## 1 Introduction  
### General Context  
The global energy crisis and escalating fuel prices have significantly increased interest in electric vehicles (EVs), making them a focal point for research and development. For instance, in India, two- and three-wheeler EVs, including goods carriers, e-bikes, and e-rickshaws, dominate the market. These segments demand efficient, cost-effective motor drive designs that balance performance with affordability [1].  
Brushless DC motors (BLDCMs) are commonly used in such EVs, as they provide high power density, efficiency and torque-to-inertia ratio [2]. In recent years, the prices of rare-earth magnet material have decreased significantly, which also favors the deployment of BLDCMs. The main drawback of BLDCMs is the need for position sensors.  
To a large extent, the position control of BLDCMs relies on Hall-effect sensors mounted on the motor yoke to estimate rotor position [3]. These sensors detect variations in the magnetic field as rotor poles pass by, providing accurate and reliable position feedback, thereby allowing precise control over the motor's performance. However, sensors are prone to mechanical wear and environmental factors, especially in harsh conditions [4]. When robust and reliable continuous performance is required, such as automotive applications, sensor-based control methods are usually redundant with sensorless methods. In less critical applications, eliminating sensors allows for notable reductions in system cost and complexity. In fact, the elimination of electromechanical sensors reduces the hardware cost, the installation complexity associated with the cabling, and the system inertia, while increasing reliability, as noise sensitivity issues are avoided.  
This paper focuses on sensorless BLDCM drive control for application in solar-powered electric vehicles. Indeed, the integration of solar photovoltaic (PV) arrays into EVs has gained considerable attention, thanks to the development of efficient maximum power point tracking (MPPT) algorithms and the exploration of various DC-DC power converters [5; 6]. Conventional boost and buck-boost converters are commonly used for MPPT; however, they often result in high ripple, causing discontinuous input and output currents. The inclusion of input and output inductors in Cuk converters helps reduce current ripple but introduces the challenge of inverting the output polarity, necessitating additional circuitry to sense the negative voltage at the DC bus. While SEPIC and Zeta converter provide non-inverted outputs, the Zeta converter exhibits input current ripple, potentially requiring a small input inductor. Among these, the SEPIC demonstrates favorable transient and dynamic behaviors, making it a promising option [7]. However, its application in solar-PV-fed EVs has not been explored extensively in the literature. This paper aims to introduce a BLDC motor drive powered by a SEPIC for solar-PV-based EV applications.  
Furthermore, regenerative braking technology, a crucial component of EV propulsion systems, has been extensively studied in the literature as a means of promoting environmentally friendly transportation. Expanding the driving range by recovering additional kinetic energy has been well documented [8]. However, braking mode involves reversing current direction, which often requires a bidirectional converter. While effective, this approach increases system cost and size [9]. In the case of BLDC motor drives, switching pulses to the voltage source inverter (VSI) can be modified to reverse current direction, enabling regenerative braking without a bidirectional converter. Methods such as single- and dual-boost switching have been developed for energy reversal. In this work, a pulse-width modulation (PWM)-based switching scheme is employed for regenerative braking, where the amount of recovered energy is directly proportional to the modulation index.