response sources do not only supplement existing fossil fuel-based spinning reserve provision, but also reduce the need to commit synchronous generators for frequency control reasons. However, given the inherent energy recovery/payback experienced by variable-speed wind turbines providing emulated inertial response when operating below rated output, it is imperative to consider the impact of such negative power trajectories on system primary frequency response requirements.