Direct Torque Control with Space Vector Modulation (DTC-SVM) of ...

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Voltage source PWM inverter for PMSM supply As a consequence when the phase current I sA is positive, the output voltage is reduced, and when the current I sA is negative the output voltage is increased (see Fig. 3.11). U0 I sA > 0 ideal voltage real voltage U I < 0 0 sA U DC 2 U DC 2 −U DC 2 deacresing −U DC 2 increasing Figure 3.11 Dead time effect on the inverter output voltage: (fat line real voltage, doted line ideal voltage). Voltage drop across power devices In real voltage source inverter power switches do not conduct ideally. When they are conducting the voltage across them is not zero and equal the voltage drop on the conducted transistor V T . Also in blocking mode the power switches have voltage drop on the conducted diode V D . More details about real IGBT module you can find in Appendices. The voltage drop across the power devices is dependent on the direction of the phase current. It has influence on the output voltage, especially at low speed operation of motor and high load current [17,20,27,30]. Fig. 3.12 shows the voltage drop influence on the output voltage. Also shows that the output voltage is asymmetric (with offset) and the voltage drop decreases the output voltage when the phase current is positive and increases the output voltage when the phase current is negative. U 0 I > 0 sA U 0 I < 0 sA U DC 2 V T U DC 2 V D V D V T −U DC 2 −U DC 2 Figure 3.12 Output voltage in voltage source inverter due to voltage drop across the power devices a) for I sA > 0 , b) I sA < 0 (fat line real voltage, doted line ideal voltage). The influence of dead time effect and voltage drop across power devices on the output voltage from inverter is illustrated in block diagram (Fig. 3.13). The ideal reference * voltage components in stationary reference frame ( U α , _ ideal * U β _ ideal ) are equal real 40
Voltage source PWM inverter for PMSM supply * ( U α , _ real * U β _ real ) and delivered to pulse width modulation (PWM) modulator block with real non-linear inverter. As a result the output voltages ( U α _ out , U β _ out ) are distorted (green signals) and as consequence the phase currents ( I α _ out , I β _ out ) in the load (red signals) are also distorted. * U * α _ideal U α _ real * * U β U _ideal β _ real PWM Modulator S A S B S C Inverter U α _out U β _out I α _ out I β _out Load Figure 3.13 Block diagram illustrated the dead time effect and voltage drop across power devices in three phase motor supplied from non-ideal voltage source inverter. Pulsation of the DC link voltage [19] In practice it should be take into account that the real input dc-link voltage required for supply VSI is not ideal. It has ripples and fluctuation, because of not ideal filtering and disadvantages of diode rectifier. Therefore, the quality of dc-link voltage has impact on the output voltage from inverter. If dc-link voltage will change we can observed the changing at the output of inverter. In order to overcome this problem: • in PWM modulator we can not assume a constant dc-link voltage and we should measured this voltage in order to calculate the modulation index (see subchapter 3.3), 41
Page 1 and 2: POLITECHNIKA WARSZAWSKA WARSAW UNIV
Page 3 and 4: Contents Table of Contents Chapter
Page 5 and 6: Introduction Chapter 1 INTRODUCTION
Page 7 and 8: Introduction to surface-mounted mac
Page 9 and 10: Introduction vector control, which
Page 11 and 12: Introduction presented and studied.
Page 13 and 14: Modeling and control modes of PM sy
Page 39 and 40: Voltage source PWM inverter for PMS
Page 43: Voltage source PWM inverter for PMS
Page 57 and 58: Control methods of PM Synchronous m
Page 69 and 70: Direct Torque Control with Space Ve
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Direct Torque Control with Space Ve
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Sensorless Speed Direct Torque Cont
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DSP implementation of DTC-SVM contr
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Summary and closing conclusion Chap
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Appendices APPENDICES A1 Rotor and
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Appendices ⎡ ⎤ ⎢ 1 0 ⎥ ⎡K
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Appendices i(t1->t0)+=it1 it1: it1=
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Appendices A7 PWM technique - six s
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List of symbol List of symbols Symb
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References Books and PhD-Thesis 1.
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References 39. J.-I. Itoh, N. Nomur
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References 74. N. Ertugrul, P. Acar
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References 108. D. Świerczyński,
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