Robust dead-beat current control for PWM rectifiers and active filters

This paper analyzes the stability limitations of the digital dead-beat curr ent control applied to voltage-source three-phase converters used as pulsew idth modulation rectifiers and/or active filters. In these applications, th e conventional control algorithm, as used in drive applications, is not suf ficiently robust, and stability problems may arise for the current control loop. The current loop is, indeed, particularly sensitive to any model mism atch and to the possibly incorrect identification of the model parameters. A detailed analysis of the stability limitations of the commonly adopted de ad-beat algorithm, based on a discrete-time state-space model of the contro lled system, is presented. A modified line voltage estimation technique is proposed, which increases the control's robustness to parameter mismatches. The results of the theoretical analysis and the validity of the proposed m odification to the control strategy are finally verified both by simulation s and by experimental tests.