Nina Detlefsen

Methodologies to Determine Operating Reserves Due to Increased Wind Power

Power systems with high wind penetration experience increased variability and uncertainty, such that determination of the required additional operating reserve is attracting a significant amount of attention and research. This paper presents methods used in recent wind integration analyses and operating practice, with key results that compare different methods or data. Wind integration analysis over the past several years has shown that wind variability need not be seen as a contingency event. The impact of wind will be seen in the reserves for nonevent operation (normal operation dealing with deviations from schedules). Wind power will also result in some events of larger variability and large forecast errors that could be categorized as slow events. The level of operating reserve that is induced by wind is not constant during all hours of the year, so that dynamic allocation of reserves will reduce the amount of reserves needed in the system for most hours. The paper concludes with recent emerging trends.

Risk and vulnerability analysis of power systems including extraordinary events

This paper describes a framework and methodology for risk and vulnerability analysis including extraordinary events in power systems. The framework is based on a bow-tie structure and identifies threats, unwanted events, barriers and consequences. Application of the methodology is shown for a real case analyzing extraordinary events in a transmission system. In this case the consequence is unacceptable, but the risk is moderate due to the low probability for the event to occur. The case study and experience so far indicates that one of the most challenging parts of a risk and vulnerability analysis is how to identify the vulnerable operational states and extraordinary events.

Managing critical weather conditions in a large-scale wind based European power system — The twenties project

Experience from existing large offshore wind farms show that the geographical concentration of wind power leads to increased wind power variability, and that the response to storm front passages raises new issues: this may lead to a sudden shut down of the wind farm when the wind speed exceeds the cut-off wind speed (typically 25 m/s). Experience has shown that a large offshore wind farm in this way can be shut down from full power to zero power in less than 5 minutes. Thus, in the planned offshore development in the North Sea, several GW of wind power could be shut down within less than one hour as a result of a storm passage, which may impact the security of the whole European electric system. The storm passages will be a threat to the whole system reliability and stability, unless the wind power shut down is carefully coordinated.

Hydropower flexibility and transmission expansion to support integration of offshore wind

Abstract In 2013, offshore wind grew over 50%. This increase, concentrated in a relatively small geographical area, can lead to an increased variability of the power produced by offshore wind. The variability is one of the key issues, along transmission, in integrating offshore wind power. Hydro power is one of the fast responding sources of electricity, thus power systems with considerable amounts of flexible hydro power can potentially offer easier integration of offshore wind power. The interaction between offshore wind and hydro power can be benefic, especially when looking at how the flexibility of hydro generation can match the variability of offshore wind, allowing for larger shares of variable generation to be integrated in the power systems without decreasing its stability. The analysis includes two interrelated models, a market model and a flow-based model. The results show that hydropower systems are a very good option for balancing the natural variability of wind power production, especially when installed offshore. The flexibility of hydropower systems allows power systems with a high share of RES to maintain stability. The analysis presented indicates that the value of hydropower flexibility to the European power system is significant, consequently justifying the investment costs for transmission expansion.

Offshore variability in critical weather conditions in large-scale wind based Danish power system

Offshore wind power has a significant development potential, especially in North Europe. The geographical concentration of offshore wind power leads to increased variability and in the case of critical weather conditions it may lead to sudden and considerable loss of production. In this context, the chances of losing several GW of wind power due to critical weather conditions in a very short time period could potentially jeopardize the whole systems reliability and stability. Forecasting such events is not trivial and the results so far are not encouraging. When assessing the impact of the variability for the 2020 Danish power system, one can see that in the worst case, up to 1500 MW of power can be lost in 30 minutes. We present results showing how this issue is partially solved by the new High Wind Storm Controller presented by Siemens in the TWENTIES project.