Potential of demand side response aggregation for the stabilization of the grids frequency

The role of ancillary services related to the frequency control have become increasingly important in the smart grids. Demand Side Response is a competitive resource that can be used to regulate the grid frequency. This paper describes the use of heat pumps and fridges to provide ancillary services of frequency response so that to continuously balance the supply with demand. The power consumption of domestic units is usually small and, therefore, the aggregation of large numbers of small units should be able to provide sufficient capacity for frequency response. In this research, dynamic frequency control was developed to evaluate the capacity that can be gathered from the aggregation of domestic heat pumps and fridges for frequency response. The potential of frequency response was estimated at a particular time during winter and summer days. We also investigated the relationship between both loads (domestic heat pumps and fridges) to provide Firm Frequency Response service. A case study on the simplified Great Britain power system model was developed. Based on this case study, three scenarios of load combination were simulated according to the availability of the load and considering cost savings. It was demonstrated that the aggregation of heat pumps and fridges offered large power capacity and, therefore, an instantaneous frequency response service was achievable. Finally, the economic benefit of using an aggregated load for Firm Frequency Response service was estimated

Adaptive control and dynamic demand response for the stabilization of grid frequency

Over the past few years, there has been a marked increase in the output from wind and solar generation in many countries. High levels of distributed generation provide variable energy and the increasing share of converter-connected plant results in a reduction in system inertia. Consequently, the rate of change of frequency, especially during and after severe faults, becomes more rapid. This thesis describes the use of heat pumps and fridges to provide ancillary services of frequency response so that to continuously balance the supply with demand. A decentralized digital controller namely: Adaptive DeadBeat (ADB) is designed to improve the frequency behaviour in an interconnected power system during and after faults. Simulation results show that the ADB controller can be considered as a contribution of digital control application to improve the frequency behaviour in an interconnected power system with reduced system inertia. The thermal performance of domestic buildings using heat pumps, and of fridges using thermostat temperature control is modelled. A dynamic frequency control (DFC) algorithm is developed to control the power consumption of the load in response to the grid frequency without affecting the overall performance of the load. Then, the dynamic frequency control algorithm is applied to a population of over 10 million aggregated units that represent the availability of load to provide frequency response. A dynamic relationship between the temperature and pre-defined trigger frequencies is given to ensure smooth and gradual load switching. A simulation is undertaken by connecting the controllable heat pumps to the reduced dynamic model of the Great Britain power system. Following a loss of 1,800 MW of generation, it is shown that the DFC reduces 1,000 MW of heat pumps demand and hence the frequency deviation is maintained within acceptable limits. In addition, a population of heat pumps and fridges are connected to the electrodynamic master model of the GB power system that is at present used by the ii GB transmission system operator, National Grid plc. Results show that the aggregated domestic heat pumps and fridges controlled by the DFC algorithm can participate in the Firm Frequency Response (FFR) service and provide rapid frequency response to the GB power system, mimicking the behaviour of the frequency-sensitive generators

System development issues concerning integration of wind generation in Great Britain

The European Union has committed itself to sourcing 20% of its energy from renewables by 2020. Britain's excellent wind resource is expected to make a significant contribution to this target, not least from Scotland and the north of England. However, exploitation of this resource requires appropriate and timely development of the GB electricity transmission system. This depends on appropriate market signals that communicate the need for transmission investment, something that many in the industry in Britain believe current arrangements do not adequately provide. This paper describes a number of proposals currently under discussion, outlines their interactions and highlights some of the key issues currently being debated

Generation Adequacy and Investment Incentives in Britain: from the Pool to NETA

Three years after the controversial change of the British market design from compulsory Pool with capacity payments to decentralised energy-only New Electricity Trading Arrangements (NETA) market framework, we compare the two designs in terms of investment incentives. We review the biases of the Pool capacity payments design, the drought of investment following the introduction of NETA, and the reaction of the market during the first “stress-test” of NETA during the winter 2003. In an energy-only market such as NETA, it is essential that price signals are right and the system operator has a crucial role in contracting ahead for reserve. We recommend that NETA adopt a single marginal imbalance price as dual imbalance pricing distorts price signals in times of scarcity. The lack of long-term contracting that causes hedging and financing difficulties for power projects can becompensated by vertical and horizontal reintegration at a cost of increased market power

Frequency and duration of low-wind-power events in Germany

In the transition to a renewable energy system, the occurrence of low-wind-power events receives increasing attention. We analyze the frequency and duration of such events for onshore wind power in Germany, based on 40 years of reanalysis data and open software. We find that low-wind-power events are less frequent in winter than in summer, but the maximum duration is distributed more evenly between months. While short events are frequent, very long events are much rarer. Every year, a period of around five consecutive days with an average wind capacity factor below 10% occurs, and every ten years a respective period of nearly eight days. These durations decrease if only winter months are considered. The longest event in the data lasts nearly ten days. We conclude that public concerns about low-wind-power events in winter may be overrated, but recommend that modeling studies consider multiple weather years to properly account for such events.Comment: This is an update version after peer revie

Frequency support markets with wind power participation

The European Union (EU) aims to considerably reduce the emissions of harmful gases in the atmosphere, has resulted in drastic increase of power generation from renewable sources, especially wind. The nature of these sources is that it is difficult to predict their availability at certain moment of time. This increases the need to balance the generation side to the demand side and thus, the need for ancillary services (AS). In addition, the large integration of wind power on the power systems in EU imposes on markets and operators the unavoidability of wind power participation in the provision of these AS [1]. Most of the EU countries already have markets and other procurement methods for AS [2]. These procurement methods, however, are designed and based on conventional generation which limits or completely prevents the participation of wind power in the procurement of these services [3]. The challenge to reconsider the structure of current energy markets has been identified by the European Commission on the “Energy Roadmap 2050” [4]. This may contribute to provide an European common framework for the balancing markets (which is one form of a manually operated frequency control), allowing participation of wind power as well as simplified cross-border interaction. In addition, the participation in providing AS from wind power plants have been already analysed to be beneficial for both the system and the wind power producers [5]. A promising example of wind power participation on balancing markets is already happening to some extent in Denmark [6] and in Spain 3.5 GW of wind generation capacity is about to obtain the right to participate in the balancing market [7]. Also, for easing wind power participation, AS markets must be adapted for example reducing gate closure times of the markets, which will reduce wind power production uncertainty and enable offering larger capacity. The aim of the thesis is to give the state of the art of AS for frequency support (FS), the important requirements that would encourage or discourage the participation of wind power generation in their provision and to analyse the potential economic benefits they would have from this provision

Dynamic frequency response from controlled domestic heat pumps

The capability of domestic heat pumps to provide dynamic frequency response to an electric power system was investigated. A thermal model was developed to represent a population of domestic heat pumps. A decentralized dynamic control algorithm was developed, enabling the heat pumps to alter their power consumption in response to a system frequency. The control algorithm ensures a dynamic relationship between the temperature of building and grid frequency. The availability of heat pumps to provide low-frequency response was obtained based on data supplied by Element Energy. Case studies were carried out by connecting a representative model of the aggregated heat pumps to the regional Great Britain (GB) transmission system model, which was developed by National Grid. It was shown that the dynamically controlled heat pumps distributed over GB zones have a significant impact on the GB system frequency and reduce the dependency on frequency services that are currently supplied by expensive frequency-sensitive generators. The rate of change of frequency was also reduced when there is a reduction in system inertia