Regenerative and ride-through capability for AC drives through thyristor-based extensions of the diode front-end

This paper presents SCR-based circuit extensions to a diode rectifier to allow regeneration during braking and ride-through during voltage sags. The proposed topology uses two line-commutated SCR bridges-one connected to the DC bus rails and the other to the DC bus center-tap. The inverting SCR bridge connected to the DC bus rails transfers energy from the DC link to the mains during regeneration. The bridge connected to the center-tap provides improved commutation to the inverting bridge. In addition, it can be used to boost the DC bus during input voltage sags. The circuit provides a lower cost alternative to PWM rectifiers and other currently used regenerative and ride-through modules. Advantages of the proposed SCR-based circuit include low cost and ruggedness. Simulation waveforms are presented to indicate circuit operation.