Operating in the Fog: Security Management Under Uncertainty

Abstract

O OVER THE LAST TEN YEARS, WE HAVE HEARD SO OFTEN IN CONFERENCES,seminars, and workshops that the power system will soon be operated very near to its limits that this statement has become a cliché. Unfortunately, it is no longer possible to comply with the classical preventive N-1 security standards during all of the hours in a year. The system is indeed no longer able to survive all single faults without postfault actions. More and more corrective (i.e., postfault) actions are defi ned and prepared by operators, and the "cliché" is now a reality, as a matter of fact. To be more precise, it is no longer possible to maintain the N-1 security of the system at all moments by using only preventive actions, and the number of hours during which the system requires corrective actions to be secure is increasing. More and more, new special protection schemes (SPSs) are deployed to implement some of these corrective actions automatically. Devices such as phase-shifting transformers (PSTs) and static var compensators (SVCs) are added in the system to increase its controllability. As a result, the system becomes more and more complex. This state of affairs has various causes that will not disappear in the near future. One is that it is more diffi cult than ever to build new overhead lines because of the "not in my backyard" (NIMBY) attitude. People are more and more afraid of hypothetical electromagnetic effects, or they just don't like to see big towers in the landscape. This is particularly the case in protected areas, which are becoming more and more numerous around Europe. It is very diffi cult to explain the need for new interconnection lines to people who already have access to electricity at a reasonable price and with high availability. An increase in European social welfare with a positive feedback for the European economy and hopefully for all European citizens is a concept that is too theoretical compared with the negative local impact. Alternative solutions are technically complex, costly, and need even more time to be deployed.The second main reason is the massive integration of renewable but generally intermittent generation in the system. Power fl ows in the grid are created by difference in location between power sinks and sources. With a signifi cant amount of intermittent power generation, the predictability of the sources (location and levels of power injections) decreases and strongly affects the predictability of power fl ows. Furthermore, these new power plants are generally

A Gaussian mixture approach to model stochastic processes in power systems

“…8064 observations) of the aggregated power consumption of 200 residential consumers, while the second dataset has 182 time series (i.e. 104832 observations) of wind speed measurements 1 . The electrical system D used for security analyses is the IEEE 33-bus distribution test system with three additional wind farms, as illustrated in Figure 1.…”

“…The recent massive integration of renewable generation has increased the level of uncertainty in power systems, to the extent that probabilistic methods are emerging for operating electrical networks [1]. This is particularly true for the operation of distribution systems, which is progressively migrating from a fit-and-forget doctrine to Active Network Management (ANM) strategies [2].…”

Modeling and control of HVDC grids: A key challenge for the future power system

“…How this is done depends largely on expected level of reliability, the number of parallel paths (both in AC, DC and the combined system) and the involved stakeholders. It is important to note that the system reliability management occurs in different steps, from the operational planning phase up to operations [73], [74]. These steps involve different decisions in which the operation of HVDC converters needs to be taken into account.…”

“…These steps involve different decisions in which the operation of HVDC converters needs to be taken into account. They can be used to enlarge system capacity on the capacity market, reduce congestion and perform preventive or curative actions [74]. They can additionally also contribute to the exchange of ancillary services.…”

Evaluating composite approaches to modelling high-dimensional stochastic variables in power systems

“…The vast number of stochastic variables beyond the operator's control are expanding the range of possible system states, thus rendering experience-based operational practices inefficient or even obsolete [1]. Under this new reality, the use of historical data will be instrumental in informing operators of possible system states likely to occur in the near-term and providing useful information regarding the risk the system is likely to face.…”