Overview

Use of the appropriate control technology cannot be overstated with regard to hybrid propulsion systems. The traction and ancillary electric machines are pushed to their absolute limits in terms of fundamental constraints on electric, magnetic, thermal, mechanical and packaging. Without the proper control techniques many of the benefits gained through innovative design can be washed away. Asynchronous machines, for example, work just fine under volts/hertz control, but this would not be an appropriate strategy in a hybrid propulsion system because its torque/amp and transient performance would be far inferior to field oriented control. All the scalar control methods noted fall short of the transient performance afforded by vector control approaches.

This chapter gives an assessment of the most popular and relevant control techniques for hybrid propulsion systems. Generally confined to the traction system 'outer loop', the techniques to be described determine how torque is regulated and speed controlled. Because of the presence of multiple torque sources in the hybrid drivetrain it is necessary to employ torque control of all the sources, including engine, hybrid M/G(s), and any other source of motive power (flywheels).

Sensorless control is gaining more acceptance, especially for brushless dc and induction machines. This chapter looks at some promising sensorless control techniques and gives an assessment of where this technology is going.

Fault management, diagnostics and prognostics are important aspects of hybrid powertrain development. How are faults sensed, what the consequences of a faulted driveline component, particularly the electric M/G are, and how fault recovery is...