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Recent Developments of Electrical Drives - Part 28

Recent Developments of Electrical Drives - Part 28. The book stating the recent developments of electrical drives, can be useful for engineers and researchers investigating and designing electrical and electronic devices as well as for students and young researchers dealing with electrical and electronic engineering, computer sciences (advanced computer modelling, sophisticated control systems with artificial intelligence tools applied, optimal design bye use of classical and genetic algorithms employed), applied mathematics and all the topics where electromagnetic, thermal, mechanical phenomena occur | II-11. Direct Power and Torque Control Scheme 263 Direct power and direct torque control space vector modulated DPT-SVM scheme Direct Power Control DPC for PWM rectifier is based on instantaneous control of active p and reactive q power flow from to the line and to from active load. In classical approach 7 8 of DPC there are two power control loops with hysteresis comparators and switching table. Therefore the key point of the DPC implementation is sufficiently precise and fast estimation of the instantaneous line powers. The most significant drawbacks of the hysteresis-based DPC are variable switching and high sampling frequency. Introducing a Space Vector Modulator SVM in control strategy 9 10 allows to eliminate the both mentioned problems. Moreover the line voltage sensors can be replaced by Virtual Flux VF estimator which introduces technical and economical advantages to the system simplification reliability galvanic isolation cost reduction . Such control system is called Virtual Flux Based Direct Power Control Space Vector Modulated DPC-SVM scheme 11 . Summarised in this method linear PI controllers with Space Vector Modulator replace hysteresis comparators and switching table Fig. 3 . Similarly like DPC for the classical Direct Torque Control DTC 12 the command stator flux sc and commanded torque Mec values are compared with the actual stator flux and electromagnetic torque Mec values in hysteresis flux and torque controllers respectively. Therefore the well known disadvantages of DTC are variable switching frequency 1 switching over dc-link voltage Udc current and torque distortion caused by sector changes as well as high sampling frequency requirement for digital implementation of the hysteresis controllers. All above difficulties can be eliminated when instead of the switching table a SVM is used. Hence the DTC-SVM strategy 13 for control of the inverter motor part is proposed Fig. 3 . Simplified mathematical model of the system in stationary a ft .