Optimal control of regenerative braking for SPM synchronous machines with current feedback

This paper formulates and solves the problem of controlling an SPM synchronous machine, with viscous friction load, such that the electric energy recovered during braking events is maximized. The optimal control law is compatible with the torque-command structure of commercially available power converters that incorporate current feedback loops. When properly tuned, the current feedback imposes a time-scale separation property that leads to order reduction and simplified design of the optimal control law. Simulations and experiments are used to illustrate the main results.