# Investigation of Regenerative Braking Performance of Brushless Direct Current Machine Drive System
## 1 Introduction
Additionally, a novel control approach based on the monitoring of a dc-link current of the motor controller is proposed to overcome the limitation and enable dynamic detection of a low-speed cutoff point (LSCP). In [19], the regenerative braking performance of an electrical machine is enhanced by using a downshifting system at the machine operation points. A load commutated multilevel current source inverter fed open-ended winding induction motor drive with regeneration capability is presented in [20]. The proposed approach is related to a decrease in the effect of low back EMF and increase in the amplitude of regenerative braking torque. In [21], a slip-rate control strategy based on sliding mode control and braking force control strategy based on the Economic Commission for Europe's (ECE) regulation are presented to improve the efficiency of recovered electrical energy. A novel two-boost method which is exploiting the motor converter as a cascade connected two-level boost converter is asserted for BLDC motor regenerative braking [22]. In [23], a downshifting strategy is described to improve recovery energy by adjusting operating regions of electric motor for electric and hybrid vehicles with stepped automatic transmissions. The method proposal includes a downshifting control strategy using cluster-based stochastic dynamic programming (SDP). Although numerous methods and approaches are presented in recent literature, most of them accommodate complex mathematical modeling or additional circuits and of course, those extra features hinder the possibilities of practical application of regenerative braking. The suitable solution implies not using any additional circuits, implementing a braking control strategy without compromising the regenerative braking performance [24]. The fundamental principle of regeneration is relied on using an inverter as a boost converter and machine stator winding as boosting inductors. However, this method has some limitations due to the nonlinear effects of the drive circuit. The limitations of voltage boosting are mainly caused by SoC and the thermal structure of a battery pack, winding resistance, non-ideal effects, and voltage drops of semiconductors [25]. Battery heating is dependent on ambient and operation conditions [26]. Basically, because of the electrochemical structure, heating is a major deteriorating factor for any battery type. In [27], internal resistance and capacity of battery are investigated for different operation conditions. It is indicated that temperature rise due to ambient and/or operation conditions negatively affect power and the energy capacity of a battery and vehicle performance consequently. Sometimes an improper regenerative braking operation may cause overheating which disrupts the overall battery performance [28]. A mathematical approach to single-switch regeneration scheme with maximum conversion ratio for BLDC motors is proposed in [13]. However, the change of internal resistance of battery-related heating is not taken into account. In [15], for a commercial electric vehicle (Nissan Leaf), the variation of battery internal resistance is presented for different SoC values during charging and discharging. Battery open circuit voltage depending on SoC and internal resistance shows the effects of ambient temperature and operation conditions. Temperature rise, i.e., heating, affects the performance, reliability, and life span of a battery package. Its effect on internal resistance also hampers regenerative braking efforts [19]. Tracking of internal resistance variation and controlling battery performance improve the quality of regenerative braking. In this study, all constraints emerge from non-ideal elements of the motor control inverter, which is reduced to a single-switch boost converter model, such as on-state resistances, threshold voltage drops, and dynamic variation of battery internal resistance are taken into account to achieve maximum regeneration at the specific duty ratio.