Alon Kuperman

Topological Overview of Powertrains for Battery-Powered Vehicles With Range Extenders

The paper presents a topological overview of hybrid powertrains for battery-powered vehicles reinforced by range extenders. First, tradeoffs of employing high energy versus high power battery are revealed. Then, different topologies of battery-ultracapacitor hybrids are discussed, highlighting pros and cons of each configuration. The superiority of fully active hybrids is indicated, obtained at the expense of increase of power electronic circuitry, control effort, and efficiency. The second part of the paper focuses on two types of range extenders: renewable energy and fuel-based units. The operation strategy is shown to be different for each range extender type. The renewable-energy-based range extender should be operated employing either passive or active maximum power point tracking strategy and hence not be involved in the powertrain energy balancing. It is shown that such a strategy allows the rest of system to perceive the renewable energy range extender (RERE) as a part of the load and act accordingly. Solar array is given as an example of a RERE and the possible connection topologies are discussed. On the other hand, the fuel-based range extender (FBRE) should be operated near the lowest specific fuel consumption point employing maximum efficiency point tracking strategy. Fuel cells and internal combustion engines are specified as examples of FBREs. The complete powertrain is shown to resemble a dc microgrid with source, storage, and load units connected through power management circuitry to a common dc link.

Design of a Semiactive Battery-Ultracapacitor Hybrid Energy Source

Design of a battery-ultracapacitor semiactive hybrid for powering pulsed current loads is presented in this paper. The semiactive hybrid energy source consists of an ultracapacitor assisted Li-Ion battery, connected to the load via a dc-dc converter. The system is controlled such that the battery is supplying a near-constant current to satisfy the average load demand while the ultracapacitor supplies the dynamic component of the load current. The control algorithm is based on a well-known capacitance-emulating approach. As a result, a high-energy battery can be used despite the high-power load demand spikes. In addition, the battery-load voltage matching is not required and the control algorithm does not require load current sensing. It is shown that the proposed system performance is equivalent to the performance of a passive hybrid, employing a very high nonfeasible capacitance. Moreover, it is revealed that the battery current is independent of the capacitor size, which affects the load voltage ripple only. Extended simulation and experimental results are presented to demonstrate the feasibility of the approach.

Battery Charger for Electric Vehicle Traction Battery Switch Station

This paper presents the functionality of a commercialized fast charger for a lithium-ion electric vehicle propulsion battery. The device is intended to operate in a battery switch station, allowing an up-to 1-h recharge of a 25-kWh depleted battery, removed from a vehicle. The charger is designed as a dual-stage-controlled ac/dc converter. The input stage consists of a three-phase full-bridge diode rectifier combined with a reduced rating shunt active power filter. The input stage creates an uncontrolled pulsating dc bus while complying with the grid codes by regulating the total harmonic distortion and power factor according to the predetermined permissible limits. The output stage is formed by six interleaved groups of two parallel dc-dc converters, fed by the uncontrolled dc bus and performing the battery charging process. The charger is capable of operating in any of the three typical charging modes: constant current, constant voltage, and constant power. Extended simulation and experimental results are shown to demonstrate the functionality of the device.

Proportional-Resonant Current Controllers Design Based on Desired Transient Performance

Stationary reference frame proportional-resonant (PR) controllers have recently became a viable alternative to rotation reference frame proportional-integrative compensators in ac applications because of their ability of achieving zero steady-state error without the need for computational-intensive reference frame transformations. While extensive efforts have been put into performance comparison of the two control schemes, design of PR controllers according to desired closed-loop time-domain transient performance was barely investigated. This letter proposes a method for deriving PR controller structure and coefficients according to desired transient behavior of ac signal amplitude, applied to typical power converter current loop. The method is based on the fact that if ac signal envelope is perceived as dc signal, its transient behavior may be easily shaped utilizing well-known approaches employed in dc systems loop shaping while keeping zero phase tracking error at all times. On the other hand, while desired transient performance is easily achieved, the relation between crossover frequency and transient processes time constant is not as straightforward as in dc systems. The validity of the presented theoretical analysis is evaluated by simulations.

Supercapacitor Sizing Based on Desired Power and Energy Performance

In this paper, instantaneous power and energy capabilities of supercapacitor (SC) connected to a power element are derived for an arbitrary power profile, given either in analytical or statistical distribution form. A class of applications is considered where the device is used as deeply cycled energy storage with significant capacity, absorbing/supplying the whole power flow or its significant component rather than shaving low-energy high-frequency peaks. The analytical derivation of SC behavior is based on simple RC model with parameters taken from a manufacturer datasheet. It is shown that the commonly adopted “state-of-charge” indication based on terminal voltage only is insufficient to reflect the energy balance for both charging and discharging; hence an alternative definition of “state-of-energy” is proposed for each direction of energy flow, depending on both instantaneous power and terminal voltage. A simplified quick noniterative sizing procedure is proposed at the expense of a slightly oversized SC. Comprehensive example is provided in order to reinforce the proposed method of analyzing SC performance and demonstrate sizing procedure.

Issues in Modeling Amorphous Silicon Photovoltaic Modules by Single-Diode Equivalent Circuit

In this paper, the applicability of the well-known single-diode equivalent circuit to modeling amorphous silicon photovoltaic modules is questioned. It is shown that, unlike in mono- and polycrystalline modules, all of the equivalent circuit parameters are irradiation dependent. This dependence may be derived from either manufacturer-provided or measured I-V curves for different irradiation levels. In order to extract the equivalent circuit parameters, the suggested approach combines numerical solution of two transcendental and two regular algebraic equation systems with single-parameter fitting procedure. Two additional parameters are introduced to describe temperature dependence of photocurrent and diode reverse saturation current. As result, a set of seven parameters is obtained, comprehensively describing the panel performance for arbitrary ambient conditions. It is shown that characteristic curves obtained using the proposed approach match well the manufacturer-provided data for various values of temperature and irradiation.

Virtual torque and inertia loading of controlled electric drive

This work presents a simple method to obtain effects similar to those obtained by real mechanical loading and real inertia variation but without any mechanical parts supplementary to the electric motor of the studied electric drive. The electric motor itself produces the load torque and the inertia variation using digital signal processing software. Therefore, the electric drive is virtually torque and inertia loaded, while its behavior is similar to that of the actual loaded drive. The present method could be used to test the implementation of control algorithms or for didactic purposes using motion control kits found on the market. The present method is used with laboratory works of the DSP Fundamentals in power electronics course at the Department of Electrical and Computer Engineering, Ben-Gurion University of the Negev, Beer-Sheva, Israel.

Analysis of Dual-Carrier Modulator for Bidirectional Noninverting Buck–Boost Converter

A pulse-width modulation modulator for a noninverting bidirectional buck-boost converter is analyzed and a corresponding average-mode current controller design is revealed. The main feature of the modulator is the ability to create switching sequences for both converter legs without requiring any information regarding either operation mode or the direction of power flow. The modulator receives a control signal generated by the current controller, and a triangular carrier and generates driving signals with two different duty cycles, allowing tight control of the inductor current throughout the entire operating range. The underlying circuitry is thus relatively simple; moreover, the proposed method greatly simplifies the outer loop controller design. The revealed findings are supported by simulations and experiments.

Five-parameter model of photovoltaic cell based on STC data and dimensionless

This paper offers a novel approach of the “singlediode” equivalent circuit model estimation, which is based on analysis of the characteristics of the solar panel supplied by the manufacturer. The method combines solution of a system of algebraic equations with optimization algorithm for extracting the seven photovoltaic module parameters of the single diode lumped circuit model. These parameters are the photocurrent, the reverse bias saturation current, the ideality factor, the series resistance, the shunt resistance, the bandgap energy, and the temperature coefficient of the photo-generating current. A minimal set of experimental data is required for parameter extraction. In many cases, the required parameters can be extracted directly from the manufacturers data. The number of solar panels of different types of manufacturers were analyzed. All the models have been obtained from the manufacturers data only. The precision of simulation results is about 0.1%-0.5% for STC.

Performance and Limitations of a Constant Power-Fed Supercapacitor

Analytical description of a constant power fed supercapacitor behavior is revealed in the paper. The derivation is based on a simple RC model with parameters taken from a manufacturer datasheet. Different power and energy-related figures of merit are obtained using the derived expressions. It is shown that some of the performance figures used in datasheets are strictly theoretical and cannot be achieved in practice. The process of Ragone plot construction based on the proposed method is described as well. Moreover, it is shown that the upper limit of a supercapacitor voltage imposes certain limits on power and energy capabilities of the device. Extended simulation and experimental results are provided in order to reinforce the proposed method and justify the selected model for describing supercapacitor performance. Appropriate comparison of simulations and experiments shows that the simple first-order model may be utilized to predict supercapacitor behavior with reasonable accuracy to perform an initial design.