Zhenpo Wang

Research on Quantitative Models of Electric Vehicle Charging Stations Based on Principle of Energy Equivalence

In order to adapt the matching and planning requirements of charging station in the electric vehicle (EV) marketization application, with related layout theories of the gas stations, a location model of charging stations is established based on electricity consumption along the roads among cities. And a quantitative model of charging stations is presented based on the conversion of oil sales in a certain area. Both are combining the principle based on energy consuming equivalence substitution in process of replacing traditional vehicles with EVs. Defined data are adopted in the example analysis of two numerical case models and analyze the influence on charging station layout and quantity from the factors like the proportion of vehicle types and the EV energy consumption at the same time. The results show that the quantitative model of charging stations is reasonable and feasible. The number of EVs and the energy consumption of EVs bring more significant impact on the number of charging stations than that of vehicle type proportion, which provides a basis for decision making for charging stations construction layout in reality.

Finite Element Thermal Model and Simulation for a Cylindrical Li-Ion Battery

Due to the advantages of high energy density, no memory effect, and long cycle life, Li-ion batteries are being widely studied and proverbially used as power sources for electric vehicles. The performance of Li-ion battery systems is largely dependent on the thermal conditions and the temperature gradient uniformity inside. In order to tackle with the inconsistency problems of temperature distribution among battery cells in a battery pack, a thermal model for a cylindrical battery based on the finite-element method was developed. Physical structure and electrochemical reactions were both considered, and the initial conditions, boundary conditions, and thermal characteristic parameters of the battery components were determined through theoretical calculation and experiments. The discharge thermal characteristics were further investigated. In addition, the experiments were conducted to verify the accuracy of the presented model. Comparing the theoretical analysis with experimental results, it shows that the relative errors between the simulation and the tests are small at varied ambient temperatures and discharge rates. Therefore, the model can be efficiently applied to predicting the thermal behaviors of Li-ion batteries in practical applications.

Ultracapacitor modelling and parameter identification using the Extended Kalman Filter

Energy storage systems (ESSs) play an important role in sinking and sourcing of power in an electric vehicle and ensuring operational safety. Ultracapacitors (UCs) are a recent addition to the types of energy storage unit that can be used in an electric vehicle as an ESS because of their high power density, fast charging or discharging, and low internal loss. They can be used in parallel with batteries or fuel cells to form a hybrid energy storage system that makes better use of merits of each component and offsets their drawbacks. Establishing a good model with properly identified parameters to precisely represent the UC dynamics is vital for energy management and optimal power control; but this is challenging. This paper firstly presents the classic circuit equivalent model that consists of a series resistance, a parallel resistance and a main capacitor. The model dynamics are described with the state space equations. The Extended Kalman Filter is then used to simultaneously estimate the state and the model parameters through a simple constant-current charging test. Finally, the obtained model is validated through a dynamic test. The model output shows a good agreement with the experimental results. They verify that the model is sufficiently precise to represent the dynamics of an UC.

Vehicle sideslip angle estimation for a four-wheel-independent-drive electric vehicle based on a hybrid estimator and a moving polynomial Kalman smoother

This paper presents a vehicle sideslip angle estimation scheme against noises and outliers in sensor measurements for a four-wheel-independent-drive electric vehicle. The proposed scheme combines a robust unscented Kalman filter estimator based on the 3-DOF vehicle dynamics model and an extended Kalman filter estimator based on the kinematic model to form a hybrid estimator through a weighting factor. The weighting factor can be dynamically adjusted in real time to optimize the overall estimation performance under different driving conditions. The main contributions of this study to the related literature lie in two aspects. Firstly, a robust unscented Kalman filter estimator was incorporated to improve the robustness of dynamics-based estimation to sensor measurement outliers. Secondly, a novel moving polynomial Kalman smoother was included to filter out the noises in sensor measurements. Co-simulations of Matlab/Simulink and Carsim software were conducted under typical vehicle maneuvers and show that the proposed vehicle sideslip angle estimation scheme can obtain satisfied estimation results, with the moving polynomial Kalman smoother exhibiting better phase characteristics and filtering performance relative to commonly-used finite impulse response filters, and the robust unscented Kalman filter estimator being robust to sensor measurement outliers.

Analysis of energy consumption characteristics of dual-source trolleybus

Making use of the grid in Beijing, a dual-source trolleybus was developed, and achieved driving it by battery packs in off-grid area. Because of using a composite power system, the energy flow of the vehicle is multi-directional and multi-dimensional. To use the energy rationally, the energy flow was researched and energy consumption was tested with grid accessing The energy consumption distribution of dissipative components was obtained, influencing factors on energy consumption including vehicle body construction, speed and temperature were analyzed. This paper proposed four methods to reduce energy consumption and improving efficiency.

Battery system matching and design for a formula student electric racecar

As energy storage system which should supply enough energy to the racecar, battery system shouldnt weight too much in order to build a lightweight, energy-saving and competitive car. The energy consumed by the motor can be known using power balance equation with racecar velocity information obtained in previous competition, and thus the number of cells is determined after battery selection. As for battery system container, the use of polycarbonate plastic helps a lot to reduce weight and the well-designed structure for ventilation turns out to be effective for cooling the battery.

Impact Safety Control Strategy for the Battery System of an Example Electric Bus

This paper proposes a side impact safety control strategy for the battery system, aiming at defusing the hazards of unacceptable behaviors of the battery system such as high-voltage hazards. Based on some collision identification metrics, a side impact discrimination algorithm and a side impact severity algorithm are developed for electric buses. Based on the study on the time to break for power battery, the side impact discrimination algorithm response time is about 20u2009ms posing a great challenge to the side impact discrimination algorithm. At the same time, the reliability of the impact safety control strategy developed in this paper is evaluated for other plausible side impact signals generated by finite element analysis. The results verify that the impact safety control strategy exhibits robust performance and is able to trigger a breaking signal for power battery system promptly and accurately.

Research on impact safety control for the battery system of electric bus

Electric vehicles are gaining increasing popularity and mass acceptance all over the world, thanks to the use of electricity that can diversify the power sources of vehicles. The safety issue of power battery system onboard poses a particular challenge to ensuring the overall safety performance, especially in the serious collisions. This paper presents a design and implementation of a safety control system for the battery system in electric vehicles, aimed at defusing the hazards of unacceptable behaviors of the battery system such as flaming or even exploding in a collision accident. The presented system is composed of seven modules including main program, system initialization, self-checking, A/D conversion, timing sample, control algorithm and real-time self-checking. A 16-bit HC9S12DP512 microcontroller and a MMA3202 accelerometer are employed as the hardware to exert the purported functionality. According to a well-established control strategy, the voltage broken-down can be realized in collisions to avoid even severe safety issues, thus enhancing the safety performance. The experimental results show that the control system exhibits high reliability, real-time performance, anti-jamming and flexibility and can be extended easily with good accurate.

Research on characteristics of power Li_4 Ti_5 O_12 batteries

Batteries are a critical component that largely governs the performance and cost of an electric vehicle. There are a variety of types of batteries competing for use, each with cons and pros. Among these options, Li_4 Ti_5 O_12 batteries excel with superior performance in terms of safety, stability, service life. In order to make better use of its merits for electric vehicle applications, understanding its charging/discharging characteristics becomes of necessary importance. To this end, this paper experimentally investigates internal resistance evolution, cathode thermal properties, charging/discharging characteristics against different rates, as well as the influence of temperature on charging/discharging process. Then, charging/discharging ca d analyzed in detail. The results show that mass energy density of Li4 Ti_5 O_12 battery is only 69.45Wh/kg, the volume energy density is only 82.94Wh/L, DC resistance is just pacity and energy against -30°C and 45°C are selected an only 0.5~1.2mΩ, Charging/discharging capacity and energy against high temperature increases by 50mAh and 240mWh, whereas, the same process against Low temperature only lasts 20s, leading to sharply decline of capacity and energy.

Analysis of collision safety of power battery system of electric bus with simulation

Aiming to improve the collision safety of power battery system, the study established the finite element models of the whole bus skeleton, power battery system and moving deformable barrier. A side collision was simulated on the position of battery box of the bus based on the collision law. The work carried out equivalent stress analysis of battery module and deformation analysis of battery pack and the rear panel of battery box. Measures were put forward to improve the collision safety of power battery system.