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Coordinated Control of a Variable Speed Drive System


M. Rozou

Master Thesis, FS13 (10248)

The main objective of the present work is the design of a coordinated control strategy for an AC/DC/AC converter for a variable speed drive system (VSD). Variable speed drives are used to improve the power efficiency in applications that demand dynamic control of mechanical loads such as conveyor belts, rolling mills, and pumps. The drive system that is used in this work consists of two power converters: an AC/DC rectifier, which converts the three-phase AC voltage of the main power supply into a DC voltage and a DC/AC inverter, that impresses three-phase AC currents of adjustable amplitude and frequency in the stator winding of the machine. The AC/DC/AC conversion is achieved through control of semiconductor switches of the two converters in real time. It is a very common practice to control the two power conversion stages separately, with two decoupled control loops. Though this simplifies the whole problem, the lack of coordination between the rectifier and the inverter can lead to over/under-voltage trip failures due to conflicting control objectives. The main goal of this thesis is to establish a method to control both the rectifier and the inverter into one common loop. Therefore, a mathematical model of the overall electrical drive system is derived. The coordinated control strategy of the two power conversion stages is based on model predictive control technique. In a next step, the coordinated model predictive controller is compared with the state of the art decoupled control strategy. The performance of the coordinated control strategy is tested both in transients and in steady state conditions.


Type of Publication:

(12)Diploma/Master Thesis

J. Lygeros

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% Autogenerated BibTeX entry
@PhdThesis { Xxx:2013:IFA_4550
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