Preben Nyeng’s research while affiliated with Technical University of Denmark and other places

The EcoGrid EU project was a research and demonstration project conducted from March 2011 to August 2015. Its purpose was to demonstrate the operation of a power system with high penetration of renewable and variable energy resources. The demonstration took place on the Danish island of Bornholm with more than 50% of the electricity consumption covered locally by renewable energy production. A real-time market concept for activating small-scale DER and demand response was a cornerstone in the project. The market was designed specifically to utilise small units down to household level installations in the balancing of the power system. To that end, the market architecture utilises a bid-less structure, where prices are published every 5 minutes for the participants’ voluntary response. The demonstration period was about two and a half years from late 2012 to spring 2015. The setup included approximately 2,000 installations, divided in different customer segments, including private homes and industrial applications. Some had automatic control equipment to control e.g. electric heating or heat pumps whereas others were to manually adapt their consumption to price signals. Installation and tuning of the demonstration setup was an ongoing, iterative activity throughout the entire period. Several issues were detected and addressed along the way, and eventually all equipment performed to the satisfaction of project partners as well as of the involved customers. The project partners gained important knowledge in this process. Involving the participants was crucial to the success of the project. It took a large effort to fulfill the target of attracting almost 10% of all residential electricity customers on Bornholm as well as to identify and recruit industrial customers. On the whole, customers indicated that they were happy with their participation in the project. The demonstration has been evaluated according to several measures, including economic efficiency and its ability to activate demand response. The demonstration has shown that: •There is significant demand response to be obtained from electrically heated and heat pump houses by means of automatic control equipment •A real-time price signal can be used to activate the potential •The response can be forecast – with some uncertainty – resulting in an overall improved efficiency of the system. The results also showed drawbacks of the market concept. It did not succeed in resolving distribution feeder congestion, and customers without automatic equipment did not exhibit demand response. We conclude that the market concept is a potentially efficient tool to activate the demand side in the electricity market and particularly utilise it for power system balancing. Particular care must be taken when designing the market algorithm, considering the real-time market’s interaction with day-ahead, intra-day and balancing markets. All in all we believe the EcoGrid EU project fulfilled its overall objectives and has created value to the society as a whole as well as for the involved partners. The experience gained from the project may prove very valuable for system/network operators and industrial parties in the future conversion of the energy system to mainly use renewable energy sources.

Industrialized countries are increasingly committed to move towards a low carbon generating mix by increasing the penetration of renewable generation. Additionally, the development in communication technologies will allow small end-consumers and small-scale distributed energy resources (DER) to participate in electricity markets. Current electricity markets need to be tailored to incorporate these changes regarding how electricity will be generated and consumed in the future. The EcoGrid EU is a large-scale EU-funded project, which establishes the first prototype of the future European intelligent grids. In this project, small-scale DERs and small end-consumers can actively participate in a new real-time electricity market by responding to 5-min real time electricity prices. In this way, the market operator will also obtain additional balancing power to cancel out the production variation introduced by renewable electricity generation. The real-time market concept architecture for EcoGrid EU is introduced in this paper, which provides a market-based platform and information and communication technology (ICT) infrastructure that extends the current electricity market to a shorter time horizon and to smaller assets.

The EcoGrid concept proposes to extend the current wholesale electricity market to allow participation of Distributed Energy Resources (DERs) and domestic end-consumers in system balancing. Taking advantage of the smart grid technology, the EcoGrid market publishes the real-time prices that entail an appropriate response of DERs and flexible customers to cope with the production deviation of renewable generating units. In the EcoGrid model the relation between the retailer and the customer stays entirely in the liberalized market, opening opportunities for new retail-level products and contracts supporting desired trade-offs of risk and benefit levels. The concept increases the market value of wind power, which in the long run is expected to provide the economic incentives to a higher wind power penetration. Hence, for a Europe-wide uptake of demand response, a good accordance between the EcoGrid concept and the new ENTSO-E Network Code on Electricity Balancing will be vitally important.

The paper introduces an algorithm for control of autonomous loads without digital communication interfaces to provide both frequency regulation and voltage regulation services. This hybrid controller can be used to enhance frequency sensitive loads to mitigate line overload arising from reduced load diversity. Numerical simulations of the hybrid controller in a representative distribution system show the peak system load was reduced by 12% compared to a purely frequency sensitive load controller.

As renewable energy sources increase their penetration, the traditional providers of frequency regulation service, i.e., fossil fueled thermal power plants, will be displaced, motivating the search for novel providers such as demand-side resources. This paper presents the results of field experiments using demand as a frequency controlled reserve (DFCR) on appliances with programmable thermostats. The experiments conducted showed the response of a population of thermostatically controlled loads acting as normal reserves (up and down regulation) and disturbance reserves (up regulation only) as defined by the Nordic Grid Codes . In addition, industrial pump loads and relay-controlled loads were tested as DFCR. The tests show that a population of refrigerators was able to deliver frequency reserves approximately equal to their average power consumption. Electric space heaters in the autumn season were able to provide frequency reserves of a magnitude 2.7 times their average power consumption.

This paper provides an overview of the Ecogrid EU project, which is a large-scale demonstration project on the Danish island Bornholm. It provides Europe a fast track evolution towards smart grid dissemination and deployment in the distribution network. Objective of Ecogrid EU is to illustrate that modern information and communication technology (ICT) and innovative market solutions can enable the operation of a distribution power system with more than 50% renewable energy sources (RES). This will be a major contribution to the European 20-20-20 goals. Furthermore, the proposed Ecogrid EU market will offer the transmission system operator (TSO) additional balancing resources and ancillary services by facilitating the participation of small-scale distributed energy resources (DERs) and small end-consumers into the existing electricity markets. The majority of the 2000 participating residential customers will be equipped with demand response devices with smart controllers and smart meters, allowing them to respond to real-time prices based on their pre-programmed demand-response preferences.

This paper investigates the possibility of applying electric heat pumps with the control-by-price-concept in order to avoid overload in a local distribution system. The proposed control algorithm is based upon a centrally dispatched real-time market price, reflecting the state of a larger power system, and is extended with a local price control for overload elimination on the corresponding feeder. The paper presents the mathematical models of a two-node system with price-responsive heat pumps, the chosen methodology of the central price calculation, and the proposed local feedback control architecture. The simulations of overload elimination have been carried out in Matlab. The results show the possibility of such auxiliary service by flexible units, which could be used for peak shaving in order to minimize the necessary oversizing of the power system components.

One of the challenges in electric power systems with a high penetration of renewable generation is the provision of ancillary services. Traditionally these services have been provided by conventional generation, but as power from renewable sources (wind and PV) displaces conventional generation, new providers of ancillary services are needed. Frequency regulation is critical because fluctuating energy sources increase the need for this service. At very high levels of renewable penetration, all available frequency regulation services will be called on, including demand-side resources. Electric loads that provide thermal energy services are attractive because their heat capacity allows electric power consumption to be moved in time without degrading the quality of service. This concept is being demonstrated in field tests on the island of Bornholm, Denmark.

The control-by-price concept fits well with controlling small-scale generation, storage and demand. In this paper, we investigate the required information and communications systems that are needed to realize the control-by-price concept for such units. We first present a proposal for overall infrastructure and subsystem design and secondly focus on the design and implementation of the end-user price-responsive controller, interfaces, and communications. The design and its applicability on existing devices is verified through laboratory tests with two cases: electric space heating thermostat control and a small combined heat and power unit. The results show that the price-responsive controller reduces the end user's electricity cost, or increases his income respectively, by about 7%. At the same time, the price-responsive controller provides an interface for the transmission system operator to utilize distributed energy resources and flexible demand as a regulating resource. Furthermore, the results illustrate and verify the applicability of the concept and the proposed infrastructure for controlling distributed energy resources and flexible demand.