Ancillary Services Research Articles

Optimal scheduling of flexible grid-side resources and auxiliary service cost allocation model considering renewable-energy penetration

Abstract Renewable energy has penetrated power grid enterprises on a large scale. Due to the intermittency and volatility of renewable energy generation, it is necessary to build new flexible grid-side resources to ensure the safe and stable operation of the power grid, which will cause great pressure on cost allocation for power grid enterprises. This article considers four types of flexible grid-side resources and constructs a dual-level configuration optimization model for flexible grid-side resources under the penetration of renewable energy. Based on the configuration results, the cost scale of flexible grid-side resources is estimated and an improved ancillary service cost allocation model based on the Shapley value method is proposed to smooth the allocation of ancillary service costs in the cost of flexible grid-side resources between the two main bodies of renewable energy and load. The calculation results show that, when the penetration rate of renewable-energy power is 30% and 35%, respectively, the cost of flexible grid-side resources is 9.606 billion yuan and 21.518 billion yuan, respectively. The proportion of ancillary service costs allocated to load is relatively high—about five times that of the ancillary service costs allocated to renewable energy—and the higher the penetration rate of renewable energy, the higher the proportion of ancillary service costs allocated to renewable energy.

Incentive-compatible primary frequency response ancillary service market mechanism for incorporating diverse frequency support resources

Frequency vulnerability will be prominent in future low-inertia power systems with high renewable penetration, which calls for primary frequency response (PFR) services from a wide range of entities. The challenge, however, is to design effective and fair market mechanisms to incentivize diverse PFR resources. To this end, this paper proposes a PFR ancillary service market mechanism to ensure the security of frequency nadir and quasi-steady-state (QSS) frequency while providing equitable settlements to multiple PFR providers. First, bidding rules are designed for accurate depictions of dynamic performances from diverse PFR resources. Then, a PFR market-clearing model, incorporating frequency security constraints that explicitly express PFR providers' contributions, is developed to deploy sufficient PFR resources while maximizing social welfare. Finally, two unified marginal PFR prices are derived to reflect the scarcity of frequency support capabilities for maintaining frequency nadir and QSS frequency security, enabling fair settlements to successful bidders based on their contributions. Moreover, the pricing and settlement mechanism is theoretically proven incentive-compatible, ensuring the PFR market stability. Case studies verify the proposed PFR market's effectiveness in ensuring frequency security, providing fair incentives to diverse PFR providers, maintaining market stability, and supporting scalable implementations.

A Bi-Level Optimized Dispatching Method for Grids with High Penetration of New Energy Considering Ancillary Service Costs

To address the issue of high auxiliary service costs caused by the grid connection of new energy generation, a dual layer optimization scheduling method for high penetration new energy power grids is proposed, taking into account the auxiliary service costs of grid connection. The correlation between the output fluctuations and load fluctuations of new energy generation is analyzed, and a calculation model for auxiliary service costs caused by grid connection of new energy generation is established. Taking into account the timescale division requirements for grid energy trading and auxiliary service market transactions, a new high penetration energy grid two-level optimization scheduling model is established. The upper level scheduling model aims to minimize the sum of grid energy procurement costs and auxiliary service costs caused by new energy generation and completes the optimization scheduling of the grid for several hours. The lower level scheduling model aims to closely follow the upper level scheduling plan for new energy power plants/groups. Optimization and scheduling of the power grid for tens of minutes is completed, taking into account the balanced allocation of wind and solar losses among various power plants within the new energy power plant group. The simulation results show that the method proposed in this paper can reduce the energy transaction costs and auxiliary service transaction costs of the power grid during low and peak load periods.

A Method for Calculating the Adjustable Capacity of Feeder Load Aggregators Considering the User’s Wishes

Abstract With the deepening of China’s energy reform, large-scale renewable energy access has put forward higher requirements for the flexible adjustment ability of the power system. The research and application of mining flexible and adjustable resources on the user side to participate in the peak regulation and frequency regulation of the power grid have received extensive attention. With the gradual opening of the power market and the deepening of the reform of the power system, the feeder load aggregator has gradually become a new role in the power market, and the feeder load aggregator plays an important role in the centralized management of users, the optimization of distribution, and the realization of market-oriented transactions. However, the research on the participation of feeder loads in the auxiliary services of power grid peak regulation and frequency regulation is not perfect. In this context, this paper proposes a method for calculating the adjustable capacity of feeder load aggregators considering the wishes of users, in which the maximum voltage adjustable at the feeder and the change of the capacity of each user caused by the feeder voltage regulation are calculated by the feeder load aggregator through the power flow relationship, and finally the adjustable capacity declaration for the ancillary service market is completed.

Hierarchical control on EV charging stations with ancillary service functions for PV hosting capacity maximization in unbalanced distribution networks

PV hosting capacity of a practical three-phase unbalanced distribution network is expected to increase, thus increasing safe PV penetration and speeding up the decarbonization of power systems. However, power unbalances and bus voltage violations are two major obstacles limiting further increases in the PV hosting capacity. With the popularization of electric vehicles (EVs), EV charging stations (EVCSs) as controllable loads can effectively provide grid ancillary services, which helps enhance the PV hosting capacity. In this regard, this paper proposes a hierarchical control method for EVCSs in an unbalanced network, consisting of central day-ahead scheduling and local real-time dynamic control. It is novel that the local control capability of EVCSs is reserved in the central scheduling. A three-phase day-ahead EV charging scheduling optimization model is developed to reduce the power unbalance and the bus voltage violation, and in turn, improve the PV hosting capacity. Moreover, active power transfer and voltage droop control are developed as two ancillary service functions for local real-time control responding to dynamic network operating conditions. Numerical simulations verify the effectiveness of the proposed method in enhancing PV hosting capacity and providing grid ancillary services.

Empowering offshore wind with ES-STATCOM for stability margin improvement and provision of grid-forming capabilities

Offshore wind power plants (WPPs) play a pivotal role in achieving a CO2-neutral electricity sector. However, their grid connection presents significant challenges and costs. High-voltage alternating current (HVAC) offers a cost-effective solution, but it may necessitate the installation of a static synchronous compensator (STATCOM) at the onshore bus to ensure stability and compliance with connection requirements. Integrating energy storage into the STATCOM (ES-STATCOM) enables the provision of ancillary services, such as inertial response and frequency support, which require active power. This paper utilizes the generalized Nyquist criterion to demonstrate that operating the ES-STATCOM with grid-forming control enhances the stability margin of the grid-connected WPP when compared to operating it with grid-following control. Furthermore, it illustrates through network frequency perturbation (NFP) plots that the overall WPP, comprising grid-following wind turbines and a grid-forming ES-STATCOM, imparts grid-forming behavior at the grid-connection point.

Dynamic ancillary services: From grid codes to transfer function-based converter control

Conventional grid-code specifications for dynamic ancillary services provision such as fast frequency and voltage regulation are typically defined by means of piece-wise linear step-response capability curves in the time domain. However, although the specification of such time-domain curves is straightforward, their practical implementation in a converter-based generation system is not immediate, and no customary methods have been developed yet. In this paper, we thus propose a systematic approach for the practical implementation of piece-wise linear time-domain curves to provide dynamic ancillary services by converter-based generation systems, while ensuring grid-code and device-level requirements to be reliably satisfied. Namely, we translate the piece-wise linear time-domain curves for active and reactive power provision in response to a frequency and voltage step change into a desired rational parametric transfer function in the frequency domain, which defines a dynamic response behavior to be realized by the converter. The obtained transfer function can be easily implemented e.g. via a proportional-integral (PI)-based matching control in the power loop of standard converter control architectures. We demonstrate the performance of our method in numerical grid-code compliance tests, and reveal its superiority over classical droop and virtual inertia schemes which may not satisfy the grid codes due to their structural limitations.

Flexibility modeling for parking lots with multiple EV charging stations

The paper proposes an aggregated model that represents the flexibility potential of car parks equipped with multiple electric vehicle (EV) charging stations. The model is used in a stochastic optimization procedure to estimate in advance the maximum flexibility margins of the parking lot. The EV aggregator responsible for the charging stations offers intra-day ancillary services to the grid by specifying the possible margins within which the absorbed power can be varied, either up or down. These adjustments are made at the request of the distribution system operator, ensuring an appropriate level of EV charging. The effectiveness of the model is evaluated for parking lots with different numbers of charging stations and different daily profile forecasts of the number of EV arrivals and departures.

Analyzing impact of network constraints on feasible operation region of the radial distribution networks

Recently, there has been lot of research on finding the feasible operating region (FOR) of the active distribution network (ADN) to provide ancillary services to the transmission grid. The current focus of research is on finding methods that can accurately determine the shape of the FOR and have fast computation time. However, there is little focus on analyzing how network constraints impact the shape of the FOR. This paper attempts to address this issue and provides a mathematical derivation of how network constraints, such as cable loading and voltage limits, would influence FOR. The approach is based on a linear distflow mathematical analysis. The relations derived in the analysis are verified with numerical simulation on radial low-voltage (LV) and medium-voltage (MV) networks. The results show that cable loading constraints cut the FOR in a circular way and voltage constraints cut the FOR with a straight line of slope −ϵ, which is the ratio Rn/Xn of the path from root node to the node under analysis of the radial distribution network.

ANALYSIS OF MERCHANT BANKING IN INDIA Niranjan Kumar Jha

Original Definition: A Merchant Bank is a British term for a bank providing various financial services such as accepting bills arising out of trade, providing advice on acquisitions, mergers, foreign exchange, underwriting new issues, and portfolio management. The Focus Definition: A Merchant Bank can be generally described as a financial services company with a private equity investment arm offering investment banking and ancillary services as well. Because a merchant bank acts not only as an advisor and broker but also as a principal, a merchant bank has a longer-term approach than a typical investment bank and is highly concerned with the viability of each investment opportunity and providing the right advice for a strong partnership with each client company. Modern Definition: A merchant bank is a financial institution providing capital to companies in the form of share ownership instead of loans. A merchant bank also provides advisory on corporate matters to the firms in which they invest. In the United Kingdom, the historical term "merchant bank" refers to a bank. A Merchant Bank can be generally described as a financial services company with a private equity investment arm offering investment banking and ancillary services as well. Because a merchant bank acts not only as an advisor and broker but also as a principal, a merchant bank has a longer term approach than a typical investment bank and is highly concerned with the viability of each investment opportunity and providing the right advice for a strong partnership with each client company. In banking, a merchant bank is a traditional term for an Investment Bank. It can also be used to describe the private equity activities of banking. This article is about the history of banking as developed by merchants, from the Middle Ages onward. Merchant banking is an important service provided by a number of financial institutions that helps in the growth of the corporate sector which ultimately reflects into the overall economic development of the country. Merchant banks were expected to perform several functions like issue management, underwriting, portfolio management, loan syndication, consultant, advisor and host of other activities. Merchant banking is a combination of banking and consultancy services.

Real-time V2G simulator for grid system frequency and voltage regulation with fault ride-through capabilities

Electric vehicles (EVs) have become one of the promising power grid ancillary services. They can help reduce the intermittent of renewable energy sources by supporting active power and frequency control services. Additionally, bi-directional chargers included into EV batteries can supply/consume reactive power for voltage regulation. To improve voltage quality, a unique control approach is devised to offer fault ride-through. In this study, real-time charging optimization schemes based on particle swarm optimization are developed to coordinate the EVs charging/discharging power with the grid power dispatches depending on the charging priority and preferential electricity prices. Five different car user profiles including different initial state of charge and plug in state have been depicted. Different optimum issues are carried out with comprehensive simulations employing hardware in the loop via real-time simulation for a modified IEEE 14-bus test system. Where different frequency and voltage controls, management strategies, variant fault scenarios, benefits, and challenges for power system regulation with EVs are illustrated. According to the simulation results, the proposed optimized charging strategies reduce the total expenses of EV parking station by 40 % compared to other cases, hence maximizing EV owner satisfaction. The net load curve is smoothed and reduced by 11 %, particularly during peak period.

Commercial electric vehicle fleets in U.S. ancillary services markets: A stochastic analysis to inform utility rate design

For commercial fleets in the United States, traditional electricity tariffs can disincentivize vehicle-to-grid (V2G) participation and render electrification less attractive. First, we show that absent a rate redesign, opportunities for both fleets and the grid are missed. We propose a rate design modification: demand charge relaxation during off-peak (overnight) hours. This approach would enable fleets to shift additional load share to overnight hours and increase ancillary service revenues without the expectation of impacting local grid cost drivers (i.e., coincident peak load). Applied to a California case study, operational savings spanning 7.5% and 20.6% are realized via increased capacity revenues and deferred demand charges.

Optimal trading with regime switching: Numerical and analytic techniques applied to valuing storage in an electricity balancing market

Accurately valuing storage in the electricity market recognizes its role in enhancing grid flexibility, integrating renewable energy, managing peak loads, providing ancillary services and improving market efficiency. In this paper we outline an optimal trading problem for an Energy Storage Device trading on the electricity balancing (or regulating) market. To capture the features of the balancing (or regulating) market price we combine stochastic differential equations with Markov regime switching to create a novel model, and outline how this can be calibrated to real market data available from NordPool. By modelling a battery that can be filled or emptied instantaneously, this simplifying assumption allows us to generate numerical and quasi analytic solutions.We implement a case study to investigate the behaviour of the optimal strategy, how it is affected by price and underlying model parameters. Using numerical (finite-difference) techniques to solve the dynamic programming problem, we can estimate the value of operating an Energy Storage Device in the market given fixed costs to charge or discharge. Finally we use properties of the numerical solution to propose a simple quasi-analytic approximation to the problem. We find that analytic techniques can be used to give a benchmark value for the storage price when price variations during the day are relatively small.

Exploring the service needs and the common-suited strengthening paths for bicycle-sharing services based on the AIA-NRM technique in consideration of various users

ABSTRACT Near metro stations in urban areas, a public bicycle rental service allows users to rent bicycles for leisure, short-distance connections, and daily commuting. This study aims to explore the driving factors of bicycle-sharing service systems (BSSSs) and different users’ preferences and service needs (leisure & recreation users, short-connection users, and daily commuting users). The four driving forces (primary services, primary facilities, ancillary services, and ancillary facilities) are applied to evaluate the BSSSs. The researcher used the attention and importance analysis (AIA) technique to assess service driving factors’ attention and importance status in the bicycle-sharing service systems (BSSSs). The DEMATEL technique was also employed to establish a network relation map (NRM) approach for different users. The researcher also combines the AIA and NRM techniques to provide the AIA-NRM technique for identifying common applicable paths and enhancement strategies for the BSSS. Furthermore, this study analyzes various institutions and BSSS service providers from multiple users’ perspectives, determines the development direction of BSSSs, evaluates related challenges, and finds sustainable strategies for strengthening BSSSs.

(113) PRACTICAL DISTRESS AT DIAGNOSIS PORTENDS WORSE SEXUAL WELL-BEING DURING BREAST CANCER TREATMENT

Abstract Introduction A breast cancer diagnosis and subsequent treatment can have profound impacts on patients' body image and sexual health. Sexual health and well-being are an unmet concern for many and declines in sexual function have been associated with higher distress and anxiety. Objective Our study aims to evaluate how distress at diagnosis is related to sexual well-being and referral to ancillary resources during breast cancer treatment at a comprehensive cancer center. Methods All patients with newly diagnosed breast cancer were offered a distress screening tool which measures distress in the emotional (I.e. worry, nervousness), physical (I.e. nausea, sexual intimacy, fatigue), social (I.e. relating with others), and practical domains (I.e. bills, housing, transportation). High distress in a domain was defined as a score greater than 5. Patients were then invited to complete the Breast-Q module, a validated patient reported outcome (PRO) scale that quantifies outcomes related to sexual well-being (SW). Participants who had at least one distress measure at baseline and at least one PRO at either baseline or 6-months post-operatively were eligible for inclusion. Chart review was conducted for referral to and utilization of ancillary services including sexual health consultation. Multivariable linear mixed models were used to compare high and low distress with an interaction between distress and time. Results 227 patients were included in the study population. The median baseline SW score was 55.4 (standard deviation = 22.9). High practical distress was found in 18.4% of patients, however, those with high practical distress at baseline were more likely to have greater decline in their SW scores between the pre-operative and 6-month post-operative time points (p = 0.03) (Figure 1). After adjusting for age, stage, and treatment received, this relationship remained significant. Of the available ancillary resources, social work and care management services were the most common referrals with 135 patients seen. Only 4 patients attended a sexual health consultation based on clinician discretion. Change in pre-operative and 6-month post operative SW was not related to emotional, physical, or social distress. Conclusions Sexual well-being trajectories are related to practical distress at diagnosis. This suggests that patients who are already struggling with the logistics of a new breast cancer diagnosis may suffer the most when it comes to their sexual health. Most patients here received some ancillary support however it is clear something is still missing given the observed declines in sexual well-being. Further study is necessary to understand the drivers of this relationship and how these patients can receive early intervention to prevent worsening of their sexual well-being during breast cancer treatment. Disclosure No.

Modelling and Assessing the Advantages of Integrating Wind, Solar, and Coal Systems within an Annual Bilateral Trading Setting

The integration and co-location of new energy sources and thermal power generation within the same grid connection point, under the management of a single market operator, provide noteworthy potential for exploration in the northern part of our nation. This method is based on the premise of allocating new energy resources primarily for generating contracted electricity, while using thermal power to offer ancillary services. This strategy aims to integrate and use the distinct benefits of both thermal power and new energy sources. The yearly bilateral trade market has significant potential for growth and development. In order to model and evaluate the income generated by the interconnected system’s involvement in the yearly bilateral trading market, this study first establishes the definition of the interconnected system and examines its research significance in engaging in annual bilateral trading. This study utilizes the theoretical framework of master-slave games to analyze the involvement of a coupled system in yearly bilateral trade. The specific case examined in this research is a wind-solar-thermal coupling system located in a particular location of Liaoning Province. This study examines the economic advantages of engaging in the electricity market by considering the marginal cost and LCOE (Levelized Cost of Electricity) perspectives. The findings suggest a notable enhancement in the advantages of the integrated system inside the yearly bilateral trade market, in contrast to conventional power sources present in the market, as well as instances when these sources function autonomously without integration.

Multi-agent deep reinforcement learning based fully decentralized aggregation frequency regulation of electric vehicle

Electric vehicles (EVs) are high-quality flexible resources to provide frequency regulation services. However, the EV real-time participation in ancillary service market for frequency regulation (FRASM) under the existing aggregation framework faces data privacy and interest conflicts problems. To solve these issues, this paper proposes the fully-decentralized aggregator (FDA) as a trusted and non-profit agent to replace the traditional aggregator and help EVs interact with FRASM in a decentralized manner. Then a fully decentralized aggregation framework based on consortium blockchain is constructed to protect the interaction data security during frequency regulation process. Furthermore, the inference network is introduced so that EVs can learn better performance and optimize regulation mileage without sharing their private data. This paper proposes an inference network based multi-agent soft actor-critic (IN-MASAC) method that realizes the decentralized interaction between EVs and FRASM and considers multiple user preferences. The case studies demonstrate the efficiency and scalability of the fully decentralized aggregation framework and IN-MASAC method.

Aggregation of building predictive energy flexibility in smart microgrid

Numerous demand-side resources possess significant potential to offer substantial flexible reserves and ancillary services, thereby enhancing the economic and technical performance of power systems within the demand response domain. A novel approach to aggregating the energy flexibility of buildings based on the virtual battery model is proposed in the smart microgrid, employing predictive control techniques while ensuring consumer privacy. The individual approximation process is implemented to extract the flexible capacity of local resources while protecting information privacy. Subsequently, the aggregator collects the flexibility information to develop an optimization strategy for maximum flexibility aggregation at the upper level, enabling the broader exploitation of global flexibility. The feasibility of power disaggregation is guaranteed according to the aggregation procedure. Furthermore, the comprehensive framework accommodates temporal preferences for flexibility requests from the aggregator. Numerical simulations are conducted to perform a comparative analysis with existing state-of-the-art methods. The results demonstrate that the proposed approach exhibits improved adaptability in characterizing the aggregate flexibility from buildings, effectively managing the heterogeneity of load characteristics and the variability in the collected flexibility information. Microgrids can realize cost savings and achieve dynamic flexibility utilization. This methodology can be extended and applied to diverse types of flexible resources.

Developing and Evaluating the Operating Region of a Grid-Connected Current Source Inverter from Its Mathematical Model

Grid-connected power inverters are indispensable in modern electrical systems, playing a pivotal role in enhancing the integration of renewable energies into power grids. Their significance, primarily when functioning as grid-forming inverters, extends to maintaining the grid’s inertia and strength—a distinct advancement over traditional grid-following operations. As grid-forming inverters, these devices emulate the characteristics of synchronous generators and can act as robust voltage sources, providing essential ancillary services. This behavior is particularly relevant when integrating energy storage systems on the converters’ direct current side. Among the various inverter topologies, the current source inverter (CSI) has emerged as a promising yet underexplored alternative for grid-forming applications. CSIs, when paired with their AC output filters, can effectively operate as voltage sources, utilizing control strategies that facilitate the integration of renewable energies into the electrical system. Their design inherently manages output current fluctuations, reducing the need for restrictive current limitations or additional protective measures. This paper examines the operational region of CSIs, obtained through detailed modeling, to explore their advantages, challenges, and potential for enhancing grid-connected systems. Analyzing the operating region from the converter model verifies the limits of where the converter can operate in a plane of active and reactive powers. For a small prototype model operating with 7 amperes in DC and 120 V in AC, it is possible to supply or absorb active power exceeding 1000 W and manage maximum reactive power values around 500 VAr, as determined by its operating region. Simulations also confirm that small changes in the control reference, as little as 5%, towards the region’s right limits cause significant oscillations in the dynamic control responses. This research aims to deepen our understanding of CSIs’ operational capabilities and highlight their unique benefits in advancing grid-connected systems and promoting the integration of renewable energy using this technology.

Energy Storage Improves Power Plant Flexibility and Economic Performance

Most existing coal-fired power plants were designed for sustained operation at full load to maximize efficiency, reliability, and revenue, as well as to operate air pollution control devices at design conditions. Depending on plant type and design, these plants can adjust output within a fixed range in response to plant operating or market conditions. The need for flexibility driven by increased penetration of variable and non-dispatchable power generation, such as wind and solar, is shifting the traditional mission profile of thermoelectric power plants in three ways: more frequent shutdowns when market or grid conditions warrant, more aggressive load ramp rates (rate of output change), and a lower minimum sustainable load, which provides a wider operating range and helps avoid costly plant shutdowns. Recent studies have shown that the flexibility of a coal-fired power plant can be improved by energy storage. The objective of this work was to analyze a set of energy storage options and determine their impact on the flexibility and economics of a representative coal-fired power plant. The effect of three energy storage systems integrated with a coal power plant on plant flexibility and economics was investigated. The results obtained in this project show that energy storage systems integrated with a thermal power plant improve plant flexibility and participation in the energy and ancillary services markets, which improves plant financial performance. The study was funded by the U.S. Department Office of Fossil Energy FE-1 under award number DE-FE0031903.