Kevin Hua Bai

Extended Kalman Filter based battery state of charge(SOC) estimation for electric vehicles

This paper proposed a battery state of charge (SOC) estimation methodology utilizing the Extended Kalman Filter. First, Extended Kalman Filter for Li-ion battery SOC was mathematically designed. Next, simulation models were developed in MATLAB/Simulink, which indicated that the battery SOC estimation with Extended Kalman filter is much more accurate than that from Coulomb Counting method. This is coincident with the mathematical analysis. At the end, a test bench with Lithium-Ion batteries was set up to experimentally verify the theoretical analysis and simulation. Experimental results showed that the average SOC estimation error using Extended Kalman Filter is <;1%.

Back-EMF-Based Sensorless Control Using the Hijacker Algorithm for Full Speed Range of the Motor Drive in Electrified Automobile Systems

This paper presents an open-loop control strategy, dubbed the Hijacker algorithm, which governs startup from standstill, low-speed operation in open-loop, the transition to closed-loop, and sensorless motor control. The goal of the Hijacker is to eliminate the torque ripple encountered by a sudden switch from the open to closed loop operation, providing a smooth transition between the two control mechanisms and reliable operation over the motors entire speed range without the use, or added cost of speed/position sensors. Implementation of the Hijacker exhibits extreme simplicity, so as not to add heavy computational loads on the processor. The algorithm, along with its development and justification, is then validated through both simulation and the test bench using a 1.4-kW/4500 rpm brushless dc motor.

A novel energy balanced variable frequency control for input-series-output-parallel modular EV fast charging stations

At present time, the most common electrical vehicle (EV) chargers employ a two-stage design, i.e., a front-end AC/DC stage + an isolated DC/DC converter. In this paper, an isolated dual-active-bridge (DAB) based single-stage AC/DC converter was proposed, which has the power-factor-correction (PFC) and zero-voltage-switching (ZVS) functions over the full-load range. By reducing one power stage and eliminating the large DC link capacitor, a high efficiency and high power density are achieved. Such topology can be used as a modular building block to scale up to 50kW by serial connecting the input terminals and paralleling output terminals. A novel energy-balanced variable switching frequency control for such input-series-output-parallel (ISPO) modular designed is proposed. A single-phase d-q transformation is implemented to achieve zero steady-state error. Simulation analysis and experimental validation are presented.

Design of a 2.5kW 400V→M2V high-efficiency DC/DC converter using a novel synchronous rectification control for electric vehicles

This paper proposes the design and development of a 2.5kW 400V→12V high-efficiency DC/DC converter with a wide input voltage range (450V~220VDC) and output voltage range (16V~6VDC). The designed DC/DC converter will be used in the electric vehicle as an electric alternator. An LLC half bridge topology is adopted as the primary side of the isolated DC/DC converter. For the secondary side, a novel rectification control strategy is developed to turn on/off the rectifier MOSFETs by actively tracking the exact triggering moments. A 2.5kW prototype to charge the on-board 12V battery was built to experimentally verify the theoretical analysis. The overall system efficiency was ~92% and the maximum is 93.2%.

A novel soft starting strategy of an LLC resonant DC/DC converter for plug-in hybrid electric vehicles

Usually a high-efficiency Level 1~2 battery charger consists of an AC/DC (PFC) part and a DC/DC part, which in this paper is a CoolMOS based 97%-efficiency full-bridge LLC resonant DC/DC converter. Due to the existence of the output capacitance and high input voltage (usually 400VDC), the inrush current of the DC/DC converter in the starting process is inevitable, which requires an effective soft starting strategy. This paper proposed an effective soft starting strategy to gradually charge the output capacitor, decrease the inrush current and, more importantly, avoid the hard switching in the starting process, which is a must to the CoolMOS. The proposed starting strategy has been experimentally validated on a 10kW LLC resonant DC/DC converter.

Design of a high-efficiency 12V/1kW 3-phase BLDC motor drive system for diesel engine emissions reductions

For the conventional vehicle, an efficient and effective heat source that provides autonomous exhaust temperature control is of interest, and one solution is a diesel burner which needs to adjust its air delivery based on transient operating conditions through a three-phase motor drive system powered by a 12V lead-acid battery. The system proposed in this paper consists of a series-resonant LLC MOSFET full-bridge converter, which provides high-efficiency energy transfer through implementing Zero Voltage Switching, and an IGBT inverter which provides the high-side phase currents to a 1kW brushless DC motor. Experimental results on this prototype system demonstrate the LLC DC/DC part efficiency is 97.6% and the inverter efficiency is 92%.

Mobile phone mid-range wireless charger development via coupled magnetic resonance

In this paper, wireless power transfer for mobile phones via coupled magnetic resonance with multiple transmitters (Txs) and / or receivers (Rxs) are investigated and tested. The system is able to charge cellphones with more than 3 W in a distance between 5 and 15 cm and also in different angles. The resonant frequency is 6MHz. For lower charging powers the distance between the Tx and Rx can go up to 20 cm. Additionally, the three-dimensional movement of the Rx and its effect to the charging power is tested, as self-rotation and rotation around the Tx coil. This achievement is significant to improve user experience of wireless charging for portable electronic devices.

System optimization of a high-power and high-step-down accessory power module for electric vehicles

In previous work, a novel design of a 2.5kW 400V-12V 93.2%-efficiency DC/DC converter with a triggering angle tracking synchronous rectifier was proposed for use in an electric vehicle to replace the electric alternator. This paper is focused on the further enhancement of the DC/DC converter to improve the system efficiency and wide-range input/output performance.

A hybrid observer for the full-speed-range sensorless control of interior permanent magnet motor drives

This paper presents a method for the sensorless control in full speed range for an interior permanent-magnet synchronous motor (IPM). At standstill and very low speed region, high frequency (HF) injection technique is used to detect the rotor initial position. A hybrid observer is applied to realize a smooth transition from low to high speed. When the rotor speed goes up to a certain value where back EMF can provide adequate information, a back EMF observer will dominate. The hybrid observer is verified through simulation and experimental results using a three-phase 1-kW IPM motor drive.