A Reformatory Model Incorporating PNGV Battery and Three-Terminal-Switch Models to Design and Implement Feedback Compensations of LiFePO4 Battery Chargers

Abstract

This study developed and implemented a LiFePO4 battery pack (LBP) rapid charger. Using the three-terminal switch and partnership for a new generation of vehicles (PNGV) battery models, this study could obtain a small-signal system matrix to derive transfer functions and further analyze frequency responses for the charge voltage and current loops; therefore, both voltage and current feedback controllers could be designed to fulfill the constant-voltage (CV) and constant-current (CC) charges. To address practical applications, the proposed equivalent model also considered the wire resistance-inductance of the power cable. According to the derived high-order transfer function, the pole-zero break frequency in the Bode plot was observed that approximated the practical measurement; therefore, the pole-zero compensation could be accomplished for both charge loop requirements. Moreover, the design features for implementing the CV and CC charges are presented in detail herein, and the current overshoot during the start-up phase could be mitigated using the method of zero break frequency shifting and a novel proportional shifting proportional-integral control. The LBP parameter estimations, model construction processes, and frequency response analyses are also presented. The feedback compensation design based on the proposed model was validated through simulations and experiments. The results were determined to be in excellent agreement with theoretical derivations.

Real‐time identification of partnership for a new generation of vehicles battery model parameters based on the model reference adaptive system

“…44,48 In the RC network, the polarization voltage reaches 95% of the maximum value after 5τ p and τ p are obtained. 48 Based on this, C p can be calculated using the formula, C p = τ p /R p . This is the second method for calculating the RC network parameters.…”

“…44 Moreover, the PNGV model can reflect the change of open-circuit voltage (OCV) with the current accumulation effect. 38,39,45 With these advantages, the PNGV model is very suitable for battery characteristics analysis (such as the change of internal resistance with battery SOH 46 and battery performance analysis 44,47 ), charger design, 48 and SOC estimation 41,49,50 in a BMS. Due to diverse types of batteries, different ambient temperatures, SOC, and SOH, the PNGV model parameters will be very different.…”

“…41,49 The second method takes R o at the beginning and end of charging/discharging as different and uses their average value as the real R o. 44,48 The equivalent capacitance C b describes the variation of OCV with the accumulative effect of current and can be calculated based on this definition. 41,44,48,49 Within the test pulse, the polarization voltage (the voltage of the RC network) is regarded as a zero-state and zero-input response.…”

“… 41,49 The R p , τ p , and C p can be obtained based on this relationship. At the initial stage of the test pulse, the charge transfer and diffusion in the electrochemical reaction increases exponentially, and the ratio of voltage‐to‐current difference can be used to obtain R p during this time 44,48 . In the RC network, the polarization voltage reaches 95% of the maximum value after 5 τ p and τ p are obtained 48 .…”