IEEE TRANSACTIONS ON POWER ELECTRONICS, VOL. 30, NO. 4, APRIL 2015 2275 A Simple Current Control Strategy for a Four-Leg Indirect Matrix Converter Crisitian Garc´ ıa, Member, IEEE, Marco Rivera, Member, IEEE, Miguel L ´ opez, Jos´ e Rodriguez, Fellow, IEEE, Rub´ en Pe ´ na, Member, IEEE, Patrick W. Wheeler, Senior Member, IEEE, and Jos´ e R. Espinoza, Member, IEEE Abstract—In this paper, the experimental validation of a predic- tive current control strategy for a four-leg indirect matrix converter is presented. The four-leg indirect matrix converter can supply en- ergy to an unbalanced three-phase load while providing a path for the zero sequence load. The predictive current control technique is based on the optimal selection among the valid switching states of the converter by evaluating a cost function, resulting in a simple approach without the necessity for modulators. Furthermore, zero dc-link current commutation is achieved by synchronizing the state changes in the input stage with the application of a zero-voltage space vector in the inverter stage. Simulation results are presented and the strategy is experimentally validated using a laboratory prototype. Index Terms—AC–AC conversion, current control, four-leg con- verters, matrix converter, modulation schemes, predictive control. NOMENCLATURE i s Source current [i sA i sB i sC ] T . v s Source voltage [v sA v sB v sC ] T . i i Input current [i A i B i C ] T . v i Input voltage [v A v B v C ] T . i dc dc-link current. v dc dc-link voltage. i Load current [i u i v i w ] T . v Load voltage [v u v v v w ] T . i ∗ Load current reference [i ∗ u i ∗ v i ∗ w ] T . C f Filter capacitor. L f Filter inductor. R f Filter resistor. R Load resistance. L Load inductance. Manuscript received October 26, 2013; revised March 3, 2014; accepted April 14, 2014. Date of publication May 2, 2014; date of current version November 3, 2014. This work was supported by CONICYT Initiation into Research 11121492 Project, and by CONICYT/FONDAP/15110019. The work of C. F. Garc´ ıa was supported by CONICYT Scholarships for Ph.D. studies in Chile and Programa de Iniciaci´ on a la Investigaci´ on Cient´ ıfica financed by Universidad T´ ecnica Federico Santa Mar´ ıa. Recommended for publication by Associate Editor M. Malinowski. C. Garc´ ıa, M. L´ opez, and J. Rodriguez are with the Department of Elec- tronics Engineering, Universidad T´ ecnica, Federico Santa Mar´ ıa, Valpara´ ıso 239-0123, Chile (e-mail: garciap7@gmail.com; miguel.elopezg@gmail.com; jrp@usm.cl). M. Rivera is with the Department of Industrial Technologies, Universidad de Talca, Curic´ o 3341717, Chile (e-mail: marcoriv@utalca.cl). R. Pena and J. R. Espinoza are with the Department of Electrical Engineer- ing, Universidad de Concepci´ on, Concepci´ on 4070386, Chile (e-mail: rupena@ udec.cl; jose.espinoza@udec.cl). P. W. Wheeler is with the Department of Electrical and Electronic En- gineering, University of Nottingham, Nottingham, NG7 2RD, U.K. (e-mail: pat.wheeler@nottingham.ac.uk). Color versions of one or more of the figures in this paper are available online at http://ieeexplore.ieee.org. Digital Object Identifier 10.1109/TPEL.2014.2321562 I. INTRODUCTION I N recent years, the interest in matrix converters applications has increased [1]–[3]. Matrix converter topologies offer an “all silicon solution” for ac–ac power conversion, achieving sinusoidal input and output waveforms with bidirectional power flow and being capable of operating under high temperatures and pressures [4]–[6]. Moreover, due to the absence of electrolytic capacitors, matrix converters could be more compact, robust, and reliable when compared to conventional topologies [2]. Compared to a conventional back-to-back converter, the phys- ical space saved by a matrix converter has been estimated as 60%. This characteristic makes the matrix converter a suitable topology for specific applications such as wind–diesel topolo- gies, distributed generation applications, emergency vehicles, military and aerospace applications, external elevators for build- ing construction, and skin pass mills [2], [7], [8]. As reported in [6], there are a number of different topologies for direct ac–ac converters. Among them, the indirect matrix converter (IMC) has a similar performance to the standard direct matrix converter (DMC). The IMC is very similar to a back-to- back converter but includes bidirectional switches in the rectifier and has no dc-link capacitor. The lack of a storage element offers the possibility to reduce losses because the commutation of the input stage can be achieve with zero dc-link current [9], [10]. When energy is supplied to a three-phase load, it may be necessary to take into account the unbalance nature of the load and the need for a path for the zero-sequence current. This path could be provided by connecting the neutral of the load to the neutral point of a zig-zag transformer [11]–[13]. How- ever, this topology could be costly and bulky. Another option is to use a four-leg voltage source converter on the load side where the fourth leg would then provide the needed neutral connection for the load. As reviewed in [14], there are several topologies that can handle zero-sequence voltage and current caused by an unbalanced source and/or load in three-phase four- wire systems. As reported in [15]–[18], a matrix converter can also be used to supply energy to an unbalanced three-phase load. The four-leg indirect matrix converter (4Leg-IMC) can be controlled and modulated using a carrier-based pulse width modulation (PWM) and three-dimensional space vector modu- lation (3D-SVM) techniques [17]–[22]. Compared to the carrier- based PWM technique, the 3D-SVM offers many advantages such as good dc-link utilization and minimum output distor- tion, but it has complex modeling and a higher computational requirements and is, therefore, not intuitive for implementation [21], [22]. 0885-8993 © 2014 IEEE. Personal use is permitted, but republication/redistribution requires IEEE permission. See http://www.ieee.org/publications standards/publications/rights/index.html for more information.