Transportation electrification involves the wide utilization of power electronics based dc distribution networks and the integration of a large amount of power electronic loads. These power ...electronic loads, when tightly controlled, behave as constant power loads (CPLs) and may cause system instability when interacting with their source converters. In this paper, a composite nonlinear controller is proposed for stabilizing dc/dc boost converter feeding CPLs by integrating a nonlinear disturbance observer (NDO)-based feedforward compensation with backstepping design algorithm. First, the model is transformed into the Brunovsky's canonical form using the exact feedback linearization technique, to handle the nonlinearity introduced by the CPL. Second, the NDO technique is adopted to estimate the load power variation within a fast dynamic response, serving as a feedforward compensation to increase the accuracy of output voltage regulation. Then a nonlinear controller is developed by following the step-by-step backstepping algorithm with strictly guaranteed large signal stability. The proposed controller not only ensures global stability under large variation of the CPL but also features fast dynamic response with accurate tracking over wide operating range. Both simulations and experiments are conducted to verify the proposed strategy.
•We investigate Blockchain adoption cases in financial services.•We summarize current status of Blockchain practices.•We use interviews to investigate Blockchain adoption.•We identify ...knowledge-hiding as a main barrier for financial industry.•We make several recommendations and four propositions.
FinTech (Financial Technology) and Blockchain are prevalent topics among technology leaders in finance today. This article describes the impact and revolution of FinTech and Blockchain in the financial industry and demonstrates the main characteristics of such technology. Then, we present three critical challenges as well as three ethical issues about using Blockchain technology. Next, we discuss the development of Blockchain for the financial sector. In addition, we describe the real motivations for banks to explore Blockchain, and problems they face. In order to have a good understanding of the industry, a qualitative method was adopted, and sixteen experts were interviewed. It was identified that knowledge hiding in Blockchain was common and the rationale behind was analyzed using the TPB (Theory of Planned Behavior) approach. The analysis results suggested that knowledge hiding was due to affective, behavioral and cognitive evaluations. The interviewees also provided several recommendations and success factors to overcome current issues in Blockchain adoption. Therefore, four important propositions have been developed. Finally, this article suggests how financial services should respond to this new technology and how to manage knowledge sharing in a more structured way. This article contributes to the literature related to the current entrepreneurial finance landscape for Blockchain.
This paper presents a distributed secondary control scheme for accurate power allocation and voltage restoration in islanded dc microgrids. Conventionally the droop control function is employed in ...the primary control layer to realize power sharing among the distributed generators (DGs) in a decentralized fashion. However, the dc bus voltage may deviate from its nominal value due to different load profiles. In order to restore the dc bus voltage to its nominal value while maintaining the power sharing accuracy, a distributed control scheme is proposed in the secondary control layer. By using limited information of dc bus voltage and the secondary control inputs of their neighboring controllers, a distributed secondary control input can be designed and then sent to its corresponding primary controller. Besides, compared to most existing methods, no global information is required and only dc bus voltage feedback is needed. In addition, by employing the idea of pinning control, our proposed secondary control can be further simplified by only sending the dc bus voltage to one DG. An islanded dc microgrid test system is built in the MATLAB Simulink environment to validate our proposed method. An experimental prototype consisting of two DGs is designed to demonstrate the newly proposed approach and verify the obtained theoretical results.
The high penetration of power electronic converters into dc microgrids may cause the constant power load stability issues, which could lead to large voltage oscillations or even system collapse. On ...the other hand, dynamic performance should be satisfied in the control of power electronic converter systems with small overshoot, less oscillations, and smooth transient performance. This article proposes an offset-free model predictive controller for a dc/dc buck converter feeding constant power loads with guaranteed dynamic performance and stability. First, a receding horizon optimization problem is formulated for optimal voltage tracking. To deal with the unknown load variation and system uncertainties, a higher order sliding mode observer is designed and integrated into the optimization problem. Then an explicit closed-loop solution is obtained by solving the receding horizon optimization problem offline. A rigorous stability analysis is performed to ensure the system large signal stability. The proposed controller achieves optimized transient dynamics and accurate tracking with simple implementation. The effectiveness of the proposed controller is validated by simulation and experimental results.
Economic operation is a major concern for microgrids (MGs). System operation cost is optimized when the incremental costs (ICs) of all distributed generators (DGs) reach equality. Conventionally, ...economic dispatch of DGs is solved by centralized control with optimization algorithms or distributed control with consensus algorithms. To improve the reliability, scalability, and economy of MGs, a fully decentralized economic power sharing strategy is proposed in this paper. As frequency is a global state in ac MG and dc bus voltage serves as a natural indicator in dc MG, a frequency-IC droop scheme is proposed for ac MG, a voltage-IC droop scheme is proposed for dc MG, and a normalization scheme is proposed for hybrid ac/dc MG. By using the proposed technique, ICs of DGs reach equality with the convergence of the system global indicator (frequency or dc bus voltage). Then power sharing of each DG is automatically achieved based on its relevant IC function and the total operating cost can be optimized without any communication or central controllers. The proposed approach is implemented in an ac MG, a dc MG, and a hybrid ac/dc MG in MATLAB/Simulink to verify its effectiveness.
For hybrid energy storage system in dc microgrid, effective power split, bus voltage deviation, and state-of-charge (SoC) violation are significant issues. Conventionally, they are achieved by ...centralized control or hierarchical control methods with communications. This paper proposes a simple and effective strategy to solve the problem in a decentralized manner. A high-pass filter-based droop (HPFD) controller is proposed to regulate the battery converter, and a virtual capacitance droop (VCD) controller is implemented for a supercapacitor (SC) converter. The cooperation of HPFD and VCD first achieves autonomous power split that high-frequency fluctuation is buffered by SC and low-frequency power is supplied by battery. Meanwhile, the bus voltage deviation induced by the droop-based power sharing is eliminated automatically at steady state. The resulted bus voltage restoration simultaneously enforces SC SoC back to its nominal value, and, thus, ensures continuous operation of SC as a power buffer without the violation of its SoC boundary. A design guideline is developed to ensure expected system dynamics. The effectiveness of the proposed method and analytical results are validated by simulations and experiments.
Power allocation is a major concern in hybrid energy storage system. This paper proposes an extended droop control (EDC) strategy to achieve dynamic current sharing autonomously during sudden load ...change and resource variations. The proposed method consists of a virtual resistance droop controller and a virtual capacitance droop controller for energy storages with complementary characteristics, such as battery and supercapacitor (SC). By using this method, battery provides consistent power and SC only compensates high-frequency fluctuations without the involvement of conventionally used centralized controllers. To implement the proposed EDC method, a detailed design procedure is proposed to achieve the control objectives of stable operation, voltage regulation, and dynamic current sharing. System dynamic model and relevant impedances are derived and detailed frequency domain analysis is performed. Moreover, the system level stability analysis is investigated and system expansion with the proposed method is illustrated. Both simulations and experiments are conducted to validate the effectiveness of the proposed control strategy and analytical results.
Multi-level energy management system (EMS) is proposed for dc microgrids operations to ensure system reliability, power quality, speed of response, and control accuracy in this paper. System ...distributed control is scheduled as the primary control. Battery energy storages (BESs) operate in voltage regulation mode with droop control for power sharing. However, bus voltage deviation and power tracking error due to line impedance are the main drawbacks of distributed control. To enhance the system power quality and control accuracy, bus voltage restoration and power sharing compensation are implemented in secondary control. Economic dispatch based on comparison of system units' marginal operation costs is carried out in tertiary control to minimize the system operation cost. Detailed elaboration has been derived to quantify BES utilization cost due to the cumulated lifetime degradation. In case of communication failure, system operation can still be retained with primary control without operating mode change so that to enhance system reliability. A lab scale dc microgrid is developed for the verification of the proposed multi-level EMS and relevant control techniques.
The advancement in technology has fostered the prevalence of the Internet of Things (IoT), which enhances healthcare business quality, offers a seamless customer experience, and maximizes turnovers ...and profits. Consequently, omnichannel services have emerged by integrating online and offline channels and providing customers with more real-time information and services to increase their engagement. Healthcare wearable devices appear as a salient tool to connect healthcare providers and patients and thus become an essential part of the omnichannel environment. Along with this trend, the ethical concerns while using these devices have increasingly intensified and are significant barriers to market expansion. Nevertheless, there is a lack of studies discussing the role of wearables in omnichannel hospital supply chain management and examining the influence of those above concerns on healthcare wearables adoption. Therefore, this study explores these gaps through an integrated approach. Furthermore, we proposed a framework integrating the traditional statistical and machine learning-based approach to analyze a large amount of data; and thereby facilitate a data-driven analytic model to manage omnichannel healthcare supply chain businesses.
This research studies the motivation of customers to choose the QR code as a payment tool by developing an integrated model based on UTAUT 424 valid responses were collected from diversified ...socio-economic backgrounds to validate the proposed framework. Compared with the original UTAUT model, the new one integrates ‘perceived security’, ‘perceived benefits’ and excludes ‘social influence’ to provide more comprehensive and consistent guidance. PLS-SEM technique was performed as in the data analysis process using SmartPLS. Our study concluded that seven of nine hypotheses are supported by the use of PLS-SEM technique. Customers' intention (R2=0.87) to use QR code as the payment tool is jointly contributed by their attitude, perceived usefulness, and subjective norms toward using QR code as the payment method. The formation of customers' attitudes (R2=0.79) towards using QR code is affected by their perceived usefulness, perceived benefits, and subjective norms. Discussion and strategies for the third parties of QR payment providers and future research directions are also presented.
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