Large-scale Renewable Integration Research Articles

Offshore oil and gas infrastructure electrification and offshore wind: a legal exploration

Abstract The oil and gas and renewable energy sectors are increasingly coming together as traditional hydrocarbon producers are exploring the large-scale integration of renewables in fossil-fuel projects. One option is the electrification of oil and gas production platforms in the offshore environment utilizing offshore wind energy to power the asset’s operations. This article assesses the rationale for such a shift as well as regulatory avenues and barriers to the electrification of offshore oil and gas assets through offshore wind energy technology. While the article’s explorations are of a general conceptual nature, this article studies existing and planned developments in Norway and Atlantic Canada. This article discusses key factors to determine the legal nature of different electrification project models and proposes solutions to identify the likely legislative and regulatory regime(s) which will govern. The article concludes that reforms for a forward-thinking legal and regulatory environment for the offshore space will have to re-examine the role of existing (platform) and new (wind but also oil and gas) offshore infrastructure and the associated regime that applies to these projects. Currently, in the Norwegian and Canadian contexts, these discussions are somewhat exploratory. They do, however, underline the importance of planning the co-development of offshore wind energy projects with existing and future oil and gas projects and to highlight the need for greater clarity in the evolving design of legal and regulatory frameworks to support the future of the global offshore energy sector.

Multi-time-scale capacity credit assessment of renewable and energy storage considering complex operational time series

Large-scale renewable integration presents an effective way to decarbonize power grids, but carries increased risk of supply shortfalls owing to its volatility and uncertainty. Storage is a promising option to improve the generation adequacy of renewable. Thus, capacity credit assessment of renewable and storage is crucial in ensuring adequate generation capacity to meet loads. However, efficiently and accurately assessing capacity credit of these resources is challenging due to temporal dependencies in the operational time series (net loads and conventional generation units) and the need for extensive operation simulations. This paper develops a comprehensive multi-time-scale assessment framework integrating analytical and simulation methods to calculate the capacity credit of renewable and storage, thus capturing temporal features of these time series. Then, an interval-based strategy is proposed to simulate system operations, incorporating demand response in key scenarios. Furthermore, partitioning around medoids clustering and parallel computing techniques are employed to greatly accelerate the numerous operations for capacity credit assessment. The proposed method is validated using the RTS-79 system and a provincial real-world power grid in China. The results indicate that the developed framework can achieve efficient and refined capacity credit assessment and thus evaluate the impact of storage on the capacity credit.

Multi-objective reactive power optimization strategy of power system considering large-scale renewable integration

To fully tap the abilities of renewables in reactive power optimization, this paper develops a detailed model for the power regulation capabilities of wind turbines and photovoltaic units and studies their impact on the power system’s operation. First, the power system model with renewables integration is established using AC power flow. The wind turbines and photovoltaic units are modeled in detail according to their topologies and operating characteristics, and then further simplified according to the feasible region. An improved DC power flow model is adopted to handle the non-linear characteristics of the power system. On this basis, a multi-objective reactive power optimization model is constructed to minimize the power generation cost, wind and solar power curtailment, and voltage offset. Finally, comparisons between two types of models in different scenarios are designed. Numerical simulations demonstrate that the participation of renewables in reactive power regulation can improve the operational economy and voltage stability of power systems.

Sector coupling of electricity, transport and cooling with high share integration of renewables in Indonesia

Sector coupling improves energy system efficiency by maximising potential synergies among energy sectors. This paper aims to assess the sector coupling of electricity, transport, and cooling on the Java and Bali islands, Indonesia. Future energy systems in 2040, focussing on decarbonised electricity sector with high electric vehicles deployment and district cooling penetration, were simulated using EnergyPLAN. A bottom-up calculation approach was applied to determine demand in the transport sector. In the cooling sector, geospatial analysis was employed to quantify cooling demand and locate potential district cooling networks in Jakarta. Six scenarios were explored based on their energy demand and supply characteristics. Modelling results show that the sector coupling of three sectors could reduce primary energy supply (PES), CO2 emissions and annual costs. The most suitable scenario has about 8% lower PES, 14% lower CO2 emissions and 2% less annual costs compared to the business-as-usual scenario. Results also show that transport electrification could only effectively and significantly decrease CO2 emissions if its electricity demand is produced from renewables. Transport electrification with large scale integration of renewables could also lower the annual costs by decreasing fossil fuel costs in the transport and electricity sectors.

Advanced Techniques for the Modeling and Simulation of Energy Networks

The need for a “smarter” energy grid infrastructure, with the large-scale integration of renewables and a better demand–response mechanism, is leading to an ever-increasing complexity of next-generation energy networks [...]

The Impact of Overlap Period on the Stability of Current-Controlled Alternate Arm Converter Based on dq Frame Impedance Analysis

As a variant modular converter configuration, the alternate arm converter (AAC) is well-suited for high-voltage power transmission and large-scale integration of renewables. In contrast to conventional multilevel converters, the director switches in the arms of AAC lead to the introduction of an overlap period, during which circuiting current can flow through the two arms in the same phase. Thus, fixed or variable overlap period control can be implemented in AAC systems so as to dynamically balance stored arm energy. However, the control of overlap period is linked to instability issues that might impede the safe operation of AAC systems, which are yet to be reported. In this paper, the stability of an AAC system is demonstrated based on measured grid and converter impedance, in conjunction with impedance-based stability criterion in the dq frame. The interaction between harmonic sources at AC and DC sides of the AAC system is analyzed to determine resonant frequencies in the AC current when any potential resonance is identified in the dq frame. Novel results with respect to the impact of overlap period on the system stability are obtained by depicting and comparing the Eigenloci in the polar plot, which are validated by real-time simulations.

Hierarchical Power Flow Control in Smart Grids: Enhancing Rotor Angle and Frequency Stability with Demand-Side Flexibility

Large-scale integration of renewables in power systems gives rise to new challenges for keeping synchronization and frequency stability in volatile and uncertain power flow states. To ensure the safety of operation, the system must maintain adequate disturbance rejection capability at the time scales of both rotor angle and system frequency dynamics. This calls for flexibility to be exploited on both the generation and demand sides, compensating volatility and ensuring stability at the two separate time scales. This article proposes a hierarchical power flow control architecture that involves both transmission and distribution networks as well as individual buildings to enhance both small-signal rotor angle stability and frequency stability of the transmission network. The proposed architecture consists of a transmission-level optimizer enhancing system damping ratios, a distribution-level controller following transmission commands and providing frequency support, and a building-level scheduler accounting for quality of service and following the distribution-level targets. We validate the feasibility and performance of the whole control architecture through real-time hardware-in-loop tests involving real-world transmission and distribution network models along with real devices at the Stone Edge Farm Microgrid.

Large-scale integration of offshore wind into the Japanese power grid

Offshore wind power attracts intensive attention for decarbonizing power supply in Japan, because Japan has 1600 GW of offshore wind potential in contrast with 300 GW of onshore wind. Offshore wind availability in Japan, however, is significantly constrained by seacoast geography where very deep ocean is close to its coastal line, and eventually, nearly 80% of offshore wind resource is found in an ocean depth deeper than 50 m. Therefore, power system planning should consider both the location of available offshore wind resource and the constraint of power grid integration. This paper analyzes the impact of power grid integration of renewable resources including offshore wind power by considering the detailed location of offshore wind resource and the detailed topology of power grid. The study is performed by an optimal power generation mix model, highlighted by detailed spatial resolution derived from 383 nodes and 472 bulk power transmission lines with hourly temporal resolution through a year. The model identifies the optimal integration of power generation from variable renewables, including offshore wind, given those predetermined capacities. The results imply that, together with extensive solar PV integration, total 33 GW of offshore wind, composed of 20 GW of fixed foundation offshore wind and 13 GW of floating offshore wind could contribute to achieve 50% of renewable penetration in the power supply of Japan, and that scale of offshore wind integration provides a technically feasible picture of large-scale renewable integration in the Japanese power sector.

Impact of hydrogen admixture on interacting premixed flames in domestic boilers

The injection of hydrogen into the natural gas network can contribute to the large-scale integration of renewables, as hydrogen can be easily produced through electrolysis from wind or solar energy. However, the addition of hydrogen to natural gas influences fuel properties, asking for the assessment of the safe and efficient operation of existing end-user equipment, such as domestic burners and boilers. In this work, 3-dimensional resolved numerical simulations based on Computational Fluid Dynamics are carried out to shed light on the effect of H2 addition on the combustion process occurring in condensing boilers equipped with perforated cylindrical burners. To this purpose, multi-hole geometries emulating a portion of a perforated burner are analyzed. Since the burner holes are positioned very close to each other, the interaction of the adjacent laminar premixed flames is observed to occur with influence on the flow and thermo-chemical fields which differ from those of a single premixed flame. The addition of hydrogen was found to lead to an anticipation of the reaction zone, although the general features observed with the G222 gas (23% H2, 77% CH4 ) were alike those of the G20 gas (100% CH4).

Flexibility Assessment of Multi-Energy Residential and Commercial Buildings

With the growing concern about decreasing CO 2 emissions, renewable energy sources are being vastly integrated in the energy systems worldwide. This will bring new challenges to the network operators, which will need to find sources of flexibility to cope with the variable-output nature of these technologies. Demand response and multi-energy systems are being widely studied and considered as a promising solution to mitigate possible problems that may occur in the energy systems due to the large-scale integration of renewables. In this work, an optimal model to manage the resources and loads within residential and commercial buildings was developed, considering consumers preferences, electrical network restrictions and CO 2 emissions. The flexibility that these buildings can provide was analyzed and quantified. Additionally, it was shown how this model can be used to solve technical problems in electrical networks, comparing the performance of two scenarios of flexibility provision: flexibility obtained only from electrical loads vs. flexibility obtained from multi-energy loads. It was proved that multi-energy systems bring more options of flexibility, as they can rely on non-electrical resources to supply the same energy needs and thus relieve the electrical network. It was also found that commercial buildings can offer more flexibility during the day, while residential buildings can offer more during the morning and evening. Nonetheless, Multi-Energy System (MES) buildings end up having higher CO 2 emissions due to a higher consumption of natural gas.

Sizing and Allocation of Battery Energy Storage Systems in Åland Islands for Large-Scale Integration of Renewables and Electric Ferry Charging Stations

The stringent emission rules set by international maritime organisation and European Directives force ships and harbours to constrain their environmental pollution within certain targets and enable them to employ renewable energy sources. To this end, harbour grids are shifting towards renewable energy sources to cope with the growing demand for an onshore power supply and battery-charging stations for modern ships. However, it is necessary to accurately size and locate battery energy storage systems for any operational harbour grid to compensate the fluctuating power supply from renewable energy sources as well as meet the predicted maximum load demand without expanding the power capacities of transmission lines. In this paper, the equivalent circuit battery model of nickel–cobalt–manganese-oxide chemistry has been utilised for the sizing of a lithium-ion battery energy storage system, considering all the parameters affecting its performance. A battery cell model has been developed in the Matlab/Simulink platform, and subsequently an algorithm has been developed for the design of an appropriate size of lithium-ion battery energy storage systems. The developed algorithm has been applied by considering real data of a harbour grid in the Åland Islands, and the simulation results validate that the sizes and locations of battery energy storage systems are accurate enough for the harbour grid in the Åland Islands to meet the predicted maximum load demand of multiple new electric ferry charging stations for the years 2022 and 2030. Moreover, integrating battery energy storage systems with renewables helps to increase the reliability and defer capital cost investments of upgrading the ratings of transmission lines and other electrical equipment in the Åland Islands grid.

Multi-Flexibility Option Integration to Cope With Large-Scale Integration of Renewables

Conventional electrical networks are slowly changing. A strong sense of policy urges as well as commitments have recently been surfacing in many countries to integrate more environmentally friendly energy sources into electrical systems. In particular, stern efforts have been made to integrate more and more solar and wind energy sources. One of the major setbacks of such resources arises as a result of their intermittent nature, creating several problems in the electrical systems from a technical, market, operation, and planning perspectives. This work focuses on the operation of an electrical system with large-scale integration of solar and wind power. In order to cope with the intermittency inherent to such power sources, it is necessary to introduce more flexibility into the system. In this context, demand response, energy storage systems, and dynamic reconfiguration of the system are introduced, and the operational performance of the resulting system is thoroughly analyzed. To carry out the required analysis, a stochastic mixed-integer linear programming operational model is developed, whose efficacy is tested on an IEEE 119-bus standard network system. Numerical results indicate that the joint deployment and management of various flexibility mechanisms into the system can support a seamless integration of large-scale intermittent renewable energies.

On the Inertia of Future More-Electronics Power Systems

Inertia plays a vital role in maintaining the frequency stability of power systems. However, the increase of power electronics-based renewable generation can dramatically reduce the inertia levels of modern power systems. This issue has already challenged the control and stability of small-scale power systems. It will soon be faced by larger power systems as the trend of large-scale renewable integration continues. In view of the urgent demand for addressing the inertia concern, this paper presents a comprehensive review of inertia enhancement methods covering both proven techniques and emerging ones and also studies the effect of inertia on frequency control. Among those proven techniques, the inertia emulation by wind turbines has successfully demonstrated its effectiveness and will receive widespread adoptions. For the emerging techniques, the virtual inertia generated by the dc-link capacitors of power converters has a great potential due to its low cost. The same concept of inertia emulation can also be applied to ultracapacitors. In addition, batteries will serve as an alternative inertia supplier, and the relevant technical challenges as well as the solutions are discussed in this paper. In future power systems where most of the generators and loads are connected via power electronics, virtual synchronous machines will gradually take over the responsibility of inertia support. In general, it is concluded that advances in semiconductors and control promise to make power electronics an enabling technology for inertia control in future power systems.

Flexible Modern Power System: Real-Time Power Balancing through Load and Wind Power

Increasing large-scale integration of renewables in conventional power system has led to an increase in reserve power requirement owing to the forecasting error. Innovative operating strategies are required for maintaining balance between load and generation in real time, while keeping the reserve power requirement at its minimum. This research work proposes a control strategy for active power balance control without compromising power system security, emphasizing the integration of wind power and flexible load in automatic generation control. Simulations were performed in DIgSILENT for forecasting the modern Danish power system with bulk wind power integration. A high wind day of year 2020 was selected for analysis when wind power plants were contributing 76.7% of the total electricity production. Conventional power plants and power exchange with interconnected power systems utilize an hour-ahead power regulation schedule, while real-time series are used for wind power plants and load demand. Analysis showed that flexible load units along with wind power plants can actively help in reducing real-time power imbalances introduced due to large-scale integration of wind power, thus increasing power system reliability without enhancing the reserve power requirement from conventional power plants.

The reliability and operation test system of power grid with large-scale renewable integration

This paper proposes a reliability and operational test system named XJTU-ROTS2017, characterized by large-scale renewable power integration and long-distance transmission. The test system has 38 nodes, 63 lines, 15 transformers and 20 generators in three areas, with peak load 10,421 MW and total installed capacity 16050 MW. Electricity primarily transmits from a resource-rich area to a load area, carrying wind/solar power generation. The determination of component parameters and grid topology is based on design manuals and typical practices. The test system can be conveniently applied to reliability evaluation and operation optimization of composite power systems integrating coal/hydro/solar/wind resources. Finally, the extended applications to AC/DC hybrid power systems and interconnected power systems are discussed.

Simulation and Analytical Tools of Power Supply and Demand Balance for Large Scale Renewable Integration Study

Simulation and Analytical Tools of Power Supply and Demand Balance for Large Scale Renewable Integration Study

Economic and environmental benefits from integrated power grid infrastructure designs in the North Sea

The North Sea Offshore Grid (NSOG) is considered an important contributor towards large-scale integration of renewables and electricity market coupling. Different typologies have been studied for such a multinational power grid, ranging from radial point-to-point connections to more integrated meshed typologies. An artificial island enables a high level of integration of both offshore wind power and transnational trade due to economies of scale. This paper present multiple case studies of the Power Link Island (PLI) which is visioned by TenneT in the Doggerbank area. Our results demonstrate that the capabilities of such an island could add significant value to the system as a result of more efficient use of geographically spread, cost-efficient resources. However, depending on the future level of grid integration and generation mix, the added value of a PLI varies between e0.15bn to e20bn. Consequently, this could result in 18% more efficient utilization of renewable resources, primarily offshore wind, and significant reductions of CO2 emissions.

Toward the Next Generation of Multiperiod Optimal Power Flow Solvers

Distributed energy storage devices are commonly employed as an effective approach for addressing operational challenges introduced by the large scale integration of renewables. However, the modeling of storage devices results in intertemporal coupling of the individual optimal power flow (OPF) problems defined at each subdivision of the time period of interest. The resulting multiperiod optimal power flow (MPOPF) problem becomes intractable prohibiting, forecasting, and planning over long time periods. Interior point (IP) methods have been extensively employed for the solution of OPF and MPOPF problems. This work proposes an efficient IP algorithm, BELTISTOS, particularly designed for MPOPF problems. The structure of the linear system associated with the Karush-Kuhn-Tucker conditions is revisited, and a Schur-complement-based approach tailored to its structure is proposed. Through benchmark cases involving power-grid models of increasing complexity, the BELTISTOS algorithm is demonstrated to provide several orders of magnitude faster solution times than standard optimization methods, such as IPOPT, MIPS, and KNITRO, using significantly less memory.

Stochastic Unit Commitment With Topology Control Recourse for Power Systems With Large-Scale Renewable Integration

In this paper, we model topology control through transmission switching as a recourse action in the day-ahead operation of power systems with large-scale renewable generation resources. We prove that transmission switching could only reduce the linear objective value of direct current optimal power flow when congestion exists. However, we also show, through a simple example, that unit commitment cost could be reduced by transmission switching even in the absence of congestion. To solve the stochastic unit commitment with topology control within reasonable computational time, we proposed a heuristic that first decomposes a practical system into zones and then solves the problem for each zone in parallel. The benefit of topology control recourse is demonstrated on a network representing the Central European System. We compare the costs of the network with different loading and renewable generation conditions. The cost reduction of the test system can reach 3.34% with heavy load and large-scale renewable generation while in a single zone the cost reduction can be above 7%.

Interactive game vector: A stochastic operation-based pricing mechanism for smart energy systems with coupled-microgrids

To accommodate the large scale of renewable energy resources now widely integrated into power systems, an interactive two-level pricing mechanism for coupled microgrids (MG) in a smart energy system is proposed that considers operational quality and renewable generation uncertainty. In the upper level of the pricing mechanism, the distribution energy market operator (DEMO) guarantees operational quality by trading energy with coupled microgrids, while the actual transactions between networked microgrids is performed at the lower level. Stochastic programming is applied to handle the uncertainty caused by large-scale renewable integration. An innovative time-varying game vector and energy transaction strategy deal with the spatio-temporal market interaction of the networked microgrids, where each microgrid is able to directly trade all types of energy with any other microgrid at any time. The proposed model is solved using a customized hierarchical genetic algorithm. Case studies on an IEEE bus test feeder and an existing energy system in China demonstrate the effectiveness of the proposed methodology.