Static synchronous compensator (STATCOM) can effectively improve the power quality in the mediumvoltage distributed energy system (DES). In order to keep the system stable operation, fault-tolerant ability should be maintained to improve the reliability of STATCOM. With the idea of virtual capacitor voltage, a simplified fault-tolerant control scheme is proposed for popular cascaded H-bridge (CHB) based STATCOM. First, an improved modulation method is adopted to significantly reduce these carrier waves. Then, based on the virtual capacitor voltage, the control scheme during the cell fault can be further simplified. Finally, the detailed postfault operation principle is presented according to different operation conditions of STATCOM, where the capacitor voltages in the faulty phase can remain unchanged in certain cases. Validation results verify the effectiveness of the proposed fault-tolerant scheme.
This paper presented a torque distribution strategy based on linear time-varying quadratic programming (LTV-QP) for yaw stability control of all-wheelindependent- drive electric vehicles. A two-degree-offreedom vehicle dynamic model was established to figure out the desired vehicle states including sideslip angle of the centroid of vehicle and the yaw moment, which was used as the reference signal of the LTV-QP controller. However, the influence of the time-varying steering angle was generally not taken into account. A QP-based torque distribution strategy is put forward to reduce the yaw rate error caused by them. The proposed strategy is evaluated in Matlab/Simulink to track the reference yaw moment and optimize the torque distribution. The results indicate that the LTV-QP controller can effectively distribute the torques of four in-wheel motors and significantly improve the vehicle yaw stability.
A 2D filter is proposed for battery incremental capacity curve filtering in a cyclic aging test. The filter works in two directions, namely, from time to time and from batch (cycle) to batch. In details, a simple low-pass filter is applied in the batch direction, and a bias-corrected Gaussian filter is applied in the time direction. Experimental results show that the root-meansquare-error of the proposed method is 20% lower than the neural-network-based benchmarking algorithm. Over-fitting and under-fitting could also be resolved.
STRACT Phase change material (PCM) emulsions have played increasingly important roles in many industrial fields as thermal energy storage media and heat transfer fluids. Precise size control of PCM emulsions is an important prerequisite for achieving consistent and repeatable performances. The present study introduced a novel co-flow microfluidic method to prepare uniform PCM emulsions in a controllable and reproducible manner. The droplet formation and size distribution of PCM emulsions were recorded in real time by a highspeed camera. The formation mode transition and droplet size variation were investigated by changing the flow rates of dispersed PCM and continuous water phases. The results showed that PCM emulsions with high uniformity and monodispersity can be attained in the squeezing and dripping modes, and the emulsion size increases with increasing flow rate of dispersed PCM and decreasing flow rate of continuous water. This study can provide technology support for future application of microfluidics in size-control of PCM emulsions.
The global energy Internet is one of the effective ways to solve the global energy crisis and environmental problems. The AC/DC hybrid power distribution network can accommodate a variety of new energy sources, providing conditions for the wide access of distributed power sources and new loads. The important development direction of the power grid form, and the wide-area interconnection of power systems with different voltage levels and different regional networks can be realized, which is the basis for building a global energy Internet. Based on the grid-connected characteristics of new energy sources, this paper proposes a design of AC/DC hybrid experimental system considering new energy access, studies the key equipment requirements of AC/DC hybrid test system, and designs the topology of each key device and its control strategy. Relying on the constructed AC/DC hybrid experimental system, this paper was verified.
Concentrated solar power (CSP) systems are acknowledged as a promising technology for solar energy utilisation. Supercritical CO2 (SCO2) cycle systems have emerged as an attractive option for power generation in CSP applications due to the favourable properties of CO2 as a working fluid. In order to further improve the overall performance of such systems, organic Rankine cycle (ORC) systems can be used in bottoming-cycle configuration to recover the residual heat. This paper presents a thermodynamic performance assessment of a combined SCO2/ORC system in a CSP application using parabolictrough collectors. The parametric analysis indicates that the heat transfer fluid (HTF) temperature at the inlet of the cold tank, and the corresponding HTF mass flow rate, have a significant influence on the overall system performance. The results suggest that the combined system can offer significant thermodynamic advantages at progressively lower temperatures. Annual simulationsfor a case study in Seville (Spain) show that, based on an installation area of 10,000 m2 , the proposed combined cycle system could deliver an annual net electricity output of 2,680 MWh when the HTF temperature at the cold tank inlet is set to 250 °C, which is 3% higher than that of a stand-alone CO2 cycle system under the same conditions. Taking the size of the thermal storage tanks into consideration, a lower HTF temperature at the cold tank inlet and a lower mass flow rate would be desirable, and the combined system offers up to 66% more power than the stand-alone version when the HTF inlet temperature is 100 °C.
Gas hydrate, as an effective method for Carbon dioxide (CO2) capture, is facing the problem of the slow kinetics associated with hydrate formation. Adding promoters such as tetrahydrofuran(THF) and sodium dodecyl sulfate(SDS) has become a good solution to promote the formation. In this paper, the formation process of CO2 hydrate in the presence of 5.56mol% THF with and without 500ppm SDS has been studied combined with morphology. The experiments are carried at the temperature from 279K to 283K and the pressure of 3Mpa. The results show that the combination of THF and SDS has a better effect than adding THF alone. And it provides morphological changes during the formation process. When ΔT≤10K, the hydrates with needle-like morphology are observed and when ΔT>10K, there are dendrite-like crystals.
ESI is expected to create new interactions and interdependencies within the WES including power, gas, heat and transport. This makes existing evaluation frameworks incapable of assessing the performance of future integrated WESs, particularly due to multi-vector integration. Accordingly, this paper proposes an evaluation framework that addresses the gaps existing frameworks exhibit regarding the evaluation of such systems and capture their complexity. The framework starts with system analysis using a SoS approach to model the system under study in a way that facilitates its evaluation. This approach enables evaluation considering different system levels and multiple perspectives. The next step is MCA where appropriate evaluation criteria and a comprehensive set of indicators are derived and interpreted. These are related to system objectives and requirements and are linked to the different system components and functions. The framework could then be applied to case studies under various scenarios to realise trade-offs or synergies. This should serve as evidence for informing decision-making on the future system and the potential benefits of ESI.
Areas dealing with poor air quality may be significantly supported in their struggles, if district heating systems are established. Unfortunately, it is not always feasible to supply detached houses in comparatively remoted districts. Yet, all those buildings are usually connected to local electric grid, which may be easily upgraded. Thus, there is a real opportunity to use electric grid as a mean to reduce air pollution. Simultaneously, wind turbines present potential in providing electric energy with low CO2 footprint, what not always is a case if electricity is bought from national grid. This paper is to present a concept of heat receivers supplied in heat with electricity produced in dedicated wind farm and transferred via local electric grid. Simulation of needed system size and assessment of the potential for Kraków, Poland (Central Europe) is presented along with algorithm and analysis of system performance over typical meteorological year.
In order to understand in depth that Diesel/Methanol Dual Fuel (DMDF) could gain ultra-low emissions and high thermal efficiency, P-V map and φ-T map were analyzed at full load @1660 r/min. Based on the analysis of P-V map, the reasons for the increase in thermal efficiency at DMDF mode are as follows: First, the effective work of DMDF mode reduced at DMDF mode. Then, methanol evaporated in the intake manifold and cylinder will absorb large amount of heat, which will achieve waste heat recovery; Finally, the energy carried away by the exhaust gases is reduced, which is due to low exhaust temperature.
In DMDF mode, the intersection of φ-T map and NO generation region is obviously reduced, compared with the diesel mode. Meanwhile, φ-T map of DMDF mode is not covered the highest NO generation rate region. This is the reason of achieving ultra-low NOx emissions. The φ-T map of DMDF mode avoids soot generation regions at CA05 and CA50. This is the key to achieve ultra-low soot emissions.