An SCR-based regenerative converter for VSI drives

This paper presents an SCR-based topology for transferring braking energy from the DC link to the mains for voltage-source inverter (VSI) drives. The proposed topology uses a line-commutated SCR bridge in conjunction with a controlled connection between the neutral and the DC bus capacitance center-tap. It is shown that the center-tap connection provides improved commutation margins and obviates the requirement for matching transformers generally used with line-commutated regenerative circuits. The circuit provides a lower cost alternative to PWM rectifiers and other currently used regenerative modules. An additional function that the circuit can perform is ride-through during input voltage sags. Advantages of the proposed SCR-based circuit include low cost and ruggedness. Disadvantages include elevated neutral current and harmonics during regeneration. Simulation waveforms are presented to indicate circuit operation.