Power supply and power control for 200 kW servoalternator

A digitally controlled constant-voltage DC power reticulation system powers a number of PWM (pulse-width-modulation) controlled synchronous AC motors used for the direct drive of elevators. The control and protection strategies used by the digital controllers in the DC supply and in the BJT (bipolar junction transistor) bridge inverters in the individual servo drives are described. It is shown that the use of DSP (digital signal processing) controllers allows control strategies which minimize modulation noise while taking switch snubbing delays into account. More complex control strategies are required when using resonant PWM topologies. These may be readily implemented with a DSP and a small amount of additional logic