Control Strategies for Active Power Sharing in a Fuel-Cell-Powered Battery-Charging Station

This paper presents an effective system design for a fuel-cell-powered battery-charging station and three control strategies for active power sharing among the batteries. This battery-charging station allows multiple batteries to be simultaneously charged. Three control strategies were investigated to coordinate the active power distribution among the battery-charging branches. The baseline control strategy Was equal rate charging. Two advanced control strategies, proportional rate charging and pulse current charging, were compared to the baseline strategy. These control strategies were realized in MaTLaB/Simulink, and the current and voltage regulations were implemented using the classical proportional-integral control approach. The system simulation was conducted in the Virtual Test Bed by embedding Simulink objects of the controller and co-simulating with MaTLaB. The experimental tests were performed by compiling Simulink codes of the controller and downloading to the dSPaCE platform to control real hardware. The simulation and experimental results are given. Experimental tests validate these control strategies

High Performance Micropane Electron Beam Window

A silicon disk etched so that it contains a multitude of microscopic and thin window panes (micropanes) can potentially transmit a larger average electron beam current density and absorb a smaller fraction of the beam energy than a common metal foil window. The enhanced performance is achieved by a combination of decreased power loss due to the extremely small window thickness (~1 μm), and increased conductive cooling due to the small diameter (~50 μm) of the micropanes and the large cross section of the honeycomb structure that supports the micropanes. Beam current densities up to 34 A/cm2 are permitted within each micropane. When integrated over many micropanes across the face of a window, average current densities up to 1 A/cm2 are permitted—at least three orders of magnitude larger than the ≪mA/cm2 typical of foil windows. The small mass thickness yields high transparency, even for low energy beams. The transmission efficiency for a 100 keV beam is 99.5. © 2000 American Vacuum Society

Synergetic Control of Power Converters for Pulse Current Charging of Advanced Batteries From a Fuel Cell Power Source

This paper presents a synergetic controller for pulse current charging of advanced batteries from a fuel cell power source. Pulse current charging protocol that has been shown to have many advantages over the traditional constant current/constant voltage protocol is applied in a fuel cell powered battery-charging station to reduce the total charging time. Strong nonlinearity and dynamics exist in such systems. In this paper, the synergetic control approach is applied to regulate the buck converters that control the pulse charging currents to the many batteries. A practical synergetic controller to coordinate pulse current charging of the battery is synthesized and discussed. It provides asymptotic stability with respect to the required operating modes, invariance to load variations, and robustness to variation of the input and converter parameters. The synergetic controller is then implemented in Simulink. The dynamic characteristics of the synergetic controller are studied and compared with PI controller by conducting system simulation and experimental tests. Simulation and experiment results show the synergetic controller is robust for such nonlinear dynamic system and achieves better performance than the standard PI controller

Miniature Circularly Polarized Rectenna with Reduced Out-of-Band Harmonics

Wireless embedded sensors are becoming increasingly important for many safety critical applications. Sensor batteries or capacitors must be charged as needed in order to achieve high data rate communications. A miniature circularly polarized rectenna operating at 5.5 GHz is introduced which, with the help of an integrated band-reject filter, reduces out-of-band harmonic emission significantly. The rectenna has a conversion efficiency of 74% with more than 50 dB out-of-band harmonic suppression at 11 GHz

Flexible Multiobjective Control of Power Converter in Active Hybrid Fuel Cell/Battery Power Sources

Hybrid power sources composed of fuel cells and secondary batteries can combine the high energy density of fuel cells with the high power density of batteries. A dc/dc power converter can be placed between the fuel cell and the battery to balance the power flow and greatly augment the peak output power. This paper presents a novel, flexible strategy for multiobjective control of the power converter in the hybrid power source. The control strategy is able to regulate the output current of the fuel cell and the charging current or voltage of the battery while limiting the discharging current of the battery. It can be used in two different configurations without any change. The control strategy is implemented in MATLAB/Simulink and tested by simulation and experiments. Simulation and experimental results show that the multiobjective control strategy is able to select the regulation mode correctly and the fuel cell current, battery current and battery voltage are regulated appropriately. Experiment results demonstrate the great flexibility and generality of the control strategy and validate that the peak power capacity of the active hybrid power source is increased significantly. Simulation and experiment results also show that power converter can be appropriately regulated to meet the multiple objectives required by hybrid power sources

Power Enhancement of an Actively Controlled Battery/Ultracapacitor Hybrid

An actively controlled battery/ultracapacitor hybrid has broad applications in pulse-operated power systems. A converter is used to actively control the power flow from a battery, to couple the battery to an ultracapacitor for power enhancement, and to deliver the power to a load efficiently. The experimental and simulation results show that the hybrid can achieve much greater specific power while reducing battery current and its internal loss. A specific example of the hybrid built from two size 18650 lithium-ion cells and two 100-F ultracapacitors achieved a peak power of 132 W which is a three-times improvement in peak power compared to the passive hybrid power source (hybrid without a converter), and a seven times improvement as compared to the lithium-ion cells alone. The design presented here can be scaled to larger or smaller power capacities for a variety of applications

Adaptive Control Strategy for Active Power Sharing in Hybrid Fuel Cell/Battery Power Sources

Hybrid systems composed of fuel cells and batteries combine the high energy density of fuel cells with the high power density of batteries. A dc/dc power converter is placed between the fuel cell and the battery to balance the power flow between them and greatly increase the peak output power of the hybrid. This paper presents an adaptive control strategy for active power sharing in the hybrid power source. This control strategy can adjust the output current setpoint of the fuel cell according to the state-of-charge (or voltage) of the battery, and is applicable in two topologies of active fuel cell/battery hybrids. The control strategy is implemented in Simulink and then tested under arbitrary load conditions through simulation and experiments. Simulation and experimental results show that the adaptive control strategy is able to adjust the fuel cell output current to adapt to the charge state of the battery, and appropriately distribute the electrical power between the fuel cell and the battery. Experiments demonstrate the generality of the adaptive control strategy

Symbolically Aided Model Development for an induction Machine in Virtual Test Bed

A new phase-domain induction machine model for use in power system dynamic simulation is developed with the aid of a symbolic tool. The symbolic tool can automatically construct a time-domain power system component model in the resistive companion form (RCF) that is widely used in time-domain simulators. The automatic differentiation technique (aDT) is utilized within the context of a symbolic modeling language, and the tool has been implemented for the virtual test bed (VTB) simulation environment. The new induction machine model was used to study start-up transients of an induction motor. The new model was verified by comparing the simulation results to those obtained from a standard d-q model. This paper also demonstrates that a symbolically assisted technique can provide an efficient and rapid path for developing complex nonlinear device models for power system simulations

A Miniature Energy Harvesting Device for Wireless Sensors in Electric Power System

A novel energy harvesting device called the energy coupler is proposed which can provide power to small wireless sensors in a power system. The energy coupler when coupled electromagnetically to a nearby current carrying conductor scavenges ac power from the conductor. The proposed energy coupler converts the harvested ac power into dc using a passive voltage multiplier circuit. The design of the energy coupler is such that the dc power obtained is adequate to charge a miniature 1.2-V rechargeable battery. It is demonstrated that the energy coupler is capable of delivering 10 mW of dc power to a 50-Ω load. An analytical model is also presented which agrees well with measurement results within a margin of error of 10%

Rapid Prototyping of Digital Controls for Power Electronics

The process for designing digital controls for power electronics is typically quite convoluted and affords many opportunities for errors to occur. We present here a new and complete, method for rapid prototyping of digital controls that allows rapid realization of new designs. The approach uses a collection of tools that include both software (the virtual test bed (VTB) and Matlab/Simulink) and hardware (dSpace DSP). An example application of the methodology completes the discussion