Analysis of a Modified Equivalent Circuit Model for Lithium-Ion Battery Modules in CubeSats

Failure of the electrical power system (EPS) to meet mission requirements is a common problem in nano-size satellites commonly referred to as CubeSats. The motivation for this research stems from the desire to prevent EPS failure through a process of testing and space qualification of components. Utilizing models to predict the behavior of an EPS before it is designed, built, and tested for space can provide critical insight in areas of limitation in performance and survivability. Modeling an entire EPS system is challenging because it requires extensive knowledge of all components and their behavior. This research focuses specifically on the storage component of the EPS often referred to as secondary batteries. The secondary batteries, such as Li-Ion battery cells, are modeled to predict the performance of the storage component in the space environment. Experimental test data is collected under a simulated space environment through the use of a Thermal Vacuum Chamber (TVAC). Data collected from battery testing in the space environment is used to validate a modified Thevenin Equivalent Circuit model. The experimental test data and battery model are compared and evaluated resulting in a promising model that can reasonably predict performance of a battery pack in a two-series two-parallel configuration

SoC estimation for lithium-ion batteries : review and future challenges

ABSTRACT: Energy storage emerged as a top concern for the modern cities, and the choice of the lithium-ion chemistry battery technology as an effective solution for storage applications proved to be a highly efficient option. State of charge (SoC) represents the available battery capacity and is one of the most important states that need to be monitored to optimize the performance and extend the lifetime of batteries. This review summarizes the methods for SoC estimation for lithium-ion batteries (LiBs). The SoC estimation methods are presented focusing on the description of the techniques and the elaboration of their weaknesses for the use in on-line battery management systems (BMS) applications. SoC estimation is a challenging task hindered by considerable changes in battery characteristics over its lifetime due to aging and to the distinct nonlinear behavior. This has led scholars to propose different methods that clearly raised the challenge of establishing a relationship between the accuracy and robustness of the methods, and their low complexity to be implemented. This paper publishes an exhaustive review of the works presented during the last five years, where the tendency of the estimation techniques has been oriented toward a mixture of probabilistic techniques and some artificial intelligence

Methods for improving stability and power quality in networks with high levels of power electronics

Advanced power electronics are essential to the development of fully active electric power systems. There are, however, potential problems that can arise when high levels of power-electronic systems are distributed throughout a network. Most importantly, power electronics can degrade the quality of the power that is delivered by utility companies; furthermore, they can cause instabilities that lead to complete failures. New "smart" power systems are highly dynamic, meaning that a regulated converter thought to be stable under ideal conditions could easily become unstable for reasons well outside of the designer's control. This thesis addresses the issue of improving power quality in networks with high levels of power electronics. The core concept presented here is an effective on-line approach for the estimation of network impedance, a time-varying quantity that plays a key role in reducing power quality. Real-time information about the network impedance at the Point of Common Coupling (PCC) can produce more stable power converters and pave the way for new measurement techniques that help to monitor power quality. This thesis also examines the application of network impedance measurements for producing model-based adaptive controllers that allow power-electronic systems to remain stable when connected to "non-stiff" networks. This work can be applied in any system that is heavily dependent on power electronics, including terrestrial "Smart Grids," all-electric ships, aircraft, and spacecraft

An improved rainflow algorithm combined with linear criterion for the accurate li-ion battery residual life prediction.

Li-ion battery health assessment has been widely used in electric vehicles, unmanned aerial vehicle and other fields. In this paper, a new linear prediction method is proposed. By weakening the sensitivity of the Rainflow algorithm to the peak data, it can be applied to the field of battery, and can accurately count the number of Li-ion battery cycles, and skip the cumbersome link of parameter identification. Then, a linear criterion is proposed based on the idea of proportion, which makes the life prediction of Li-ion battery linear. Under the verification of multiple sets of data, the prediction error of this method is kept within 2.53%. This method has the advantages of high operation efficiency and simple operation, which provides a new idea for battery life prediction in the field of electric vehicles and aerospace

Battery thermal management for electric vehicles operating in cold climates

Electromobility has gained significance over recent years in an attempt to reduce greenhouse gas emissions which contribute to climate change. The requirements on the performance and efficiency of electric vehicles are high to make them an attractive alternative to the conventional fossil-fuel driven vehicles. Lithium-ion batteries are the primary energy source for electric vehicles as they have high power and energy density, excellent storage capabilities and long cycling life when operated under conducive conditions, i.e a temperature range of 15\ub0C to 35\ub0C. However, their performance and cycling life are drastically affected when the operating temperature is outside this range. Therefore, battery packs must be heated to optimal temperatures under cold climates. This energy is often provided by the packs themselves, which results in reduced driving range.This work investigates thermal encapsulation of battery packs as a means of passive battery thermal management to improve the battery performance and decrease heating demand during the initial phase of driving in cold climates. In order to predict the effects of battery pack encapsulation, a robust battery model that captures the dynamic behaviour of large battery packs is necessary in addition to other simplified vehicle and powertrain subsystems. The presented work proposes an integrated simulation methodology that enables numerical simulation of the relevant phenomenon at battery module, powertrain and vehicle levels.The battery modeling strategy uses a one-dimensional module discretized electrical-thermal approach. An electrical circuit model with 2RC Thevenin branches was used to capture the electrical performance and the Bernardi\u27s heat generation equation was used to estimate the heat generated from each module. The developed strategy was found to be in good agreement with measured test data. Vehicle simulations were performed under parking-driving scenarios to investigate the effectiveness of battery pack encapsulation at different ambient temperatures. It was found that the percentage of energy saved with battery pack encapsulation increased with decreasing ambient temperatures. The thermal resistance of the encapsulation material played a significant role in reducing heat loss to the environment. The simulations indicated that there is a potential of approximately 15% energy savings as a result of increased initial battery temperatures

Electronic identification systems for asset management

Electronic identification is an increasingly pervasive technology that permits rapid data recovery from low-power transponders whenever they are placed within the vicinity of an interrogator device. Fundamental benefits include proximity detection not requiring line-of-sight, multiple transponder access and data security. In this document, electronic identification methods for asset management are devised for the new target application of electrical appliance testing. In this application mains-powered apparatus are periodically subjected a prescribed series of electrical tests performed by a Portable Appliance Tester (PAT). The intention is to enhance the process of appliance identification and management, and to automate the test process as far as possible. Three principal methods of electronic identification were designed and analysed for this application: proximity Radio Frequency Identification (RFID), cable RFID and power- line signalling. Each method relies on an inductively coupled mechanism that utilities a signalling technique called direct-load modulation. This is particularly suited to low- cost passive transponder designs. Physical limitations to proximity RFID are identified including coil size, orientation and susceptibility to nearby conducting surfaces. A novel inductive signalling method called cable RFID is then described that permits automatic appliance identification. This method uses the appliance power cable and inlet filter to establish a communication channel between interrogator and transponder. Prior to commencing the test phase, an appliance is plugged into the PAT and identified automatically via cable RFID. An attempt is made to extend the scope of cable RFID by developing a novel mains power-line signalling method that uses direct-load modulation and passive transponders. Finally, two different implementations of RFID interrogator are described. The first takes the form of an embeddable module intended for incorporation into electronic identification products such as RFID enabled PAT units. Software Defined Radio (SDR) principles are applied to the second interrogator design in an effort to render the device reconfigurable

Battery Energy Storage Emulation for Power System Applications

The concept of energy storage for power systems has received increasingly more attention in recent decades, and the growing penetration of renewable energy sources has only escalated demand for it. Energy storage systems are excellent for balancing generation and load, for suppressing power fluctuations, and for providing other ancillary services to the grid. The Hardware Testbed (HTB) is a novel converter-based grid emulator created for studying the needs associated with high renewable penetration, but the system currently lacks a battery storage emulator. Thus, this work documents the development of a battery energy storage system (BESS) emulator for the HTB. The BESS emulator includes internal battery models for Lithium Ion, Lead Acid, and Vanadium redox flow battery technologies. The emulated BESS contains a two-stage power electronics interface using a DC-DC converter and a boost rectifier separated by a DC link. Controllers for active power output, reactive power output, and DC link voltage are designed for the power electronics interface, and application-specific control loops for primary frequency regulation, inertia emulation, and voltage support are also added. The models and control for this emulated BESS are implemented on a digital signal processor that controls one voltage source inverter on the HTB as if it were the BESS’s boost rectifier. Consequently, the voltage source inverter mimics the behavior of a BESS at its point of common coupling with the HTB’s power system. The BESS emulator is simulated and then tested experimentally on the HTB, and all of its control functions demonstrate correct operation. The BESS emulator’s primary frequency regulation and inertia emulation functions nearly eliminate the system frequency swing following a step change in load, and the voltage support keeps the BESS terminal voltage at a safer level following the disturbances. These three support functions are concluded to be capable of simultaneous operation, which allows the BESS emulator to support the HTB’s power system in multiple ways at the same time. In the future, the BESS emulator can be used on the HTB to study how battery storage can be used to support renewables and other dynamic power system needs

CMOS/Bipolar current conveyor design and development

The aim of this research programme was to design and develop a novel CMOS current conveyor, to improve areas such as bandwidth, slew rate, gain, and Powe- Supply Reject Ratio (PSRR). The current conveyor can be used in low frequency applications such as LED drivers for mobile phones and televisions, and high frequency applications such as mixers for up/down converters used in anything from radios to mobile phones. The initial part of the research looked into improving the Power Supply Rejection Ration (PSRR) of the current follower (mirror) by increasing its output impedance. Several types of current mirror were compared using analytical and simulation methods, using a new generic low frequency transistor model which was used to highlight the differences in impedance between BJT and CMOS current mirrors. It was found that the best type of mirror was the regulated cascode current mirror which offered the largest value of output impedance when built from CMOS transistors. Work then moved onto the voltage follower. By initially using a typical CMOS source follower, it was found that the voltage gain suffered from low values transconductance, drain/source resistance, and a larger than expected value of source resistance, which was extracted from simulation and was found to be around 300- 350Q. The best design was a two stage un-buffered amplifier which offered the best Power Supply Rejection (PSRR) voltage gain and bandwidth. Several different types of current conveyor (CCII+) were simulated and the results were compared. It was found that the best types of current conveyor were the cascode type conveyors which offered a voltage gain error of less than 1%. The regulated cascode type current conveyor offered the highest figure of PSRR that of around 60dB. Finally the new cascode type current conveyors were used to build examples of current feedback operational amplifiers (CFOAs), and the cascode type CCIl+ offered a voltage gain error of less than I%, largest bandwidth and best P SRR