Joint Control Research Articles

Effect of operating temperature on the performance of expansion joints between tube and tube plate

Effect of operating temperature on the performance of expansion joints between tube and tube plate

Modelling situated intent for human-autonomy teaming: a human-centric approach

Entering an era where humans and synthetic agents are supposed to collaborate and cooperate, adequate models of human intent are crucial for coordinated teamwork. Unfortunately, although there is a need for such models, the concept of intent is ambiguous and approaches to model intent from a human-centric perspective are scarce. Building upon theoretical and methodological foundations, this study aims to address these gaps by presenting a conceptualisation of intent alongside an approach. Specifically, leveraging the six levels of cognitive control outlined in the Joint Control Framework, a provisional model of human intent alongside a defined and operationalised concept is presented. Building on these foundations, a novel approach is proposed. Utilising seven scenario-based interviews, the value of these contributions is demonstrated through an example case in the context of Manned-Unmanned Teaming. It is concluded that intent should be understood as a multi-faceted concept shaped by situated constraints, where intent is formed through a commitment to choices by context-situation and means-end reasoning. It is also concluded that the approach is useful, particularly since it can glean insights from choices considered and committed, both being essential in the design of synthetic teammates’ capability to adapt to their human partner’s agency.

Long-term ambient ozone exposure and incident cardiovascular diseases: National cohort evidence in China

BackgroundLong-term ozone (O3) exposure has been associated with cardiovascular disease (CVD) mortality in mounting cohort evidence, yet its relationship with incident CVD was poorly understood, especially in low- and middle-income countries (LMICs) experiencing high ambient air pollution. MethodsWe carried out a nationwide perspective cohort study from 2010 through 2018 by dynamically enrolling 36948 participants across Chinese mainland. Warm-season (April–September) O3 concentrations were estimated using satellite-based machine-learning models with national coverage. Cox proportional hazards model with time-varying exposures was employed to evaluate the association of long-term O3 exposure with incident CVD (overall CVD, hypertension, stroke, and coronary heart disease [CHD]). Assuming causality, a counterfactual framework was employed to estimate O3-attributable CVD burden based on the exposure-response (E-R) relationship obtained from this study. Decomposition analysis was utilized to quantify the contributions of four key direct driving factors (O3 exposure, population size, age structure, and incidence rate) to the net change of O3-related CVD cases between 2010 and 2018. ResultsA total of 4428 CVD, 2600 hypertension, 1174 stroke, and 337 CHD events were reported during 9-year follow-up. Each 10-μg/m³ increase in warm-season O3 was associated with an incident risk of 1.078 (95% confidence interval [CI]: 1.050–1.106) for overall CVD, 1.098 (95% CI: 1.062–1.135) for hypertension, 1.073 (95% CI: 1.019–1.131) for stroke, and 1.150 (95% CI: 1.038–1.274) for CHD, respectively. We observed no departure from linear E-R relationships of O3 exposure with overall CVD (Pnonlinear= 0.22), hypertension (Pnonlinear= 0.19), stroke (Pnonlinear= 0.70), and CHD (Pnonlinear= 0.44) at a broad concentration range of 60–160 µg/m3. Compared with rural dwellers, those residing in urban areas were at significantly greater O3-associated incident risks of overall CVD, hypertension, and stroke. We estimated 1.22 million (10.6% of overall CVD in 2018) incident CVD cases could be attributable to ambient O3 pollution in 2018, representing an overall 40.9% growth (0.36 million) compared to 2010 (0.87 million, 9.7% of overall CVD in 2010). This remarkable rise in O3-attributable CVD cases was primary driven by population aging (+24.0%), followed by increase in O3 concentration (+10.5%) and population size (+6.7%). ConclusionsLong-term O3 exposure was associated with an elevated risk and burden of incident CVD in Chinese adults, especially among urban dwellers. Our findings underscored policy priorities of implementing joint control measures for fine particulate matter and O3 in the context of accelerated urbanization and population aging in China.

К оценке техникo-эксплуaтaциoннoгo сoстoяния гoрoдских железoбетoнных мoстoв и путепрoвoдoв

To consider the issue of assessing the technical and operational condition of urban reinforced concrete bridges and overpasses. Study technical passports of about 300 reinforced concrete bridge structures in Tashkent. Analyze in detail and formulate the main technical and operational indicators (TEI) as criteria for assessing the technical condition of bridge structures in Tashkent. Methods: methods for assessing the technical condition of the city’s bridge park objects have been determined — absolute and relative. For this purpose their purposes are indicated. Results: the statistics were compiled on the basis of the bridge park of the city of Tashkent, carried out by the authors of a survey of 30 city bridge structures. Based on the results of the examination of selected bridge structures, it was established that the main damage to the spans and supports of reinforced concrete bridges and overpasses is caused, first of all, by the poor condition of waterproofing, expansion joints and lack of water water pipes. The main technical and operational indicators (TEI) are formulated as criteria for assessing the technical condition of bridge structures in Tashkent, such as “safety and traffic comfort”, “durability”, “load capacity”, “throughput”, and “maintainability”. Practical importance: taking into account the specifics of a large metropolis, managing the technical condition of bridge structures in Tashkent is an extremely responsible and complex task. For use in practical operation of reinforced concrete bridge structures as the most widespread objects of the city’s road transport infrastructure, a statistical analysis was performed. From a practical point of view, this information will make it possible with a sufficient degree of probability to ensure and maintain the specified regulatory (design) levels of reliability, safety and durability of bridge structures.

Small organic molecules for aqueous zinc-ion batteries with stable structure and ultrafast H-ion and Zn-ion diffusion kinetics via coating

Aqueous Zn-ion batteries (AZIBs) with excellent electrochemical performance are achieved by using small organic molecules VO(acac)2 (IV) as cathode. The surface area and electrical conductivity of IV are increased by coating wrinkled rGO, thereby improving the electrochemical sluggishness of IV cathode. The VO(acac)2@rGO (IV@rGO) aqueous battery can display a high capacity of 327.2 mAh g−1 at 100 mA g−1. The Zn2+ and H+ con-insertion/extraction reactions within IV@rGO are a joint control of pseudocapacitance and diffusion process. The in-situ XRD combinded with ex-situ Raman and XPS reveal that the multivalent transition of vanadium and coordination reaction of organic functional groups (VO), and no significant volume change of IV structure implying near-zero expansion characteristic during charging/discharging process.

Finite element (FE) analysis of thermal stress in production process of multi-layer lining ladle

This paper presented the development of the thermo-mechanical coupling model and simulation analysis of a composite refractory layer ladle. The thermomechanical modeling of the ladle was carried out using the Finite Element Method (FEM), taking into account the joints between the slag line bricks as well as the contact between the composite refractory layers. The temperature and thermal stress characteristics of the overall ladle structure under different transit conditions were investigated using the finite element analysis software ANSYS. We also performed a comparative analysis on the improvement effect of thermal stresses by expansion joints of different sizes. The simulation results were validated with previous studies. The results showed that the installation of expansion joints within a suitable range did not significantly change the thermal expansion characteristics of the refractory lining, but it also reduced the thermal stress level of the lining to a large extent. A larger temperature gradient produced higher thermal stresses, and in the direction of the ladle height, the more downward the position of its maximum compressive stress was greater. Under different working conditions, compared with the axial and hoop stress, the radial stress was small in magnitude. Axial stress exhibited a greater degree of sensitivity to pressure variations than hoop stress. The developed thermodynamic model considering the full contact between the bricks and the refractory layer gave us a more complete view of the physical field laws inside the ladle.

Design and position-tracking control of a flexible joint based on the tendon-sheath mechanism

In this study, a flexible joint comprising active and passive driving modes was designed based on the tendon-sheath mechanism. Further, angle sensors and series elastomers (SE) were integrated inside the joint to produce a compact and flexible structure. First, a model of the flexible joint was established based on the involved stiffness relation, and this model was validated using the dSPACE system. Next, to respond to the low control accuracy and poor anti-interference ability of the flexible joints, a sliding-mode controller (SMC) was designed to facilitate the precise position control, as well as achieve improved robustness. However, the flexible joint was prone to considerable tremors when the overall system was subjected to a large load mass. Therefore, a fuzzy-modified adaptive SMC (FMASMC), which adaptively adjusts the SMC parameters, was designed based on the historical-state data of the system. This control method could suppress the trembling phenomenon of the system while improving its control accuracy. Finally, it was experimentally verified that the compliant joint could achieve the expected functions. Compared with the proportional–integral–derivative (PID) and SMC control algorithms, the FMASMC algorithm could effectively overcome the tremors of the compliant actuation system and improve its control accuracy; moreover, it is also suitable for controlling other compliant joints.

Investigating the Application of Smart Materials for Enhanced Maintenance of Rubber Expansion Joints in Bridge Expansion Joint Systems

In South Korea, the public infrastructure encompasses 172,111 facilities, with bridges accounting for a significant segment (totaling 34,199). These bridges undergo expansion due to traffic, vehicular loads, and temperature fluctuations. Expansion joint devices are installed to maintain vehicle stability and driving performance across expansion gaps. While these devices effectively ensure vehicular stability and performance, they do not address issues such as leakage and debris fall; therefore, rubber expansion joints should be installed. However, these rubber joints are prone to damage from various factors, resulting in secondary issues such as girder corrosion and accidents under bridges. Because of these inherent vulnerabilities, these joints require frequent replacements, making continuous bridge maintenance challenging. Therefore, this study explores the development of novel expansion joints using superelastic shape memory alloys to overcome the limitations of traditional rubber expansion joints. A comparative finite element analysis was conducted on the developed superelastic shape memory alloy and traditional rubber expansion joints. This study also assessed the long-term usability of these novel joints, particularly their ability to revert to their original shape post load removal. This research presents a promising alternative to conventional expansion joints and holds potential implications for enhancing the durability and safety of bridge infrastructure.

Совершенствование технологий ремонта и изготовления соединений с натягом элементов колесных пар железнодорожного подвижного состава

In this article the main directions for increasing the operational reliability of tension joints for wheel pair elements of railway rolling stock have been given. Particular attention has been paid to such joints as “axis – wheel hub”, “axis – inner rings of axis bearings”, “wheel center – tire”. A number of technical and technological solutions have been proposed aimed at improving the technology for repair work and control of tension joints. These solutions ensure the cost reduction of repair work, as well as the increase in the safety of train traffic.

Modeling assessment of air pollution control measures and COVID-19 pandemic on air quality improvements over Greater Bay Area of China

A remarkable progress has been made toward the air quality improvements over the Guangdong-Hong Kong-Macao Greater Bay Area (GBA) of China from 2017 to 2020. In this study, for the first time, the emission reductions of regional control measures together with the COVID-19 pandemic were considered simultaneously into the development of the GBA's emission inventories for the years of 2017 and 2020. Based on these collective emission inventories, the impacts of control measures, meteorological variations together with temporary COVID-19 lockdowns on the five major air quality index pollutants (SO2, NO2, PM2.5, PM10, and O3, excluding CO) were evaluated using the WRF-CMAQ and SMAT-CE model attainment assessment tool over the GBA region. Our results revealed that control measures in the Pearl River Delta (PRD) region affected significantly the GBA, resulting in pollutant reductions ranging from 48 % to 64 %. In contrast, control measures in Hong Kong and Macao contributed to pollutant reductions up to 10 %. In PRD emission sectors, stationary combustion, on-road, industrial processes and dust sectors stand out as the primary contributors to overall air quality improvements. Moreover, the COVID-19 pandemic during period I (Jan 23-Feb 23) led to a reduction of NO2 concentration by 7.4 %, resulting in a negative contribution (disbenefit) for O3 with an increase by 2.4 %. Our findings highlight the significance of PRD control measures for the air quality improvements over the GBA, emphasizing the necessity of implementing more refined and feasible manageable joint prevention and control policies.

Facilitating the emergence of intraverbal tacts by autistic children via joint control.

Rodriguez et al. (2022) discovered that teaching four component skills was sufficient to facilitate the emergence of intraverbal tacts across four applications with three participants. Our study replicated and evaluated an extension of this procedure that was directed at facilitating intraverbal tacts when a child learns the component skills but continues to fail to produce intraverbal tacts. The extension consisted of procedures to enhance the divergent control exerted by the auditory stimulus (i.e., the question) and the discriminability of joint control. Intraverbal tacts emerged for all three participants after undergoing the extension procedures. These results are discussed in the context of a conceptual analysis of intraverbal tacts and the potential role of joint control.

Abstract P393: Trends in Risk Factor Control Among US Adults With Cardio-Kidney-Metabolic Multimorbidity, 1999-2020

Background: Risk factor control is foundational to preventing the onset and progression of cardiovascular, kidney, and metabolic (CKM) syndrome. Although risk factor control has been evaluated for these conditions individually, less is known about individuals with CKM syndrome. Objective: To evaluate the control of key risk factors among US adults with CKM syndrome. Methods: Nationally representative, cross-sectional data on US adults from the 1999-2020 NHANES cycles were evaluated. CKM conditions included cardiovascular disease (ASCVD or HF), at least moderate-risk chronic kidney disease, and type 2 diabetes (self-reported or HbA1c ≥6.5%). Among adults with advanced-stage CKM syndrome (≥2 conditions), the proportion with joint control of risk factors was estimated. Risk factor control was defined as: BP <140/90 mmHg, HbA1c <8%, and LDL-C <100 mg/dL. Sensitivity analyses included a stricter definition (BP <130/80, HbA1c <7%, and LDL-C <70) and an expanded set of risk factors (BMI <30 kg/m 2 and current non-smoking status). Results: Between 1999-2014, the proportion of US adults with CKM syndrome with joint control of BP, HbA1c, and LDL-C increased from 10.5% (95% CI: 7.8%, 13.2%) to 32.5% (29.6%, 35.5%), then declined to 28.8% (24.4%, 33.1%; estimated number without joint control = 14.5 million) in 2015-2020, per the main definition ( Figure ). Considering more contemporary thresholds, joint risk factor control was observed in less than 1 in 10 US adults across the study interval. Using the most comprehensive definition (BP <130/80, HbA1c <7%, LDL-C <70, BMI <30, non-current smoking) only 2.2% (1.3%, 3.1%) demonstrated optimal control in 2015-2020. Conclusions: Despite improvement between 1999-2014, comprehensive risk factor control among US adults with CKM syndrome declined in 2015-2020. More than 2 in 3 contemporary US adults with CKM syndrome are estimated to have suboptimal risk factor control, amplifying the need for integrative approaches in this high-risk population.

Full-scale experimental investigation on the performance of seamless asphalt plug joint through mixture design and structural enhancements

The seamless asphalt plug expansion joint integrates a traditional asphalt plug joint (APJ) with an overlying continuous asphalt concrete layer, preventing block failure of the asphalt plug joint and enhancing driving comfort. However, typical damages such as fatigue cracking, rutting, and permanent deformation often occur in the upper asphalt layer. This is attributed to the inadequate stiffness of the lower joint plug mastic, particularly under high temperatures and heavy loads. To extend the service life of asphalt plug expansion joints under such conditions and enhance their durability, efforts were made to bolster the performance of the lower asphalt plug joint mixture and improve anti-rutting performance. This study involved: (1) Qualifying APJ mixture requirements under high temperature and heavy load by focusing on two critical material properties: good rutting resistance and permanent deformation resistance. High temperature rheological properties of these binders were examined through temperature scanning tests and multi-stress creep recovery tests (MSCR). (2) Exploring the impact of binder-aggregate ratios and specimen molding methods (standard compaction, paving vibration and pre-mixing) on the bonding strength and rutting resistance of the APJ mixture. This analysis was conducted using pull-off tests and dynamic stability tests. (3) Development of a novel APJ featuring dowel bars to enhance vertical deflection resistance and joint horizontal movement. Comprehensive laboratory tests showcased the modified joint structure's resilience after numerous test cycles, demonstrating exceptional resistance to bending and vertical deformation. The significant findings from this research provide valuable insights for optimal material selection, appropriate joint design, and installation guidelines for seamless asphalt plug expansion joints.

Synergistic controls of water column stability and groundwater phosphate on coastal algal blooms

Algal blooms have been identified as one major threat to coastal safety and marine ecosystem functioning, but the dominant mechanism regulating the formation of algal blooms remains controversial, ranging from physical control (via water column stability), the chemical control (via coastal nutrients) to joint control. Here we leveraged the unique data collected in the Hong Kong water over the annual cycle and past three decades, including direct observations of algal blooms and coastal nutrients and process model output of water column stability, and evaluated the differential competing hypotheses in regulating algal blooms. Our results demonstrate that the joint mechanism rather than the single mechanism effectively predicts all algal blooms. Meanwhile, we observed that the adequate nutrients (phosphate, PO43−) significantly originate from coastal groundwater. The production and fluctuation of PO43− in beach aquifers are primarily governed by groundwater temperature, leading to a sustained and sufficient supply of PO43− in a low groundwater temperature environment. Furthermore, along with submarine groundwater discharge (SGD), the ongoing release of PO43− in groundwater enters coastal waters and serves as sufficient nourishment for promoting algal blooms in coastal areas. These results highlight the importance of both physical and chemical mechanisms, as well as SGD, in regulating coastal algal blooms. These findings have practical implications for the prevention of coastal algal blooms and provide insights into mariculture, water security, and the sustainability of coastal ecosystems.

A quantitative analysis of causes for increasing ozone pollution in Shanghai during the 2022 lockdown and implications for control policy

Ground-level ozone (O3) pollution is a major air quality issue in densely populated urban areas. Despite a significant decline in human activities in the megacity Shanghai from March 28 to May 31, 2022, ground-level measurements indicate a rise in maximum daily average 8-h (MDA8) O3 concentrations in comparison to the corresponding period in 2021. There is a need for quantitative analysis to identify the reasons behind this increasing O3 concentration. We analyzed ground measurements of O3 and its precursors and meteorological parameters made in Shanghai, using random-forest (RF) model and chemical box model to elucidate the roles of meteorological and chemical factors in influencing O3 concentrations. Across urban, suburban, semi-rural, and coastal sites, the urban center of Shanghai experienced the largest decreases in the concentrations of nitrogen oxides (NOx; 53%) and volatile organic compounds (VOCs; 52%), with the most notable rise in MDA8 O3 concentrations (16%). RF modeling indicates that meteorological factors reduced MDA8 O3 concentrations by a marginal 3%, whereas a decline in anthropogenic emissions resulted in a 17% increase in MDA8 O3 concentrations. Chemical box modeling at the Pudong urban site indicates that while the decline in VOCs reduced O3 production by 42%, this was negated by a reduction in NOx from traffic emissions, which enhanced O3 production by 51%, resulting in an increase in O3 production overall. Despite a halving in precursor levels, Shanghai's urban centre remains predominately under VOC-limited conditions throughout the study period, with high NO2 levels from the petrochemical industry and traffic emissions. Joint control of anthropogenic VOCs (AVOCs) and NOx, with a ratio greater than 1.29, could help avoid exacerbation of O3 pollution and reduce NO2 pollution. Our findings emphasize the necessity of reducing industrial emissions along with ongoing green transportation strategies for alleviating O3 pollution in megacities like Shanghai.

Ozone and its precursors at an urban site in the Yangtze River Delta since clean air action plan phase II in China

In response to regional ozone (O3) pollution, Chinese government has implemented air pollution control measures in recent years. Here, a case study was performed at an O3-polluted city, Wuhu, in Yangtze River Delta region of China to investigate O3 variation trend and the relationship to its precursors after implementation of Clean Air Action Plan Phase II, which aims to reduce O3 pollution. The results showed that peak O3 concentration was effectively reduced since Clean Air Action Plan Phase II. Due to significant NOx reduction, O3 formation tended to shift from volatile organic compound (VOC)-limited regimes to NOx-limited regimes during 2018–2022. VOC/NOx ratios measured in 2022 revealed that peak O3 concentration tended to respond positively to NOx. Apart from high-O3 period, Wuhu was still in a VOC-limited regime. The relationship of maximum daily 8-h ozone average and NO2 followed a lognormal distribution with an inflection point at 20 μg m−3 of NO2, suggesting that Wuhu should conduct joint control of VOC and NOx with a focus on VOC reduction before the inflection point. Alkenes and aromatics were suggested to be preferentially controlled due to their higher ozone formation potentials. Using random forest meteorological normalization method, meteorology had a positive effect on O3 concentration in 2018, 2019 and 2022, but a negative effect in 2020 and 2021. The meteorology could explain 44.0 ± 19.1% of the O3 variation during 2018–2022. High temperature favors O3 production and O3 pollution occurred more easily when temperature was over 25 °C, while high relative humidity inhibits O3 generation and no O3 pollution was found at relative humidity above 70%. This study unveils some new insights into the trend of urban O3 pollution in Yangtze River Delta region since Clean Air Action Plan Phase II and the findings provide important references for formulating control strategies against O3 pollution.

Snake Robot with Motion Based on Shape Memory Alloy Spring-Shaped Actuators.

This study presents the design and evaluation of a prototype snake-like robot that possesses an actuation system based on shape memory alloys (SMAs). The device is constructed based on a modular structure of links connected by two degrees of freedom links utilizing Cardan joints, where each degree of freedom is actuated by an agonist-antagonist mechanism using the SMA spring-shaped actuators to generate motion, which can be easily replaced once they reach a degradation point. The methodology for programming the spring shape into the SMA material is described in this work, as well as the instrumentation required for the monitoring and control of the actuators. A simplified design is presented to describe the way in which the motion is performed and the technical difficulties faced in manufacturing. Based on this information, the way in which the design is adapted to generate a feasible robotic system is described, and a mathematical model for the robot is developed to implement an independent joint controller. The feasibility of the implementation of the SMA actuators regarding the motion of the links is verified for the case of a joint, and the change in the shape of the snake robot is verified through the implementation of a set of tracking references based on a central pattern generator. The generated tracking results confirm the feasibility of the proposed mechanism in terms of performing snake gaits, as well as highlighting some of the drawbacks that should be considered in further studies.

Fault Detection of In-Service Bridge Expansion Joint Based on Voiceprint Recognition

Bridge expansion joints (BEJs) in service are susceptible to damage from various factors such as fatigue, impact, and environmental conditions. While visual inspection is the most common approach for inspecting BEJs, it is subjective and labor-intensive. In this paper, we propose a novel methodology for detecting the fault status of BEJs, inspired by voiceprint recognition (VPR) based on audio signals. We establish an Artificial Neural Network to filter nonevent segments from low signal-to-noise ratio signals, achieving an AuC value of 0.981. We design and improve ConFormer VPR models with a multifeature aggregation strategy and cascade them to realize fault detection of BEJs. For three successive tasks in classifying environment sound types, vehicle impact types, and faults, the ConFormer VPR models achieve AuC values of 0.975, 0.925, and 0.886, respectively, demonstrating the feasibility of our methods for unmanned inspection of BEJs. In future research, the introduction of multiple types of damage and the implementation of benchmarking tests are planned to further enhance the capabilities of the system.

Modelling operator control work across traffic management domains: implications for interaction design

Traffic management in aviation, shipping, and rail transport shows similarities and dissimilarities in the work process. For example, they share the temporal aspect, but different levels of urgency in the control work set different requirements on monitoring, decisions, and actions. However, few studies have been presented that model and compare the different domains in terms of temporal decision-making. The Joint Control Framework (JCF) is an approach to analyse and temporally model operators’ control processes from a cognitive systems engineering perspective. In this study, we have used JCF to map, and compare, cognitive joints, such as perceptions, decisions, and actions, in temporally challenging control situations in air traffic control, maritime vessel traffic service, and train traffic management. Data was collected collaboratively with traffic operators, focusing on (1) identifying challenging traffic situations and (2) jointly modelling the temporal decision-making patterns of these situations using simplified JCF. Post-analysis was done by breaking down the results into different processes and comparing domains to ascertain how operators maintain control. An intermediate level of activity—between general monitoring and work with specific vehicles—was identified: processes-in-focus. A shared problem arises in the shift between general monitoring and the processes-in-focus. All processes-in-focus comprise cognitive joint cycles of perceptions, decisions, and actions. However, depending on the framing of processes-in-focus, the patterns of joints, such as temporal extension and complexity, differ. In the remainder of the article, implications for the interaction design, in particular the potential for human–AI/automation teaming with higher levels of automation and cognitive autonomy, are discussed.

VSG Frequency Regulation Strategy for Adaptive Model Predictive Control

When the active power of a Virtual Synchronous Generator (VSG) is unbalanced, the frequency will fluctuate significantly. Based on this, this article proposes an adaptive model predictive control method. By introducing a hyperbolic tangent function to construct an adaptive moment of inertia that includes frequency change and frequency change rate to provide the inertia for the island microgrid system, and the predicted model is updated in real-time; At the same time, model predictive control is used to calculate the optimal power reference value of VSG, strengthening the power support of VSG. The results indicate that under joint control improves the frequency regulation capability of VSG units and further enhances the system frequency performance, and the frequency deviation reduces from 0.15Hz to 0.05Hz, and the frequency change rate reduces from 0.58Hz/s to 0.5Hz/s. It is proved that the proposed control strategy can effectively suppress the maximum frequency offset and maximum frequency change rate during power fluctuations.