Response improvements in industrial DC drives derived from optimal analysis

A computer-based solution of the equations arising from the application of optimal control theory to a wide-speed-range DC drive reveals the manner in which the control should operate to achieve minimum error-squared performance. An examination of simulated conventional spillover schemes confirms that these are least able to approach the optimal performance in the spillover field-weakening control itself. An alternative field-weakening signal using a mix of speed reference, speed error and current signals is proposed which, simulation indicates, performs more closely to the optimised system in the upper speed ranges. Practical results from a laboratory implementation of this controller suggest that the modest performance improvement is achievable on industrial drives.