Additional Transmission Capacity Research Articles

Cost-Effective Target Capacity Assessment in the Energy Transition: The Italian Methodology

Long-term transmission expansion planning has to face the energy transition in a restructured electricity market environment. Increased transmission capacity within and between Member States is likely to play an essential role in maintaining the secure and economic operation of the whole European power system and ensuring the integration of growing renewable generation. This paper proposes a novel iterative methodology aimed at assessing an optimal level of interconnection between relevant bidding zones, simultaneously investigating different potential alternatives. Starting from a reference grid, a multi-criteria analysis is adopted to select the additional transmission capacities to be tested in each iteration via network and market simulations in order to confirm that transmission expansion benefits outweigh the estimated realization costs. The proposed approach is applied to the Italian case in two contrasting energy scenarios for the mid-term 2030 and very-long-term 2040 horizons: different development strategies are derived, and the least regret criterion is applied to define the most cost-effective as the target development strategy for the Transmission System Operator (TSO). Furthermore, sensitivity analyses on relevant input data variation are performed to test the robustness of the results obtained.

Long-Term Multiyear Transmission Expansion Planning in Turkish Power System

To sustain the clean energy transition without interruption and to ensure the reliable operation of the transmission system, it is required to have enough additional transmission capacity in the future horizons. The transmission expansion planning (TEP) problem is a core issue in deciding additional transmission capacity in the planning activities. TEP aims to find the best expansion plan while satisfying technical and economic constraints. In this study, a new binary version of the original FBI algorithm called the BFBI (binary forensic-based investigation) algorithm is developed to solve the binary TEP problem. The effectiveness and performance of the developed BFBI are assessed by implementing it in two different test systems: the standard Garver 6-bus test system and the modified 400 kV Turkish grid. Seasonal scenarios are created for 5- and 10-year planning periods to cover all possible generation and load conditions and to assess the impact of the increased share of RES on the grid in the TEP studies conducted for the modified 400 kV Turkish grid created as a bulk realistic grid. The TEP problem is solved by including investment, reliability, and operational costs in two different objective functions for cases while considering the N-1 contingency criterion. The efficacy and robustness of the BFBI algorithm are justified by comparing it with well-known algorithms such as GA and PSO.

Influence of bioenergy and transmission expansion on electrical energy storage requirements in a gradually decarbonized European power system

With the ongoing energy transition in Europe, the share of variable renewable energies (VRE) in the power system increases steadily and different flexibility options gain importance. This work investigates the deployment of supply side flexibility options in the future European power system by energy system modelling focusing on classic power storage technologies, hydrogen storage, generation by biomass and grid expansion. While investigating different flexibility availability scenarios, for the first time the competition of long-term flexibility options is investigated across a broad decarbonization spectrum. In all scenarios, an increasing need for additional flexibility options is found for moderate decarbonization levels with VRE shares higher than 50%. From there on, the deployment of power storages grows nonlinearly, and eventually features a remarkable leap when approaching a zero-emission system, which is mainly driven by hydrogen storage investments. This also comes along with a leap in the total system costs. When the expansion of biomass capacities is available, biomass partly takes over the function of hydrogen as a long-term flexibility option. When enabling grid expansion, additional transmission capacities lead to a stronger integration of wind generation, while (especially short-term) storage requirements for higher decarbonization levels decrease. Both the additional investments into biomass generation and transmission grid result in up to 4% lower total system costs, yet, without completely displacing any other flexibility option. We conclude that the interaction of multiply flexibility options will lead to a cost minimal power system.

Minimizing habitat conflicts in meeting net-zero energy targets in the western United States

The scale and pace of energy infrastructure development required to achieve net-zero greenhouse gas (GHG) emissions are unprecedented, yet our understanding of how to minimize its potential impacts on land and ocean use and natural resources is inadequate. Using high-resolution energy and land-use modeling, we developed spatially explicit scenarios for reaching an economy-wide net-zero GHG target in the western United States by 2050. We found that among net-zero policy cases that vary the rate of transportation and building electrification and use of fossil fuels, nuclear generation, and biomass, the "High Electrification" case, which utilizes electricity generation the most efficiently, had the lowest total land and ocean area requirements (84,000 to 105,000 km2 vs. 88,100 to 158,000 km2 across all other cases). Different levels of land and ocean use protections were applied to determine their effect on siting, environmental and social impacts, and energy costs. Meeting the net-zero target with stronger land and ocean use protections did not significantly alter the share of different energy generation technologies and only increased system costs by 3%, but decreased additional interstate transmission capacity by 20%. Yet, failure to avoid development in areas with high conservation value is likely to result in substantial habitat loss.

The cost effectiveness of new reservoir hydroelectricity: British Columbia’s Site C project

Large-scale, reservoir hydroelectric facilities can play an important role in decarbonizing the electricity sector. However, new hydroelectric facilities are costly, and several recent projects in Canada have been subject to cost over-runs. In this paper, we develop a methodology for evaluating the cost-effectiveness of new reservoir hydroelectric projects. We apply this methodology to a case study of the Site C hydroelectric project currently under construction in British Columbia, Canada. Our approach makes use of a purpose-built linear programming capacity expansion and dispatch model, resolved at an hourly frequency and incorporating detailed treatment of balancing area requirements, available wind and solar resources, watershed constraints on hydroelectric potential, and endogenous electricity trade. Our simulations reveal that the value of the Site C project is unlikely to exceed its total cost, and only exceeds the avoidable cost of project cancellation in scenarios where BC and Alberta build additional inter-provincial transmission capacity and aim for 100% decarbonization of their electricity systems. Site C provides a cautionary tale for policymakers and planners pursuing large hydro-electric projects. Potential cost over-runs can render large hydroelectric projects uneconomic relative to alternatives. The decision to complete the Site C project is only justified by its high sunk costs.

The Economics of the Site C Hydroelectric Project in British Columbia

The Site C hydroelectric project is an 1100-Megawatt hydroelectric facility under development on the Peace River in British Columbia. Construction costs for the project are currently estimated to be $10.7 billion. The project has been criticized for its high cost and the impacts it will have on the river system, including the flooding of land to establish the reservoir. Project proponents argue that Site C will provide low-carbon electricity that will help BC and Canada reach their greenhouse gas emission reduction goals. In this paper, we assess the cost-effectiveness of the Site C project using a detailed linear programming capacity expansion and dispatch model of the British Columbia and Alberta electricity systems. Our model includes hourly electricity demand data for sixteen sub-regions within BC and Alberta, hourly wind resource data for 681 grid cells in the two provinces, hourly solar irradiation data from 112 weather stations to characterize the solar resource, and a detailed hydroelectric model that accounts for the chaining of hydroelectric facilities and reservoirs within the Peace River, Columbia River, Kootenay River and Bridge River watersheds. We assess the value of the Site C project by calculating the optimal electricity system for supplying BC and Alberta electricity demand in 2030 both with and without the presence of the Site C project. Our model simulations reveal that under current electricity sector policies, the Site C project is uneconomic. We find that the value created by Site C only exceeds its costs in scenarios where BC and Alberta coordinate electricity markets, build additional transmission capacity, and work to reduce greenhouse gas emissions significantly below baseline levels.

An advanced method for steady-state security assessment considering dynamic thermal capacities of grid assets

The ( $n-1$ ) criterion is a commonly used criterion for secure grid operation. Violations of this criterion lead to remedial actions in the short term and the construction of additional transmission capacities in the long term to reduce congestions in the grid. An alternative strategy in reducing necessary interventions is to consider the natural dependency of the transmission capacity of an installed grid component from its environmental conditions. The application of dynamic component rating is offering additional transmission capacities for system operation. For the consideration of these capabilities in the day-ahead operation planning, forecasting the trend of the component ratings is needed. The implementation of such methods, especially for overhead lines, is tested by different system operators around the world. A further strategy in enhancing transmission capacity for the operation is to utilize the thermal inertia of a component for small and short exceedances of the ratings without violating the component’s thermal limits. Currently available static emergency ratings of components respect this capability. Component ratings as well as emergency ratings are dependent on environmental conditions. Furthermore, the available emergency operation duration is dependent on the development of the loading current in the recent past. By equipping assets with real-time monitoring systems, utilization of the component’s current transmission capacity is possible for the different operation states. This paper presents a method to consider the thermal transmission capacity of power system components, enabled by real-time monitoring systems, in the contingency analysis. The approach is an assessment at system level combined with a time-domain simulation for the evaluation of the impact of an examined contingency on a component’s relevant thermal parameters. The result of the method is compatible with the current binary statement but extended with an availability duration if a contingency occurs in the examined grid. Introducing this duration can assist the planning of curative remedial actions for the operation. Further, three specific durations were proposed for benchmarking a contingency in the different levels of analysis. These durations are the result of the time-domain simulation. The presented method is capable of analysing a network consisting of assets equipped with a monitoring system and assets without such a system. The second part of this paper presents the operation simulation of an exemplary grid for one operational year to illustrate the effect of the approach on the results of the contingency analysis in day-ahead planning.

Social welfare impact from enhanced Trans-Asian electricity trade

Long distance power transmission is commonly considered as an option for reducing carbon footprint in future electricity systems. Accordingly, this article presents economic insights in a transcontinental power interconnection linking four Asian countries with Europe. Enhanced electricity trade through the interconnected countries is assessed via techno-economic modelling. For this purpose two electricity system scenarios are developed for the year 2040: (i) a Reference Scenario, where electricity system development follows the plans of the involved system operators and (ii) a so-called Trans-Asia Scenario, where additional power transmission capacities are added to strengthen the electricity trading route crossing the interconnected countries: Turkey, Georgia, Azerbaijan and Kazakhstan. Economic benefits arising from the proposed Trans-Asia Scenario are estimated as a change in social welfare in the electricity system. Modelling results show a 140 M€ increase in annual social welfare for the Trans-Asia Scenario. The subsequent cost-benefit analysis results in a net present value in the range of −221 M€ to 534 M€, at a discount rate of 4%. This implies that over a life-cycle period of 40 years, the evaluated economic benefit may compensate investments between 1598 M€ and 3251 M€ needed for the additional power transmission capacities.

Co-optimization of multi-stage transmission expansion planning and grid operation

The ongoing transformation of the power system characterized by an increased share of renewable energy sources requires additional transmission capacities. Nevertheless, the need for new transmission capacities can be reduced by optimizing grid operation. This contribution presents a novel approach to the co-optimization of multi-stage transmission expansion planning and grid operation within a mixed-integer linear programming formulation. The expansion via AC systems and phase shifting transformers (PSTs) is combined with the control of PSTs and the determination of congestion management interventions such as redispatch of power plants or curtailment of renewable energies. The number of potential expansion candidates is reduced by linear programming relaxations. Exemplary results based on a synthetic test system containing 120 buses evidence the impact of the proposed approach on overall system costs. The proposed co-optimization reduces the total costs by 16.5 % when applied instead of the sole expansion via AC technology.

Transmission expansion planning via power flow controlling technologies

The transition from conventional towards renewable energy systems requires additional transmission capacities and higher operational flexibility to overcome contingency situations. This study presents a novel transmission expansion planning approach for the simultaneous placement of AC systems and power flow controlling technologies including high voltage direct current, phase shifting transformers (PSTs) and thyristor controlled series compensators (TCSCs). The approach is formulated as a mixed-integer linear programming optimisation problem and the operating point of power flow controlling devices is endogenously determined by minimising expansion costs. Both PSTs and TCSCs are integrated into the optimisation problem by means of new mathematical formulations. PSTs are presented in more detail considering the PST impedance, which is modelled as an equivalent phase shift. The controllable series impedance of TCSCs is also represented as an equivalent phase shift. Exemplary results based on a synthetic 120 bus system show a significant potential of PSTs and TCSCs to reduce expansion costs as well as to lower the requirement for new transmission capacities. The simultaneous employment of these technologies reduces the expansion costs within the test system between 18.7 and 32.4% compared to those costs generated by the sole reinforcement by AC systems.

Lightening the load: quantifying the potential for energy-efficient lighting to reduce peaks in electricity demand

One of the key challenges to greater renewable electricity supplies is the temporal mismatch between non-dispatchable renewable sources and peaks in electricity demand. In addition, increased electrification coupled with the de-carbonisation of electricity generation is likely to increase the scale of demand peaks. This could force investment in carbon-intensive peaker generation or capital intensive storage capacity as well as additional transmission and distribution network capacity which may then be substantially underutilised. Whilst considerable effort has been devoted to testing a range of demand response interventions to reduce or shift consumption, less attention has been given to the ability of certain appliances to permanently reduce demand at peak through energy efficiency. In this paper, we use a published model of future energy-efficient lighting uptake together with multi-year measured lighting demand data from a sample of residential households to model the potential power (MW) and energy (MWh) reductions of a ‘business as usual’ rate of efficient lighting adoption. Our estimates suggest that whilst lighting comprises ~ 4% of overall New Zealand annual electricity consumption, it comprises up to 12% of evening peak electricity consumption in winter. As a result, we estimate that by 2029, more efficient residential lighting could reduce New Zealand’s total annual demand by 1 TWh and reduce the highest winter evening peaks (at 17:00) by at least 500 MW (9%). The winter evening demand reduction would be roughly equivalent to avoiding the need for additional generation capacity of the scale of New Zealand’s Huntly Power Stations 1–4 (coal/gas) plus the Stratford peaker plant (gas open-cycle) and has clear implications for any electricity system that is intending to transition towards ~ 100% renewable generation at least cost.

The cost of a future low-carbon electricity system without nuclear power – the case of Sweden

To achieve the goal of deep decarbonization of the electricity system, more and more variable renewable energy (VRE) is being adopted. However, there is no consensus among researchers on whether the goal can be accomplished without large cost escalation if nuclear power is excluded in the future electricity system. In Sweden, where nuclear power generated 41% of the annual electricity supply in 2014, the official goal is 100% renewable electricity production by 2040. Therefore, we investigate the cost of a future low-carbon electricity system without nuclear power for Sweden. We model the European electricity system with a focus on Sweden and run a techno-economic cost optimization model for capacity investment and dispatch of generation, transmission, storage and demand-response, under a CO2 emission constraint of 10 g/kWh. Our results show that there are no, or only minor, cost benefits to reinvest in nuclear power plants in Sweden once the old ones are decommissioned. This holds for a large range of assumptions on technology costs and possibilities for investment in additional transmission capacity. We contrast our results with the recent study that claims severe cost penalties for not allowing nuclear power in Sweden and discuss the implications of methodology choice.

Availability and Fade Margin Calculations for 5G Microwave and Millimeter-Wave Anyhaul Links

The deployment of new radio access technologies always provides a good opportunity and timing to optimize the existing mobile front- and backhaul (commonly called “anyhaul”). The legacy systems (Long-Term Evolution (LTE), High-Speed Packet Access (HSPA), third-generation mobile (3G), second-generation mobile (2G)) already extensively utilize the transmission and transport capacities of the mobile anyhaul. With the current launch of 5G (fifth-generation mobile) and recent LTE-A (Advanced Long-Term Evolution), additional new transmission capacities are required again. Depending on the traffic and network topology, additional cell sites are built, and even more locations are connected with fiber optics. The existing microwave and millimeter-wave links are rotated toward those aggregation points that already have optical-fiber access. Due to the increased cell-site density, the average distance of the radio access links can be reduced by network and topology optimization. The reduced hop lengths combined with adaptive modulation and automatic power control bring an opportunity for capacity increase in shortened radio links. Links newly deployed for 5G find a wide spectrum in the millimetric V, E, W, and D frequency bands. This paper discusses the availability and hop-length targets of the anyhaul links that should be carefully kept by proper planning and monitoring.

Quantifying the Potential Economic Benefits of Flexible Industrial Demand in the European Power System

The envisaged decarbonization of the European power system introduces complex techno-economic challenges to its operation and development. Demand flexibility can significantly contribute in addressing these challenges and enable a cost-effective transition to the low-carbon future. Although extensive previous work has analyzed the impacts of residential and commercial demand flexibility, the respective potential of the industrial sector has not yet been thoroughly investigated despite its large size. This paper presents a novel, whole-system modeling framework to comprehensively quantify the potential economic benefits of flexible industrial demand (FID) for the European power system. This framework considers generation, transmission, and distribution sectors of the system, and determines the least-cost long-term investment and short-term operation decisions. FID is represented through a generic, process-agnostic model, which, however, accounts for fixed energy requirements and load recovery effects associated with industrial processes. The numerical studies demonstrate multiple significant value streams of FID in Europe, including capital cost savings by avoiding investments in additional generation and transmission capacity and distribution reinforcements, as well as operating cost savings by enabling higher utilization of renewable generation sources and providing balancing services.

Transmission Expansion Planning Considering an Hourly Demand Curve

This paper discusses the impact that different approximations have on the Transmission Expansion Planning (TEP) problem. Due to the long decision horizons involved, the number of variables can make the problem intractable if approximations to the problem are not made. Furthermore, new emerging technologies and changes in the way we operate our systems are putting under scrutiny some of the approximations usually made to the problem. In this context, this paper evaluates the effect on investment and operational costs of including operational constraints of generators (ramping), transmission losses, and N-1 security constraints on the TEP problem. TEP is formulated as a mixed-integer linear program (MILP). We first validate our analysis using the Garver test system. Then, the importance of including the aforementioned constraints to TEP is tested with the 24-bus and 118-bus IEEE systems. Our results show that additional transmission capacity may be required to satisfy the flexibility requirements caused by net load ramps.

Households’ hourly electricity consumption and peak demand in Denmark

The electrification of residential energy demand for heating and transportation is expected to increase peak load and require additional generation and transmission capacities. Electrification also provides an opportunity to increase demand response. With a focus on household electricity consumption, we analyse the contribution of appliances and new services, such as individual heat pumps and electric vehicles, to peak consumption and the need for demand response incentives to reduce the peak.Initially, the paper presents a new model that represents the hourly electricity consumption profile of households in Denmark. The model considers hourly consumption profiles for different household appliances and their contribution to annual household electricity consumption. When applying the model to an official scenario for annual electricity consumption, assuming non-flexible consumption due to a considerable introduction of electric vehicles and individual heat pumps, household consumption is expected to increase considerably, especially peak hour consumption is expected to increase.Next the paper presents results from a new experiment where household customers are given economic and/or environmental incentives to shift consumption to or away from specified hours. The experiment focuses on the present classic consumption and shows that household customers do react to incentives, but today the flexibility of the classic consumption is limited. Considering electric vehicles and individual heat pumps, for an individual household, the consumption of each of these technologies roughly doubles the household’s consumption and considerably increases their potential for flexibility. Thus, in order to introduce incentives for demand flexibility, while considering reducing peak consumption, policy makers should initially focus on households that have a heat pump and/or an electric vehicle.

PENERAPAN DOUBLY-FED INDUCTION GENERATOR (DFIG) UNTUK PEMBANGKIT LISTRIK TENAGA ANGIN

Wind energy has become one of the most important and promising sources of renewable energy, which demands additional transmission capacity and better means of maintaining system reliability. The evolution of technology related to wind systems industry leaded to the development of a generation of variable speed wind turbines that present many advantages compared to the fixed speed wind turbines. These wind energy conversion systems are connected to the grid through Voltage Source Converters (VSC) to make variable speed operation possible. The studied system here is a variable speed wind generation system based on Doubly Fed Induction Generator (DFIG). The rotor side converter (RSC) usually provides active and reactive power control of the machine while the grid-side converter (GSC) keeps the voltage of the DC-link constant. The additional freedom of reactive power generation by the GSC is usually not used due to the fact that it is more preferable to do so using the RSC. However, within the available current capacity the GSC can be controlled to participate in reactive power generation in steady state as well as during low voltage periods. The GSC can supply the required reactive current very quickly while the RSC passes the current through the machine resulting in a delay. Both converters can be temporarily overloaded, so the DFIG is able to provide a considerable contribution to grid voltage support during short circuit periods. This report deals with the introduction of DFIG, AC/DC/AC converter control and finally the SIMULINK/MATLAB simulation for isolated Induction generator as well as for grid connected Doubly Fed Induction Generator and corresponding results and waveforms are displayed.

Stepwise Investment Plan Optimization for Large Scale and Multi-Zonal Transmission System Expansion

This paper develops a long term transmission expansion optimization methodology taking the probabilistic nature of generation and demand, spatial aspects of transmission investments and different technologies into account. The developed methodology delivers a stepwise investment plan to achieve the optimal grid expansion for additional transmission capacity between different zones. In this paper, the optimization methodology is applied to the Spanish and French transmission systems for long term optimization of investments in interconnection capacity.

Day and Night Utilization of Solar PV System Integrated with Stand Alone Wind Generator for Real and Reactive Power Management in Three Phase Unbalanced Load <sup></sup>

Utilizing the renewable energy at consumer side is not required additional transmission capacity. Solar power plant connected with wind generator can support real and reactive power to the unbalance three phase loads. The unbalance load always requires more reactive power compare to balanced load. The reactive power support demand of the unbalanced load is supplied by any conventional FACTS devices. These conventional devices add additional cost and require maintenance also. In this proposed system Voltage Source Inverter (VSI) based solar power plant acts like a STATCOM and reduces the additional cost requirement. The unbalanced three phase load have different reactive power requirement for individual phase. The PWM based FACTS devices supplies only balanced reactive power support irrespective of their requirement. It leads to poor compensation and requires large size of FACTS devices. In this paper the Individual Phase Current sensing method is used and the performance of the system is analyzed for PI controller. The MATLAB simulation verification is presented. Keywords : Solar power plant, Wind power plant, FACTS devices, IPCS, PI, Fuzzy logic.

A Novel Control Strategy for a DFIG Based Wind Power under Unbalanced Conditions <sup></sup>

This paper deals about an effective control strategy for wind power plant to bring out additional transmission capacity and better means of maintaining system reliability when compared to already existing control techniques. The rotor power of Doubly Fed Induction Generator (DFIG) is the only controlling parameter taken to determine four current reference values using this single strategy. These references are fed to rotor side and grid side current controllers which enables torque, grid side real and reactive power, as well as pitch angle control resulting in more prominent solution. This control strategy therefore relieves the need for switching between different controllers or reconfiguration of the hardware and it also provides automatic voltage and frequency regulation for network. The effectiveness and robustness of the proposed control strategy is studied through simulation carried out on detailed switched model of the system in the PSCAD/EMTDC version 4.2 software environment.