Search

Accurate battery state of charge (SOC) estimation can reflect the endurance of power batteries, which plays an important role in the battery management system (BMS). The extended Kalman filter (EKF) estimation of SOC is easily affected by the noise of sampling voltage and current, and there are problems such as low estimation accuracy and easy divergence. This paper adopts the improved EKF to estimate SOC recursively, and the estimation accuracy is improved. Firstly, the second-order RC equivalent circuit model of the battery is established, and then the pulse discharge test is performed to identify the parameters of the model. Finally, simulation verification is carried out based on the discharge conditions of the lithium-ion battery. The results show that improved EKF has better convergence and lower error than EKF, and the average absolute error is less than 0.01.

To solve the problem of low equalization or discharge efficiency, and improve the poor equalization effect due to large dispersion of individual batteries in the discharge process of redundancy equalization, a pre-equalization strategy of redundancy equalization based on K-means clustering analysis was proposed in this paper. According to this strategy, the battery pack can be divided into three classes, that is, high power type, medium power type, and low power type, which are then used as the foundation to achieve the charge and discharge between implementation classes based on Buck - Boost circuit. Compared with the traditional maximum-power battery which discharges to the minimum-power one, this strategy uses a type of battery as the balance standard, improves the balance of the efficiency of the pre-balanced adjustment battery discrete degree. At the same time, appropriate limitation is applied to the number of access to the battery to reduce the size of the equilibrium current, thereby reducing the power consumption. The simulation results of MATLAB/Simulink show that, under the condition of small battery quantity and large discrete degree of individual battery, the pre-equalization speed following clustering strategy is 4 times higher than that of traditional pre-equalization, which greatly improves the efficiency of pre-equalization, and shows certain practical value.

The redundant equalization system of lithium battery pack is generally implemented based on metal-oxide-semiconductor field-effect transistors (MOSFET). During the working process, the temperature of the MOSFET will be very high, resulting in energy waste. In order to reduce the waste, this paper proposes a power supply system for electric bicycles taillights similar to uninterruptible power supply based on thermoelectric power generation. Using thermoelectric power generation technology and referring to the design concept of uninterruptible power supply system, the power supply system called SUPS is designed. It is based on LTC3108 and STM32F407 chips. The experimental results show that SUPS can ensure the normal use of taillights and effectively use the MOSFET heating energy. The design idea of SUPS can also be used in other occasions with temperature difference energy but no suitable load to directly use it. It has reference value for the design of the system in similar scenarios.

Film bulk acoustic wave resonator (FBAR) is widely-used as RF filter or sensor due to its high frequency and Q-factor. This paper demonstrates the feasibility of FBAR as flexible magnetic sensors, like sticker. The proposed Sensor has a ZnO piezoelectric sandwich structure with magnetostrictive nickel (Ni) electrodes on the Polyimide (PI) substrate. The characteristics of the magnetic sensors have been investigated experimentally and theoretically. The testing results show its sensitivity is about 100Hz/Gs.

A novel flexible Film Bulk Acoustic Wave Resonators (FBARs) based on ZnO/PET structure was fabricated without back-etch. The PET layer is applied as acoustic reflector and substrate of FBAR. It has 1.14GHz parallel resonant frequency, 1.229GHz series resonant frequency and about 150 Q factors. The FBARs acoustic impedance is improved by using harden metal Au instead of Al as the bottom electrodes. The ZnO/PET structure FBAR is also simulated by COSMOL to confirm its working mechanism.