4372 IEEE TRANSACTIONS ON INDUSTRIAL ELECTRONICS, VOL. 55, NO. 12, DECEMBER 2008 Predictive Strategy to Control Common-Mode Voltage in Loads Fed by Matrix Converters René Vargas, Student Member, IEEE, Ulrich Ammann, Member, IEEE, José Rodríguez, Senior Member, IEEE, and Jorge Pontt, Senior Member, IEEE Abstract—Common-mode voltages (CMVs) cause overvoltage stress to the winding insulation and bearings deterioration, re- ducing the lifetime of electric machines. This paper presents a predictive strategy that effectively mitigates CMVs from matrix converters (MCs), without affecting its functionality and allowing the use of rotating vectors. The method was experimentally tested on an MC feeding an induction machine, mitigating CMVs in 70% and reducing abrupt changes. The reduction is achieved with no tradeoff on the performance of the drive until reaching 40%, point where further reduction comes with an increase on the total harmonic distortion of line side currents. The designer can adjust the method in order to protect the ac machine, extending its lifetime and reducing negative effects of CMVs, and still comply with the standard for connection to the grid due to the flexibility allowed by the proposed strategy. Index Terms—AC–AC power conversion, AC motor drives, common-mode voltage (CMV), matrix converters (MCs), predic- tive control. I. I NTRODUCTION C OMMON-MODE voltages (CMVs) produced by power converters feeding electric machines cause overvoltage stress to the winding insulation, affecting its lifetime and pro- ducing deterioration [1], [2]. Capacitive currents affect bearings and conducted or radiated electromagnetic interference affects the functionality of electronic systems. For those reasons, with the development of modern ac electrical drives [3], the topic has called the attention of researchers and the industry [4]–[9]. The matrix converter (MC) is a single-stage power converter, capable of feeding a m-phase load from a n-phase source (n × m MC) without energy storage devices [10], [11]. As drive for electric ac machines, it represents an alternative to back-to-back converters, particularly in cases where size and the absence of large capacitors or inductances to store energy are relevant issues [12]–[14]. Several modulation techniques have been developed to control an MC, which can be classified into two main groups: scalar and vectorial methods [15]–[18]. The high number of switching states, the direct interaction Manuscript received March 12, 2008; revised September 9, 2008. First published October 31, 2008; current version published December 2, 2008. This work was supported in part by the Chilean Research Fund CONICYT under Grant 1060424, by the Industrial Electronics and Mechatronics Millennium Science Nucleus, by the Universidad Técnica Federico Santa María, and by the Institute of Power Electronics and Electrical Drives, University of Stuttgart. R. Vargas, J. Rodríguez, and J. Pontt are with the Department of Electronics Engineering, Universidad Técnica Federico Santa María, Valparaíso 110-V, Chile (e-mail: rene.vargas@usm.cl). U. Ammann is with the Institute of Power Electronics and Electrical Drives, University of Stuttgart, 70569 Stuttgart, Germany. Digital Object Identifier 10.1109/TIE.2008.2007016 between source and load, and the presence of rotating vectors introduce an important complexity in the analysis and control of an electric machine through an MC [19]–[22]. To reduce the CMV produced in systems fed by MCs is a timely topic that has been investigated in recent years, with the objective of improving the performance of the converter and bringing this topology closer to industrial applications [23]–[27]. Predictive control has found applications in power converters [28]–[31]. Recently, model-based predictive control [32] has been introduced as a method to control load current from a voltage source inverter (VSI) [33], a three-level VSI [34], and an MC [35]. The method allows also to control the switching frequency and balance in the dc-link of a three-level VSI [34] and to perform input power factor (PF) regulation on an MC [35]. An additional interesting application of this control method is the torque and flux control for inverter-fed induction machines [36], [37]. All these control methods evaluate a quality function for every valid switching state of the converter over a finite receding horizon, based on predictions from a model of the system. No modulation or linear controllers are required. This paper presents a novel method to reduce CMVs in MC, based on predictive control. The approach differs from other well-known control methods for MCs, such as space vector modulation (SVM) or direct torque control (DTC), because it considers all valid switching states, including rotating vectors that in most cases are not used. This fact is a significant advantage considering that rotating vectors generate zero CMV. The effectiveness of the strategy controlling the induction machine, input currents, and considerably reducing CMVs without affecting the performance of the drive is demonstrated in simulations and experimentally. If a higher value of total harmonic distortion (THD) in the input current is acceptable according to the standard that must be fulfilled, the method allows one to further decrease the CMV by increasing this distortion in order to protect the ac machine extending its lifetime and still complying with the standard for connection to the grid. II. BASIC CONTROL STRATEGY In order to introduce the strategy to reduce CMVs, it is necessary to present the control method and power circuit in which the strategy is being applied. The basic concept to reduce CMV, which will be introduced in this paper, can be applied theoretically to any power converter feeding a three-phase load. The analysis is centered on MCs because in this converter, 0278-0046/$25.00 © 2008 IEEE Authorized licensed use limited to: Universidad Tecnica Federico Santa Maria. Downloaded on January 12, 2009 at 12:41 from IEEE Xplore. Restrictions apply.