• Energy Research

The integration of energy systems such as electricity and gas grids and power and thermal grids can bring significant benefits in terms of system security, reliability, and reduced emissions. Another alternative coupling of sectors with large potential benefits is the power and transportation networks. This is primarily due to the increasing use of electric vehicles (EV) and their demand on the power grid. Besides, the production and operating costs of EVs and battery technologies are steadily decreasing, while tax credits for EV purchase and usage are being offered to users in developed countries. The power grid is also undergoing major upgrades and changes with the aim of ensuring environmentally sustainable grids. These factors influence our work. We present a new operating model for an integrated EV-grid system that incorporates a set of aggregators (owning a fleet of EVs) with partial access to the distribution grid. Then, the Cooperative Game Theory is used to model the behavior of the system. The Core is used to describe the stability of the interaction between these aggregators, and the Shapley value is used to assign costs to them. The results obtained show the benefit of cooperation, which could lead to an overall reduction in energy consumption, reduced operating costs for electric vehicles and the distribution grid, and, in some cases, the additional monetary budget available to reinforce the transmission and grid infrastructures.

The integration of energy systems such as electricity and gas grids and power and thermal grids can bring significant benefits in terms of system security, reliability, and reduced emissions. Another alternative coupling of sectors with large potential benefits is the power and transportation networks. This is primarily due to the increasing use of electric vehicles (EV) and their demand on the power grid. Besides, the production and operating costs of EVs and battery technologies are steadily decreasing, while tax credits for EV purchase and usage are being offered to users in developed countries. The power grid is also undergoing major upgrades and changes with the aim of ensuring environmentally sustainable grids. These factors influence our work. We present a new operating model for an integrated EV-grid system that incorporates a set of aggregators (owning a fleet of EVs) with partial access to the distribution grid. Then, the Cooperative Game Theory is used to model the behavior of the system. The Core is used to describe the stability of the interaction between these aggregators, and the Shapley value is used to assign costs to them. The results obtained show the benefit of cooperation, which could lead to an overall reduction in energy consumption, reduced operating costs for electric vehicles and the distribution grid, and, in some cases, the additional monetary budget available to reinforce the transmission and grid infrastructures.

In this work, we compared the performance of the ordinary Newton-Raphson method for calculating power flows against three quasi-Newton methods: chord, “good” and “bad” Broyden's methods. First, we illustrated compared the performance of each method on systems of equations of different sizes. Secondly, we compared these methods on power flow calculation for grids of different sizes. We found that an ill-suited initial approximation strongly affects the quasi-Newton methods and makes them slower than the Newton-Raphson one. Finally, in order to fix this issue, we introduced a mixed-method: a few iterations of Newton-Raphson are used to determine a more accurate initial approximation, which can then be used in quasi-Newton methods. Numerical tests showed that this approach outperforms ordinal Newton-Raphson and quasi-Newton methods.

In this work, we compared the performance of the ordinary Newton-Raphson method for calculating power flows against three quasi-Newton methods: chord, “good” and “bad” Broyden's methods. First, we illustrated compared the performance of each method on systems of equations of different sizes. Secondly, we compared these methods on power flow calculation for grids of different sizes. We found that an ill-suited initial approximation strongly affects the quasi-Newton methods and makes them slower than the Newton-Raphson one. Finally, in order to fix this issue, we introduced a mixed-method: a few iterations of Newton-Raphson are used to determine a more accurate initial approximation, which can then be used in quasi-Newton methods. Numerical tests showed that this approach outperforms ordinal Newton-Raphson and quasi-Newton methods.

Cooperative Game Theory has recently attracted attention in power systems research as a tool for expansion planning analysis. However, this analysis is usually performed in an ex-post manner, i.e., planning and operation decisions are separated from the allocation mechanisms themselves. The existing paradigm implies selecting an allocation rule (say, the Shapley value) to share the value of cooperation and verifying its rationality (e.g., by checking the Core of the cooperative game). Additional metrics of coalitional stability are omitted. Such an ex-post approach could lead to coalitional stability issues, which may hamper the establishment of cooperation. For example, there could be a severe imbalance in players' positions, and the contribution of some players could be underestimated in the grand coalition. This paper proposes a bilevel optimization framework for explicitly incorporating Cooperative Game Theory principles into transmission expansion planning problems. Using a simple 4-system case study and a real-world case of cross-border power interconnections in Northeast Asia, we demonstrate that it is possible to make planning decisions in an anticipatory manner subject to the stability of coalitions. The identified expansion plans with enhanced coalitional stability indicate the ways of making parties more equally involved in electricity trading. Finally, we discuss the applicability of the bilevel TEP model, the properties of resulting cooperative games, and the compromise between coalitional stability and economic efficiency in transmission expansion planning.

Cooperative Game Theory has recently attracted attention in power systems research as a tool for expansion planning analysis. However, this analysis is usually performed in an ex-post manner, i.e., planning and operation decisions are separated from the allocation mechanisms themselves. The existing paradigm implies selecting an allocation rule (say, the Shapley value) to share the value of cooperation and verifying its rationality (e.g., by checking the Core of the cooperative game). Additional metrics of coalitional stability are omitted. Such an ex-post approach could lead to coalitional stability issues, which may hamper the establishment of cooperation. For example, there could be a severe imbalance in players' positions, and the contribution of some players could be underestimated in the grand coalition. This paper proposes a bilevel optimization framework for explicitly incorporating Cooperative Game Theory principles into transmission expansion planning problems. Using a simple 4-system case study and a real-world case of cross-border power interconnections in Northeast Asia, we demonstrate that it is possible to make planning decisions in an anticipatory manner subject to the stability of coalitions. The identified expansion plans with enhanced coalitional stability indicate the ways of making parties more equally involved in electricity trading. Finally, we discuss the applicability of the bilevel TEP model, the properties of resulting cooperative games, and the compromise between coalitional stability and economic efficiency in transmission expansion planning.

Dynamic capacity rating technologies of power lines has been growing in the electric power industry since 1977. Yet, its use is absent in Russia. In this study, a methodology for calculating the dynamic line rating is presented. The economic benefits related to the use of a dynamic line rating instead of the conventional static line rating is assessed for simple-but-illustrative two-zonal network representing Russia power corridor that connects Siberian and European zones. Our simulations show that the use of dynamic line rating, in comparison with a static one, results in economic savings for all the months of the year, reaching as high as 8%.