Ilan Aharon

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.

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.

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.

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.

Analysis of bi-directional buck-boost converter for energy storage applications

Energy storage backed applications require bi-directional energy flow. A dual carrier four switch buck-boost converter, which is one of the favorite options to support such an operation, is presented in the paper. Universal modulator required to drive the converter in all operation modes is analyzed first. It is shown that in case of dual loop cascaded control, a single controller is sufficient for stabilizing inductor current in all operation topologies. The controller output serves as an input signal to the pulsed width modulator block that includes two shifted carrier waves to create appropriate driving pulses for both converter legs. Simulation results are presented in support of the proposed theory.

Robust output voltage control of multimode non-inverting DC–DC converter

ABSTRACT Linear robust controller design based on Uncertainty and Disturbance Estimator theory for nonlinear uncertain single-input single-output systems with external disturbances is discussed in the paper with application to the output voltage control of a unidirectional universal multimode buck/boost/buck–boost converter. The converter is characterized by different nonlinear static and dynamic behaviour in each of the operating modes. The proposed controller forces the system to maintain nearly nominal performance through the whole range of operation space by appropriately estimating and cancelling the terms including nonlinearities, parametric uncertainties and external disturbances. In addition, measurement noise is included in the analysis to demonstrate the trade-offs of the proposed method. Despite the non-triviality and relative complexity of the method, the resulting controller structure is simple, allowing low-cost, low-part-count analogue implementation. Extended simulation results are presented to demonstrate the effectiveness of the proposed control approach.

Robust UDE controller for energy storage application

In this paper, a design of linear robust control theory is presented, the control method is based on uncertainty and disturbance estimator (UDE), first the control approach is presented, than it applied to output power loop of bi-directional non-inverting buck-boost (BDNIBB) converter, the controller is capable of transfer energy from micro grid to storage element and vice versa. The controller compels the converter to preserve nearly nominal performance through the whole operation range by rapidly estimation and canceling the uncertainties and external disturbance. The revealed findings are supported by simulations and experiments.

Uncertainty and Disturbance Estimator-Based Controllers Design Under Finite Control Bandwidth Constraint

In this paper, tracking versus disturbance rejection tradeoff is revealed and quantitatively investigated for systems utilizing uncertainty and disturbance estimator (UDE)-based controllers. The tradeoff appears to be due to finite control bandwidth, characterizing any real-world application. Based on the exposed findings, guidelines for designing UDE controllers are provided, and respective operational limits are indicated. It is shown that two operation points exist on performance envelope, characterized by similar disturbance rejection, while yielding different tracking performance. Moreover, it is demonstrated that typical proportional-integrative controllers, designed using zero-pole cancellation, are a particular case of UDE controllers. As an example, the proposed method is applied to average current control of a bidirectional noninverting multimode buck–boost converter. Simulations and experimental results are provided to validate the research outcomes.