This paper presents a battery-equalization circuit and its control strategy. Energy storage inductors are applied in the circuit and their number is less than that of the switches. The topology is simple and easy to control. The antiparallel diode of the power switches can provide freewheeling path of the inductance current, and the energy can be transferred by switching. Battery charging and discharging has constant-voltage and constant-current mode. The corresponding control strategies of the equalization circuit are different. The working principle is discussed and the control strategies in the conditions of constant-voltage and constant-current modes are analyzed. The simulation model of the active battery-equalization scheme and an equalization circuit combined with the battery management system are established. Also a comparison is made to the existing inductor-based equalization schemes. The simulation and experimental results verify the theoretical analysis. The proposed battery-equalization scheme can realize the expected effect.

Series battery equalisation can improve battery charge and discharge reliability and extend battery life. Inductor-based battery equalisation schemes have the advantages of simple topologies and control strategies. According to the energy transfer pathway, inductor-based battery equalisation schemes can be divided into cell-to-cell and cell-to-pack equalisation schemes. The control strategies of the cell-to-cell schemes are simple; the inductor can only transfer energy between the neighbouring cells, so the equalisation speed is low. The cell-to-pack schemes are able to accomplish energy transfer between the cells and pack by charging and discharging the inductors. The equalisation speed is high, but the control strategies may be complex. In this paper, different equalisation topologies are reviewed, then a unified control strategy which is applicable to all of the inductor-based equalisation topologies is proposed. The equalisation speeds and efficiencies of these different schemes, including the newly-proposed unified control strategy, are analysed and compared. Based on the theoretical analysis, simulations, and experimental verifications, it is concluded that this unified control strategy can perform the battery equalisation process quickly and efficiently.

Intelligent pedal control is a new development trend of vehicle intelligence, an important application of which is the single pedal control being the driving and braking inputs for energy management of battery electric vehicle. Usually, a constant pedal angle is used as the zero position that is a boundary between the driving and the braking. Based on the dynamic zero position that is a variable pedal angle depicting the direction switch point during pedal rotation, we show a single pedal control approach to operate the driving and the braking of battery electric vehicle, which can make full use of the pedal stroke and improve the control performance. Pedal torque demand is observed by a new pedal dynamics model that depicts the dynamic variation of pedal position. A nonlinear model predictive controller is designed to realize optimal-based energy management, satisfy dynamic demands, improve ride quality, and ensure wheel anti-slip safety. To validate the effect of the single pedal control approach, both simulations and real vehicle tests are carried out. The results illustrate that the energy consumption of single pedal control can be reduced than the dual pedal control in several representative driving cycles benefited from the more efficient use of regenerative braking.

With the increasing environmental concerns, plug-in electric vehicles will eventually become the main transportation tools in future smart cities. As a key component and the main power source, lithium-ion batteries have been an important object of research studies. In order to efficiently control electric vehicle powertrains, the state of charge (SOC) of lithium-ion batteries must be accurately estimated by the battery management system. This paper aims to provide a more accurate dynamic SOC estimation method for lithium-ion batteries. A dynamic Thevenin model with variable parameters affected by the temperature and SOC is established to model the battery. An unscented Kalman particle filter (UPF) algorithm is proposed based on the unscented Kalman filter (UKF) algorithm and the particle filter (PF) algorithm to generate nonlinear particle filter according to the advantages and disadvantages of various commonly used filtering algorithms. The simulation results show that the unscented Kalman particle filter algorithm based on the dynamic Thevenin model can predict the SOC in real time and it also has strong robustness against noises.

Battery equalization can increase batteries’ life cycle, utilization, and reliability. Compared with battery equalization topologies based on resistance or energy storage components, the topologies based on transformers have the advantages of high balancing current and efficiency. However, the existence of switching losses will reduce the reliability and service life span of the equalization circuit. Aiming at resolving this problem, a new battery equalization topology by fly-back transformer with an absorbing circuit is proposed in this paper. Compared with other transformer-based topologies, it can decrease switching losses because the voltage/current spike is solved by the absorbing circuit which is composed of inductance, capacitance and diode (LCD), and it can also maintain a high balancing current of about 1.8 A and high efficiency of about 89%, while the balancing current and efficiency of other topologies were usually 1.725 A/1.5 A and 80%/80.4%. The working principle of the balancing topology and the process of soft switching are analyzed and calculated in the frequency domain. Due to the addition of the LCD absorbing circuit, soft switching can be realized to reduce the switching losses while the high equalization speed and efficiency are still maintained. The corresponding control strategy of the balancing topology is also proposed and the timely balancing is achieved. The theoretical analysis is verified by simulation and experimental results.