AC locomotive operation without DC current sensor

A system for controlling operation of a diesel electric traction vehicle of the type including a synchronous generator driven by a diesel engine for producing alternating current (AC) electric power, the AC electric power being converted to direct current (DC) electric power and transferred over a DC link to a plurality of DC to AC inverters, each of the inverters being coupled to transfer controlled frequency power to at least one AC electric traction motor coupled in driving relationship to at least one wheel-axle set of the vehicle, a computer based control system for controlling operation of the engine, generator and inverters in response to a power command to enable operation of the vehicle, comprising:

• means for computing power supplied by the generator from calculated torque developed by the AC traction motors and electric power losses in the circuit elements coupling power from the generator to the motors;
• a comparator for comparing the computed power to the commanded power;
• and
• means for adjusting engine operation so as to minimize any difference between the commanded power and the computed power.

A method for controlling operation of a diesel electric traction vehicle of the type including a synchronous generator driven by a diesel engine for producing alternating current (AC) electric power, the AC electric power being converted to direct current (DC) electric power and transferred over a DC link to a plurality of DC to AC inverters, each of the inverters being coupled to transfer controlled frequency power to at least one AC electric traction motor coupled in driving relationship to at least one wheel-axle set of the vehicle, a computer based control system for controlling operation of the entire engine, generator, inverters and a dynamic brake resistance grid coupled in circuit with the DC link for dissipating regenerative electrical power from the motors during electrical retarding of the vehicle in response to a power command to enable operation of the vehicle, the method comprising the steps of:

• computing power supplied by the generator from calculated torque developed by the AC traction motors and electric power losses in the circuit elements coupling power from the generator to the motors;
• comparing the computed power to the commanded power;
• adjusting engine operation so as to minimize any difference between the commanded power and the computed power;
• and
• computing power during self-loading of the vehicle by measuring the DC link voltage, squaring the value of the measured voltage and dividing the squared value by the value of the resistance of the brake grid.