Solid state power controller for high voltage direct current systems

A solid state power controller (SSPC) apparatus, comprising:

• an alternating current (AC) current sensor coupled to a DC load;
• a direct current (DC) current sensor coupled to the DC load;
• a voltage sensor coupled to the DC load;
• a main switch coupled to the DC load via the AC and DC current sensors;
• an auxiliary switch coupled in parallel to the main switch;
• a current limiting resistor coupled in series to the auxiliary switch;
• and
• a SSPC controller coupled to the main switch, the auxiliary switch, the AC current sensor, the DC current sensor, and the voltage sensor.

A direct current (DC) load protection method in a high voltage DC (HVDC) system, the method comprising:

• in response to a detection of an over current condition, turning off a main switch in the HVDC system, and turning on an auxiliary switch in the HVDC system to current limit the over current through a current limiting resistor coupled to the auxiliary switch;
• in response to the over current exceeding a predetermined level, turning off the auxiliary switch;
• turning on the auxiliary switch;
• determining an initial over current condition;
• in response to detecting a HVDC system load voltage below a predetermined threshold, and a rate of current change during initial start-up, generating a pre-charge indication;
• and
• in response to detecting a load voltage above a predetermined voltage level, turning on the main switch after completion of pre-charge mode.