Yang Liu

Bio: Yang Liu is an academic researcher from Huazhong University of Science and Technology. The author has contributed to research in topics: Superconducting magnetic energy storage & Electric power system. The author has an hindex of 13, co-authored 23 publications receiving 667 citations. Previous affiliations of Yang Liu include Northwest A&F University & South China University of Technology.

Transient Performance Improvement of Microgrid by a Resistive Superconducting Fault Current Limiter

Abstract: In this paper, a resistive-type superconducting fault current limiter (SFCL) is suggested to improve the transient performance of a microgrid system during a fault. The microgrid is connected to the main network at the point of common coupling, where the resistive-type SFCL is applied. When a short-circuit fault happens at the connecting line, the SFCL can mitigate the fault current, and its action signal will be sent to the master distributed generation (DG) included in the microgrid. Accordingly, the switching between the master DG's two control patterns can be flexibly performed; furthermore the microgrid system is expected to achieve a smooth transition between its grid-connected and islanded modes. Theoretical analysis and a technical discussion are conducted, and the simulation model of a typical microgrid with the SFCL is built in MATLAB. From the demonstrated results, employing the resistive-type SFCL can effectively limit the transient fault current to a lower level, help guarantee the microgrid system's power balance, and enhance its voltage and frequency stability.

Design and advanced control strategies of a hybrid energy storage system for the grid integration of wind power generations

Abstract: Energy storage (ES) has become increasingly important in modern power system, whereas no single type of ES element can satisfy all diverse demands simultaneously. This study proposes a hybrid energy storage system (HESS) based on superconducting magnetic energy storage (SMES) and battery because of their complementary characteristics for the grid integration of wind power generations (WPG). This study investigates the mathematical model and the topology of the proposed HESS, which is equipped with a grid-side DC/AC converter, a battery buck/boost converter and a SMES DC chopper. The advanced control strategies comprised of device level and system level are designed. The control strategy for the converters which can be considered as device level is briefly discussed. The significant contribution of this study is proposing a novel system-level control strategy for reasonable and effective power allocation between SMES and battery. According to the control objectives, a fuzzy logic controller optimised with genetic algorithm is adopted. The detailed controller designs are described, meanwhile system stability and HESS operation performance are evaluated. MATLAB simulations are presented to demonstrate the effectiveness of the proposed strategies.

Application of Small-Sized SMES in an EV Charging Station With DC Bus and PV System

Abstract: As small-sized superconducting magnetic energy storage (SMES) system is commercially available at present, the function and effect of a small-sized SMES in an EV charging station including photovoltaic (PV) generation system is studied in this paper, which provides a practical application of small-sized SMES. The comparison of three quick response energy storage systems including flywheel, capacitor (super-capacitor) and SMES is also presented to clarify the features of SMES. SMES, PV generation system, and EV battery are connected to a common dc bus with corresponding converters respectively. Voltage source converter (VSC) is used for grid-connection. With characteristic of quick power response, SMES is utilized to maintain the dc bus steady. During the long-term operation of EV charging station, an energy management strategy is designed to control the energy transfer among PV units, SMES, EV battery, and power grid. The EV charging station system is modeled in MATLAB/SIMULINK and simulation tests are carried out to verify the function and performance of SMES.

Fault Ride-Through Capability Enhancement of DFIG-Based Wind Turbine With a Flux-Coupling-Type SFCL Employed at Different Locations

Abstract: Doubly fed induction generators (DFIGs) have attracted a wide interest for wind power generation, but they suffer from high sensitivity to grid disturbances, particularly grid faults. In this paper, a modified flux-coupling-type superconducting fault current limiter (SFCL) is suggested to improve the fault ride-through (FRT) capability of DFIGs. The SFCL's structure and principle is first presented. Then, considering that the SFCL can be installed at a DFIG's different locations, its influence mechanism to the DFIG's FRT capability is analyzed, and some technical discussions on the design of the SFCL are carried out. Furthermore, the simulation model of a 1.5-MW/690-V DFIG integrated with the SFCL is built, and the performance analysis is conducted. From the results, introducing the SFCL can effectively limit the fault currents across the DFIG's stator and rotor sides, and when the stator side is selected as the installation site, the terminal-voltage sag can be also improved, which helps prevent the disconnection of the DFIG from the power grid.

Application of a hybrid energy storage system in the fast charging station of electric vehicles

Abstract: Fast charging is a practical way for electric vehicles (EVs) to extend the driving range under current circumstance. The impact of high-power charging load on power grid should be considered. This study proposes an application of a hybrid energy storage system (HESS) in the fast charging station (FCS). Superconducting magnetic energy storage (SMES) and battery energy storage (BES) are included in HESS. Based on the quick response of SMES and the high energy density of BES, power magnitude and power change rate of FCS can be limited by compensation of HESS. A controller is designed to generate real-time power demand to HESS. As a part of the control strategy, the energy regulation control of SMES is highlighted. The regulation control is necessary for SMES to deal with energy imbalance in continuous operation; meanwhile it is beneficial for battery life. Finally, feasibility of this control strategy is verified by simulation.

Rolling circle amplification: A versatile tool for chemical biology, materials science and medicine

Abstract: Rolling circle amplification (RCA) is an isothermal enzymatic process where a short DNA or RNA primer is amplified to form a long single stranded DNA or RNA using a circular DNA template and special DNA or RNA polymerases. The RCA product is a concatemer containing tens to hundreds of tandem repeats that are complementary to the circular template. The power, simplicity, and versatility of the DNA amplification technique have made it an attractive tool for biomedical research and nanobiotechnology. Traditionally, RCA has been used to develop sensitive diagnostic methods for a variety of targets including nucleic acids (DNA, RNA), small molecules, proteins, and cells. RCA has also attracted significant attention in the field of nanotechnology and nanobiotechnology. The RCA-produced long, single-stranded DNA with repeating units has been used as template for the periodic assembly of nanospecies. Moreover, since RCA products can be tailor-designed by manipulating the circular template, RCA has been employed to generate complex DNA nanostructures such as DNA origami, nanotubes, nanoribbons and DNA based metamaterials. These functional RCA based nanotechnologies have been utilized for biodetection, drug delivery, designing bioelectronic circuits and bioseparation. In this review, we introduce the fundamental engineering principles used to design RCA nanotechnologies, discuss recently developed RCA-based diagnostics and bioanalytical tools, and summarize the use of RCA to construct multivalent molecular scaffolds and nanostructures for applications in biology, diagnostics and therapeutics.

Advances in microfluidic materials, functions, integration, and applications.

Abstract: Microfluidics consist of microfabricated structures for liquid handling, with cross-sections in the 1–500 μm range, and small volume capacity (fL-nL) Capillary tubes connected with fittings,1 although utilizing small volumes, are not considered microfluidics for the purposes of this paper since they are not microfabricated Likewise, millifluidic systems, made by conventional machining tools, are excluded due to their larger feature sizes (>500 μm) Though micromachined systems for gas chromatography were introduced in the 1970’s,2 the field of microfluidics did not gain much traction until the 1990’s3 Silicon and glass were the original materials used, but then the focus shifted to include polymer substrates, and in particular, polydimethylsiloxane (PDMS) Since then the field has grown to encompass a wide variety of materials and applications The successful demonstration of electrophoresis and electroosmotic pumping in a microfluidic device provided a nonmechanical method for both fluid control and separation4 Laser induced fluorescence (LIF) enabled sensitive detection of fluorophores or fluorescently labeled molecules The expanded availability of low-cost printing allowed for cheaper and quicker mask fabrication for use in soft lithography5 Commercial microfluidic systems are now available from Abbott, Agilent, Caliper, Dolomite, Micralyne, Microfluidic Chip Shop, Micrux Technologies and Waters, as a few prominent examples For a more thorough description of the history of microfluidics, we refer the reader to a number of comprehensive, specialized reviews,3, 6–11 as well as a more general 2006 review12 The field of microfluidics offers many advantages compared to carrying out processes through bulk solution chemistry, the first of which relates to a lesson taught to every first-year chemistry student Simply stated, diffusion is slow! Thus, the smaller the distance required for interaction, the faster it will be Smaller channel dimensions also lead to smaller sample volumes (fL-nL), which can reduce the amount of sample or reagents required for testing and analysis Reduced dimensions can also lead to portable devices to enable on-site testing (provided the associated hardware is similarly portable) Finally, integration of multiple processes (like labeling, purification, separation and detection) in a microfluidic device can be highly enabling for many applications Microelectromechanical systems (MEMS) contain integrated electrical and mechanical parts that create a sensor or system Applications of MEMS are ubiquitous, including automobiles, phones, video games and medical and biological sensors13 Micro-total analysis systems, also known as labs-on-a-chip, are the chemical analogue of MEMS, as integrated microfluidic devices that are capable of automating multiple processes relevant to laboratory sciences For example, a typical lab-on-a-chip system might selectively purify a complex mixture (through filtering, antibody capture, etc), then separate target components and detect them Microfluidic devices consist of a core of common components Areas defined by empty space, such as reservoirs (wells), chambers and microchannels, are central to microfluidic systems Positive features, created by areas of solid material, add increased functionality to a chip and can consist of membranes, monoliths, pneumatic controls, beams and pillars Given the ubiquitous nature of negative components, and microchannels in particular, we focus here on a few of their properties Microfluidic channels have small overall volumes, laminar flow and a large surface-to-volume ratio Dimensions of a typical separation channel in microchip electrophoresis (μCE) are: 50 μm width, 15 μm height and 5 cm length for a volume of 375 nL Flow in these devices is normally nonturbulent due to low Reynolds numbers For example, water flowing at 20°C in the above channel at 1 μL/min (222 cm/s) results in a Reynolds number of ~05, where <2000 is laminar flow Since flow is nonturbulent, mixing is normally diffusion-limited Small channel sizes also have a high surface-to-volume ratio, leading to different characteristics from what are commonly found in bulk volumes The material surface can be used to manipulate fluid movement (such as by electroosmotic flow, EOF) and surface interactions For a solution in contact with a charged surface, a double layer of charge is created as oppositely charged ions are attracted to the surface charges This electrical double layer consists of an inner rigid or Stern Layer and an outer diffuse layer An electrostatic potential known as the zeta potential is formed, with the magnitude of the potential decreasing as distance from the surface increases The electrical double layer is the basis for EOF, wherein an applied voltage causes the loosely bound diffuse layer to move towards an electrode, dragging the bulk solution along Charges on the exposed surface also exert a greater influence on the fluid in a channel as its size decreases Larger surface-to-volume ratios are more prone to nonspecific adsorption and surface fouling In particular, non-charged and hydrophobic microdevice surfaces can cause proteins in solution to denature and stick We focus our review on advances in microfluidic systems since 2008 In doing this, we occasionally must cover foundational work in microfluidics that is considerably less recent We do not focus on chemical synthesis applications of microfluidics although it is an expanding area, nor do we delve into lithography, device fabrication or production costs Our specific emphasis herein is on four areas within microfluidics: properties and applications of commonly used materials, basic functions, integration, and selected applications For each of these four topics we provide a concluding section on opportunities for future development, and at the end of this review, we offer general conclusions and prospective for future work in the field Due to the considerable scope of the field of microfluidics, we limit our discussion to selected examples from each area, but cite in-depth reviews for the reader to turn to for further information about specific topics We also refer the reader to recent comprehensive reviews on advances in lab-on-a-chip systems by Arora et al10 and Kovarik et al14

The Collagen Suprafamily: From Biosynthesis to Advanced Biomaterial Development

Abstract: Collagen is the oldest and most abundant extracellular matrix protein that has found many applications in food, cosmetic, pharmaceutical, and biomedical industries First, an overview of the family of collagens and their respective structures, conformation, and biosynthesis is provided The advances and shortfalls of various collagen preparations (eg, mammalian/marine extracted collagen, cell-produced collagens, recombinant collagens, and collagen-like peptides) and crosslinking technologies (eg, chemical, physical, and biological) are then critically discussed Subsequently, an array of structural, thermal, mechanical, biochemical, and biological assays is examined, which are developed to analyze and characterize collagenous structures Lastly, a comprehensive review is provided on how advances in engineering, chemistry, and biology have enabled the development of bioactive, 3D structures (eg, tissue grafts, biomaterials, cell-assembled tissue equivalents) that closely imitate native supramolecular assemblies and have the capacity to deliver in a localized and sustained manner viable cell populations and/or bioactive/therapeutic molecules Clearly, collagens have a long history in both evolution and biotechnology and continue to offer both challenges and exciting opportunities in regenerative medicine as nature's biomaterial of choice

Review of Energy Storage System Technologies in Microgrid Applications: Issues and Challenges

Abstract: A microgrid (MG) is a local entity that consists of distributed energy resources (DERs) to achieve local power reliability and sustainable energy utilization. The MG concept or renewable energy technologies integrated with energy storage systems (ESS) have gained increasing interest and popularity because it can store energy at off-peak hours and supply energy at peak hours. However, existing ESS technology faces challenges in storing energy due to various issues, such as charging/discharging, safety, reliability, size, cost, life cycle, and overall management. Thus, an advanced ESS is required with regard to capacity, protection, control interface, energy management, and characteristics to enhance the performance of ESS in MG applications. This paper comprehensively reviews the types of ESS technologies, ESS structures along with their configurations, classifications, features, energy conversion, and evaluation process. Moreover, details on the advantages and disadvantages of ESS in MG applications have been analyzed based on the process of energy formations, material selection, power transfer mechanism, capacity, efficiency, and cycle period. Existing reviews critically demonstrate the current technologies for ESS in MG applications. However, the optimum management of ESSs for efficient MG operation remains a challenge in modern power system networks. This review also highlights the key factors, issues, and challenges with possible recommendations for the further development of ESS in future MG applications. All the highlighted insights of this review significantly contribute to the increasing effort toward the development of a cost-effective and efficient ESS model with a prolonged life cycle for sustainable MG implementation.

Hybrid energy storage system for microgrids applications: A review

Abstract: Energy storages introduce many advantages such as balancing generation and demand, power quality improvement, smoothing the renewable resource’s intermittency, and enabling ancillary services like frequency and voltage regulation in microgrid (MG) operation. Hybrid energy storage systems (HESSs) characterized by coupling of two or more energy storage technologies are emerged as a solution to achieve the desired performance by combining the appropriate features of different technologies. A single ESS technology cannot fulfill the desired operation due to its limited capability and potency in terms of lifespan, cost, energy and power density, and dynamic response. Hence, different configurations of HESSs considering storage type, interface, control method, and the provided service have been proposed in the literature. This paper comprehensively reviews the state of the art of HESSs system for MG applications and presents a general outlook of developing HESS industry. Important aspects of HESS utilization in MGs including capacity sizing methods, power converter topologies for HESS interface, architecture, controlling, and energy management of HESS in MGs are reviewed and classified. An economic analysis along with design methodology is also included to point out the HESS from investor and distribution systems engineers view. Regarding literature review and available shortcomings, future trends of HESS in MGs are proposed.