A design of DC bus control system for EVs based on battery/ultracapacitor hybrid energy storage

Abstract

This paper presents the design of a control system suitable for EV DC bus voltage sag compensation based on the voltage PI controller and load current feedforward compensator. The superimposed PI controller and feedforward compensator references are distributed between the inner battery and ultracapacitor current-controlled DC/DC converters so that the ultracapacitor takes on the highly-dynamic (transient) current demands, while the battery covers for steady-state loads. In order to avoid deep discharges of the ultracapacitor, the DC bus control system is also equipped with auxiliary state-of-charge (SoC) controller. The functionality of the superimposed DC bus voltage control system and inner current and SoC control loops has been verified by means of simulations and experimentally on a downscaled battery/ultracapacitor experimental (HIL) setup.

Dual EKF-Based State and Parameter Estimator for a LiFePO4 Battery Cell

“…The polarization time constant does not exhibit notable dissipation with respect to SoC, and its average value  p = 24 s (cf. , and minimum integration step of 0.01 s. The particular current demand (current reference) of the battery has been obtained through vehicle simulation model [42], wherein the battery load has been scaled to the single battery cell. The results in Fig.…”

A comprehensive review on hybrid electric vehicles: architectures and components

“…Here, a battery lifetime degradation model was used to develop the relationship between the battery charge/discharge behavior and the impact on its lifetime [126,127]. The power optimization in a parallel arrangement of battery and UC was carried out using superimposed DC-bus control system which had DCbus voltage, proportional integral (PI) controllers and a feed-forward load compensator [128,129]. Wireless charging concept was used to charge the UC effectively in [130].…”

Damping Optimum-Based Design of Control Strategy Suitable for Battery/Ultracapacitor Electric Vehicles

“…where d b and d u are battery and ultracapacitor DC/DC converter pulse-width-modulated (PWM) output voltage duty cycles, respectively, which are readily available from the current controller-based voltage reference commanded to power converter [40]. Since the voltage PWM switching frequency is relatively high, the above averaged currents may be used instead of their instantaneous values within the DC bus model (4).…”

“…Since charge accumulation processes are typically slow, the battery electromotive force and ultracapacitor charge-related voltage variations are rather non-emphasized compared to voltage variations due to voltage drop across the series resistance, especially during transients. Thus, the dominant current transient dynamics may be expressed by a simple equivalent first-order transfer function model [40]:…”

“…(1) Top-down cascade control system structure, to facilitate direct saturation of current demands via power converter references [39]; (2) Bottom-up control system design wherein the current control systems for the battery and ultracapacitor ESS are designed and tested first, which is then followed by the comprehensive design of the superimposed feedback control levels [40]; (3) A direct or indirect load compensator should augment the feedback controllers to deal with potentially abrupt loads at the EV DC bus side [41,42]; (4) Variable DC bus voltage target, which is characteristic for hybrid-EVs [43,44] and those with fully electrified power-trains [45], and may also be beneficial to useful life extension of capacitors within the inverter DC bus [46]; (5) Use of control system design methodology which could facilitate straightforward tuning of the closed-loop control system response dynamics; (6) Simplicity of code implementation that would enable use on robust microcontroller platforms suitable for automotive applications.…”