Study of Power Converter Topologies with Energy Recovery and grid power flow control. Part A: 2-quadrant converter with energy storage.

In the framework of a Transfer line (TT2) Consolidation Programme, a number of studies on Energy cycling have been commissioned. Part of this work involves the study of different power electronic system topologies for magnet energy recovery [1{5]. In this report, the use of a two-quadrant (2Q) regulator connected to the DC link of a 4-quadrant magnet supply is analysed. The key objective of the study is to find control strategies that result in the control of the peak power required from the power network as well as to recover the magnet energy into capacitor banks with controlled voltage fluctuation. The study comprises the modelling of the system by means of the method of state averaging and the development of regulation strategies to energy management. The proposed control strategies can be divided in two groups: in the first group, the magnet current is used to dene the reference for the control system, while in the second group this current is considered as a perturbation and some strategies are devised to limit the power drawn from the electrical network. The control strategies of the first group (named energy balance) result in an indirect control of the grid peak power by means of achieving an energy flow balance between the magnet and the energy storing elements. In the second group, the reference of the control system is defined to bound the grid current during either generation of pulse or between pulses. Within this group, the perturbation generated by the current demanded by the magnet must be rejected by the control system in order to ensure that the grid current is bounded. The development of the required design equations is presented and the main features of each strategy are highlighted. In addition, a comparative study about the energy that must handle the 2Q converter, which allows to properly size the reactive elements, together with the current drawn from the electrical network is presented for each strategy.