Power flow control in a modular converter with energy storage

Using modularized power converters with scalable energy storage in particle accelerators can be further enhanced with controls that can be adapted to optimise different design targets, such as to minimise the front-end stage peak current, the depth of discharge of electrolytic capacitors or the thermal cycling of semiconductors. This paper proposes a control system that is able to individually adjust the power flow of the converter modules under pre-defined load profiles, and hence separates the use of energy storage and grid connection even under rapid cycling. The paper briefly summarises the characteristics of the modular converter and proposes four energy control strategies that have been validated by simulation as well as experimentally on a 800 kW full scale prototype. It is shown that by applying each strategy, the corresponding design objectives can be achieved, for example, optimal utilisation of the energy storage systems or minimised current stress in the semiconductors. This article proposes a novel energy flow control system for a modular and scalable power electronic converter that is used to electrify electromagnets in high-energy physics experiments at the European Organisation for Nuclear Research (CERN). The proposed control scheme is able to optimise the operation of the scalable converter for four different key metrics, which are validated experimentally in a full-scale, 800 kW laboratory prototype.image