Fraunhofer IISB - Battery Systems

Transcription

1 Fraunhofer IISB - Battery Systems Li-lon Batteries for Stationary Energy Storages Your R&D Partner for Innovative Solutions in Advanced Battery Systems Page 1

2 Presentation Outline 1. Introduction ; Motivation ; Cost Analysis 2. Competences and Development Flow 3. Battery Modelling and State Estimation (SOx) 4. Battery Management System (BMS) 5. Temperature Sensor & Gas Sensor for Safety 6. Antifuse for Enhanced Reliability and Availability 7. Conclusion and Outlook Page 2

3 DC-Grid: Integration of a Stationary Battery System 100 kw Bidirectional DC/DC-Converter Page kw 20 kwh Li-Ion Battery

4 Full-Custom High-Performance Stationary Battery System Modular Battery Management System Fraunhofer IISB Universal Battery Junction Box Fraunhofer IISB System Topology LTO chemistry 20Ah prismatic cells 14 daisy-chained modules 15s2p Modules Electrical Specifications 20kWh total energy 100kW maximum continuous power 320A continuous charge and discharge currents V voltage range 1.2mV precise voltage monitoring at cell level High electronic reliability achieved through redundant design for 24/7 grid applications Air cooled system Fraunhofer IISB Modular Battery System Page 4

5 Cost Analysis: Lead-Acid versus Lithium-Ion Specifications Energy that must be stored (usable) Discharge power Cycling frequency Based on the estimation made by: Page 5 Value 50kWh Average ambient temperature 23 C Expected lifespan 10kW (i.e., 5 hours runtime at C/5) 1 discharge/charge cycle per day 5475 cycles (~15 years at 1 cycle per day) Chemistry Lead-Acid AGM Lithium-Ion (LFP) Lithium-Ion (LTO) Installed capacity 100kWh 62.5kWh 50kWh Usable capacity 50kWh 50kWh 50kWh Lifespan % DOD % DOD % DOD Battery cost 15,000 (150 /kwh) (x2) 18,750 (300 /kwh) (x2) 75,000 (738 /kwh) (x1) Installation cost 2,000 (x2) 2,000 (x2) 2,000 (x1) Transportation cost 2,800 (28 /kwh) (x2) 625 (10 /kwh) (x2) 700 (14 /kwh) (x1) Total cost 19,800 (x2) 40,125 (x2) 77,700 (x1) Cost per installed kwh (over 15 years) 0.79 /kwh 0.86 /kwh 0.79 /kwh For the considered battery cell chemistries, a use-case can be found so that the considered chemistry offers a cost advantage. The central question is: does this use-case make sense in a commercial application?

6 Required Competences for Designing Battery System Solutions Development and assembly of battery packs with their thermal management system Development of electrical, mechanical and thermal battery models at cell, module and pack level Smart Power Integrated Driver Circuit Power Antifuses Development and assembly of battery monitoring and battery management system (BMS) hardware Development of battery state estimation algorithms (e.g., SOC, SOH, SOF) Development of safety sensors (e.g., temperature sensors) for enhanced safety in battery systems L R R R W Battery Modeling Development of actuators (e.g., power antifuse) for enhanced reliability and availability in battery systems Battery Monitoring and Management Hardware Battery Monitoring and Management Software Temperature Sensors on Lithium-Ion Battery Cells Page 6

7 Development Flow for Battery System Solutions System Design System Specifications (e.g., Energy, Power, Size) Safety and Reliability/Availability Requirements Cells Selection (Based on our Internal Database) Cells Modeling (Electrical, Mechanical, Thermal) Mechanical Design Battery Cell Assembly Design Battery Module Assembly Design Battery Pack Assembly Design Battery System Mechanical Design System Integration Electrical Design Battery Junction Box Design Battery Monitoring Design Battery Management Hardware Design Battery Management Software Design Cell Voltage Equalization Design Thermal Design Coupled Electro-thermal Modelling Coupled Electro-thermal Simulations Thermal Layout of the Battery System Thermal Management (Liquid, Air) Cooling & Heating System Fabrication Component Selection (e.g., Breakers, Connectors) Component Fabrication (e.g., Packages, Bus Bars) System Assembly and Integration Final Tests and Characterization Delivery of the Battery System Prototype Page 7

8 Electro-thermal Simulation Needed for Thermal Management R i Z W L Electrical model Current profile as input V oc R sd Z 1 Z 2 Dissipation calculated with R s is strongly temperature dependent Dissipation Thermal model Dissipation as input Current Calculate resulting temperature distribution Issue: long FEM simulation time Simulation: electrical model Average temperature Simulation: reduced thermal model Page 8

9 Coupled Electro-thermal Modelling Workflow Thermal Parameters R th and C th Electrical Parameters CAD Model with λ th and c th Parameter Optimization Electrical Model without Parameters Electrical Model with Parameters Electrical BMS SOC with Kalman Filter (EKF, AEKF, UKF) Model Order Reduction Coupled Electrothermal Simulations Dimensioned Battery System Reduction/expansion matrix: Expanded Model with Temperature Distribution Thermal Electro-thermal Page 9

10 Thermal Modeling Using Model Order Reduction (MOR) Aim: generate a low dimensional approximation of the system Mathematical method (i.e., does not rely on intuition) CADFEM Toolbox used here Physics & Geometry FEM System of n equations MOR Reduced system of r << n equations n~ ; r~100 Result for a pouch cell Mean temperature on electrode stack Error < 0.1 C FEM: 2000s (4 CPUs) MOR: 5s (1 CPU) 1600:1 ratio Page 10

11 Reconstruction of the Temperature Distribution Output of MOR: mean temperature of electrode stack MOR method reduction uses transformation matrices Transformation matrices enable inverse transformation Reconstruction of the temperature gradients (at 500s) Comparison FEM/MOR with reconstruction at one time step Error < 0.03 Page 11

12 Electro-thermal Coupling: Simulation versus Experiment Experiment: Real Cell Heated by Discharge Cycle Thermographic imaging Electro-thermal coupled simulation with MOR Comparison shows good accuracy in values and distribution: ΔT<1.5 C Thermocouple position Measurement TC [ C] Simulation [ C] ΔT [ C] Below MINUS tab Center below tabs Below PLUS tab Page 12

13 Battery State Estimation: Workflow and Assessment Measurement Profiles Current Measurements Voltage Measurements Temperature Measurements Measurement Synchronization Battery Model without Parameters Global Optimization Multi-objective Genetic Algorithm Simultaneous Calibration Against Multiple Profiles Selection of Champions Fraunhofer IISB Advanced Simulation Framework Constraints Local Optimization Intense Post-Optimization Levenberg-Marquardt Sequential Quadratic Programming Final Solution Further Developments Required Cutting-Edge Technology Available Model with Parameters Kalman Filter (EKF, AEKF, UKF) Particle Filter (Research Topic) SOC SOx Page 13

14 Battery Management and Monitoring: Electronic Architecture Features: Differential communication bus Monitoring IC + Battery monitoring electronics based on Linear Technology LTC state-of-the-art battery monitoring IC Module x Monitoring IC bit resolution of voltage and temperature measurements Electronics based on proven designs for mobile and stationary applications Module 2 - Software-less monitoring electronics eliminates software problems MCU Gateway IC Monitoring IC + Safety aspects: BMS Module 1 - Redundant monitoring electronics possible (main and backup path) Ultra low current consumption during sleep state (4µA) Page 14

15 Battery Management System: Hardware Overview Infineon TriBoard 32bit TC1798 MCU OSEK/AUTOSAR Automotive Operating System JTAG Interface Add On Board I Galvanically Isolated Relay Drivers Data Interface to Monitoring Circuits Real Time Clock SD Memory Card for Logging Add On Board II Galvanically Isolated Power Supply Isolated CAN Interfaces (2x) Charger Control Interface Companion IC (Infineon CIC61508) for Safety On Board Temperature Measurement Isolation Monitoring Interface Precision Voltage Reference Interface for Isolation Monitoring Companion IC Infineon CIC61508 Add On Board I Monitoring ICs Infineon TriBoard Relay Drivers 32 bit Microcontroller Infineon TriCore TC1798 Add On Board II 2 Isolated CAN Transceivers DC/DC Converter Page 15

16 Battery Management System: Software Overview Provide Safety Enhance Battery Lifetime Battery State Estimation Safety For Humans Safety for Battery Temperature Control Electric Control Functional State Explosion Overtemperature Heating Demand Charge Management SOC Fire Overvoltage Cooling Demand Power/Current Derating SOH Electric Shock Overcurrent/ Short circuit SOF Undervoltage BMS Self Diagnosis Undertemperature Page 16

17 Battery Monitoring Electronics Based on the LTC Fully Redundant Battery Monitoring with Failure Compensation No Software! Voltage measurement of the battery system (>100 Cells) in 290µs Accuracy of voltage measurements Single cell: 1.2mV Module: 1% Quasi synchronous voltage sampling Robust daisy chain communication Energy consumption at 25 C: 13mA (ON) ; <10µA (SLEEP) Fully redundant design for ASIL-D and 24/7 applications: includes functions for error&failure detection and compensation Evaluation of up to 16 external temperature sensors per module Passive balancing with failure correction Page 17

18 Battery Monitoring: Redundant Solution for 24/7 Applications MUX Temperature Measurement MUX Balancing Ctrl Backup IC 1 Main IC 1 Main IC 2 Daisy Chain Connector Passive Balancing Cooling Area Page 18 Temperature Sensor Connectors Voltage Measurement Filters

19 Printed Low-Cost Flexible Temperature Sensor High thermal sensitivity: 3% per C Designed for low-cost and fast manufacturing Highly flexible substrate Overall thickness less than 300µm 100µm flexible substrate (PI, PET etc.) 50µm screen printed contacting layer with silver compound 50µm screen printed resistive layer 100µm passivation layer passivation layer resistive layer interdigitated electrodes layer plastic substrate Page 19

20 Gas Sensor for Enhanced Safety in Battery Systems The idea is to detect dangerous operating conditions of lithium-ion battery cells by means of the cost-effective AppliedSensor iaq-100 module Accurate and reliable measurement of: Temperature Humidity AppliedSensor iaq-100 Carbon dioxide (CO 2 ) levels Volatile organic compounds (VOCs) But: only reacts to differences in temperature or composition of the gas mix Page 20

21 Gas Sensor: Battery Abuse Tests Cursor 1: Initial gas detection Δt: 40s Cursor 2: Estimated beginning of thermal runaway NMC Li-ion 5Ah cell abuse test 12C overcharge current Cell mechanically fixed No shut down after gas detection Measurements of: Gas (VOC/CO2) Cell voltage Cell temperature Page 21

22 Antifuses: New Bypass Electronic Device Battery systems for high-power applications require stacking of ~100 cells in series Bypass feature against single cell failure Power Antifuse Symbols Cell can be shorted out from the circuit Untriggered Antifuse Triggered Antifuse Page 22

23 Realization of Antifuse Devices Assembly and packaging Press-pack design Aluminum springs Mold compound for 600 C: K-Therm AS 600 M Demonstrator sample : Polycarbonate top housing Designed for 100A and 1mΩ Page 23

24 Dashboard of the Battery System Dashboard showing the major control values for the battery system: Value: Voltages, Temperatures, Current, Power Status: Power and Pre-charge Contactors, Galvanic Isolation, Voltages, Temperatures, Current Battery State Estimations: SOC, SOH, SOF, SOL Page 24

25 Conclusion and Outlook: Examples of Active Research Topics High Availability Redundant Battery Electronics (without Software Running Locally) Addressing Safety-Critical Applications (e.g., ASIL-D) Parametric Model-Order-Reduction Applied to Electro-thermal Battery System Models for Simulating Cycles at System Level (e.g., NEDC, WLTP) Reduction of Temperature Gradients in Battery Systems for Homogenous Ageing of all the Battery Cells, thus Reducing the Need for Balancing Sensorless Battery Cell Temperature Estimation, thus Enabling Safe and Cost-Efficient Accurate Battery Pack Temperature Monitoring Integration of Gas Sensors in Battery Systems for Early Fault Detection and Improved System Safety Power Antifuse as Low-Cost Device for Bypassing Faulty Battery Cells Printed Temperature Sensor for Low-Cost Temperature Sensing to Improve the Safety in Automotive Battery Systems Page 25

26 Thank you for your attention For questions, do not hesistate to contact us: Group Manager Battery Systems; Division Power Electronics Fraunhofer IISB, Schottkystraße 10 D Erlangen, Germany Telefon Page 26