Shahab Shariat Torbaghan

A Market-Based Transmission Planning for HVDC Grid—Case Study of the North Sea

Summary form only given. There is significant interest in building HVDC transmission to carry out transnational power exchange and deliver cheaper electricity from renewable energy sources which are located far from the load centers. This paper presents a market based approach to solve a long-term TEP for meshed VSC-HVDC grids that connect regional markets. This is in general a nonlinear, non-convex large-scale optimization problem with high computational burden, partly due to the many combinations of wind and load that become possible. We developed a two-step iterative algorithm that first selects a subset of operating hours using a clustering technique, and then seeks to maximize the social welfare of all regions and minimize the investment capital of transmission infrastructure subject to technical and economic constraints. The outcome of the optimization is an optimal grid design with a topology and transmission capacities that results in congestion revenue paying off investment by the end the projects economic lifetime. Approximations are made to allow an analytical solution to the problem and demonstrate that an HVDC pricing mechanism can be consistent with an AC counterpart. The model is used to investigate development of the offshore grid in the North Sea. Simulation results are interpreted in economic terms and show the effectiveness of our proposed two-step approach.

Medium-term electricity price forecasting

Medium-term price forecasting plays an important role in electricity markets. Obtaining reasonably accurate medium-term electricity price predictions is critical in many applications, such as maintenance scheduling, generation expansion planning, and bilateral contracting. Medium-term price forecasting is a complex task because of the long forecasting horizon, dependence of medium-term electricity prices to various variables, and limited availability of explanatory data. In this paper, different aspects of a medium-term electricity price forecasting are discussed, and several data-driven 12-month-ahead approaches are developed. The presented approaches are applied to Nord Pool and the Ontario electricity market to examine their performance and effectiveness.

Local market framework for exploiting flexibility from the end users

This paper introduces a decentralized implicit interaction framework for trading flexibility available from proactive end users (prosumers) in an economically-efficient way. The proposed framework consists of two mechanisms: ahead planning via markets and real-time dispatching. The ahead, market-based planning includes two mechanisms, day-ahead and intra-day, which are operated by a local flexibility market operator. Each local market seeks to adjust the energy programs before they will be forwarded to the wholesale energy market such that, if accepted, the programs will result in no congestion issues in the distribution grid. The real-time dispatching consists of a set of control actions that are determined and implemented by the DSO to resolve a network congestion issue, should the market-based planning fail. The second part of the paper focuses on establishing a strategy for the DSO to procure the flexibility it needs from the above-mentioned day-ahead and intra-day markets, as well as through real-time dispatching, at the lowest possible cost. To this end, a hierarchical, bi-level optimization problem is proposed, which is mathematically proven to yield the optimal bidding strategy (including prices and volumes) for the DSO.

The impact of energy storage on long term transmission planning in the North Sea region

This paper presents a planning framework to investigate the impact of different levels of integration of large-scale energy storage on the development plan of a meshed HVDC grid in a power system with large-scale offshore wind. In our problem formulation, the charge/discharge schedules of energy storage are modeled in such a way that market conditions in the succeeding hours are taken into account in the power dispatch at present. Both unlimited and limited energy storage capacity scenarios are considered, and compared to a no-storage reference case. The optimal plan includes grid topology, transmission capacities, energy storage capacities and optimal energy storage schedules. The optimization model sets the transmission capacities in such a way that transmission congestion revenue collected throughout the lifetime of the infrastructure pays off the investment cost of building the grid. The proposed model is applied to study the future development of an offshore grid in the North Sea. Simulation results are assessed according to various economic indicators. Investing in energy storage is shown to be economically effective for windy offshore regions.

Impact of wind energy support schemes on the development of an offshore grid in the North Sea

There is significant interest in developing offshore wind energy in Europe. Offshore wind projects require large transmission and installation investments. Therefore supporting policies are essential to make these project more economically attractive. This paper presents a optimization planning framework to investigate the impact of implementing a support instrument at different stages of planning on the final grid design and installed offshore wind capacities. For a given level of wind support, the optimal plan includes the grid and offshore wind capacities. Optimal capacities are set in such a way that congestion revenue collected throughout the life time of the project pays off the investment cost of building the grid. At the same time the remuneration of the offshore wind farm recovers the initial investment cost. The model is used to investigate the impact of implementing a wind support plan on the development of the offshore grid in the North Sea. Numerical simulation results are interpreted in economic terms and demonstrate the effectiveness of the proposed approach.

A market-based transmission planning for HVDC grid—case study of the North Sea

There is significant interest in building HVDC transmission to carry out transnational power exchange and deliver cheaper electricity from renewable energy sources which are located far from the load centers. This paper presents a market-based approach to solve a long-term TEP for meshed VSC-HVDC grids that connect regional markets. This is in general a nonlinear, non-convex large-scale optimization problem with high computational burden, partly due to the many combinations of wind and load that become possible. We developed a two-step iterative algorithm that first selects a subset of operating hours using a clustering technique, and then seeks to maximize the social welfare of all regions and minimize the investment capital of transmission infrastructure subject to technical and economic constraints. The outcome of the optimization is an optimal grid design with a topology and transmission capacities that results in congestion revenue paying off investment by the end the projects economic lifetime. Approximations are made to allow an analytical solution to the problem and demonstrate that an HVDC pricing mechanism can be consistent with an AC counterpart. The model is used to investigate development of the offshore grid in the North Sea. Simulation results are interpreted in economic terms and show the effectiveness of our proposed two-step approach.

Short term clearing of capacity markets: An alternative approach to capacity pricing

In the presence of increasing penetration from renewable energy sources, several control areas in Europe and the US have introduced Capacity Remuneration Mechanisms (CRMs) to ensure sufficient investment in firm electricity generation capacity. However, due to their long-term focus, these mechanisms are typically uncoupled from short-term electricity markets. We introduce a new CRM design, which involves shortterm clearing of a market for generation capacity in parallel with that of the wholesale electricity market. The proposed CRM allows for participation of capacity providers from both generation and demand side. Also, emerging technologies that were not able to participate in existing CRMs due to the longterm nature of those markets (e.g., storage) are able to participate in the proposed market for generation capacity. The proposed CRM is shown to satisfy the competitiveness, fairness and energy security principles defined by the European Commission. Finally, our analysis shows that the proposed CRM can ensure supply adequacy at a lower cost when compared to rival designs, by taking advantage of daily and seasonal variability in system demand.

Optimum Transmission System Expansion Offshore Considering Renewable Energy Sources

This chapter provides an overview of transmission expansion planning (TEP) methods and their practical application. First, it discusses the strategic importance of the transmission system. Next, it describes the reasons why TEP remains a challenge for systems with a large share of renewable energy. Various TEP problems are classified, as well as the approaches that are used to solve them. Finally, the method and numerical results for the problem of planning a high voltage direct current grid in the North Sea region are shown.