Experimental Study of a Matrix Converter Excited Doubly-Fed Induction Machine in Generation and Motoring Ivan Shapoval * , Jon Clare † and Eduard Chekhet * * Institute of Electrodynamics of the Ukrainian National Academy of Sciences, Kyiv, Ukraine, e-mail: chk@ied.org.ua † The University of Nottingham, Nottingham, United Kingdom, e-mail: Jon.Clare@nottingham.ac.uk Abstract—Full-scale experimental testing of the 7.5 kW doubly-fed induction machine controlled by matrix con- verter is reported. A number of doubly-fed induction ma- chine and matrix converter control algorithms have been implemented in real time using a DSP-controller. The ex- perimental rig used to control the doubly-fed induction ma- chine is described. Experimental results demonstrate that the doubly-fed induction machine control algorithms guar- antee perfect torque tracking of positive and negative trajec- tories of torque reference under the condition of unity stator side power factor. I. INTRODUCTION The vector controlled doubly-fed induction machine (DFIM) is an attractive solution for high performance, restricted speed range drives and energy generation appli- cations [1]. The typical connection scheme of DFIM is shown in Fig. 1. For limited speed variations around the synchronous speed of the induction machine, the power handled by the converter at the rotor side is a small frac- tion (depending on slip) of the overall converted power. AC-AC DFIM Line g rid Mechanical Load or Mover Control Unit Fig. 1. The typical connection scheme of DFIM. The fundamentals of DFIM vector control are pre- sented in [1] and widely used in different developments [2]-[7]. In both motor and generator applications the DFIM is able to provide torque production together with stator side power factor control. If a suitably controlled AC/AC converter is used to supply the rotor side of the DFIM, the overall system can be controlled with low harmonic distortion in the stator and rotor sides. More- over, when the DFIM is used as a variable-speed drive in the dynamic braking mode, the slip power is regenerated by the converter to the supply grid, resulting in highly efficient energy conversion. Two approaches are possible to supply the DFIM rotor circuit: a standard AC-DC-AC power converter having a vector controlled input rectifier and a direct AC-AC ma- trix converter (MC) solution. Some simulation results of MC application for DFIM control have already been re- ported in literature [8]-[10]. The aim of this paper is to present results from experi- mental testing of a MC excited DFIM as a generator and motor. The concept of indirect stator flux orientation has been implemented in a similar way to that used for indi- rect rotor flux orientation in a squirrel cage induction machine, in order to solve the full order DFIM control problem. An intensive experimental study shows that high per- formance torque tracking is achievable keeping stator side power factor at unity level during energy generation and drive regimes. Soft connection (almost transient-less) of the DFIM stator to line grid is achieved using proposed excitation-synchronization control algorithm during ini- tialization stage of DFIM operation. The paper is organized as follows. Section II presents general configuration of torque tracking control algorithm for DFIM. In Section III the short description of MC con- trol algorithm is given. Results of experimental testing of the DFIM with MC are given in Section IV. II. DFIM CONTROL ALGORITHM The equivalent two-phase model of the symmetrical DFIM with connected to line stator, represented in stator voltage-vector oriented frame (d-q) is 1 2 1 2 1 1 1 1 1 1 2 1 1 1 1 1 1 2 2 22 22 1 1 1 2 2 2 22 22 1 1 1 2 2 , , , , , , n q d d q L d d q m d q q d m q d d q d n q d q q d q n d q p i i T J Li U Li i i i p U u i i i p u (1) where 2 2 2 2 1 1 , , , , , d q d q d q u u i i are rotor voltages, rotor currents and stator fluxes, T L is a driving torque, gen- erated by the prime mover, U and 1 are stator (line) volt- age amplitude and angular frequency, and are angular position and rotor speed, 2 1 is slip angular fre- quency, p n is number of pole pairs. Positive constants re- lated to DFIM electrical parameters are defined as: 307 978-1-4244-1742-1/08/$25.00 c  2008 IEEE