Operation Mode Changes Research Articles

Adaptive CVCF controller design for an energy storage system considering an operation mode change in a standalone microgrid

Adaptive CVCF controller design for an energy storage system considering an operation mode change in a standalone microgrid

Flexible methanol production process using biomass/municipal solid waste and hydrogen produced by electrolysis and natural gas pyrolysis

Biomass-derived liquid fuels with low greenhouse gas emissions are an integral part of decarbonization plans. Three pathways for enhancing production of methanol from biomass and municipal solid waste (MSW), natural gas, and renewable electricity are explored using hydrogen produced from water electrolysis, natural gas pyrolysis, or combinations of these inputs. A combined electrolysis and natural gas pyrolysis process is designed to be flexible, changing operation modes depending on the cost of feedstocks (i.e. electricity and natural gas). A techno-economic analysis is performed to assess and compare the economic attractiveness of these processes. Hydrogen produced from natural gas pyrolysis could potentially be more economically attractive than electrolytic hydrogen using renewable electricity. Moreover, natural gas pyrolysis CO2 emissions could be substantially lower than emissions from conventional steam methane reforming (e.g., CO2 emissions which are 25 % or lower compared to CO2 emission from steam methane reforming). Hydrogen enhancement of the methanol production process results in increase of around a factor of two in carbon conversion efficiency (e.g. from 44% to 94 %). Methane pyrolysis shows high economic potential assuming the technical challenges to its commercialization are successfully addressed. Given an installed cost of electrolyzer of 1000 $/kW, electricity price of 50 $/MWh, natural gas price of 5 $/GJ and 100 $/ton selling price of carbon black, the natural gas pyrolysis design results in the lowest methanol production cost. Our analysis indicates that methanol could be produced in a price range of 300–1000$/ton depending on feedstock price (particularly electricity) and the chosen process.

Accelerating reinforcement learning with case-based model-assisted experience augmentation for process control

In the context of intelligent manufacturing in the process industry, traditional model-based optimization control methods cannot adapt to the situation of drastic changes in working conditions or operating modes. Reinforcement learning (RL) directly achieves the control objective by interacting with the environment, and has significant advantages in the presence of uncertainty since it does not require an explicit model of the operating plant. However, most RL algorithms fail to retain transfer learning capabilities in the presence of mode variation, which becomes a practical obstacle to industrial process control applications. To address these issues, we design a framework that uses local data augmentation to improve the training efficiency and transfer learning (adaptability) performance. Therefore, this paper proposes a novel RL control algorithm, CBR-MA-DDPG, organically integrating case-based reasoning (CBR), model-assisted (MA) experience augmentation, and deep deterministic policy gradient (DDPG). When the operating mode changes, CBR-MA-DDPG can quickly adapt to the varying environment and achieve the desired control performance within several training episodes. Experimental analyses on a continuous stirred tank reactor (CSTR) and an organic Rankine cycle (ORC) demonstrate the superiority of the proposed method in terms of both adaptability and control performance/robustness. The results show that the control performance of the CBR-MA-DDPG agent outperforms the conventional PI and MPC control schemes, and that it has higher training efficiency than the state-of-the-art DDPG, TD3, and PPO algorithms in transfer learning scenarios with mode shift situations.

An Improvement of Holistic Control Tuning for Reducing Energy Consumption in Seamless Transitions for a BESS Grid-Connected Converter

This paper presents an improvement of the tuning process of the holistic control published by the authors in previous research to achieve a seamless transition among three operation mode changes and load transients. The proposed tuning approach reveals an improvement in the energy consumption of the Battery Energy Storage System (BESS) during all operation mode transients compared to the holistic control. For this aim, the system addressed is a BESS with the capability to ride through three operation modes of interest: the grid-connected mode as an inverter, the grid-connected mode as a rectifier, and the islanded operation mode. The LCL filter design by using the Butterworth polynomial approach is presented in more detail, and its smooth inherent transient response is preserved when the tuning of the controller gains is carried out by using the same polynomial approach but now including the integral action within the Butterworth polynomial. To reveal the reduction in energy consumption, the closed-loop transfer functions of each mode were used to compare the previous holistic control and this new one named by the authors as the “improved holistic control”. The closed-loop system fulfills the frequency and voltage thresholds of the IEEE 1547-2018 standard seamlessly. The simulation runs were conducted on the PSCAD/EMTDC to evaluate the seamless transition among the operation mode changes and load steps. The experimental results in a 617 W, 120 VL−L three-phase converter prototype are included to demonstrate the validity of the improved holistic control.

DISTANCE LEARNING AND FACE-TO-FACE LEARNING: STUDENT PERCEPTION OF QUALITY ASSURANCE AND PROSPECTS FOR IMPROVEMENT IN EDUCATION MANAGEMENT TECHNOLOGIES

Global challenges are an objective factor influencing the development of socio-economic and socio-political subsystems of society. The influence of this factor is not uniform, causing a different impact on every social activity sphere. The actualization of challenge to people’s health risk, determined by the widespread of the COVID-19 infection in 2020, has become the cause of changes in modes of operation for most of social institutes, including that of education. To implement the national governments’ decisions concerning prevention of population’s infecting with COVID-19, the administrations of most European universities have refrained from teaching educational programs in the face-to-face mode and adopted the decision of applying the distance form of training. This forced step by the universities has determined the raise in stakeholders’ interest in the problematics of the quality of education obtained through the distance mode of higher education. In their attempt to provide the answer concerning the potential of the distance form of training in ensuring education quality, the authors of this article have conducted a poll of 544 students from higher education establishments of Eastern Ukraine. The answers obtained were analyzed by the following aspects: comparing education quality depending on the mode of obtaining it; perspectives of applying the distance form of education at each stage of higher education; efficiency of applying the distance training instruments in the training process. On the results of analyzing the respondents’ answers, recommendations and conclusions as to the state of distance education and the perspectives of its development were formulated. Besides, the article offers a classification of distance education instruments and proposes recommendations concerning their application in the training process. The article’s content will be of interest not only for specialists working at agencies that ensure quality of higher education, but also for stakeholders and administrations of the universities that are planning to raise the level of their presence at the education services market on account of implementing the distance training’s potentials.

Adaptive Distance Protection Based on the Analytical Model of Additional Impedance for Inverter-Interfaced Renewable Power Plants During Asymmetrical Faults

Due to limited amplitude and controlled phase of current supplied by inverter-interfaced renewable power plants (IIRPPs), the IIRPP-side distance protection of lines connected to IIRPPs fails to detect the fault location accurately, so it may malfunction. The composite sequence network of a line connected to an IIRPP during asymmetrical faults is analyzed, and an adaptive distance protection based on the analytical model of additional impedance is proposed in this study. Based on open circuit property of negative-sequence network at the IIRPP-side, the equivalent impedance of power grid and current flowing through fault point are calculated in real-time using local measurements, which are substituted into the analytical model of additional impedance to calculate fault location. In the case of negative-sequence reactive current injection from IIRPPs during asymmetrical faults, the error of calculating fault point current from local measurements is analyzed and corrected to ensure reliability of the proposed protection. The proposed protection alleviates the effect of fault resistance in a system with weak sources. In addition, the proposed protection can adapt to different grid codes (GCs), the operation mode change of the power grid, and the capacity change of the IIRPP. PSCAD/EMTDC test results verify the effectiveness of the proposed protection.

Symulacja procesu pracy dwuobwodowego wgłębnego systemu wypływowego

The article is devoted to a study of the flow's nature distribution in the above-bit ejection system as part of a series and parallel connection of two jet pumps designed to improve the technical and economic indicators of drilling production wells. Using the finite element method and computer programs, the critical value has been determined of the hydraulic resistance of the sludged section of the bottomhole, which provides an automatic change in the ejection system operation mode from injection to injection-suction. Regularities of changes in the hydrodynamic parameters of the ejection system have been established and the probability and conditions for the existence of non-operating modes of jet pumps have been analyzed. When conducting experimental studies, the influence of the flow rate of the working medium on the flow characteristic of a jet pump of a direct-flow and swirling working flow has also been determined. To swirl the flow, a plate with an inclination angle of the guide elements of 15° placed in the working nozzle of the jet pump has been used. The swirling of the working flow makes it possible to increase the injection ratio of the jet pump. The maximum increase in the value of the injection coefficient is 20.84% and corresponds to small (up to 104) Reynolds numbers of the working flow. The ratio between the maximum and minimum values of the injection coefficient of the flow characteristics of the jet pump when swirling the working flow is halved.

Simulation-Based Analysis of Dynamics of Autonomous Electric Power Systems

This paper is devoted to the development of a model of an autonomous electric power system to study random processes of voltage, current and power changes in emergency and dynamic operation modes. A diagram for calculating short-circuit currents has been presented, which was focused on a typical wide range of autonomous power plants with three diesel generator units. A model of an autonomous power plant has been developed, allowing to solve the assignments of determining short-circuit currents and starting currents of electric power machines. The equivalent network of the studied power system for transient calculations has been presented. Thus, the voltage waveforms have been obtained. A comparative assessment of theoretical calculation methods and simulation analysis demonstrated a high degree of accuracy of the simulation results. The use of approach suggested in the article and the developed model allows to increase the accuracy of conclusions when testing the abruptly variable processes and to make the most reasonable choice of measures to improve the quality of electricity and the reliability of electrical equipment. In particular, simulation analysis and obtaining transient curves for starting powerful consumers allow more accurately choose the type of circuit breakers used and the related configuration parameters.

Overviews of Internet of Things Applications in China’s Hospitality Industry

During the current post-epidemic period, hygiene requirements and health needs in the hospitality industry keep increasing, and consumers become more concerned about the cleanliness of hotels and have stronger demands for contactless services in hotels. The growth and popularity of IoT technology in China make it more accessible to a wider range of service industries and provides the basis for the application of IoT in the hospitality industry. The application of IoT devices in hotels mainly includes intelligent robots, intelligent guest control, systems, etc., which helps to realize contactless services in hotels. This research reviews the entire development cycle of the application of IoT in the hospitality industry, from the founding, development, and expansion of companies to their IPO and post-IPO maturity. From a perspective combined with IoT technology, we can cope with the changing industry models, business models, and operation modes in the hospitality industry more efficiently. The development of IoT in hotels will move towards humanization and service-orientation. Through the role of human–machine linkage and the reasonable management of IoT equipment, IoT technology can reasonably promote the efficiency of manual work, while injecting “warmth” and “quality” into IoT equipment.

Detection of operating mode changes, without a priori model and in uncertain environments

Starting from the general observation that a measurement delivered by a sensor is subject to an uncertainty, its use in a decision chain must take into account this imprecise character. It is thus advisable to propagate this imprecision in all the chain of treatment and use of the measurement in question. In what follows, this principle is applied to the diagnostic function, one of the components of system monitoring. More precisely, we propose to analyze the temporal data collected on a system in order to detect and locate possible changes in the behavior of this system.

Study on the tolerance of low-temperature CO methanation with single pulse experiments

In this contribution, single pulse reaction experiments are discussed in the context of dynamic reactor operation and used to determine the tolerance of reactors arising from sorption effects at the catalyst surface. A defined amount of CO is dosed together with an internal standard (He) in a constant H2 stream, and the pulse response is observed with reference to the internal standard, which is representing the fluid dynamics of the injected pulse. Different responses are obtained depending on the catalyst mass (Ni/Al2O3) and the operation temperature (170 °C-300 °C). The tolerance of the reactor can be deduced from the experimental findings. On the one hand, the catalyst adsorption capacity determines the ability to buffer fluctuations at low reaction temperatures (T<220°C), which are beneficial for full-conversion, overcoming thermodynamic restrictions. On the other hand, temperature determines the transient response of the system and is independent of the catalyst mass. From these findings the study reveals that reactors represent important buffer systems during load changes in dynamic operation modes and provide an intrinsic tolerance originating from sorption processes at the catalyst surface.

COVID-19 impact on maritime traffic and corresponding pollutant emissions. The case of the Port of Barcelona

The impact of the SARS-CoV pandemic has gone well beyond health concerns, reaching the maritime industry. The study on the environmental impact of shipping industry during COVID-19 pandemic can provide useful insights to propose new management policies regarding shipping operations, both in-port and on the route. We present a case study centred in the Port of Barcelona covering a 30 nautical miles range in the period March to July 2020, during which different levels of restrictions and stringent lockdown measures were enforced. In this paper, we assess the impact of COVID-19 on maritime traffic and its related emissions in port cities using real-time Automatic Identification System (AIS) data. Interestingly, results show that the decline in maritime traffic is not correlated with a decrease in maritime emissions due to changes in vessel operation. During lockdown (March to June 2020), we observed a 27.9% reduction in the number of port calls compared to the pre-lockdown scenario, whereas pollutant emissions show a moderate decrease (1.8% for CO2), no significant reduction (SO2 and PM) or a slight increase (1.3% for NOx). This can be directly assigned to changes in vessel operation mode, i.e. vessels switched from Underway to At Anchor or Moored status, during which auxiliary engines are used at higher loads.

Wind integration cost in China: A production simulation approach and case study

The integration cost of large-scale variable renewable energy (VRE) in China’s coal-dominated inflexible power systems is of significant concern when studying the generation cost of VRE. One key component of studies about integration cost is the question of how to estimate the impact of large-scale VRE integrated into power systems on the operation mode of conventional generators. It is intuitive to compare system-level costs with and without VRE under a benchmarked system. In this study, we employ a unit commitment (UC) model to simulate the output of various types of units based on minimizing the total power system cost. Then, we estimate the conventional generator operation cost change caused by the change of operation mode. Using the power system in Jilin province as a typical case, the integration cost will increase with increased VRE penetration, reaching 123.5 CNY/MWh at 40% penetration level. The idle cost of the coal-fired power units accounts for 69% of the integration cost at 40% VRE penetration, the highest proportion; wind curtailment cost ranks second for 26%, while the incremental operating cost of coal power accounts for 4.7%. With a long-term perspective, establishing a complete power market and adopting an appropriate pricing mechanism to incentivize system flexibility is the best solution for adopting VRE.

АНАЛИТИЧЕСКОЕ ИССЛЕДОВАНИЕ СИЛ ШЛИФОВАНИЯ ПРИ НАЛОЖЕНИИ УЛЬТРАЗВУКОВЫХ КОЛЕБАНИЙ С ВЫСОКОЙ АМПЛИТУДОЙ

An analytical study of the grinding forces under the superposition of ultrasonic vibrations (UV) with an amplitude providing intermittent contact of the abrasive grains of the circle with the workpiece, was performed. The grinding force was defined as the sum of the forces from the individual grains of the circle located on different sections of their trajectory relative to the treated surface of the workpiece. When the grain is moved in the contact zone of the circle with the workpiece, its operating mode changes and depends on the phase of vibrations. Moving relative to the workpiece, the grain performs plastic deformation and micro-cutting, on part of the trajectory it can come out of contact with the workpiece. The sequence of implementation of these modes depends on the phase of the UV. The components of the grinding force were calculated as the arithmetic mean of their values determined at different vibration phases. The coordinates of the points on the grain movement trajectory corresponding to the change in its operating mode were determined numerically. Numerical simulation of forces using the obtained dependences and experimental study were performed for flat grinding of 12H18N10T steel blanks by the periphery of the circle. The frequency of the superimposed UV is 18.6 kHz; the amplitude of the oscillations in the direction coinciding with the axis of the grinding wheel is 10 microns. To impose vibrations on the workpiece in the course of experimental studies, a device was used in which the workpiece is one of the links of the vibration system. It is established that the difference between the calculated and experimental values of the components of the grinding force is 8 ... 15%. With the imposition of a UV, grinding force is lower by 20 ... 21% than with out their use.

Estimation of energy efficiency potential of electric drive pumping units in steady operating modes

According to the results of studies of steady operation modes of electric pumping units of Ukrainian oil pumping stations, have been identified the main reasons of efficiency decrease of their performance during operation. It is determined that the normative documents regulating the efficient operation of pumping units of the main oil pipelines of Ukraine need to be improved. The assessment of energy efficiency potential of the main pumping unit on the example of pump НМ-3600-230 with synchronous electric drive СТД-2500-2 is carried out and the main ways to increase the efficiency of electricity use at oil pumping stations of main oil pipelines are analyzed. A complex mathematical-graphic model of a centrifugal pump and a synchronous electric motor is used to determine the parameters of the process of energy consumption and energy use of hydraulic and electrical subsystems of the pump unit, which allowed to take into account possible changes in equipment characteristics and modes of operation. The value of the relative specific consumption of electricity for pumping of working fluid for regulated and unregulated electric drive based on a complex electro-hydraulic model of the main pump was calculated, which allowed to promptly recalculate the characteristics of the centrifugal pump and electric motor taking into account their technical condition and to determine the potential of the pumping unit. It is determined that an effective way to reduce energy consumption by main pumping units is applying of a controlled electric drive at oil pumping stations, but the feasibility of such a measure requires additional technical and economical calculations. It is determined that to increase the efficiency of pumping units is necessary to avoid low flow-duty modes, to form maps of main oil pipelines in a way to ensure optimal in terms of energy efficiency operation modes of electro-hydraulic equipment of oil pumping stations and to change operation mode of pump and motor in terms of their technical condition.

SPV-BES System Synchronized to Three-Phase Four-Wire AC Distribution Network

Solar photovoltaic (SPV) system performance degrades due to the presence of nonlinear/unbalanced loads at the point of common coupling (PCC). These loads also cause the current in the ac network's neutral conductor, which causes additional losses and the voltage difference between the neutral conductor and the ground. This work addresses these problems and presents the control algorithm for the SPV system to improve its performance and the power quality (PQ) at the PCC, to reduce the current flow in the ac network's neutral conductor, and to maintain the balanced operation in the ac network at unbalanced loads. The battery energy storage is incorporated with the SPV system to improve the supply's reliability at the load end by operating the system in the islanded mode (ILM) when the ac network supply is interrupted. A new application of the variable zero attracting (VZA) least mean square (LMS) adaptive control algorithm is presented for the PQ improvement in both grid-connected mode (GCM) and ILM operations. The VZA component reduces the steady-state oscillation in the LMS algorithm without compromising its dynamic response. The seamless operation is used to avoid any abnormality in voltages and currents of the system operating mode changes from the ILM to the GCM after the grid recovery. The performance of the system is tested on the developed Simulation model and further verified by the experimental study performed on a reduced rating prototype.

Models and Algorithms for Predicting an Asynchronous Motor Heating when Changing Operation Modes

Models and Algorithms for Predicting an Asynchronous Motor Heating when Changing Operation Modes

A Decision Support System for Changes in Operation Modes of the Copper Heap Leaching Process

Chilean mining is one of the main productive industries in the country. It plays a critical role in the development of Chile, so process planning is an essential task in achieving high performance. This task involves considering mineral resources and operating conditions to provide an optimal and realistic copper extraction and processing strategy. Performing planning modes of operation requires a significant effort in information generation, analysis, and design. Once the operating mode plans have been made, it is essential to select the most appropriate one. In this context, an intelligent system that supports the planning and decision-making of the operating mode has the potential to improve the copper industry’s performance. In this work, a knowledge-based decision support system for managing the operating mode of the copper heap leaching process is presented. The domain was modeled using an ontology. The interdependence between the variables was encapsulated using a set of operation rules defined by experts in the domain and the process dynamics was modeled utilizing an inference engine (adjusted with data of the mineral feeding and operation rules coded) used to predict (through phenomenological models) the possible consequences of variations in mineral feeding. The work shows an intelligent approach to integrate and process operational data in mining sites, being a novel way to contribute to the decision-making process in complex environments.

Phase-chronometric diagnostic system for main drive of rolling mill

At present at the diagnostic of metallurgical equipment state, expert methods of evaluation are prevailed which have subject character. To solve the problem of information-metrological support of rolling mill stand effectively, a phase-chronometric method was proposed, elaborated in N.E. Bauman Moscow State Technical University. It was shown that increase of quality of measuring diagnostical information is provided by transfer from amplitude to chronometric scale and means of its realization at relative errors about 5×10‒4 % at the industrial frequency. At the phase-chronometric method, precision measuring of time intervals, correspondent to the phases intervals of the working cycle is used, depending on characteristic features of motion of a mechanism elements. In contrast to vibro-diagnostic method, by using the phase-chronometric method, the change of operation mode of rolling equipment can be defined hundred times quicker. Cyclicity of a mechanism motion and minimal scattering of measurement results at accomplishing working cycle enable to reveal stable in time diagnostic features and individual quantitative parameters values, which characterize technical state of a rolling mill. The proposed phase-chronometric system consists of an angle sensor of position (incremental encoder), system of information collection and defining of time intervals and personal computer with application software. The system of information collection and defining of time intervals is realized based on a plate, functionally uniting high-stability pulse generator, scale convertor, counter, measuring pulse generator and chrono-comparator. The embedded systems to realize the phase-chonometric metod are simple and reliable in operation. To realize the phase-chronometric method, a mathematical model was elaborated, comprising a system of differential equations, describing interaction of the package of interrelated multi-mass torsion systems. It was showed that verified mathematical model enabled quickly to reveal defects in a rolling mill operation.

Dynamic capacity and variable runway configurations in airport slot allocation

The airport slot allocation procedure relies on a (fixed) capacity to allocate slots to airlines, which often leads to under/over utilization of slots, depending on how conservative the airport planners are. This demand and capacity imbalance over the peak period can best be addressed during the strategic planning phase by displacing flights from their originally allocated slots to neighboring ones with available capacity. The proposed Mixed Integer Programming (MIP) model addresses peak airport traffic with a leveling effect through minor adjustment of the demand with respect to a dynamic capacity derived from an analytical capacity model. The analytical capacity model provides a dynamic capacity estimation over the planning horizon based on a varying flight mix. Our approach also allows for exploration of possible runway configurations, arrival/departure priority, and operational modes (segregated/ mixed) to ensure that the higher levels of demand during the strategic planning phase does not lead to excessive delays on the day of operations. The MIP model lexicographically optimizes the flight slots, minimizing the number of displaced flights and total slot displacement for all flights, subject to scheduling, maximum acceptable slot displacement, capacity, and runway configuration constraints.We also investigate the benefit of the proposed model over fixed declared capacity models which do not account for operational mode changes. For the test data obtained for Singapore Changi airport, the proposed MIP model can handle 20% more flights over the current schedule with demand not exceeding estimated capacity in any slot, displacing less than 14% of flights with a maximum displacement of two slots (of fifteen minutes each). In addition, we explore the impact of segregated and mixed mode of runway operations on slot displacement. The proposed MIP model has the potential to be a strategic decision support tool for airport planners to allow them to manage future increase in demand with existing airport infrastructure and with minimum schedule adjustment.