DC active power filter based on model predictive control for DC bus overvoltage suppression of accelerator grid power supply

Abstract

The China Fusion Engineering Test Reactor plans to build a 200 kV/25 A acceleration grid power supply (AGPS) for the negative-ion-based neutral beam injector prototype system. The AGPS uses a rectifier-inverter-isolated step-up structure. There is a DC bus between the rectifier and the inverter. In order to limit DC bus voltage ripple and transient fluctuations, a large number of capacitors are used, which degrades the reliability of the power supply and occupies a large amount of space. This work finds that due to the difference in the turn-off time of the rectifier and the inverter, the capacitance mainly depends on the rectifier current when the inverter is turned off. On this basis, an active power filter (APF) scheme is proposed to absorb the current. To enhance the dynamic response ability of the APF, model predictive control is adopted. In this paper, the circuit structure of the APF is introduced, the prediction model is deduced, the corresponding control strategy and signal detection method are proposed, and the simulation and experimental results show that APF can track the transient current of the DC bus and reduce the voltage fluctuation significantly.