Pre-charge circuit and control system for a power converter

A control system comprising:

• an analysis module configured to:
• analyze a plurality of electrical measurements from a power converter to determine a status output;
• and
• a control module configured to:
• determine whether to turn on a relay in a control path of the power converter based on the status output, wherein electrical current is provided to a DC link of the power converter through a pre-charge path when the relay is off, and turning on the relay causes one or more electronic switches in the power converter to conduct current such that electrical current is provided to the DC link of the power converter through a power path when the relay is on.

An apparatus comprising:

• an electrical network comprising:
• a plurality of intermediate nodes, wherein each intermediate node is configured to connect to one phase of an alternating current (AC) electrical power source, the electrical network is configured to convert AC electrical current to direct current (DC) electrical current;
• and
• an electrical network comprising a phase branch connected to each intermediate node, each phase branch comprising a thyristor and a diode;
• a DC link electrically connected to the electrical network;
• a pre-charge path electrically connected to at least one of the intermediate nodes and the DC link, the pre-charge path comprising a pre-charge impedance;
• and
• a plurality of control paths, each control path connected to one of the intermediate nodes and a gate of one of the thyristors, and each control path comprising a relay.

A method comprising:

• accessing a plurality of electrical measurements from a power converter, the plurality of measurements comprising:
• an indication of a voltage across a pre-charge impedance;
• an indication of a voltage of an AC power source connected to the power converter, and an indication of a voltage across a DC link of the power converter;
• comparing at least two indications to an associated specification to produce at least two status outputs;
• analyzing the at least two status outputs to determine whether to change a state of a relay in the power converter;
• if it is determined to turn on the relay, controlling the relay to turn on to thereby cause electrical current to flow in an electronic switch connected to the relay such that electric current flows through a power path to the DC link, the power path comprising the electronic switch;
• and
• if it is determined to turn off the relay, controlling the relay to turn off such that electric current flows through a pre-charge impedance to the DC link.