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The vanadium redox flow battery (VRB) is well-suited for applications with renewable energy devices. This paper presents a practical analysis of the VRB for use in a microgrid system. The first part of the paper develops a reduced order circuit model of the VRB and analyzes its experimental performance efficiency during deployment. The model parameters of the various VRB system components were estimated from experimental field data. The parasitic losses of the circulation pumps power consumption were predicted during different operating situations. The second part of the paper addresses the implementation issues of the VRB application in a photovoltaic-based microgrid system. Commercially available chargers designed for lead-acid battery systems were shown to be non-optimal for VRB systems and a new dc–dc converter control was proposed to provide improved charging performance. The system model was validated with field-obtained experimental data.

Maximizing profits through vehicle-to-grid interactions are in conflict with the minimizing battery degradation costs, and thus a major customer concern. A holistic scheduling problem is, therefore, required to consider the impact of the charging power and that of the switching between vehicle-to-grid and grid-to-vehicle modes to account for battery health. In this paper, we propose a mixed-objective approach toward vehicle-to-grid interactions of a residential parking lot complex. The solution makes accommodation for battery health while considering the cost/profit model for the electric vehicles. We discuss the importance of system constraints in achieving both, valley filling and peak shaving. A moving horizon model is used to determine real-time schedules for the vehicles. Customer convenience is the central focus of the proposed methodology.

Vanadium redox batteries (VRBs) have proven to be a viable energy storage technology for portable microgrids due to their rechargeability and high energy density. VRBs exhibit parasitic load loss during operation due to pumping of electrolyte across the membrane during charging and discharging cycles, as well as required temperature control in the form of heating, ventilation and air conditioning. This paper focuses on empirically characterizing VRB efficiency based on known climatic operating conditions and load requirements. A model is created to determine system performance based on known climatic and load data collected and analyzed over an extended time period. A case study is performed using known data for a week time period to characterize system performance, which was compared to actual system performance observed during this same time period. This model allows for appropriate sizing of the PV array and discretionary loads based on required energy density of the system.

Demand response is an important resource that can significantly increase the efficiency of the future power systems. It is a key component of smart grids that can bring a lot of benefits to power system operators and customers. This work assesses potential impacts of demand response on some major attributes of the distribution system such as the network losses, voltage profiles, and maximum power flow through the lines. We considered detailed and practical models of individual residential loads for flexible loads in the system. The flexible load models are various household appliances with different acceptable delay times (ADTs) within which their consumption can be shifted from the normal schedules. With these models, demand response was applied to the 33-bus IEEE test system. In this system, each bus served a specific number of aggregated individual residential loads. The obtained results have shown the great effects of demand response on distribution system attributes.

A ferromagnetic ${\mathrm{Pd}}_{97.5}{\mathrm{Mn}}_{2.5}$ alloy single crystal was studied by neutron scattering and susceptibility measurements. The diffuse satellite peaks along the [1 0 0] axis were observed for the ferromagnetic alloy. The diffuse satellite peaks, however, disappeared under a magnetic field of 5 T applied along the [0 0 1] direction perpendicular to the (0 0 1) scattering plane. Combined with the susceptibility data, we discuss several models for the ferromagnetic state of the dilute PdMn alloy.

The vanadium redox flow battery is well-suited for renewable energy applications. This paper studies VRB use within a microgrid system from a practical perspective. A reduced order circuit model of the VRB was introduced. Experimental field data are collected to estimate the key parameters of the VRB system. Methods of predicting major parasitic losses are proposed. Loss models include the circulation pumps and the HVAC system that regulates the environment of the VRB enclosure. The HVAC system can draw a significant amount of the VRB power considerably impacting its overall efficiency, but this is usually ignored by other theoretical models.

The dynamic performance of dc-dc power electronic converters is mainly determined by the output filtering capacitor and inductor, control loop(s) compensator(s), and the voltage conversion ratio. Normally, a larger capacitance and/or a smaller inductance are not recommended because of the extra cost and size of the capacitor and/or the increment of the inductor current ripple. The capacitor current feedforward method has gained popularity due its fast dynamic response, simpler structure, and less sensing losses. In applications where a large voltage conversion ratio is needed, dynamic response for a load step-down scenario is worse than that of a load step-up condition. In order to alleviate this situation, a buck derived dc-dc converter is chosen. By combing the capacitor current feed-forward control and the buck derived converter topology, a novel control scheme is proposed in this paper. Simulation results containing the voltage overshoot and settling time are presented. The proposed approach is a high performance, simple structure, and low cost/volume strategy for load step-down dynamic improvements.

This paper presents the development of a FACTS interaction laboratory (FIL) to interface a real-time power system simulator with multiple FACTS/UPFC devices via hardware-in-loop (HIL) to study their dynamic responses and test control approaches. The HIL line includes a synchronous machine, a UPFC device and a load device to simulate the dynamics of the UPFC sub-network. The practical feasibility of the proposed HIL scheme has been demonstrated by implementation on a PC-DSP-based UPFC platform. A detailed design of the HIL distributed control system including synchronous machine, UPFC and load is presented.

Natural mica crystals have been characterized for use as reflectors for an ultracold neutron source using Bragg scattering of cold (400 m/s) neutrons from a moving mica reflector, recently installed at the Los Alamos neutron science center (LANSCE). In particular, the triotahedral Mg-rich mica phlogopite has been obtained in large sheets. The structure factor for the first-order Bragg reflection is a factor of four larger than for muscovite, the first variety of mica examined. The observed peak reflectivity for a phlogopite of 0.25 mm thickness is about 8.2% at 1.9 A, with a mosaic spread of about 0.3° FWHM, in good agreement with the ideally imperfect crystal model. This can be extrapolated to a reflectivity of about 63% at the 17.4 A operating wavelength of the ultracold neutron source. Improvements are possible by obtaining Fe-rich mica, which should be almost as effective as the alternative approach of using synthetic perfluorinated mica.