Implement direct torque and flux controller (DTFC or DTC) model
Simscape / Electrical / Specialized Power Systems / Electric Drives / Fundamental Drive Blocks
The Direct Torque and Flux controller (DTC) directly controls the torque and stator flux of a machine, using inverter voltage vectors typically selected from an optimal switching table. For an explanation, see Direct Torque Control.
The Direct Torque controller (DTC) is built with two types of modulation, hysteresis modulation and space vector modulation (SVM). The following figures present the block diagram of the controller for the two types of modulation.
The Torque & Flux calculator block estimates the motor flux αβ components and the electromagnetic torque. This calculator is based on motor equation synthesis.
The magnetization control unit contains the logic for switching between magnetization and normal operation modes.
The Flux Sector Seeker block finds the sector of the αβ plane in which the flux vector lies. The αβ plane is divided into six different sectors spaced by 60 degrees.
The Flux & Torque Hysteresis block contain a two-level hysteresis comparator for flux control and a three-level hysteresis comparator for the torque control.
The Switching Table block contains two lookup tables that select a specific voltage vector in accordance with the output of the flux and torque hysteresis comparators. This block also produces the initial flux in the machine.
The Switching Control block limits the inverter commutation frequency to a maximum value that you specify.
The Torque PI and Flux PI blocks are proportional-integral regulators. The commanded electromagnetic torque and commanded stator flux amplitudes are compared with the estimated actual values of torque and flux. The torque and flux errors are fed to the PI controllers. The output signals are the commanded stator voltage components Vqs and Vds, respectively.
The Vector Sector block is used to find the sector of the αβ plane in which the voltage vector lies. The αβ plane is divided into six different sectors spaced by 60 degrees.
The Ramp Generator block is used to produce a unitary ramp at the PWM switching frequency. This ramp is used as a time base for the switching sequence.
The Switching Time Calculator block is used to calculate the timing of the voltage vector applied to the motor. The block input is the sector in which the voltage vector lies.
The Gates Logic block receives the timing sequence from the Switching Time Calculator block and the ramp from the Ramp Calculator block. This block compares the ramp and the gate timing signals to activate the inverter switches at the proper time.
Select hysteresis or space vector modulation. The default is Hysteresis
.
The torque hysteresis bandwidth, in newton-meters. This value
is the total bandwidth distributed symmetrically around the torque
set point. The figure shows a case where the torque set point is Te*
and the torque hysteresis bandwidth is set to dTe. This parameter
is enabled only when the Modulation type parameter
is set to Hysteresis
. The default value
is 0.5
.
The torque controller proportional gain. This parameter is enabled
only when the Modulation type parameter is set
to SVM
. The default value is 1.5
.
The torque controller integral gain. This parameter is enabled
only when the Modulation type parameter is set
to SVM
. The default value is 100
.
The stator flux hysteresis bandwidth, in webers. This value
is the total bandwidth distributed symmetrically around the flux set
point. The figure shows a case where the flux set point is ψ*
and the torque hysteresis bandwidth is set to dψ. This parameter
is enabled only when the Modulation type parameter
is set to Hysteresis
. The default value
is 0.01
.
The flux controller proportional gain. This parameter is enabled
only when the Modulation type parameter is set
to SVM
. The default value is 250
.
The flux controller integral gain. This parameter is enabled
only when the Modulation type parameter is set
to SVM
. The default value is 4000
.
The sample time of the direct torque controller, in seconds.
The default value is 20e-6
.
The controller sampling time, in seconds. The sampling time
must be a multiple of the simulation time step. The default value
is 1e-6
.
The maximum inverter switching frequency, in hertz. The default
value is 20000
.
The fixed inverter switching frequency, in hertz. This parameter
is enabled only when the Modulation type parameter
is set to SVM
. The default value is 20000
.
The cutoff frequency of the first-order low-pass filter applied
to the DC bus voltage measurement, in hertz. This parameter is enabled
only when the Modulation type parameter is set
to SVM
. The default value is 50
.
The stator resistance, in ohms. The default value is 0.435
.
The initial stator flux for the machine, in webers. The default
value is 0.3
.
The number of pole pairs. The default value is 2
.
Torque*
The torque reference, typically provided by a speed controller.
Flux*
The flux reference, typically provided by a speed controller.
V_abc
The three-phase voltages of the induction machine.
I_ab
The line currents Ia and Ib of the induction machine.
MagC
This binary signal indicates if the machine is magnetized enough to be started (1) or not (0).
Gates
The pulses for the six inverter switches.
The Direct Torque Controller block is used in the AC4 block of the Electric Drives library.
[1] Bose, B. K. Modern Power Electronics and AC Drives. NJ: Prentice-Hall, 2002.
Bridge Firing Unit (AC) | Bridge Firing Unit (DC) | Current Controller (Brushless DC) | Current Controller (DC) | Field-Oriented Controller | Regulation Switch | Six-Step Generator | Space Vector Modulator | Speed Controller (AC) | Speed Controller (DC) | Speed Controller (Scalar Control) | Vector Controller (PMSM) | Vector Controller (WFSM) | Voltage Controller (DC Bus)