As a conventional transportation modality, bicycles have been gradually electrified to meet the desire for convenient and green commuting patterns, especially in developed urban areas. The electric bicycle battery pack and its management system are core elements that determine key performance metrics such as electric range and output power. With respect to electric bicycle applications, focused research on the battery, its management system, and performance has received less attention compared to other energy storage applications. In this thesis, a well-developed conversion kit produced by BionX is studied. A data collecting system is first installed to record both mechanical and electrical data, such as speed, power and voltage; this enables defining two standard riding cycles at different riding conditions. Two benchmarking tests are performed to investigate the battery life in pure electric mode and at different threshold levels of optimal assistance. A novel quadratic programming based fitting algorithm is derived and applied in both time and frequency domain parameter identification tests. The proposed algorithm is able to fit single/multiple pulses by applying a masking vector. Sensitivity study and experimental results show the high robustness and fast computation time of the approach compared to existing and commonly used methods, such as fmincon. The comparison between hybrid power pulse characterization (HPPC) and electrochemical impedance spectrum (EIS) tests are performed in terms of extracted internal resistance. A second-order RC battery model is developed using parameters extracted from HPPC tests. The model is validated by experimental riding cycles and used to generate the reference SOC profiles that are employed in a SOC estimation study. Four estimation strategies, including extended Kalman Filter (EKF), Sigma point Kalman Filter (SPKF), Cubature Kalman Filter (CKF), and joint extended Kalman Filter (JEKF), are compared systematically in terms of accuracy, robustness and computation complexity. / Thesis / Master of Applied Science (MASc)

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This thesis suggests a new approach to extend the lifetime of Lithium-ion batteries for a Home Energy Storage System equipped with a renewable energy source. The new configuration improves the lifetime of the energy storage device by using the pulsed charge-discharge method. The batteries in this system can be charged either using solar panels when solar energy is available or by the grid power during off-peak hours when the electricity cost is at its lowest rate. In the new configuration, the battery bank is split into two equal sections to employ pulsed charge-discharge method. Interrupting the charge or discharge current provides a relaxation time for the lithium ions to diffuse gradually into the electrodes material of Lithium-ion batteries, this reduces the damage in the microstructure of the electrodes and thus it helps to prolong the battery lifetime. The spilt bank strategy improves the longevity of Lithium-ion batteries while maximizing the solar energy utilization. This strategy leads to reduce the reliance on the grid power which decreases the consumer’s total energy cost as well. To show the usefulness of the new approach, different modes of operation are discussed in details along with simulation results. An experimental setup is also developed to evaluate the effectiveness of the new approach in extending the Lifetime of Lithium-ion batteries. / Thesis / Master of Applied Science (MASc)

In this dissertation, three major contributions are presented in a photovoltaic (PV) energy system. Firstly, a three-port grid-forming (GFM) microinverter and a lithium-ion battery pack are integrated at the back of PV panel. As a result, they form an AC-PV energy system module that produces an AC output voltage. The technoeconomic analysis, battery capacity optimization, PV panel size optimization, electrical and thermal model of batteries, battery heat generation model, battery management system and thermal management system are discussed in the AC-PV module by using stochastic analysis and battery test results. Secondly, a three-phase 540 KVA bidirectional inverter and a 1.86 MWh lithium-ion battery energy storage system (BESS) were integrated at the Florida Solar Energy Center (FSEC). A case study is performed for this system by acquiring the energy consumption of the building, the reduced energy consumption, the battery testing, the load shifting, and the peak shaving. The total harmonic distortion (THD) values are also provided. Among eight power management scenarios, the scenarios that include PV panels are satisfied via simulation. However, the scenarios that do not include PV panels are analyzed and presented based on the real-world setting measurements. Thirdly, a modified droop control method is designed for grid-tied and off-grid scenarios. The simulation results are obtained based on three scenarios. The first one is that the voltage and frequency regulation control algorithm is discussed when GFM inverters have the equal power ratings. Then, the load sharing control algorithm is determined based on different GFM inverters' power ratings. The last scenario includes Grid connection. Loads are added and removed from the system to ensure that the frequency and voltage stability is the range of continuous operation. The coupling reactance effect on power sharing is investigated.

Battery packs consists of several smaller cells that can drift apart from each other and cause imbalance to the system. These imbalances can be balanced by either dissipating some energy (passive method) or redistributing the excess energy between the cells (active method). In this project they energy efficiency and balancing speed of two active method is investigated and compared to a traditional passive balancing method for 9 cells connected in series. The two active method investigated is the delta structured switched capacitor (DSSC) and chain structure switched inductor (CSSI) method. These methods have the ability to balance any cell with any other cell at any time, which, given the same initial imbalanced cells, results in a much faster balancing speed compared to the passive method.   The energy efficiency and balancing speed was investigated further by examining the energy gained when continuously charging and discharging the cells to model real drive cycles of the cells. This resulted in energy saving corresponding up to 5 Wh more energy per cycle after simulating for about 1900 cycles. This energy gain started however after 1000 cycles due to small imbalance between the cells. The energy gain of the active methods are however not sufficient enough to compensate for their higher component cost when considering the whole life of the cell. However, looking only the second part of the cell’s life, cycled more than 1000 cycles, the energy gain became more clear and the DSSC method start to be more beneficial to use.

Current consumption measurements are useful in a wide variety of applications, including power monitoring and fault detection within a lithium battery management system (BMS). This measurement is typically taken using either a shunt resistor or a Hall-effect current transducer. Although both methods have achieved accurate current measurements, shunt resistors have inherent power loss and often require isolation circuitry, and Hall-effect sensors are generally expensive. This work explores a novel alternative to sensing battery current by measuring terminal voltages and cell temperatures and using an unknown input observer (UIO) to estimate the battery current. An accurate model of a LiFePO4 cell is created and is then used to characterize a model of the proposed current estimation technique. Finally, the current estimation technique is implemented in hardware and tested in an online BMS environment. Results show that the current estimation technique is sufficiently accurate for a variety of applications including fault detection and power profiling.

Electrical vehicles are getting more popular as the technology around batteries and electrical motors are catching up to the more common combustion engines. Electrical boats are no exception but there are still a lot of boats using old combustion engines that have a big impact on the environment. This study aims to deepen the understanding of the integration of electrical motors into boats by proposing a design of a system using a bidirectional synchronous buckboost converter. This converter is designed to handle the power transfer in a dual battery application, namely consisting of a 12 V battery and a 48 V battery. The converter includes proposed components, a PCB design, as well as the software that is required for the control of the power transfer. The results show that the converter design meets specification and, when using a test-bench, the software is capable of controlling the converter to achieve constant current and constant voltage in both directions.

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