A hybrid structure using phase-controlled rectifiers and high-frequency converters for magnet-load power supplies

Thyristor rectifiers are still the preferred choice for large magnet power supplies. However, large harmonic voltages, resulting in large current ripple, and slow dynamic response are major drawbacks of these converters. This paper presents a topology and a control technique for hybrid large-power high-precision magnet power supplies. The system consists of a phase controlled rectifier connected in series with a high-frequency PWM converter. The rectifier is designed to handle the main output power and the PWM converter is used only for harmonics cancellation and error compensation. A feedforward control scheme is proposed to ensure that the desired power sharing is maintained during both the steady state and transient operations. The operating principles of the proposed structure are discussed in the paper, and the results from a 1 kVA experimental setup are provided to validate the proposed topology