Wen Changyun

Li-ion battery SOC estimation using particle filter based on an equivalent circuit model

In this paper, a method for Li-ion battery state of charge (SOC) estimation using particle filter (PF) is proposed. The equivalent circuit model for Li-ion battery is established based on the available battery block in MATLAB/Simulink. To improve the models accuracy, the circuit parameters are represented by functions of SOC. Then, the PF algorithm is utilized to do SOC estimation for the battery model. From simulation it reveals that PF provides accurate SOC estimation. It is demonstrated that the proposed method is effective on Li-ion battery SOC estimation.

A fuzzy logic-based model for Li-ion battery with SOC and temperature effect

In this paper, a fuzzy logic-based model for Li-ion battery considering SOC and temperature effect is proposed. So far, the equivalent circuit model for Li-ion battery is common-used for its simplicity and suitability for control and estimation. However, among existing equivalent circuit models, it is seldom to consider the temperature effect, which has significant influence on electric vehicles (EVs) performance. It is difficult to find the relationship between equivalent circuit parameters and state of charge (SOC) and temperature. In our paper, the methodology of fuzzy logic is applied to model Li-ion battery. By using fuzzy rules, SOC and temperature effect on parameters is described simultaneously with simplicity and clarity. Simulation and experiment results show that the fuzzy logic-based model has good accuracy at different temperatures.

Design of a highly reliable three-phase four-leg inversion power supply for more electric aircraft

In a more electric aircraft (MEA), there are always needs of inversion power supplies to power a bunch of legacy loads that need 115VAC/400Hz electric power. Space vector pulse width modulation (SVPWM) controlled three-phase three-leg inverter is usually adopted as the inversion power supply at present. The drawback of such inverter is that it does not have the ability to operate under unbalanced load conditions, especially under short-circuit condition, which makes it hard to be implemented in future commercial and especially military MEAs. Sinusoidal pulse width modulation (SPWM) controlled three-phase four-leg inverter may be a solution to such a problem, however, its DC voltage utility is low compared to the SVPWM controlled inverters. As a result, higher input DC voltage is required, which not only increases the voltage stresses of power switches but also deteriorates the system efficiency. Therefore, in this paper, a new saddle pulse width modulation (SAPWM) method is proposed and applied to a three-phase four-leg inverter to form a highly reliable inversion power supply which is very suitable for future MEAs. The way to generate the saddle pulse width modulation waveform using analog circuits, the system control method and the operational principle of the inversion power supply are elaborated. A 6kVA simulation platform is designed in Saber. The validity of the proposed inversion power supply is verified by simulation results.

Power control strategy for variable-speed fixed-pitch wind turbines

Variable-speed fixed-pitch (VSFP) wind turbine is widely used in small-to-medium scale wind turbine markets due to its simple structure, low cost and high reliability features. However, power control, especially maximum power limitation control at high wind velocities, of such turbine concept is hard to realize and it has not been studied much in existing researches so far. To overcome this difficulty, we propose a simple power control strategy for VSFP wind turbines, covering the entire range of wind velocity. The proposed strategy contains a novel maximum power point tracking (MPPT) control method, a constant-speed (CS) soft-stalling control method and a constant-power (CP) soft-stalling control method. These three sub-control methods are appropriately combined in a way to realize seamless transitions among different operational modes (MPPT, CS and CP). The system structure and operational principle of the proposed strategy are thoroughly analyzed. Theoretical analysis is verified by simulation and experimental results performed by a 1.2kW fixed-pitch variable-speed wind turbine prototype.

Stability analysis of decentralized adaptive backstepping control systems with actuator failures

In this paper, we analyze the stability of a class of interconnected systems with subsystem unmodeled dynamics and dynamic interactions employing decentralized adaptive controllers designed in [Wen, C., et al.] in the presence of actuator failures. It will be shown that the global stability of rest closed-loop system can still be achieved and the outputs can be regulated to zeros when some subsystems break down.

Stabilization of Power Systems by Switched Controllers

An interesting application of switched control is provided in the field of power systems with either temporary fault or permanent fault. Such a power system is modelled by a switched linear system. A switched controller is design to stabilize the overall system and to improve the transient performance of the closed-loop system.