US Patent 9132736 Methods, systems, and vehicles with electromechanical variable transmission

One embodiment provides a method of operating a first motor/generator and a second motor/generator in a vehicle drive. The first motor/generator is electrically coupled to the second motor/generator by a DC bus. The vehicle drive is configured to propel a vehicle. The method includes operating the first motor/generator as a generator, providing electrical power to the DC bus. The first motor/generator provides the electrical power required by the second motor/generator and the electrical power required to offset losses. The method also includes operating the second motor/generator as a motor, consuming electrical power from the DC bus. The sum of the electrical power provided, the electrical power losses, and the electrical power consumed is zero. The first motor/generator provides electrical power and the second motor/generator consumes electrical power without providing electrical power to an energy storage device or consuming electrical power from an energy storage device.