Electric drive system, powertrain, and electric vehicle

An electric excitation circuit, comprising:

• a first input terminal, a second input terminal, a third input terminal, an output terminal, and a control terminal;
• the first input terminal is connected to a positive bus of an electric drive system, the second input terminal is connected to a bus midpoint, and the third input terminal is connected to a negative bus of the electric drive system;
• the output terminal is configured to connect to an exciting winding of a motor, and is configured to output an excitation current to the exciting winding;
• the control terminal is further configured to receive a control signal;
• and
• the electric excitation circuit is configured to balance an electric potential of the bus midpoint under the control of the control signal.

A powertrain, the powertrain comprising an electric drive system, wherein the electric drive system is configured to connect to a power battery pack to drive a motor, wherein the motor comprises an exciting winding, and the electric drive system comprises a bus, a three-level inverter circuit, an electric excitation circuit, and a controller;

• the bus comprises a positive bus and a negative bus;
• the three-level inverter circuit comprises 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;
• and
• the controller is further configured to control a working state of the electric excitation circuit, to balance an electric potential of the bus midpoint;
• and the powertrain further comprises a motor;
• the motor is a hybrid excitation motor or an electric excitation motor;
• the motor is connected to an output terminal of a three-level inverter circuit;
• and
• the motor is configured to convert electrical energy into mechanical energy to drive an electric vehicle.