Session 15: Ancillary Services
The Impact of Electricity Market Design on Periodic Network Frequency Excursions
Eindhoven University of Technology, Netherlands, The
In an electrical power system there must always be a balance between generation and load of electricity. Any mismatch between generation and load will, in a synchronous system, instantaneously lead to a deviation of the grid frequency from its nominal value in the whole system. It is observed that grid frequency deviations occur at hourly and half-hourly transitions, especially during morning and evening hours when the rate of change of load is high. The origin of these frequency deviations lies in the economic dispatch of generation which is ever more cost optimized. As generation companies have the obligation to provide a certain amount of energy per trading period (defined as Program Time Unit), they have little (or no) incentive to follow the power demand profile and therefore rather optimize their generation based on this energy constraint, which results in stepwise power generation profiles. The restructuring of the electricity business is considered a plausible cause for this, as it provides an incentive to further optimize the economic dispatch without taking into account mismatch between generation and load within the program time unit.
Ancillary Services in the Iberian Electricity Market – Current Situation and Harmonization Approaches
1FEUP, INESC Porto; 2FEUP
This paper addresses the provision of ancillary services in Portugal and Spain in the scope of the Common Iberian Electricity market. The paper reviews the definitions and the international practice regarding ancillary services with emphasis on primary, secondary and tertiary reserves and describes the procedures adopted by the Portuguese and Spanish TSO’s to procure and allocate reserve levels. On the other hand, the paper discusses the models that can be used to enlarge the integration of the reserve markets, namely regarding tertiary reserve. Using data from 2009, the paper presents the results of the simulations that were performed for several situations including an ideal unlimited interconnection capacity, the existing interconnection capacity and an interconnection capacity increased by 300 MW. The results obtained indicate that the adoption of a common tertiary reserve list would ultimately be beneficial for the consumers since the cost of tertiary reserve would be reduced. However, a larger integration and cooperation between the two TSO’s would be clearly required.
Wind Power Plant as Ancillary Service Provider
Faculty of Electrical Engineering, Mechanical Engineering and Naval Architecture, Croatia
Rapid growth of wind power sector presents great challenge for power system operators in aspect of generation scheduling, grid management, balancing and ancillary services. Traditionally ancillary services are obtained from conventional power plants. However nowadays, through different set of control possibilities, wind power plants are able to partly participate in provision of ancillary services.
This paper discusses the possibilities of providing ancillary system services by wind power plants, primarily regarding reactive power control and partially frequency control. In addition, real example is used to demonstrate the benefits from reactive power support by wind power plant to maintain regular voltage conditions in distribution network.
Combined Bidding at Power and Ancillary Service Markets
Eindhoven University of Technology, Netherlands, The
Power and ancillary service markets are strongly coupled. However, at the moment auctions are organized in such a manner that the coupling is not taken into account. Every market participant submits bids at power and/or AS markets without possibility to adjust with respect to the outcome of the other market. Inexact approximations of the actual market price induce deviations from the optimal social welfare value. In this paper, we firstly describe and analyze the consequences of power and ancillary service market coupling. Secondly, we present two different market design strategies, both of which are based on the idea of iterative auction and have goal to optimally account for power and AS coupling, enabling the overall system to maximize its social welfare. Illustrative example is used to present potential benefits and downsides that might arise as a result of introducing proposed market arrangements.
Use of the Energy Box Acting as an Ancillary Service
1Instituto Superior Tecnico (IST/UTL) - Massachusetts Institute of Technology (MIT), Portugal; 2Instituto Superior tecnico (IST/UTL)
The ancillary services are a group of power markets with the objective to support the basic services of generating capacity, energy supply and power deliver. The identification of the ancillary services depends on the grid itself and the regulation of the energy market. The possibility of the use of an Energy Box (EB) to work as an ancillary service to place bids on the Portuguese tertiary market is suggested in this work. In Portugal, among other ancillary services, it is chosen to analyze the possibility of the EB to supply power to the “tertiary reserve” (reserva terciária). This reserve is used to replace the secondary reserve allowing it to maintain the level established by the system. It is important to notice that the secondary reserve is negotiated in the previous day according to forecasts of the demand and the probability of generators failure. The tertiary reserve is negotiated posterior so it has a higher cost and requires a fast response time, characteristics that can be matched by the EB. In our paradigm the grid operator would negotiate directly with the aggregator (similar to what happens nowadays with the regular market agents), which would have centralized the biding of all the EB’s inside the microgrid and compute the aggregator’s bid.
User P-Q Diagram as a Tool in Reactive Power Trade
1Faculty of electical engineering and computing, Croatia; 2HEP d.d., Croatia
Trading with reactive power will soon become a very important part of electric energy trade. However, while trading, voltage regulation in portable and distribution systems must not be neglected. In order to balance the technical and economic aspects it is necessary to be familiar with the electric power system, the source of electric energy most of all, meaning the synchronous generator and its possibilities. These possibilities are shown in the synchronous generator P-Q diagram. We nowadays use static P-Q diagrams, provided by generator producers, which in most cases refer only to generators. This article presents a dynamic user P-Q diagram containing changeable parameters and showing a real availability of a synchronous aggregate.