# An EV SRM Drive and Its Interconnected Operations Integrated into Grid, Microgrid, and Vehicle
## 1 Introduction  
In recent years, the climate warming and energy crisis due to extra consumption of fossil fuels is becoming worse and has received much attention worldwide. The employment of EVs to replace the conventional internal combustion engine (ICE) vehicle can effectively reduce fossil energy consumption and carbon dioxide emissions, thus lessening the aforementioned problems. Similarly, the popularization of a microgrid using renewable sources also possesses these benefits. Moreover, the cooperated M2V/V2M operations can further boost these purposes. The development of EV SRM drives and performing M2V/V2M operations are presented in this paper. Basically, EVs can be categorized into hybrid EV (HEV), plug-in HEV (PHEV), and battery EV (BEV). Until now, although various types of EVs have been extensively commercialized, there are still many technical aspects that need to be continuously improved and developed. The reviews for existing EV technologies can be referred to in [1; 2; 3], and the future development trends and challenges are explored in [2; 3]. In the comparative environment aspects between ICE vehicles and EVs, much typical research has been made from the viewpoints of eco-driving effects [4], urban traffic energy chain and efficiency [5], well-to-wheel emission [6], and carbon footprint of city electric buses [7], etc. Until now, the induction motor (IM) and the permanent magnet synchronous motor (PMSM) have been the mainstream motors for EVs due to their high power density, highefficiency, and mature technologies. However, the switched reluctance motor (SRM) still possesses potential for EV application [8; 9; 10] owing to its inherent merits. It is (i) suited for high speed driving with its simple and rigid structure; (ii) it has no magnet on its rotor, reducing the cost, and is cogging torque free; (iii) it has high generating torque and acceleration capability like a series DC motor. But, some key issues [11; 12; 13; 14; 15; 16; 17] should be properly treated to counteract its nonlinear torque generating characteristics and back electromotive force (EMF) effects. The current control should be the first concern [11; 12; 13; 14]. The hysteresis current control and average PWM current control are typical methods for SRM. The hysteresis current control is robust and model-free. Regarding the average PWM current control, its control characteristics are highly affected by the design of the feedback controllers. It is suggested to apply the back-EMF feedforward control to compensate the influence of back-EMF [14]. When SRM is driven at high speed, the winding back-EMF will worsen the current response. To reduce the effects, it is necessary to adopt the commutation shifting approach to properly adjust the turn-on and turn-off angles of the phase current [14; 15]. As generally recognized, SRM inherently possesses higher ripple torque, vibration, and acoustic noise owing to the doubly salient structure and concentrated armature windings. A typical example that studies the reduction of these defects can be found in [16; 17]. In the propulsion system, there are two DC-link structures. One is the battery direct-powered DC-link. Without voltage boosting ability, the battery voltage level must be adequately set considering speed and load ranges. The other is the battery with followed interface converter. Adding a bidirectional DC/DC converter between the motor drive and the battery can make the motor drive DC-link voltage more stable and adjustable [18; 19]. The battery voltage selection will be more flexible, and better driving performance over wide speed range can be achieved. In addition, the propulsion system with this structure makes the onboard battery more compatible with other hybrid energy storage sources. In [20], DC-link voltage and temperature variations are considered in the EV traction system design. And the voltage control approach for a \(Z\)-source inverter-fed PMSM drive is presented in [21]. Some DC/DC converters used for interface converters can be found in [18; 22; 23; 24].