Sun Zechang

A new SOH prediction concept for the power lithium-ion battery used on HEVs

One of the most important tasks of the battery management system (BMS) is to estimate the battery states which mainly include the State of Charge (SOC) and State of Health (SOH). Compared with the SOC estimation technology, which progresses a lot currently, the study of SOH prediction method is in its junior state. In this paper, a SOH prediction concept was proposed. Main points of this concept include the aging process of the battery, the definition of the SOH, and prediction of the batterys healthy state etc. Aiming at the application mode of the battery packs on hybrid electric vehicles (HEVs), ageing processes of the battery were discussed and several accelerated life test results were listed. Then according to the aging process studies, a power- reflecting SOH definition was proposed. Based on these, a parameter system identification based SOH prediction method was designed. To validate the SOH prediction concept we presented, a simulation test was designed, and test result show that the concept is feasible to predict SOH online.

A battery model including hysteresis for State-of-Charge estimation in Ni-MH battery

According to the measurement of the Ni-MH battery electrochemical impedance spectroscopy (EIS) and the relationship of the OCV-SOC , one basic equivalent-circuit model structure including hysteresis voltage for Ni-MH battery is presented, which can be applied for the estimation of battery state of charge (SOC). The model approach is evaluated by comparing the measured and the simulated battery voltage corresponding to several current profiles. Voltage hysteresis is shown to play a critical role in the Ni-MH battery model. Then the relationships among different physic variables and states variables of this model are expressed by the discrete-time state-space functions. Based on the Extended Kalman Filter, the Stare of Charge (SOC) for the Ni-MH battery model is estimated by using the date such as current and voltage which are real-time tested by the battery test instrument. Finally, the behavior of the algorithm in terms of accuracy is examined. Voltage hysteresis is shown to play a critical role, and this effect makes determining the SOC particularly difficult for Ni-MH batteries relative to other battery systems.

Research on Electro-hydraulic Parallel Brake System for Electric Vehicle

This paper introduces a electro-hydraulic parallel brake system suitable for electric vehicle by changing the conventional hydraulic brake system. This structure is able to achieve the parallel distribution strategy between the regenerative brake force and the hydraulic brake force and can recover the brake energy effectively. By analyzing the simulation of the typical brake process and regenerative energy in three standard cycle modes, its feasibility and practicability are verified.

Battery management systems in the China-made “Start” series FCHVs

In the China-made ldquoStartrdquo series fuel cell hybrid vehicles (FCHVs), the power battery pack, which contains a series of Lithium-ion batteries, plays an important role in the dynamic system. For developing the vehicles with high performance and good reliability, the batteries have to be managed to obtain maximum performance under various operating conditions. In this paper, a battery management system (BMS) was introduced which was designed for optimizing the use of the batteries. This system was a level-based system which contains a high-level system called ldquoCentral ECUrdquo (CECU) and several low-level systems called ldquoLocal ECUrdquo (LECU). The software of the battery management system was designed based on the UC/OS-II to guarantee the real-time requirement. The system performs such several tasks including states monitoring (State of Charge, SOC and State of Health, SOH), creepage detection, cell balance, thermal management, power limitation, diagnostics etc. In the two experiments shown in the paper, results indicate that this BMS performs well in managing the power batteries used in ldquoStartrdquo series FCHVs, it could estimate the states of the battery accurately, detect the creepage and do some protect in real time, balance the cell very well and maintain the temperature of the battery pack in a satisfactory manner. Other critical functions have also been tested during the vehiclepsilas on-road testing.

A method of insulation failure detection on electric vehicle based on FPGA

Currently, the voltages of power supply on electric vehicle are far higher than the level that people can endure. How to resolve the insulation failure detection in all kinds of electric vehicle have not been concluded. Aiming at the high voltage safety of electric vehicle, a solution based on FPGA is introduced in this paper. It first gives the analysis of people getting electric shock in EV, and then presents the principle of the detecting method and its realization. In the solution, a kind of filter circuit is provided for the power supply on electric vehicle while the device of FPGA is used to count the insulated resistance of power supply and control the switches. The result of experiment indicates that, applied on electric vehicle, this solution takes effect on the detection and protection for the creepage of power supply and personpsilas getting an electric shock.

Study on Electro-Hydraulic Parallel Brake System using HILS

Regenerative brake system (RBS) has been one of the most important systems which can improve vehicle economy efficiency along with the development of clean energy vehicle (CEV), such as HEV (hybrid energy vehicle) and FCV (fuel cell vehicle). This paper provides a simple and reliable Electro-Hydraulic Parallel Brake System (EHPBS) based on the conventional vehicle brake system. This EHPBS can implement parallel distribution strategy between regenerative brake force and the hydraulic brake force thereby achieves kinetic energy regeneration. Because of the difficulty and the danger of brake system experimentation, this paper tests the EHPBS in HILS (Hardware-In-the-Loop Simulation) environment, and the experiment data prove the system to be available and effective.

EMC comparison of unshielded twisted pair and shielded twist pair in automotive CAN-bus

EMC performance of transmission medium in real time on-board network is one of those important factors affecting the control property of the distributed system. Now twisted pair is the most commonly used transmission medium in vehicles. Twisted pair can be divided into shielded twisted pair and unshielded twisted pair. The difference between them is that the former one has a metallic tape which has some shielding effect. Theoretically shielded twisted pair should have better EMC performance, but in practical applications unshielded one may perform better. In order make a comparison of EMC performances for these two types of transmission medium used in automotive CAN-bus, firstly the paper develops testing plan and evaluation methods for EMC performance of twisted pair according to the existing standards. Then the testing plan is developed, afterwards test results are achieved and analyzed. Finally comparison is executed and suggestions of the selection of these two different twisted pair used in automotive CAN-bus are given.

Preliminary Study of a Distributed Thermal Model for a LFP Battery in COMSOL Inc. Multiphysics(MP) Software

In order to better understand the thermal behavior of high capacities and large power lithium-ion batteries for electric vehicle application, a distributed thermal model of a LFP battery is proposed. The model includes a 3-D electrode plate pair model based on porous-electrode theory and a 3-D battery model solving the temperature distribution of the battery. These models are coupled through heat generation rate and transient temperature during discharging process.

The offline fault diagnosis of FCV powertrain based on CAN bus

This paper introduces an offline fault diagnosis method based on CAN Bus for fuel cell vehicles powertrain, which synthetically applies CAN Bus communication technology, embedded system development technology, hierarchical fault processing technology and computer technology. Meanwhile, PC was applied as upper machine while the vehicle management system controller (VMS) based on MPC555 as lower machine. The upper machine and under-bit machine realize communication through CANdela protocol to record, upload and statistics analyses the fault. Such fault diagnosis system, which successfully complete the online fault record and offline fault diagnosis for powertrain, has been applied to “START III” fuel cell car developed by shanghai FCV powertrain Co., Ltd.

MODELING AND POWEER CONTROL STRATEGY DESIGN FOR FUEL CELL HYBRID VEHICLE

An integrated procedure for math modeling and power control strategy design for a fuel cell hybrid vehicle (FCHV) is presented in this paper. Dynamic math model of the powertrain is constructed first, which includes four modules: fuel cell engine, DC/DC inverter, motor-driver, and power battery. Based on the math model, a power control principle is designed, which uses full-states closed-loop feedback algorithm. To implement full-states feedback, a Luenberger state observer is designed to estimate open circuit voltage (OCV) of the battery, which makes the control principle insensitive to the battery SOC (state of charge) estimated error. Full-states feedback controller is then designed through analyzing step in responding to the powertrain and testing data. In the end, the results of simulation and field test are illustrated. The results show that the proposed power control strategy takes into account the performance and economic characteristics of FCHV powertrain components and achieves control object.