Analysis of Back-EMF Protection Strategies for PM Synchronous Motor Based 2W/3W Electric Vehicles

<div class="section abstract"><div class="htmlview paragraph">The use of electric vehicles (EVs) has been on the rise in recent years and this trend is expected to continue in the upcoming years. There are several reasons for the increasing popularity of EVs, including environmental concerns, advances in technology, and government incentives. The 2W/3W EV powertrain comprises components such as the battery, traction motor, motor controller, charger, and DC-DC converter, etc. Essential components which impact the power, efficiency, and range of the vehicle are a motor (generally PMSM or BLDC) and a motor controller. PMSMs can produce more output power than BLDC motors of the same size, making them suitable for high-power applications. While the EV powertrain allows for greater flexibility in designing electric vehicle architectures, it also exhibits new challenges in meeting all the essential requirements. When a motor rotates, as per Lenz’s law, an opposing voltage (Back-EMF) is generated in a motor whose magnitude is proportional to its angular velocity and does not exceed the applied voltage by a motor controller in normal working conditions. However, when a motor experiences an uncontrolled generator fault, sudden change in its direction, decelerates, or stops abruptly, the magnitude of Back-EMF induced goes above the supply voltage of the motor controller [<span class="xref">5</span>]. This may cause the motor power supply and the associated components in the circuit to be subjected to conditions that are outside of their maximum ratings and may get damaged. There exist several methods such as shunting of the back-EMF, Series thyristors in phases, delta connected thyristors in motor winding, and chopper-based shunting to mitigate the failures in motor controllers caused by an unintended back-EMF. Through the MATLAB-based simulation, this piece of work describes these Back-EMF protection strategies and aims to compare their performance, and ease of implementation for a permanent magnet synchronous motor (PMSM) controller.</div></div>