Power conversion system with inverter for pre-charge and discharge operations

A power conversion system configured to convert electric power from direct current into alternating current, the power conversion system comprising:

• a battery configured to transmit and receive the electric power in direct current, the battery having a positive node and a negative node;
• a motor having a stator and a rotor, the rotor having a first node and a second node for receiving and transmitting the electric power, wherein the stator is configured to receive electric power in alternating current to rotate the rotor;
• and
• an electric line couples the positive node of the battery to the negative node of the battery;
• a rotor electric line having a first end coupled to the electric line and a second end coupled to the rotor;
• an inverter including a first relay, a second relay, a capacitor and a charging circuit, wherein the first relay is disposed on the electric line, the second relay disposed on the rotor electric line, the capacitor is connected the electric line and in parallel with the rotor, and wherein the charging circuit is electrically coupled to the rotor and in parallel with the capacitor, the charging circuit including a plurality of switches in parallel with each other, wherein one of the plurality of switches is connected to the first node of the rotor and another one of the plurality of switches is connected to a second node of the rotor;
• and
• a controller configured to actuate the charging circuit to execute a pre-charging operation and a discharging operation, wherein in the pre-charging operation the second relay is closed, the first relay is open and the plurality of switches are actuated to form an electric path for charging the capacitor wherein electric power from the battery is transmitted to the capacitor through the rotor, the rotor providing a resistance limiting an inrush of current to the capacitor and in the discharging operation, the second relay is open and the first relay is open to isolate the battery from the inverter and the plurality of switches are actuated to form an electric path for discharging the capacitor through the rotor.

An electric vehicle including a battery configured to transmit and receive electric power in direct current, the battery having a positive node and a negative node and configured to power a motor for generating a driving force, the motor having a stator and a rotor, the motor to be actuated by receiving electric power in alternating current, the rotor having a first node and a second node for receiving and transmitting the electric power, the electric vehicle comprising:

• an electric line couples the positive node of the battery to the negative node of the battery;
• a rotor electric line having a first end coupled to the electric line and a second end coupled to the first node of the rotor;
• an inverter including a first relay, a second relay, a capacitor and a charging circuit, wherein the first relay is disposed on the electric line, the second relay disposed on the rotor electric line, the capacitor is connected to the electric line and is in parallel with the rotor, and wherein the charging circuit is electrically coupled to the rotor and in parallel with the capacitor, the charging circuit including a plurality of switches in parallel with each other, wherein one of the plurality of switches is connected to the first node of the rotor and another one of the plurality of switches is connected to a second node of the rotor;
• and
• a controller configured to execute a pre-charging operation and a discharging operation, wherein in the pre-charging operation the second relay is closed, the first relay is open and the plurality of switches are actuated to form an electric path for charging the capacitor wherein electric power from the battery is transmitted to the capacitor through the rotor, the rotor providing a resistance limiting an inrush of current to the capacitor and in the discharging operation, the second relay is open and the first relay is open to isolate the battery from the inverter and the plurality of switches are actuated to form an electric path for discharging the capacitor through the rotor.