Digitally Controlled PWM Rectifier for Harmonic Reduction and Bidirectional Power Flow

In particle accelerators, magnet power supplies play a crucial role in controlling particle beams using electromagnets. Various types of power supplies are used in accelerators, including DC, ramping, and pulsed supplies. DC power supplies are typically employed in transport lines and storage rings, while ramping and pulsed power supplies are used for particle energy boosting and beam injection-extraction respectively. However, most of these power supplies, whether utilizing conventional rectifiers (uncontrolled / controlled) as pre-regulators or main regulators, suffer from poor line harmonic distortion and low power factor. To address these challenges, a Pulse Width Modulated Rectifier (PWMR) can be used as a utility interface, significantly improving performance at the cost of additional control and power electronic circuitry. This paper presents the simulation, digital controller implementation, and experimental demonstration of PWMR aimed at reducing line-side harmonic pollution, enhancing input power factor, and enabling bidirectional power flow. Control loop simulations of the PWMR were conducted to understand its dynamics, and Proportional-Integral (PI) controller parameters were tuned to achieve optimal control. An experimental demonstration of the digitally controlled PWMR was carried out using Digital Signal Processor (DSP). The experimental results from the prototype PWMR (100 V, ±5 A) align well with the theoretical analysis.