Provide Ancillary Services Research Articles

A New Control Strategy for Energy Management of Bidirectional Chargers for Electric Vehicles to Minimize Peak Load in Low-Voltage Grids with PV Generation

This paper introduces a new bidirectional vehicle-to-grid (V2G) control strategy for energy management of V2G charging points equipped with photovoltaic systems (PVs), considering the interaction between V2G chargers, electric vehicle (EV) owners, and the network operator. The proposed method aims to minimize peak load, grid infeed power, feeder loading, and transformer loading by scheduling EVs charging and discharging. The simulation experiments take into account three EV battery capacities as well as two levels of EV penetration. In order to validate the effectiveness of the proposed approach, five scenarios are studied in a single feeder of a low-voltage (LV) distribution network in DIgSILENT PowerFactory, which comprises a combination of residential and commercial loads as well as PV systems. Simulation results demonstrate that the proposed V2G strategy improves the paper’s objectives by providing ancillary services to the grid.

New Trends in the Control of Grid-Connected Photovoltaic Systems for the Provision of Ancillary Services

The gradual displacement of conventional generation from the energy mix to give way to renewable energy sources represents a paradigm shift in the operation of future power systems: on the one hand, renewable technologies are, in general, volatile and difficult to predict; and on the other hand, they are usually connected to the grid through electronic power converters. This decoupling due to power converters means that renewable generators lack the natural response that conventional generation has to the imbalances between demand and generation that occur during the regular operation of power systems. Renewable generators must, therefore, provide a series of complementary services for the correct operation of power systems in addition to producing the necessary amount of energy. This paper presents an overview of existing methods in the literature that allow photovoltaic generators to participate in the provision of ancillary services, focusing on solutions based on power curtailment by modifying the traditional maximum power point tracking algorithm.

Power management optimization of electric vehicles for grid frequency regulation: Comparative study

Electric vehicles (EVs) have shown promise in providing ancillary services, e.g., frequency regulation. This is mainly due to their capacities and fast response. On the contrary, the rapid integration of EVs in the grid poses challenges, such as frequency and voltage stability. In order to mitigate the above-mentioned issues, several dispatching strategies have been introduced in the recent literature to optimize the charging/discharging rates of EVs. In this paper, a comparative study of power management strategies for secondary frequency regulation (SFR) employing a fleet of EVs is presented. A hierarchical control scheme is employed to compare two cases, namely control at the charging station (CS) level and novel control at the EVs level. Under both cases, a multi-objective optimization approach is utilized to define the optimal charging and discharging rates of EVs using a pattern search algorithm. Furthermore, the performance of the two models is experimented under contingency cases, a notable contribution of this study. Finally, simulations are carried out using OPAL-RT real time simulator to validate the performance of the two models based on real-time traces obtained from Pennsylvania, New Jersey, and Maryland (PJM) interconnection and California independent system operator (CAISO). To further validate the proposed model, a comparison with a mixed-integer linear programming (MILP) based model is presented.

Ecosystem for Demand-side Flexibility Revisited: The Danish Solution

Denmark has recently set a legislation called Market Model 3.0 to make the ecosystem for demand-side flexibility more attractive to stakeholders involved. The main change is to relax the previous mandate that required each aggregator to be associated with a retailer and a balance responsible party. We explain the rationale behind such a change and its implications, particularly on the pre-qualification of demand-side portfolios providing ancillary services.

TSO/DSO Coordination for RES Integration: A Systematic Literature Review

The increasing penetration of large-scale Renewable Energy Sources (RESs) has raised several challenges for power grid operation. Power management solutions supporting the integration of RESs, such as those based on energy storage technologies, are generally costly. Alternatively, promoting a more proactive role of the Distribution System Operator (DSO) to successfully manage RESs’ uncertainty, and take advantage of their flexible resources for the provision of ancillary services, can avoid installing expensive devices in the network and reduce costs. In this line, improved coordination between Transmission System Operators (TSOs) and DSOs is highly desirable. In this paper, the feasibility of solving different aspects of the integration of RESs through an improved TSO/DSO coordination is evaluated. In particular, a Systematic Literature Review (SLR) is conducted to study the most relevant TSO/DSO coordination approaches, exclusively focused on integrating distributed RESs, currently available in the literature. Their main operational, managerial, economic, and computational challenges, advantages, and disadvantages are discussed in detail to identify the most promising research trends and the most concerning research gaps to pave the way for future research toward developing a solid TSO/DSO coordination mechanism for integrating RESs efficiently. The main results of the SLR show a clear trend in implementing decentralized TSO/DSO coordination models since they provide efficient facilitation of RESs’ services, while reducing computational burden and communication complexity and, consequently, reducing operative costs. In addition, while different aspects of the TSO/DSO coordination implementation, such as reactive power and voltage regulation, operational cost minimization, operational planning, and congestion management, have been thoroughly addressed in the literature, further research is needed regarding data exchange mechanisms and RESs’ uncertainty modeling and prediction. In this line, the development of standardized communication solutions, based on the Common Grid Model Exchange Standard (CGMES) of the International Electrotechnical Commission (IEC), has shown promising interoperability results, whereas the use of learning-based approaches to predict RESs’ uncertain behavior and distribution networks’ responses, using only historical data, which relieves the need for access to commercially sensitive and proprietary network data, has also shown itself to be a promising research direction.

Management and Control of Load Clusters for Ancillary Services Using Internet of Electric Loads Based on Cloud–Edge–End Distributed Computing

The Internet of Things (IoT) connects electric devices to a network in order to realize virtual control. Demand-side loads can provide ancillary services that optimize energy structures and promote supply–demand balance. For load management, this article proposes Internet of Electric Loads (IoEL) as a service-centric network, and the edge subcloud is introduced in the distributed computing system. The intelligent thermostatically controlled loads constitute the physical perceptual layer of the IoEL. Each subcloud controls a type of loads under the same regional distribution grid to form a stable and controllable aggregation system. The subclouds interact with the load cloud to form a platform layer. Through the interaction between the platform and physical perceptual layers, loads are controlled to realize the load transfer and provide ancillary services for the application layer. IoEL utilizes computing resources from different layers to form a distributed computing system made up of cloud, edge, and end devices. The load management is divided into four steps, namely, load aggregation in the edge–end interface, evaluation of load capacity in the edge, task allocation in the cloud–edge interface, and load control in the edge–end interface. The loads upload the physical properties to the subclouds and are then aggregated according to similarities of properties. The subclouds then evaluate schedulable capacity and upload these evaluations to the cloud, which then allocates tasks to each subcloud accordingly. The edge is responsible for receiving tasks from the cloud and controlling loads. The effectiveness of the method was verified by providing clean energy output tracking.

Frequency Regulation With Thermostatically Controlled Loads: Aggregation of Dynamics and Synchronization

Thermostatically controlled loads (TCLs) can provide ancillary services to the power network by aiding existing frequency-control mechanisms. TCLs are, however, characterized by an intrinsic limit cycle behavior, which raises the risk that these could synchronize when coupled with the frequency dynamics of the power grid, i.e., simultaneously switch, inducing persistent and possibly catastrophic power oscillations. To address this problem, schemes with a randomized response time in their control policy have been proposed in the literature. However, such schemes introduce delays in the response of TCLs to frequency feedback that may limit their ability to provide fast support at urgencies. In this article, we present a deterministic control mechanism for TCLs such that those switch when prescribed frequency thresholds are exceeded in order to provide ancillary services to the power network. For the considered scheme, we provide analytic conditions, which ensure that synchronization is avoided. In particular, we show that as the number of loads tends to infinity, there exist arbitrarily long time intervals where the frequency deviations are arbitrarily small. Our analytical results are verified with simulations on the Northeast Power Coordinating Council 140-bus system, which demonstrate that the proposed scheme offers improved frequency response compared with existing implementations.

Newton Method for Stochastic Control Problems

We develop a new iterative method based on Pontryagin principle to solve stochastic control problems. This method is nothing else than the Newton method extended to the framework of stochastic controls, where the state dynamics is given by an ODE with stochastic coefficients. Each iteration of the method is made of two ingredients: computing the Newton direction, and finding an adapted step length. The Newton direction is obtained by solving an affine-linear Forward-Backward Stochastic Differential Equation (FBSDE) with random coefficients. This is done in the setting of a general filtration. We prove that solving such an FBSDE reduces to solving a Riccati Backward Stochastic Differential Equation (BSDE) and an affine-linear BSDE, as expected in the framework of linear FBSDEs or Linear-Quadratic stochastic control problems. We then establish convergence results for this Newton method. In particular, sufficient regularity of the second-order derivative of the cost functional is required to obtain (local) quadratic convergence. A restriction to the space of essentially bounded stochastic processes is needed to obtain such regularity. To choose an appropriate step length while fitting our choice of space of processes, an adapted backtracking line-search method is developed. We then prove global convergence of the Newton method with the proposed line-search procedure, which occurs at a quadratic rate after finitely many iterations. An implementation with regression techniques to solve BSDEs arising in the computation of the Newton step is developed. We apply it to the control problem of a large number of batteries providing ancillary services to an electricity network.

Role of optimal sized dual energy storage based microgrid for ancillary service support to utility grid

Electrical energy storage system (ESS) has been used worldwide as ancillary support to the grid, aiding in frequency regulation and grid stability. Intermittent renewable energy sources (RESs) can be effectively integrated into the grid by maintaining power balance using different types of energy storage. However, the power requirement during small frequent, and large persistent power variations in the load demand can be more effectively controllable with the combination of the different energy storage according to their operational characteristics. This paper evaluates the suitability of a dual energy storage system (DESS) integrated in a grid connected microgrid (MG) system for providing ancillary services to the utility grid. The DESS is a combination of battery bank storage (BBS) and pump hydro storage (PHS). The BBS is very fast responding and it can counter the immediate variations in the power whereas, the PHS system can counter the large variations of the power as needed in the MG system. Four different operating cases have been studied to obtain the optimal size of the DESS for optimizing not only the operational cost but also for the best combination size of the storage systems to counter the variability in power generations and the load demand in the power system. Day-ahead electricity market scheduling has been performed on the MG to control the net power demand variations on the distribution feeder of the utility grid. The simulation results show that the higher capacity of the DESS does not always provide the optimal operational cost of the MG system during the grid-connected mode. Therefore, optimal sizing of the storage system also plays an important role in providing the optimal solution. It has been found that the optimal size of the individual energy storage and the DESS is different for microgrids supporting or not supporting the grid. The study enables the system operator (SO) to choose the best combination of storage systems for the supportive and non-supportive operation of microgrid system.

Optimization of multiple battery swapping stations with mobile support for ancillary services

The recent developments in electric vehicles (EVs) causes several issues that have not been satisfactorily addressed. One of the foremost problems is the charging–discharging processes of EV batteries with diverse characteristics. Although a charging station is the first choice in this regard, a battery swap station (BSS) is also a suitable alternative solution as it eliminates long waiting periods and battery degradation due to fast charging. BSS has the capability to ensure prompt and efficient service for electric vehicles. Since BSS has a large number of battery systems, optimum planning of the charging–discharging operations of the batteries is critical for both BSS and the grid. This study presents an optimal charging–discharging schedule for multiple BSSs based on the swap demand of privately owned EVs and electric bus (EB) public transportation system. In addition, BSSs reinforce the power grid by providing ancillary services such as peak shaving and valley filling with demand response programs. In order to increase the flexibility of the operation, the mobile swapping station (MSS) concept, an innovative and dynamic service, is introduced to the literature and added to the model. The results indicate that BSS is an essential agent in the ancillary services market and the MSS concept is a yielding solution for both BSSs and power networks. Last, the data utilized in the study for swap demand calculation and power grid analysis are real-world data from Berlin, Germany.

Decentralized Operation of an Isolated Microgrid with Storage Systems Using Multipliers with Alternating Directions

In view of the challenging task of the operation of microgrids, this work presents a distributed strategy to manage an isolated system by the optimal dispatch of active and reactive power. The ADMM (alternating directions method of multipliers) is adapted to solve two optimization problems, finding power profiles along the day for generators and storage systems, taking into account the power flow and demand coverage constraints. The joint dispatch allows the solution to minimize the generation cost and provide ancillary services such as voltage regulation and losses reduction. The method is tested in a study case with batteries and renewable sources to quantify the effects of the proposed strategy and compare with a centralized optimization.

Optimization of turbine start-up sequence of a full size frequency converter variable speed pump-turbine

The stability of the electricity grid will be disrupted by the massive integration of new renewable energies. Hydropower plants have a major role to play in this transformation of the electricity market by increasing their operational flexibility and their ability to provide ancillary services. However, this flexibility may lead to an accelerated degradation of mechanical components. By changing the turbine operating point far from the best efficiency point or by increasing the number of transient manoeuvres such as start and stop sequences, unsteady flow phenomena, cavitation development and additional wear and tear stress the unit’s components and impact its lifetime. The present work aims to provide preliminary insight on the optimization of the start-up sequence of a 5 MW reversible Francis pump-turbine equipped with a Full Size Frequency Converter (FSFC). The goal of the optimization approaches are to determine a start-up sequence which minimizes the runner damage, the penstock fatigue and the water losses. The objective functions are evaluated by 1D hydraulic transient simulations with the SIMSEN software and which it allow to compare the relative mitigation between the conventional fixed-speed start-up and the linear variable-speed start-up equipped with a Full Size Frequency Converter.

Pushing the envelope of ancillary services with variable speed technology

Hydropower is the backbone of energy transition thanks to its operational flexibility and ability to provide ancillary services. These grid support capabilities are called upon to play a major role to maintain the grid vulnerability at acceptable levels in view of the increasing penetration of stochastic and intermittent renewable energies. In this context, variable speed reversible pump-turbine technology is a key asset as it can extend the head operating range of a powerplant, enable power network control in pump mode and further increase the flexibility services to the electrical grid. Furthermore, by taking advantage of the so-called flywheel effect, variable speed enables the fast active power injection/absorption in pumping and generating mode. The additional degree of freedom offered by the variable speed opens the door to different control strategies for the hydroelectric plant, as the converter can be used for speed or power control. This can be exploited to maximize either the efficiency or the power reserve dedicated to grid support. In this paper, the strategies to maximize the ancillary service of Frades 2 pumped storage power plant (PSPP) are investigated. The plant features two high-head single-stage reversible variable speed units, coupled with 420 MVA doubly-fed induction motor-generators (DFIM). Using a 1D numerical model to simulate the power plant behavior, it is explored to which extent Frades 2 can deliver frequency containment reserve (FCR) power, while complying with the ENTSO grid code, and speed deviation constrains inherent to DFIM. By choosing a strategy which fully exploits the flywheel effect, it is established that the FCR power band can be equal to the whole operating range of the power plant. Moreover, the fast frequency response capacity (FFR) is also evaluated. It is found that by maximizing the energy stored in the rotating masses, each unit of Frades 2 can deliver up to 110 MW of active power in 1.3 seconds.

Droop-Inspired Nonlinear Control of a DC Microgrid for Integration of Electrical Mobility Providing Ancillary Services to the AC Main Grid

The present paper describes an Electric Vehicle (EV) charging station that provides ancillary services to the main AC grid, as for example frequency support and synthetic inertia. Due to the Direct Current (DC) nature of these loads and the easier integration of renewable energies, a DC Microgrid is considered to power the charging station. Targeting both DC grid voltage stability and the capability to support the main AC grid, nonlinear control laws based on Lyapunov theory and backstepping are developed for local and primary control levels (droop control). The proposed controllers are validated via MATLAB-Simulink simulations in a 25 kW DC Microgrid with PV production, Vehicle to Grid (V2G) mode of operation, fast and slow vehicle charge, ancillary services to the AC main grid and islanded mode operation.

Energy management in Converter-Interfaced Renewable Energy Sources through ultracapacitors for provision of ancillary services

The ever-growing penetration of Converter-Interfaced Renewable Energy Sources (CI-RES) and the gradual decommission of synchronous generators (SGs) are posing several challenges to guarantee the stability and robustness of the electric power system. A possible solution to overcome the foreseen problems is to enable the provision of ancillary services (AS) by advanced CI-RES emulating the SG performance. However, given the fact that most of the CI-RES operate at maximum power point, it will be required to rely on energy storage systems (ESS) to deal with active power related ASs. The ESS integration can be done in a straightforward manner within the CI-RES DC bus by means of a DC/DC converter. It is required, however, an adequate DC energy management to properly control the DC bus voltage, the ESS energy and the power delivered to the grid by the primary power source. This is a major challenge which must be solved to unlock the AS provision by means of CI-RES. With this regard, the main contribution of the paper is the design of an energy management system to simultaneously regulate the CI-RES DC bus voltage using the UC and also maintain the UC voltage within their safety limits while a given AS is provided. The control strategy is validated experimentally using a prototype with results that reveal a reliable and stable operation.

Optimal management strategy for a shared EVs aggregator participating in electricity and frequency regulation reserves markets

The use of shared electric vehicles has spread widely in response to the global need of reducing CO2 emissions. Hence, in the literature, authors have proposed strategies to minimize the operative costs of shared EVs, such as the provision of electrical ancillary services. However, to provide these kinds of services jointly with transportation, charging/discharging and fleet management strategies are required. And, the currently available strategies from the literature do not consider shared EVs. Therefore, to fill this gap, this paper presents an optimization-based management strategy for shared EVs that provide ancillary services and sell energy, which is applied to a study case located in Colombia. Additionally, it includes the analysis of the economic contracts that should be established between the EVs operator and the energy retailer; in which, it was found that the best option for EVs operator is to purchase the energy at the stock electricity price and establish a bilateral contract for energy sales. Moreover, it suggests that EVs be charged at the early morning hours when the stock price is lowest, that the ancillary services be provided at hours with the highest stock price, and that the energy be sold at the hours in which the provision of ancillary services is not suitable. Finally, the paper suggests, from the application of a Lagrangian parametric technique, an incentive of at least $ 115 [COP/kWh], to make the electrical services competitive with the car-sharing transportation service, which is paid at a price 23 times higher, within the Colombian context.

ASITA'S IN MANAGEMENT OF TRAVEL AGENCY IN SOUTHERN TANGERANG AS CULTURAL TOURISM BUSINESS OPPORTUNITIES IN THE ERA OF DIGITALISATION

Many travel agency business owners face a tourism industry crisis that has not improved in the last two decades due to the effects of the covid 19 outbreak, which has been the focus of community service efforts in recent years. The South Tangerang ASITA community, in conjunction with the South Tangerang City Tourism Office (Dispar), recently hosted a Travel Agency (BPW) Training and deliberations on the Tangerang Association of The Indonesia Tour & Travel Agencies (ASITA) branch as part of efforts to revitalise the city's tourism industry during the current endemic period. Southern Tangerang also cooperates with Universitas Respati Indonesia and LSP WHI. This training event proves that ASITA South Tangerang is ready to exist again as an entry point for Banten tourism and alternative tourism for residents and foreign tourists. As a result, ASITA is reaching out to travel agents to explore online travel business opportunities in this age of rapid digitalisation together. South Tangerang's tourist attractions are evidence of the region's appeal to domestic and international travellers; seizing this opportunity, ASITA members have relaunched their tour and travel agency. South Tangerang City's tourism industry players need to get creative in the face of digital disruption if they want to grow their enterprises and thrive in the emerging market conditions. Tourism marketing management has undergone significant transformations to adapt to the digital age. South Tangerang City's government, hotels, gastronomic SMEs, the Creative Economy, and ancillary service providers are all working together to boost the quality of their human resources in the tourism sector. Then, employ digital tourism for more proactive advertising and to maintain infrastructure on access to tourist destinations and communities near tourist destinations

Technical and economic analysis of the provision of ancillary services through the flexibility of HVAC system in shopping centers

To address the increasing demand for ancillary services, new demand response strategies (DR) are being developed that involve the building sector to provide flexibility to the transmission system operator (TSO). In this respect, commercial buildings have great potential to become key players in providing flexibility to the TSO by changing their load profiles for heating, ventilation and air conditioning. This study presents a case study of a Mediterranean shopping centre heated and cooled by a heat pump and participating in the ancillary services market according to the specific rules of the Italian pilot project UVAM. The analyses start from the daily consumption profile assuming conventional operation for the HVAC system (baseline) during cooling and heating periods. Then two DR strategies are investigated, the first of which is to change the indoor set point temperature and the second is to reduce the electricity power to the HVAC systems, without introducing pre-cooling or pre-heating periods. The results show that the studied flexibility strategies allow to obtain, for each DR event, over 60 kW of downward flexibility power and a reduction of energy consumption between 128 and 160 kWh during summer, and over 50 kW of downward flexibility power and a reduction of energy consumption between 40 and 160 kWh. This study identifies opportunities and barriers for commercial buildings to participate in the ancillary services market. However, the proposed DR strategies may lead to an unacceptable percentage of dissatisfaction (PPD), especially during the cooling season.

Identification and quantification of the flexibility potential of a complex industrial process for ancillary services provision

As the share of variable renewable energy sources in the electricity generation mix increases, so does the need for power system flexibility. Demand side flexibility has been identified as a great opportunity to facilitate the integration of this volatile production. An important part of demand side flexibility is the modulation of the consumption of industrial processes. With the emergence of ancillary services markets, operating industrial processes in a flexible manner might generate additional value. This paper proposes a flexibility assessment tool to quantify the potential of a given industrial plant for grid services provision. We start by formulating the feasible operating region of a given industrial asset, generating a set of operating points and their corresponding power ramping potential. A weekly simulation is then performed which leads to a set of most-observed operating points, themselves leading to a set of potential ancillary services bids from the industrial process.

An aggregator-oriented hierarchical market mechanism for multi-type ancillary service provision based on the two-loop Stackelberg game

In order to utilize demand-side flexibility and meet system requirements, the aggregator (AGG) has become a vital role in the ancillary service market. To reflect the willingness of each market subject, a tri-layer ancillary service market framework for ancillary service market operator (ASMO), AGG, and users is proposed in this paper, which contains the interactions between different layers including ASMO and AGG, AGG and users. We develop a detailed market timeline that takes multi-type ancillary services into account. Moreover, due to the hierarchical market structure, we conduct a two-loop Stackelberg game to depict the effect of each market subject’s strategic behavior. Based on the game models of all the market subjects, the existence and uniqueness of the game equilibrium point are proved. In addition, considering the correlation between multi-type ancillary services, the clearing process is decomposed into two sub-problems and a distributed joint market clearing based on the particle swarm optimization algorithm is presented. Case study shows that the proposed method is profitable for all the market subjects, the market timeline is reasonable, and the joint clearing method is effective.