Start-up Method Research Articles

Optimization research on control strategies for photovoltaic energy storage systems considering multi-mode operation

In this paper, a selective input/output strategy is proposed for improving the life of photovoltaic energy storage (PV-storage) virtual synchronous generator (VSG) caused by random load interference, which can sharply reduce costs of storage device. The strategy consists of two operating modes and a power coordination control method for the VSGs. Firstly, a selective VSG input strategy is proposed based on the magnitude of disturbances, a method of offline solving model equation is used for determine the VSG input time. An online method is used for matching the disturbance frequency variations, which enables a selective VSG startup method, allowing the grid to prioritize the utilization of the generator's physical inertia. Secondly, a dynamic VSG exit strategy is developed based on dynamic frequency characteristics to prevent secondary oscillations in the frequency recovery phase of the PV-storage VSG following grid disturbances. This strategy is crucial as grid variations may affect energy storage lifespan and reduce frequency recovery speed. Finally, the proposed approach is validated for correctness and effectiveness through computer simulations and semi-physical experiments using the NI-PXI + LabVIEW platform. Through the above optimization and research, the selective start of VSG is realized, the energy storage life is improved, the capacity of charge and discharge cycles is reduced by 37.82 % compared with the strategy without investment and withdrawal, and the life loss in the secondary charge and discharge process of PV-storage VSG is avoided, which is conducive to frequency recovery.

Simulation study on the dynamic characteristics of natural circulation coupled phase change material for equal height difference passive containment cooling system

The passive containment cooling system (PCCS) plays a significant role in ensuring the safety of nuclear power plants. To further reduce peak pressure in the containment during a loss of coolant accident (LOCA), phase change materials (PCMs) are utilized to improve the system’s cooling effectiveness. The dynamic simulation model of PCCS has been developed using Apros software. This article focuses on examining the system’s dynamic characteristics related to various tube startup methods and comparatively analyzing the impact of different PCM thicknesses on heat transfer capacity. The results indicate that post-accident, PCM significantly suppresses peak pressure in the containment. Under the full tube startup method with 4 mm PCM, the peak pressure decreases to 1.75 MPa, whereas under the empty tube startup method, it is reduced to 1.69 MPa. With natural circulation empty tube startup method, PCM can reduce pressure change intensity in the containment but negatively affects natural circulation heat transfer. Although the full tube startup method underperforms the empty tube startup method on suppressing peak pressure, PCM can positively affect natural circulation heat transfer in the early stages of the accident. Empty tube startup offers the advantages of higher heat transfer capacity and lighter weight, making it the optimal choice for ocean nuclear platforms. Additionally, the higher peak power of PCM heat transfer under the empty tube startup method indicates that system can withstand larger thermal shocks.

Studies of the outer-off-midplane lower hybrid wave launch scenario for plasma start-up on the TST-2 spherical tokamak

Establishment of an efficient central solenoid (CS) free tokamak plasma start-up method may lead to an economical fusion reactor. CS-free start-up using lower hybrid (LH) waves has been studied on the TST-2 spherical tokamak. Plasma current of about a quarter of CS-driven discharges has been obtained fully non-inductively using the outer-midplane and top LH launchers. Recently, an outer-off-midplane LH launcher was developed to achieve higher plasma current by optimizing for core absorption and minimal fast electron losses. Using the (outer-)off-midplane launcher, fully non-inductive plasma current start-up up to about 8 kA was achieved. Coupled ray-tracing and Fokker–Planck simulation was performed on equilibria reconstructed with an extended MHD model. It was found that the experimentally observed plasma current was in reasonable agreement with the numerical simulation. The simulation predicted appreciable orbit losses for the off-midplane launcher driven discharge at the present parameters, which was consistent with the experimentally observed x-ray radiation characteristics. The simulation showed that the current density was saturated for the present off-midplane launcher discharges and higher density and higher LH power was necessary to achieve higher plasma current.

Perancangan Startup Aqibers Platform Penyedia Jasa Aqiqah Metode Lean Startup

Startup Aqibers is a platform providing aqiqah services that uses the Lean Startup method in its design. This method is used to optimize innovation, efficiency and resource management. In the design phase, Startup Aqibers focuses on identifying market needs through in-depth research. StratupAqibers aims to simplify the aqiqah process by providing an online platform that makes it easier for users to choose an aqiqah package, confirm orders and make payments. Through the use of Lean Startup methods, Aqibers was able to identify the key features most desired by customers, improve user experience, and reduce product development risk. By leveraging continuous customer feedback, Aqibers was able to quickly iterate on its platform, ensuring that the solution they created offer in line with changing market needs. In this way, Aqibers is expected to achieve sustainable growth and provide significant added value for consumers who are looking for practical and reliable aqiqah services.

Enhanced degradation and methane production of food waste anaerobic digestate using an integrated system of anaerobic digestion and microbial electrolysis cells for long-term operation.

The integrated system of anaerobic digestion and microbial electrolysis cells (AD-MEC) was a novel approach to enhance the degradation of food waste anaerobic digestate and recover methane. Through long-term operation, the start-up method, organic loading, and methane production mechanism of the digestate have been investigated. At an organic loading rate of 4000mg/L, AD-MEC increased methane production by 3-4 times and soluble chemical oxygen demand (SCOD) removal by 20.3% compared with anaerobic digestion (AD). The abundance of bacteria Fastidiosipila and Geobacter, which participated in the acid degradation and direct electron transfer in the AD-MEC, increased dramatically compared to that in the AD. The dominant methanogenic archaea in the AD-MEC and AD were Methanobacterium (44.4-56.3%) and Methanocalculus (70.05%), respectively. Geobacter and Methanobacterium were dominant in the AD-MEC by direct electron transfer of organic matter into synthetic methane intermediates. AD-MEC showed a perfect SCOD removal efficiency of the digestate, while methane as clean energy was obtained. Therefore, AD-MEC was a promising technology for deep energy transformation from digestate.

A Reliable and Efficient I-f Startup Method of Sensorless Ultra-High-Speed SPMSM for Fuel Cell Air Compressors

Extended back electromotive force (EEMF)-based position sensorless field-oriented control (FOC) is widely utilized for ultra-high-speed surface-mounted permanent magnet synchronous motors (UHS-SPMSMs) driven fuel cell air compressors in medium-high speed applications. Unfortunately, the estimated position is imprecise due to too small EEMF under low speed operation. Hence, current-to-frequency (I-f) control is more suitable for startup. Conventional I-f methods rarely achieve the tradeoff between startup acceleration and load capacity, and the transition to sensorless FOC is mostly realized in the constant-speed stage, which is unacceptable for UHS-SPMSM considering the critical requirement of startup time. In this article, a new closed-loop I-f control approach is proposed to achieve fast and efficient startup. The frequency of reference current vector is corrected automatically based on the active power and the real-time motor torque, which contributes to damping effect for startup reliability. Moreover, an amplitude compensator of reference current vector is designed based on the reactive power, ensuring the maximum torque per ampere operation and higher efficiency. Furthermore, the speed PI controller is enhanced by variable bandwidth design for smoother sensorless transition. These theoretical advantages are validated through experiments with a 550 V, 35 kW UHS-SPMSM. The experimental results demonstrated the enhanced startup performance compared with conventional I-f control.

Ultra-rapid achievement of denitrifying nitrite accumulation using anoxic starvation treatment

Partial denitrification (PD) can stably supply nitrite (NO2–) for Anammox, and their combined processes have sprung up in recent decades. However, behind this prosperity, the existing starting methods still restrict the establishment of PD systems to months. This study proposed a novel PD start-up method, “anoxic starvation treatment”, and explored its feasibility and effectiveness. Results showed that denitrifying nitrite accumulation immediately occurred after 5-day starvation, and the nitrate-to-nitrite transformation ratio at 20th min was kept at ∼72 % within the 9-day normal operation. During starvation, it was essential to regularly evaluate the NO2– accumulation potential via assaying denitrifying activity, which helped set the duration of starving treatment. Besides, additional starvation treatment during normal operations could also improve the NO2– accumulation performance by relieving further NO2– reduction. After three operation rounds, the high-throughput sequencing analysis showed that Exiguobacterium became the dominant genus (∼40 %). However, Thauera, the widely recognized candidate for PD, merely shared 3.57 % in relative abundance, raising speculation about whether Thauera is a promoter or beneficiary.

A comparative analysis of lean start-up and design thinking and its integration

Purpose This study aims to emphasize the integration of lean start-up and design thinking approaches and investigate how they may be used together. Design/methodology/approach The report uses a systematic literature review methodology to analyze and summarize previous research on combining lean start-up and design thinking. Inferences were discovered and analyzed after relevant publications were chosen based on predetermined inclusion criteria. Findings The research shows that combining lean start-up and design thinking significantly impacts entrepreneurship. Start-ups can efficiently uncover consumer needs, reduce risks and improve their product or service offerings by combining the client-centricity of design thinking with the iterative and data-driven concepts of lean start-up. This integration promotes an innovative culture, gives teams the freedom to try new things and learn from mistakes and raises the possibility of start-up success. Research limitations/implications The dependence on pre-existing literature, which might cover only some potential uses and circumstances, is a weakness of this research. It is advised that more empirical research be conducted to determine the precise circumstances in which the integrated strategy performs best. Future studies should also explore the difficulties and drawbacks of using these approaches to offer suggestions for overcoming them and maximizing their advantages. Practical implications The findings have significant ramifications for business owners and other professionals working in the start-up environment. The combination of lean start-up and design thinking emphasizes the relevance of early customer interaction and empathy-driven design. To foster creativity and hasten the expansion of start-ups, practitioners are urged to create a comprehensive strategy that integrates the advantages of both techniques. Through this integration, business owners may develop solutions that appeal to their target market, increasing adoption rates and market competitiveness. Originality/value This study is interesting in comparing lean start-up and design thinking, emphasizing the overlaps and benefits of their application to entrepreneurship. This study discusses successful start-up methods by offering suggestions for future research and practice. It also provides a basis for further developing and adopting the integrated approach.

Business Models and Lean Startup

We explore the intersection between the lean startup methodology and research on business models. We note that both perspectives are anchored on a systematic approach to needs discovery and highlight the importance of value creation (vs. value appropriation). However, while the lean startup is centered on creating value for customers through discovery of product-market fit, research on business models concerns value creation for all stakeholders through establishing product-market-business model fit. We also discuss how the lean startup method informs research on business models and vice versa. We observe that the promise of applying lean startup to business models lies in probing the viability of new business models with an efficient and effective process. We find that business model research, in turn, can contribute to the lean startup methodology by (a) suggesting extensions to the method that derive from the holistic, system-level nature of the business model construct and (b) highlighting a range of specific experimental subprocesses, refinements, and tools that could be applied to refine the customer needs discovery process.

Startup control strategies for pre-fabricated synchronous condensers using static frequency converters

In ultra-high voltage transmission systems, a considerable number of dynamic reactive power compensation devices must be equipped. Synchronous condensers are capable of providing substantial amounts of dynamic reactive power. Therefore, distributed prefabricated synchronous condensers can be deployed in ultra-high voltage transmission systems to supply reactive power support to the power grid. The start-up of synchronous condensers can only be achieved through external means. Currently, there are multiple start-up methods available for small-capacity prefabricated synchronous condensers. With the rapid advancements in frequency conversion technology and power electronics, static frequency converters (SFCs) can be utilized to initiate synchronous condensers. This paper investigates the principles of SFC start-up and coordinated control while also configuring protective devices for SFCs based on their structural characteristics and operational principles. A validation platform consisting of one SFC starting two synchronous condensers was established to analyze their start-up time, yielding results demonstrating the ability of SFC-driven distributed small-capacity synchronous condensers to rapidly adjust the power quality of the power grid.

Electromagnetic and mechanical analyses for the vacuum vessel of NCST

The NanChang Spherical Tokamak (NCST) is a new tokamak with low aspect ratio, which is designed to investigate merging compression startup methods. In this paper, 2D and 3D models are built to analyze eddy currents and optimize the vacuum vessel design. The structure of the vacuum vessel is analyzed by ANSYS Mechanical. The maximum stress and maximum displacement of vacuum vessel during plasma operation are 80 MPa and 0.85 mm respectively. The results show that the vacuum vessel can meet the design requirements.

An Ultra-Fast and Wide-Safe-Range Start-Up Method of DAB Converters with Straightforward Frequency-Phase Closed-loop Control

An Ultra-Fast and Wide-Safe-Range Start-Up Method of DAB Converters with Straightforward Frequency-Phase Closed-loop Control

Design and analysis of thermoelectric energy harvester with 85.6% peak end-to-end efficiency and 38 mV self-startup using 4.13 mΩ/°C indirect temperature dependent MPPT

We present an efficient power management system (PMS) to harvest energy from thermoelectric energy generators (TEGs) via indirect temperature tracking. The PMS includes a power converter with an indirect temperature-dependent (ITD) maximum power point tracking (MPPT) controller and two complementary self-startups. The ITD-MPPT controller consists of an ITD input sampling circuit (ITD-ISC) and an ITD impedance matching circuit (ITD-IMC). The ITD-ISC detects and samples the TEG voltage (VTEG) under dynamically varying temperature gradients. The ITD-ISC removes unnecessary detachments of the converter from multi-mode reconfigurable TEGs to recover the otherwise wasted power using an adaptive input sampling (AIS) technique. The ITD-IMC adjusts the on-time of the power switch to control the input impedance (RIN) of the converter with a relatively high resolution of 4.13 mΩ/°C. This approach provides an ultrawide range source tracking from 2 Ω to 200 Ω. We also present a precision zero current switching (ZCS) controller to manage the on-time of the two power switches simultaneously. Two complementary self-startup components are realized using transformer-based (TSC) and charge-pump-based startup circuits (CSC). Integrated circuits for the PMS are fabricated using 180 nm and 28 nm CMOS processes for high efficiency and low voltage, respectively. The measurements indicate that the proposed PMS achieves an end-to-end efficiency (ηEE) above 80% over a wide source VTEG range (100 mV – 450 mV). The peak ηEE of 85.6% is achieved for VTEG = 200 mV, demonstrating the high-performance MPPT using indirect temperature tracking. TSC and CSC demonstrate successful self-startups at input voltages of 38 mV and 200 mV, respectively, thus providing reliable startup methods for various renewable energy sources.

Experimental studies of a continuous catalytic distillation column from startup to steady state for the production of methyl acetate

Abstract Esterification of acetic acid with methanol to produce methyl acetate and water has been studied in a continuous packed bed catalytic reactive distillation. The key challenge is the startup method of the experiments fora continuous reactive distillation as well as reactive zone height selection. In the present study, the effect of various operating conditions on the methyl acetate composition (mole fraction) is studied. Indion 180 ion-exchange resin solid catalyst is used in the reactive zone. The catalyst is immobilized by using a novel equivalent Katapak-S in the reactive section. Experiments were performed under different operating conditions to find the high purity methyl acetate product in the distillation. The experiments were performed for various conditions like total feed flow rate, reboiler temperature, reflux ratio, methanol to acetic acid mole ratio and catalyst loading with the time. The experiments were carried out till the system reaches to the steady state under different conditions. The maximum methyl acetate concentration is obtained at 80 °C reboiler temperature, 2.01 reflux ratio, 16.3 g/min flow rate, 60 g catalyst loading and 1 mol ratio of methanol to acetic acid. The highest purity of methyl acetate obtained under optimal condition is 95 % by mole.

Hybrid Control-Based Closed-Loop Soft Start-Up Method for LLC Resonant Converters

LLC resonant converters are prone to generating a large inrush current during the start-up process, which will cause damage to the resonant elements and threaten the safe operation of the circuit. In this study, we investigate the soft-start method to suppress the inrush current of an LLC resonant converter. Based on the traditional frequency-decreasing method, we integrate PWM control to broaden the output voltage gain range during the start-up. Additionally, to ensure the smooth establishment of the output voltage, the controller performs the closed-loop control of the duty cycle and frequency in sequence based on the rate of output voltage rise. A prototype experiment based on STM32F334C8T6 is established to experimentally validate the presented soft start-up method. The experiment results indicate that the soft start-up method improves the start-up performance, reduces the maximum inrush current by 47.5% compared with that of the frequency-decreasing method, and builds up the output voltage quickly. The start-up process is smooth, which improves the reliability of the LLC resonant converter.

Analysis of Internal Flow Characteristics of the Bearingless Direct-Drive Centrifugal Pump System during Transient Start-Up

Traditional shaft-sealed centrifugal pumps exhibit problems, such as liquid leakage and reduced efficiency, due to mechanical seal failures. To address the issue, the bearingless direct-drive centrifugal pump system (BDDCPS) has been designed with bearingless motor technology. This may cause a new issue of rotor eccentricity displacement, which can lead to a reduction in pump performance. Compared to a stable state, the changes in characteristics, such as flow rate, head, and pressure, during the transient start-up process are more severe, increasing the likelihood of system failure and requiring greater attention. In order to ensure safety and reliable operation during the transient start-up process, this paper investigates the working principle of the BDDCPS and analyzes transient start-up characteristics with three different start-up methods. The external characteristics, pressure field distribution, velocity field distribution, and hydraulic losses analysis of the pump are determined for comparative analysis. Finally, it is found that the linear acceleration start-up method is the most suitable and efficient for the BDDCPS.

대학 창업 교과목 운영 사례

The purpose of this study was to derive implications for start-up education and effective teaching methods for start-up courses through the operation of social entrepreneurship courses in the university's regular start-up curriculum. In order to develop, operate, and analyze the effectiveness of social entrepreneurship courses, data were collected through self-evaluation surveys and post-class reflection reports, and the collected data was categorized based on the corresponding sample t-test and important events. First, the main research results showed that all factors of innovation, initiative, and risk-taking in entrepreneurship increased after the start-up course class, and innovation and initiative increased statistically significantly. Second, as a result of the survey, it was found that all factors of community consciousness, empathy, and help in prosociality increased after the start-up subject class, and community consciousness and empathy increased statistically significantly. Third, in the post-class reflection report, the positive effects of learners' cooperative participation-oriented practical teaching strategies were the effect of participating in learning activities and results through team activities, raising awareness of start-ups as career options, and difficulties in the start-up idea and development process. This study is meaningful in that it proposed a practical teaching strategy centered on the cooperative participation of learners as an effective educational method for university start-up education. The results of this study are expected to be used as evidence for supporting effective learner-centered teaching methods in university start-up education.

How Applying the Lean Start-up Methodology can Affect Business Model Innovation

Start-ups often apply entrepreneurial approaches like the Lean Start-up Method (LSM) and Business Model Innovation (BMI). LSM emphasises experimentation during product development and testing in close interactions with potential customers to get first-hand feedback. Lessons learned are implemented so that improved product variants go through further feedback loops and so on. Products are developed by rapidly getting closer to what customers really want. BMI focuses on altering existing or developing new business models to enable differentiation from competitors. Typical elements of business models include target customer segments, value propositions, value chains and revenue mechanisms. BMI is assumed to take place when at least two of these elements are innovated in conjunction. Going beyond typical product or process innovation in isolation, BMI suggests to holistically consider interdependencies within the entire business model. The need for a better understanding on connections between LSM and BMI is expressed in the literature and this work’s goal is to contribute to this discussion. More specifically, this work seeks to address the question of how the application of LSM can affect BMI. In search of answers, business plans of 25 finalist start-ups in the 2022 edition of an annual innovation competition in Switzerland are reviewed. While the evidence on the connection between LSM and BMI is not entirely convincing, reviewed business plans reveal insights into LSM-related factors at play that can support business model changes and trigger BMI.

Dynamic performance analysis of the discharging process of a solar aided liquid air energy storage system

As a clean and high energy density large-scale energy storage technology, liquid air energy storage (LAES) has great development prospects. Among various LAES technologies, solar aided liquid air energy storage (SALAES) is becoming a hotspot for its cleanness and high efficiency, but its dynamic performance characteristics have not yet been revealed. In this paper, the dynamic model and control systems of the discharging process of an SALAES system considering the metal thermal inertia and axial heat conduction are established and two different start-up methods, rated parameter start-up and variable parameter start-up, are proposed and compared. Meanwhile, a parabolic trough collector control strategy with fixed outlet fluid temperature is designed to avoid DNI fluctuations that greatly affect the system's operation. Furthermore, off-design start-ups and predictable molten salt-air heat exchangers trip due to the lack of solar energy caused by continuous bad weather are noted and analyzed. Research results show that the variable parameter start-up is faster and more stable, in which the heat exchange time of two evaporators is about 895 s, the rotor speed stability time is about 12–15 s, and the load stability time is about 75–80 s. The required air quantity for the design condition start-up is 6.84 tons and will rise to 9.02 tons for the off-design start-up. The response times for the unit load to decrease from the rated value to different levels (taking 75 %, 50 %, and 25 % of the rated load as examples) are around 15–20 s, and for the trip of salt-air heat exchangers, the response time is about 20–25 s, resulting in a load fluctuation from 85.5 % to 103.6 %. The research results of this study can guide the dynamic operation of the SALAES system.

A Simple and Fast Start-Up Strategy for Dual-Active-Bridge Converters With DC Bias Suppression

High power dual active bridge (DAB) converters are widely adopted in DC and hybrid AC/DC micro-grids, for which <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">fast start-up dynamics</i> of DAB converters is a key requirement. Conventional start-up methods usually require complex operation stages, and a time-consuming parameter-tuning process, resulting in slow dynamics. In this work, we propose a new simple and optimal start-up method for DAB converters. Major contributions lie in <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">three-folds</i> . (i) We theoretically analyze the transmission power and the peak inductor current of extended phase-shift modulation. (ii) A new Lagrange Multiplier method is proposed to solve the optimal phase-shift ratios of the underlying control problem, resulting in very fast control dynamics at maximum power transmission, fully respecting the system permissible current limit. (iii) An effective and simple strategy by <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">solely</i> manipulating the gate signals in the first switching period is newly proposed to eliminate the magnetic bias. The proposed method avoids complex parameter-tuning procedures. Experimental results demonstrate the effectiveness of the proposed method. Results confirm that with the proposed solution a <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">much faster</i> start-up process with a controllable inductor current <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">without</i> DC bias is achieved, in comparison with the recently reported start-up methods.