Braking scheme for vector-controlled induction motor drives equipped with diode rectifier without braking resistor

Abstract

Abstract-This paper deals with sensorless vector control of PWM-inverter-fed induction motor drives equipped with a threephase diode rectifier. An electronically controlled braking resistor across the dc link is not used. Instead, the power regenerated during braking is dissipated in the motor while a dc-link overvoltage controller limits the braking torque. Losses in the motor are increased by an optimum flux-braking controller, maximizing either the stator voltage or the stator current depending on the speed. Below the rated speed, the braking times are comparable to those achieved using a braking resistor. The proposed braking scheme is very simple and causes no additional torque ripple. Experimental results obtained using a 2.2-kW induction motor drive show that the proposed scheme works well.

A Simple Braking Method for Six-Phase Induction Motor Drives With Unidirectional Power Flow in the Base-Speed Region

“…In such a case, the braking power cannot be delivered to the grid and needs to be absorbed somewhere. For dissipation purposes, it is possible to add an electronically controlled braking resistor across the dc-link, but it increases the cost, complexity and size of the drive [7]. Aiming to eliminate the power electronic components and electronic control circuits associated to this braking unit, different studies have investigated the braking capability of the drive without additional hardware [7][8][9][12][13].…”

“…It is worth highlighting in any case that this feature is common to all methods that use the loss manipulation to help the braking process (e.g. in the loss manipulation strategy incorporated in DTC-based ABB drives [6] or those suggested in [7,9,12], to mention a few).…”

“…The most popular method is the flux braking, which increases the reference flux of the machine to induce extra losses and allow a controlled braking process [6][7]9]. Interestingly enough, the strategy during braking is to make the motor as inefficient as possible within physical limits.…”

“…Following this procedure, the drive serves itself as a virtual braking resistor, dissipating the braking power within the inverter/motor. The dc-braking [7] or the high-slip braking [8] are examples of strategies that aim to increase the braking torque by increasing the system losses. However, these methods are focused on stopping the motor rather than obtaining a high-performance braking operation.…”

“…Even though copper losses can be relatively small in high-power high-efficiency systems, they can significantly help the braking process in low-to medium-power induction motor drives [6][7]. Following this procedure, the drive serves itself as a virtual braking resistor, dissipating the braking power within the inverter/motor.…”