Electrical power system converter control

A method of controlling an electrical power system comprising an electrical machine, a DC electrical network and a power electronics converter connected between the electrical machine and the DC electrical network, the method comprising:

• generating AC using the electrical machine and supplying the AC to an input of the converter;
• controlling switching of transistors of the converter to rectify the AC input to a DC output and supply the DC output to the DC electrical network;
• determining a condition to the effect that there is a fault in the DC electrical network;
• responsive to the determination, controlling a voltage source to inject a voltage to bias diodes of the converter;
• and
• after controlling the voltage source to inject a voltage to bias diodes of the converter, controlling switching of the transistors of the converter to control a level of current supplied to the DC electrical network,
• wherein controlling switching of the transistors of the converter to control the level of current supplied to the DC electrical network comprises modulating a pulse width modulation control parameter to control the level of current supplied from the electrical machine to the faulted DC electrical network, and
• wherein the voltage source comprises a resistor and a switch, the switch is a semiconductor switching component, and controlling the voltage source to inject the voltage to bias the diodes of the converter comprises operating the semiconductor switching component in a linear operating region to produce the voltage to bias the diodes.

A controller for an electrical power system configured to:

• during normal operation of the electrical power system, control switching of a plurality of transistors of a power electronics converter to rectify AC received by the converter from an electrical machine;
• and
• responsive to a determination to the effect there is a fault in a DC electrical network connected to a DC side of the converter, control a voltage source to inject a voltage to bias diodes of the converter, and control the switching of the transistors to control a level of current supplied to the faulted DC electrical network,
• wherein controlling the switching of the transistors to control the level of current supplied to the faulted DC electrical network comprises modulating a pulse width modulation control parameter to control the level of current supplied from the electrical machine to the faulted DC electrical network, and
• wherein the voltage source comprises a resistor and a switch, the switch is a semiconductor switching component, and controlling the voltage source to inject the voltage to bias the diodes of the converter comprises operating the semiconductor switching component in a linear operating region to produce the voltage to bias the diodes.