Methods, systems, and vehicles with electromechanical variable transmission

A method of operating a first motor/generator and a second motor/generator in a vehicle drive, the first motor/generator electrically coupled to the second motor/generator by a DC bus and the vehicle drive configured to propel a vehicle, the method comprising:

• operating the vehicle drive in a first operating mode by:
• operating the first motor/generator as a generator, wherein the first motor/generator provides electrical power to the DC bus to maintain a first voltage on the DC bus when operated as a generator, and wherein the first motor/generator provides all of an electrical power required by the second motor/generator and an electrical power required to offset electrical power losses;
• and
• operating the second motor/generator as a motor, wherein the second motor/generator consumes electrical power from the DC bus when operated as a motor, and wherein a sum of the electrical power provided by the first motor/generator, the electrical power losses, and the electrical power consumed by the second motor/generator is zero;
• wherein the first motor/generator provides electrical power to the DC bus and the second motor/generator consumes electrical power from the DC bus without doing either of (a) providing electrical power to an energy storage device or (b) consuming electrical power from an energy storage device;
• and
• operating the vehicle drive in a second operating mode by:
• operating both the first motor/generator as a generator and the second motor/generator as a generator when the electrical power losses are greater than the electrical power provided by the first motor/generator, wherein the first motor/generator and the second motor/generator provide electrical power to the DC bus to maintain a second voltage on the DC bus when operated as generators, and wherein the first motor/generator and the second motor/generator provide all of the electrical power required to offset electrical power losses;
• wherein the first motor/generator and the second motor/generator provide electrical power to the DC bus without doing either of (a) providing electrical power to an energy storage device or (b) consuming electrical power from an energy storage device.

A system for operating a first motor/generator and a second motor/generator in a vehicle drive, the first motor/generator electrically coupled to the second motor/generator by a DC bus and the vehicle drive configured to propel a vehicle, the system comprising a processing circuit configured to:

• operate the vehicle drive in a first operating mode by:
• operating the first motor/generator as a generator, wherein the first motor/generator provides electrical power to the DC bus to maintain a first voltage on the DC bus when operated as a generator, and wherein the first motor/generator provides all of an electrical power required by the second motor/generator and an electrical power required to offset electrical power losses;
• and
• operating the second motor/generator as a motor, wherein the second motor/generator consumes electrical power from the DC bus when operated as a motor, and wherein a sum of the electrical power provided by the first motor/generator, the electrical power losses, and the electrical power consumed by the second motor/generator is zero;
• wherein the first motor/generator provides electrical power to the DC bus and the second motor/generator consumes electrical power from the DC bus without doing either of (a) providing electrical power to an energy storage device or (b) consuming electrical power from an energy storage device;
• and
• operate the vehicle drive in a second operating mode by:
• operating both the first motor/generator as a generator and the second motor/generator as a generator when a first power generation capability associated with the first motor/generator is below a first threshold level, wherein the first motor/generator and the second motor/generator provide electrical power to the DC bus to maintain a second voltage on the DC bus when operated as generators, and wherein the first motor/generator and the second motor/generator provide all of the electrical power required to offset electrical power losses;
• wherein the first motor/generator and the second motor/generator provide electrical power to the DC bus without doing either of (a) providing electrical power to an energy storage device or (b) consuming electrical power from an energy storage device.