Method of controlling a multi-level inverter having inputs connected to a gate drive unit controlling the inverter and an output connected to a load, the multi-level inverter capable of generating a PWM voltage signal having three or more modulation levels, the inverter powered by a voltage supply and comprising at least one neutral point (NP), the method comprising operating the multi-level inverter in a standard modulation pattern having three or more modulation levels when one or more parameters representative of neutral point stability each have a value within a first range indicative of a high neutral point stability, and operating the multi-level inverter with a two-level modulation pattern when said one or more parameters representative of neutral point stability each have a value within a second range indicative of a low neutral point stability, the first range separated from the second range by a threshold value.

A motor control unit includes a three-phase full-bridge three-level inverter circuit and a control apparatus. The three-phase full-bridge three-level inverter circuit includes a vertical bridge circuit and a horizontal bridge circuit. A current capacity of a switching transistor in the vertical bridge circuit is greater than or equal to a maximum current of a motor. A current capacity of a switching transistor in the horizontal bridge circuit is less than the current capacity of the switching transistor in the vertical bridge circuit. The control apparatus is configured to control the switching transistor in the horizontal bridge circuit based on torque of the motor, a current output by an output terminal of the vertical bridge circuit, a temperature of the switching transistor in the horizontal bridge circuit, and a terminal voltage of the switching transistor in the horizontal bridge circuit.

An electric motor has a stator defining multiple stator poles with associated electrical windings, and a rotor having multiple rotor poles. The rotor has flux barriers between adjacent rotor poles, the flux barriers each having a material with an electrical conductivity higher than the rotor pole material. The flux barriers are electrically isolated from one another external to the ferromagnetic material. Eddy currents are induced in the flux barrier to cause destructive interference of an impending magnetic field, such that the flux barrier effectively acts to inhibit magnetic flux during motor operation, which in some cases will result in a repulsive force that will act to increase an induced motive force on the rotor poles.

An electric drive system is connected to a power battery pack to drive a motor, the motor includes an exciting winding, and the electric drive system includes a bus, a three-level inverter circuit, an electric excitation circuit, and a controller. The bus includes a positive bus and a negative bus. The three-level inverter circuit includes a first bus capacitor and a second bus capacitor. The first bus capacitor is connected between the positive bus and a bus midpoint, and the second bus capacitor is connected between the negative bus and the bus midpoint. A first input terminal of the electric excitation circuit is connected in parallel to the first bus capacitor, a second input terminal of the electric excitation circuit is connected in parallel to the second bus capacitor, and an output terminal of the electric excitation circuit is connected to the exciting winding of the motor.

A conveyance system includes a machine having a motor; a source of AC power; a drive system coupled to the source of AC power, the drive system to provide multi-phase drive signals to the motor, the drive system including: a first drive having a first converter and a first inverter, the first convertor including a first positive DC bus and a first negative DC bus; a second drive having a second converter and a second inverter, the second convertor including a second positive DC bus and a second negative DC bus; wherein the first positive DC bus and the second DC positive bus are electrically connected and the first negative DC bus and the second negative DC bus are electrically connected.

A method is provided for operating a multi-phase inverter connected to an electric machine using a control device, wherein the inverter comprises a plurality of switch devices and the control device controls the inverter to adjust a control variable by means of space vector modulation. The method includes providing a number of possible space vectors for representing the control variable according to a number of phases of the inverter. The method further includes assigning each possible space vector a disturbance variable in the electric machine occurring in a switching state of the switch devices of the inverter described by the respective space vector. The method further includes selecting one or more control space vectors according to the control variable from the number of possible space vectors for representing the control variable. The selected one or more control space vectors represent control variable and have the respective smallest associated disturbance variable of the possible space vectors.

A method is provided for operating a multi-phase inverter connected to an electric machine using a control device, wherein the inverter comprises a plurality of switch devices and the control device controls the inverter to adjust a control variable by means of space vector modulation. The method includes providing a number of possible space vectors for representing the control variable according to a number of phases of the inverter. The method further includes assigning each possible space vector a disturbance variable in the electric machine occurring in a switching state of the switch devices of the inverter described by the respective space vector. The method further includes selecting one or more control space vectors according to the control variable from the number of possible space vectors for representing the control variable. The selected one or more control space vectors represent control variable and have the respective smallest associated disturbance variable of the possible space vectors.

An electric motor has a stator defining multiple stator poles with associated electrical windings, and a rotor having multiple rotor poles. The rotor has flux barriers between adjacent rotor poles, the flux barriers each having a material with an electrical conductivity higher than the rotor pole material. The flux barriers are electrically isolated from one another external to the ferromagnetic material. Eddy currents are induced in the flux barrier to cause destructive interference of an impending magnetic field, such that the flux barrier effectively acts to inhibit magnetic flux during motor operation, which in some cases will result in a repulsive force that will act to increase an induced motive force on the rotor poles.

Capacitor balancing of a dual three-level (3L) T-type converter based on silicon carbide (SiC) discrete semiconductors was performed with the converter feeding an open-ends induction motor (OEIM). A model predictive control (MPC) using a two step cost function calculation was developed to balance the DC link capacitors and control the machine torque simultaneously. The number of redundant switching states used was reduced without affecting the operating voltage vectors, which substantially reduced the computational time. A simulation and experimental results are in good agreement.

An electric drive system includes a rechargeable energy storage unit, a power inverter, an electric motor and a controller having a processor and tangible, non-transitory memory on which instructions are recorded. A transfer of electrical power between the rechargeable energy storage unit and the electric motor is governed by a pulse width modulation (PWM) switching frequency. The controller is configured to determine a current switching frequency based in part on a PWM type, a PWM switching frequency style and an inverter direct current voltage. A PWM scalar is determined based in part on the current switching frequency and a maximum value of a control reference frequency. The controller is configured to transmit a command signal to regulate the transfer of electrical power based in part on the PWM scalar, the PWM switching frequency being proportional to a product of the PWM scalar and the control reference frequency.