**3.1. New definitions of mathematical modeling integration from ESS to motor**

*2.2.2.3. Soft-switching technology*

8 New Applications of Electric Drives

*2.2.2.4. Switching device*

**2. Driver**

module, etc.

**3. Power converter**

interference (EMI), are also limited effectively [16].

Converters can be classified into two main categories: hard-switched and soft-switched for DC-DC converters and inverters. Soft-switching is a technology in which zero-voltage switching (ZVS) and/or zero-current switching (ZCS) of the switches are achieved mostly using the parasitic and/or additional components. Soft-switching reduces switching stresses (high voltage and current peaks) on the power devices during the turn-on and turn-off transients, which results in oversizing the safe operating area (SOA). Switching losses decrease for overlap size reduction of voltage and current. Severe *di/dt* and *dv/dt*, which produce electromagnetic

For the driving system, the high-power converter module is used. Converters control the high electric power. Insulated gate bipolar transistors (IGBTs) are used in the high-power modules as the switching devices. Other power electronics modules control the middle and low power, in which metal-oxide-semiconductor field effect transistors (MOSFETs) are used as the switching devices. The majority of devices used in power electronics are enhancement

The main problem of the high-power modules is high electric power loss, which requires the liquid cooling system. For the future, power switching devices, very low on-resistance, and high-temperature operation are expected to simplify the cooling system of the converter. Silicon Carbide (SiC) or Gallium Nitride (GaN) devices are possible candidates. For the middleand low-power modules, lower breakdown voltage is required. For these applications, high-

The electronic controller consists of hardware circuit and control software. The hardware circuit mainly contains microprocessor and its minimum system, the detection circuit of motor current, voltage, speed, temperature, all kinds of hardware protection circuit, and the com‐ munication circuit (CAN Bus) with the external control unit like the vehicle controller and battery management system to exchange data. The control software realizes corresponding control algorithm depending on different types of motors. For instance, the strategies of flux weakening control, id=0 control and MTPA control are widely used in PMSM control software.

It converts the motor control signal which comes from microcontroller to PWM signal, which drives the power converter and implements the isolation of power signal and control signal.

The power converter controls the motor current. The power devices that are widely used in electric vehicles contain the gate-turn-off thyristor (GTO), MOSFET, IGBT, and smart power

transistors, respectively, n-channel-enhancement power MOSFETs and IGBTs [17].

frequency operation is expected, which leads to small capacitors and reactors.

**1.** The motor control unit (MCU) has main components:**Electronic controller**

*2.2.3. Functions and design key points of Motor Control Units (MCUs)*

*3.1.1. Purposes and meanings of multidomain coupling unified mathematical expressions for electric drives*

In the past decade, plenty of literature has focused on the operation performance, parameter optimization, and control strategies of components in AFV electric drives. These researchers mostly use DC power supplies or electronic loads to simulate input/output characteristics of components, and meanwhile realistic influence between components (e.g., battery and traction motor) is seldom considered. To the author's best knowledge, there are no publications that regard the electric drive system as a whole for the systematic research on multidomain (dynamics, electromagnetics, electrochemistry, etc.) coupling mechanism.

The electric motors are required to operate in complicated conditions of frequent start/stop and acceleration/deceleration. High torque is needed at low speeds or when running uphill, while low torque is needed at high speeds. In the meantime, speed adjusting range should be very wide. This is significantly different from the industry applications where usually rated conditions are assigned to the electric motors. Therefore, the transient performance require‐ ments for the AFV electric motors are very high and, further, are transferred to high transient requirements on the ESS through three-phase inverter. Additionally, the switching frequency of switching devices (e.g., IGBT) is high up to several or tens of kHz, the switching commu‐ tation time is extremely short, and the disturbance currents including diode recovery current exist, so the uncertain high-frequency transient chaotic currents should be produced across the ESS. The phenomenon will do harm to the stability and even lifetime of the ESS. Detailed descriptions can be found in section 3.2.1.

On the other hand, the ESS (battery for specific) AC impedance (including ohmic resistance, polarization resistance, capacitive reactance, Warburg impedance, and so on) characteristics will have impact on the transient performance of traction motors. The AC impedance charac‐ teristics of the battery determine the battery output power capability (supposing the electro‐ chemical potential is a constant) and further influence the transient output power capability of the traction motor via the inverter. Consequently, the motor transient performance could be somehow restricted.

Thus, this section is aimed at importing new definitions of electric drive unified mathematical expressions for systematic exploration of transient multidomain coupling mechanism from dynamics-electromagnetics-electrochemistry based on the ESS, traction motor, inverter, and DC-DC converter in the AFV electric drive system. Multiple subjects could be melted including energy storage, electric machine, and power electronics. The entire electric drive can be regarded as a whole without separating relationships between components, and a unified and general mathematic expression is capable of identifying specific numeric relations between transient requirements and parameters of components. In addition, the systematic-, circuit-, and component-class parameter optimization aimed at efficiency improvement in electric drives of alternative fuel vehicles could be achieved.
