Direct Torque Control with Space Vector Modulation (DTC-SVM) of ...
Direct Torque Control with Space Vector Modulation (DTC-SVM) of ...
Direct Torque Control with Space Vector Modulation (DTC-SVM) of ...
You also want an ePaper? Increase the reach of your titles
YUMPU automatically turns print PDFs into web optimized ePapers that Google loves.
Introduction<br />
vector control, which is based on relation valid for dynamics states, not just magnitude and<br />
frequency (angular speed), but also instantaneous position <strong>of</strong> voltage, current and flux space<br />
vectors are controlled. Thus, the control system adjust the position <strong>of</strong> the space vectors and<br />
guarantee their correct orientation for both steady states and transients.<br />
The scalar constant V/Hz control for PMSM <strong>with</strong>out damper winding (squire cage) is not<br />
simple as for induction motor. It requires additional stabilization control loop, which can be<br />
provide by feedback from: rotor velocity perturbation, active power or DC-link current<br />
perturbation [9].<br />
The most popular vector control method developed in 70s, known as field oriented control<br />
(FOC) [31] gives the permanent magnet synchronous motor high performance. In this method<br />
the motor equation are transformed in a coordinate system that rotates in synchronism <strong>with</strong><br />
permanent magnet flux. It allows separately and indirectly control flux and torque quantities<br />
by using current control loop <strong>with</strong> PI controllers like in well known DC machine control [3].<br />
In search <strong>of</strong> a simpler and more robust high performance control system in 80s new vector<br />
control called direct torque control (<strong>DTC</strong>) was developed [50]. It was innovative studies at<br />
this time and completely different approach which depart from the idea <strong>of</strong> coordinate<br />
transformation and the analogy <strong>with</strong> DC motor control. It allows direct control flux and torque<br />
quantities <strong>with</strong>out inner current control loops. Using bang-bang hysteresis controllers for flux<br />
and torque control loops made this control concept very fast and not complicated. However,<br />
the main disadvantage <strong>of</strong> <strong>DTC</strong> is fast sampling time required and variable switching<br />
frequency, because <strong>of</strong> hysteresis based control loops. In order to eliminate above<br />
disadvantages and kept basic control rules <strong>of</strong> classical <strong>DTC</strong>, at the beginning <strong>of</strong> 90’s a new<br />
developed control technique called direct torque control <strong>with</strong> space vector modulator (<strong>DTC</strong>-<br />
<strong>SVM</strong>) has been introduced [54,55]. However, from the formal consideration this method can<br />
also be viewed as stator flux oriented control (SFOC). This control employed instead <strong>of</strong><br />
hysteresis controller as for classical <strong>DTC</strong>, the PI controllers and space vector modulator<br />
(<strong>SVM</strong>). It allows to achieve fixed switching frequency, what considerably reduce switching<br />
losses as well as torque and current ripples. Also requirement <strong>of</strong> very fast sampling time is<br />
eliminated [113,115,117]. Therefore, this new method is subject <strong>of</strong> this thesis. In spite <strong>of</strong><br />
many control strategies there is no one which may be considered as standard solution.<br />
5