Battery Emulator Research Articles

A high-fidelity lithium-ion battery emulator for electric vehicle application

Lithium-ion (Li-ion) battery has played a key role for the development of electric vehicle (EV) at present, while the Li-ion batteries in the market come from different manufactures. Verifying the performance of the battery management system (BMS) for various battery chemistries is a complex undertaking. This paper proposes a high-fidelity Li-ion battery emulator for EV applications. The emulator utilizes a battery model parameterized by a series of performance tests and a special-designed hardware platform. A three-order battery equivalent circuit model (ECM) is selected to provide the voltage and current reference signal in the processor. Subsequently, the hardware generates the high voltage and current signal in accordance with the reference. To ensure the high accuracy of the battery ECM, a 37 Ah nickel manganese cobalt (NMC) battery was selected for testing under both charge and discharge conditions, as well as across a temperature range of − 30℃ to 45℃. The battery emulator is verified on charge and discharge mode for both accuracy and dynamic performance validations.

A modular IGBT power stack − based and open hardware framework for small wind turbines assessment

Wind energy technologies have emerged as the predominant renewable energy source within the framework of present-day electric power systems. Their design process, aligned with foundational theories, ought to be precision-engineered and systematized to fully maximize the potential of this energy source. This study presents a platform as solution designed and built to characterize and assess Small Wind Turbines (SWT), based on free software and open hardware. Additionally, the developed methodology step-by-step guide is disclosed. The characterization is based on the use of Permanent-Magnet Synchronous Generator (PMSG) as machine widely adopted in Wind Energy Conversion System (WECS) less than 100 kW. The core theoretical background is detailed to confirm the accuracy of the parameters procedures acquisitions. Poles number, machine design constant, armature reactance, synchronous reactance, and power-dynamic characteristic related to WECS are determined. This laboratory set-up is composed of variable industrial fan, rectifier, boost converter and a bidirectional Direct-Current (DC) source as a battery emulator. All components have been assembled within the laboratory environment using commercially available elements. Low implementation cost and versatile methods determine the real input in practice of this platform. To validate the effectiveness for any SWT, a real one is tested, and every parameter proposed is calculated.

Open Hardware/Software Modular Battery Emulator for Battery Management Systems Development and Functional Testing

Open Hardware/Software Modular Battery Emulator for Battery Management Systems Development and Functional Testing

Battery Emulator for Coupled Electro-Thermo Powertrain Testing

Approved, DCN# 543-443-23Battery emulation systems are useful for testing and evaluating powertrain systems; but typically,only consider the electrical characteristics of a battery. Powertrains with shared cooling components/systems between batteries and power electronics would benefit from hardware-in-the-loop testing facilities that consider both the electrical and thermal aspects of energy storage. In this work a battery emulator that physically emulates both the electrical and thermal characteristics with a coupled electro-thermal powertrain testbed is demonstrated. The coupled electro-thermo model links the electrical and thermal outputs together and calculates them in real-time. The electrical model is an equivalent circuit representation of a battery making use of experimental data from tested cells. The electrical model is coupled to the thermal model through temperature-dependent parameters of the cell resistance and open circuit voltages. The thermal model is a lumped isothermal reduced order heat generation model. This model will calculate the net heat generated from the ohmic losses, entropic losses, and losses to cooling (liquid and ambient). The thermal model is coupled to the electrical model by being dependent on the cell’s state of charge and using the cell’s current and voltage outputs for its governing equations. Models are parameterized on experimental data acquired through pulsed hybrid testing. In this work, a 3.5 kWh battery pack with a discharge of 40 amps at 48 volts generating 38.4 Watts of heat is emulated in an electro-thermo powertrain testbed configured to represent an electric naval platform such as a small autonomous boat subjected to both baseline and pulsed loading. The electrical emulation is performed through a bidirectional power supply and thermal emulation through a resistive heater. The electro-thermo powertrain testbed then dissipates the emulated electrical energy through power convertors and electronic loads while the thermal energy is dissipated through a heat exchanger that also cools the power convertors. Numerical and experimental validation demonstrate that the coupled electro-thermo battery emulator is capable of accurately representing the electrical and thermal aspects of a 3.5 kWh battery. Limitations in terms ofemulating batteries at higher temperatures and current draws are discussed. Effects of scaling the coupled electro-thermo battery emulator are also presented.Acknowledgment: This work was supported in part by the Office of Naval Research under contract NO.N00014-22-C-1003DISTRIBUTION STATEMENT A. Approved for public release: distribution unlimited

Predictive Speed Control of a DC Universal Motor Applied to Monitor Electric Vehicle Batteries

This article deals with the design of a simple predictive control algorithm applied to a bidirectional DC-DC power converter for the angular speed control of a DC motor. We used the dynamics of a DC motor but mathematically reduced them to arrive at a simple model that is ideal for our purpose, not only to meet the control objective but also to generate reliable data for further analysis. This predictive control approach is based on the discrete time mathematical model of a DC motor. A huge capacitor to emulate an electric vehicle battery was then successfully connected to our experimental platform. Due to the robustness of the proposed control algorithm, the same predictive control scheme provided sufficient information to monitor the battery’s state. On this basis, and due to the system’s efficiency, it was possible to configure a fault detection scheme in our electric car battery emulator using only classical statistical tools. A PIC18F252 microcontroller was used in our experimental platform to implement our predictive control algorithm. It was then appropriately coupled to the power electronics required by the DC-DC converter to drive the DC motor. Our experimental results proved the excellent performance of the control method and also of the health monitoring system. On the other hand, the main difficulty in achieving our main goal was the realization of discrete control, which had to be as simple as possible while maintaining the control objective and while also being capable of generating reliable data for the health monitoring stage. Thus, the primary contribution of this work was the development of the predictive control of the speed of a universal motor, followed by the modification of the experimental design to simulate an electric car battery and the introduction of a novel statistical method for fault detection.

Modular Battery Emulator for Development and Functional Testing of Battery Management Systems: Hardware Design and Characterization

Battery Management Systems are essential for safe and effective use of Lithium-Ion batteries. The increasing complexity of the control and estimation algorithms requires deeper functional testing and validation phases of BMSs. However, the use of real batteries in such phases leads to hazards and safety risks. Battery emulators and the Hardware-in-the-Loop approach can instead speed-up and increase the safety of the functional testing and algorithm validation phases. This work describes the design and the characterization of a low-cost modular multi-cell battery emulator which provides a complete emulation of cell voltage, temperature, and current. This platform can be used to carry out Hardware-in-the-Loop tests on custom and commercial Battery Management Systems. The paper describes the platform design constraints derived from the most diffused Battery Management System architectures, the main design and implementation choices, and the platform characterization results. The proposed emulation platform is compared with literature and commercial ones showing a very good trade-off between performance and cost. This characteristic makes it appealing for small-size laboratories that develop and test Battery Management Systems. The project has therefore been made available to the scientific community as a freely downloadable open hardware platform.

Agent-Based Decentralized Model Predictive Control for Plants With Multiple Identical Actuators

This article proposes a decentralized model predictive control (DMPC) algorithm without communication for systems consisting of multiple identical, independent actuators acting on a single central plant. The particular system design is relevant for applications where modularity is paramount and for highly dynamic systems, e.g., battery emulator systems controlled by multiple dc–dc converter modules. Each agent, consisting of an actuator and a DMPC, controls a virtually scaled version of the plant to implicitly consider the effects of other agents. The set of DMPCs achieves the same plant performance as a corresponding centralized model predictive controller (CMPC) in unconstrained operation. Also, the states of the independent agents converge toward the globally optimal CMPC solution. This is obtained by dividing the CMPC’s objective function into local objective functions related to the subsystems. The optimality and stability of the DMPC in unconstrained operation are shown analytically. The stability of control input-constrained operation is analyzed by computing the region of attraction. Numerical studies of a battery emulator system compare the performance of the DMPC with the global optimum in detail.

Design of a 350 kW DC/DC Converter in 1200-V SiC Module Technology for Automotive Component Testing

In this paper, the design and implementation of a DC/DC converter for automotive component testing with state-of-the art performance is described. The converter is the core of a battery emulator for the characterization and development of automotive batteries, electronic chargers, traction inverters, DC-DC converters, E-motors and E-axles. Cutting edge performance, flexibility and compactness are obtained by exploiting 1200-V SiC modules, high switching frequency, planar transformer technology, suitable topology solutions and fast digital control strategies. The implemented system is a liquid-cooled, bidirectional converter with galvanic isolation capable of 350 kW continuous output power, output voltage range 48–1000 V, continuous output current up to 800 A (1600 A peak), voltage/current ramp-up time below 10/2 ms and 0.1% current/voltage accuracy. The entire instrument is implemented in a standard full-height 19-inch rack cabinet.

Design and implementation of a parametric battery emulator based on a power converter

Real batteries used for the performance testing and evaluation of the drive systems of electric vehicles (EVs) are being replaced by battery emulators (BEs) because of the high test costs, long test cycles, and difficulty in adapting to extreme operating conditions associated with the use of real batteries. A parametric BE for a lithium-ion battery based on a voltage source converter is presented. First, a Thevenin model of the battery is established, and a parameter identification method is proposed to obtain the relationship between the parameters of the battery model and the characteristics of the external electrical port (i.e. I–V characteristics) of the battery. Subsequently, based on the I–V characteristics, the topological structure of the power electronic device of the BE is designed, and the working modes under charging and discharging conditions are presented. Finally, an experimental prototype of the BE is designed and tested. The experimental results show that the proposed BE power converter can successfully simulate the external port voltage and current characteristics of the battery, which can replace the real battery to provide an effective test environment for the test and evaluation of the electric drive system of EVs.

Modular Battery Emulator for Development and Functional Testing of Battery Management Systems: The Cell Emulator

Battery Management Systems are fundamental components of the present battery generation. The development and characterization phases of a BMS often require an emulator of the battery cells with which the Battery Management System functions can be assessed with no safety risks as it would instead happen using a real battery. This work describes the design and characterization of a modular cell emulator circuit to be used as platform for the Hardware-in-the-loop test of a Battery Management System. The design constraints and choices are first described. Then, the experimental characterization of the cell emulator is shown and discussed. The proposed circuit shows a voltage resolution of 76 μV, an accuracy of 2.17 mV, and a setting time of 340 μs. Its cost is around 40 USD. The circuit results to be a very good trade-off between performance and cost. The Project is available to the scientific community as open hardware platform freely downloadable. It could be useful to small-size laboratories to self-produce a low-cost battery emulator with good performance for the development and the functional test of custom Battery Management Systems.

A Comprehensive Study and Validation of a Power-HIL Testbed for Evaluating Grid-Connected EV Chargers

Integration of excessive electric vehicle (EV) chargers into the low-voltage (LV) network may introduce new challenges. Power hardware in the loop (PHIL) simulations can be used for evaluating such systems as it provides a flexible testing platform to study the overall system as well as individual devices. To facilitate a proper PHIL simulation, a precise mathematical model of the PHIL testbed is required. This article presents a comprehensive small-signal model capable of describing the dynamics of a PHIL testbed developed for evaluating grid-connected EV chargers. The PHIL testbed consists of a PHIL-based battery emulator (BE) and a grid emulator (GE) to mimic the dc side battery energy storage system (BESS) and the ac side LV grid behavior, respectively. A mathematical framework is developed to analyze the stability and predict the accuracy of both PHIL-based emulators. The BE in this article considers a switch-mode power amplifier (PA). Thus, design strategies for its linear controller are also discussed in the context of cascaded dc–dc configuration. An experimental PHIL platform based on a real-time simulator (RTS) has been used to validate theoretical predictions and confirm developed models. Finally, the validated PHIL test has been employed for analyzing the performance of a commercial EV charger and its interactions with a weak LV network simulated in RSCAD/EMTDC.

Binary Sequences for Online Electrochemical Impedance Spectroscopy of Battery Cells

Online diagnostic of lithium-ion battery (LIB) cells may have significant impact on chemical energy storage systems. Electrochemical impedance spectroscopy (EIS) is widely used for the characterization of LIBs and could be the most appropriate technique for online diagnostic, but its response time should be shortened. This work investigates the usage of multisine excitation to shorten the measurement time and simplify the hardware implementation for EIS of battery cells. Two types of multisine binary sequences are considered: sigma–delta modulated multisine sequences (SDMSs) and maximum length binary sequences (MLBSs). Their applicability to online and <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">in situ</i> EIS monitoring is evaluated by designing a measurement architecture also suitable to be implemented in a system-on-chip. The calibrated measurement system is compared with a benchtop reference instrument, reporting an RMSE deviation smaller than 5% in the frequency range of interest 1–200 Hz. The realized system is then used for online monitoring of the discharge process of a commercial 18650 LIB cell. The two proposed sequences are compared in terms of accuracy using a digital battery emulator circuit. Both the sequences demonstrated to be suitable for fast measurement and simple hardware integration, enabling online <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">in situ</i> EIS monitoring at cell level.

Flatness-Based Discrete-Time Control of a Battery Emulator Driving a Constant Power Load

In this article, a new method for controlling battery emulators in the shape of bidirectional step-down converters driving constant power loads (CPL) is presented. The CPL introduces nonlinear behavior into the system and causes unstable system dynamics. This property and the discontinuity introduced by the switches make it challenging to develop a suitable control strategy. Usually, switching frequencies are assumed to be fast enough for the controller to neglect the fact that the switches are either ON or OFF. As the desired dynamics of the system approaches the switching frequency of the converter, the discontinuity of the switches can no longer be ignored and the controller has to generate a suitable piecewise constant control input. A novel approach for arriving at a piecewise constant control input is presented and compared to state-of-the-art approaches. The advantages of the new control method are demonstrated with simulations as well as measurements from a hardware-in-the-loop testbed.

Stability analysis of a flatness-based controller driving a battery emulator with constant power load

Abstract This contribution deals with the control of a battery emulator used in automotive testbeds for electric drivetrains. The battery emulator, which is realized as a DC-DC converter, is connected to a unit-under-test (UUT), e. g., an electric motor inverter. To accurately emulate the dynamic impedance of a battery, a highly dynamic output is required. Additionally, battery emulators should be applicable for a large variety of UUTs, hence robust performance in a large operating range is also required. This is especially challenging when the UUT behaves like a constant power load, as this can cause stability issues. To meet the requirements, a flatness-based control concept is presented that establishes feedback equivalence between a nonlinear and a linearized system representation. By examining the stability of the concept, an estimation of the region of attraction is found.

Exploiting dynamic modeling, parameter identification, and power electronics to implement a non-dissipative Li-ion battery hardware emulator

More and more applications encompass battery energy storage systems (BESSs) based on Li-ion batteries. However, when designing the power converter of a BESS or when studying the interaction between BESSs and other application components, relying on a real battery makes the process cumbersome, expensive, and time-consuming. Moreover, the battery could even suffer damages. The aim of the work is to show that it is possible to exploit suitable battery models and related parameter identification methodologies, as well as power converters and related control techniques, to develop a hardware device that emulates any given battery. In particular, this paper shows the design and the experimental prototype of a Li-ion battery emulator that is capable of both sourcing and sinking power at kilowatt scale. Unlike other similar devices available in the market or described in the technical literature, the proposed device is low-cost, it injects power into the grid during sink operation, and it can also reproduce battery dynamics. Design criteria are given in the manuscript. The proposed battery emulator has been tested and experimentally validated. The obtained device allows reducing the cost, time, and complexity of performing system tests in Li-ion BESS applications.

Design and Implementation of a Lead-Acid Battery Emulator

Design and Implementation of a Lead-Acid Battery Emulator

Estimation and compensation of DC-Link voltage disturbances in a DC–DC converter for battery emulation

ABSTRACT Battery emulation is essential for reliable testing of powertrains of electric and hybrid vehicles under repeatable conditions. For that purpose, a DC voltage controller provides fast reference tracking capabilities. Due to imperfect conversion of AC current to DC current, the DC voltage source of the battery emulator does not provide constant voltage but is subject to periodic fluctuations. This disturbance is propagated through the system to the battery emulator's output. In this paper, an observer-based compensation strategy is deployed. As the structure of the multiplicative perturbation is known, it is integrated into the battery emulator model yielding a state-affine system. An appropriate observer provides asymptotically correct estimates of the disturbance, which are then used to adequately manipulate the control variable without interfering with stability properties of the closed-loop system. Simulation and experimental results show the improvements achieved by the disturbance rejection.

Design of LLC Resonant Converters Based on Operation-Mode Analysis for Level Two PHEV Battery Chargers

In this paper, the efficiency-oriented design considerations are discussed based on the operation-mode analysis of the <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">LLC</i> converter considering the characteristics of charging profiles. The mode boundaries and distribution are obtained from the precise time-domain model. The operation modes featuring both-side soft-switching capability are identified to design the operating trace of the charging process. Then the design constraints for achieving soft switching with the load varying from zero up to the maximum are discussed. Finally, a charging trajectory design methodology is proposed and validated through experiments on a prototype converting 390 V from the dc power source to the battery emulator in the range of 250–450 V at 6.6 kW with a peak efficiency of 97.96%.

Power converter-based electrochemical battery emulator

In this paper experimental assessment of converter-based emulator of voltage characteristics of electrochemical batteries is presented. The described emulator, which is part of the laboratory set for testing an electric vehicle powertrain system, allows to imitate an electrochemical energy storage. An AC grid supplied power electronic converter system enables to emulate both the battery discharge and charge modes. In order to emulate Li-ion battery behavior a mathematical model of a battery has been developed. The model of electrochemical cell has been created on the basis of the characteristics of Li-ion battery determined experimentally. Voltage characteristics take into account the change in battery voltage caused by state of charge, temperature and current. The model is dynamic, i.e. it reflects the transient state of battery output voltage. edowego pojazdu elektrycznego, pozwala na odw- zorowanie elektrochemicznego magazynu energii. Przeksztaltnikowy uklad zasilany z trojfazowegosieciowego pozwala zarowno na emulacje baterii w trybie rozladowania, jak i ladowania. W celu odwzorowania baterii Li-ion opracowano jej model matematyczny. Model ogniwa elektro- chemicznego wykonano na podstawie charakterystyk baterii Li-ion wyznaczonych douwzgl ˛ edniaj ˛ acych zale˙ zno´ snapi ˛ ecia na zaciskach ogniwa od stanu jego naladowania, temperatury i nat ˛ e˙ zenia pr ˛ adu. Opracowany model jest modelem dynamicznym tj. odzwierciedla stany przej´ napi ˛ ecia wyjbaterii. (Przeksztaltnikowy emulator baterii elektrochemicznych)

Model predictive control of a DC–DC converter for battery emulation

A battery emulator is used instead of a real traction battery to supply an electric motor inverter on a test bed for hybrid and electric powertrains under deterministic conditions. The use of virtual battery models eliminates the need for expensive battery prototypes. Virtual battery properties such as chemistry, state of charge or state of health can be changed instantly. However, the control of a battery emulator is a challenging problem. Very fast reference tracking is required for battery impedance emulation but motor inverters act as constant power loads that have a negative influence on the tracking performance and can even lead to instability. In this paper an MPC strategy is proposed for solving this problem. Scheduling of local controllers is utilized in order to handle the nonlinear and destabilizing load. Furthermore, a fast algorithm is presented that allows real-time MPC subject to input and output constraints. Experimental results obtained with a battery emulator supplying an electric drive inverter demonstrate the performance of the stabilizing controller.