Abstract—An optimized set-up for controlling PWM rectifiers is proposed in this paper. In particular, the control part is based on a predictive estimation algorithm which guarantees the imposed value of the dc link output voltage and, at the same time, a unity power factor behavior at the mains. The modulation part consists on a digital space vector modulator, which eliminates the drop voltage due to the dead time effect and, also, avoids the current zero clamping phenomenon. The results achieved by means of an experiment confirm that improvements on the AC source current waveforms and controllable dc bus voltage are achieved with the proposed system. Index Terms--Active filters, pulse width modulated power converters, AC-DC power conversion. I. INTRODUCTION Nowadays, new standards and directives concerning electrical power quality give limits regarding harmonic stress on the mains by power electronic systems. Therefore, in some applications in which the amount of large harmonics injected in the network is considerable, a filtering action has to be performed. In this field, pulse-width modulation (PWM) rectifier [1]-[10] are used to supply input power to an ac-dc power conversion plant. They guarantee to achieve unity power factor at the mains, voltage regulation and, also, a bi- directional power-flow. The control of PWM rectifiers is usually performed by pulse-width modulation techniques which allows to achieve the above mentioned features and, at the same time, to shape as much as possible the input currents of the rectifier in a sinusoidal waveform. All these techniques perform a control of the switching status of a whole leg of the rectifier and, most of them, require a blank time to be added on the rising-edge of all the switching signals in order to avoid short circuits on the dc link. Unfortunately, this blank time generates a distortion on the voltage and current waveforms and can drastically deteriorate the efficiency and performances of the rectifier, especially if high switching frequencies are used. Besides, when predictive algorithms are adopted for controlling the rectifier power modules, the prediction operation can strongly mismatch the actual values. In this case, the consequent distortion of the ac source current can be transferred on the dc link voltage and the size of the capacitor has to be increased to smooth the ripple. In this paper, an C. Attaianese and G. Tomasso are with the University of Cassino, Italy, Department of Automation, Electromagnetism, Computer Science and Industrial Mathematics - via G. Di Biasio, 43 I-03043 Cassino (FR), Italy phone:+39 0776 299685 fax: +39 0776 299707 (e-mail: attaianese@ieee.org). optimized setup for PWM rectifiers is proposed. In particular, a digital space vector modulator without dead time generation is introduced, which is optimized also for avoiding the current zero-clamping phenomenon. The modulator is controlled by means of a predictive algorithm which allows to achieve a full control on the dc bus rectified voltage and a unity power factor at the mains. The whole set-up guarantees a sensible improvement of the ac current waveforms with respect to the traditional PWM rectifier set-up. II. PWM RECTIFIER ANALYTICAL MODEL With reference to fig. 1, the mathematical model of the PWM rectifier with a resistance as load can be written by means of the electric and power balances of the input and output circuits of the PWM rectifier. In particular, the following system of differential equations is carried out: e i i f f i - - = = - = • R S | | | T | | | L d dt R V C dV dt I V R I line line c DC DC DC DC DC c 3 2 b g (1) with e line voltage space vector; i line current space vector; L line line boost inductance; R line line resistance; V DC dc link voltage; I DC dc link current; C dc link smooth capacitor; R load resistance f c PWM rectifier commutation function. III. PWM RECTIFIER PREDICTIVE SVM CONTROL Controlling the PWM rectifier means to generate the commutation function f c on the base of the control targets. In particular, the proposed control of the PWM rectifier is structured on a predictive algorithm. In order to achieve the desired value of the dc link voltage and to keep a unity power factor at the mains, the following can be performed: by measuring the actual value of the dc voltage and comparing it with the desired one, an image of the power required by the load can be evaluated by means of a PI regulator, as shown in fig. 1. The output of the regulator, in particular, the amplitude Optimized Modulation for PWM Rectifiers Ciro Attaianese Member, IEEE - Giuseppe Tomasso Member, IEEE 1264 0-7803-7322-7/02/$17.00 © 2002 IEEE