Implements a three-phase inverter model for AC Motor Drives
Simscape / Electrical / Specialized Power Systems / Electric Drives / Fundamental Drive Blocks
The Inverter (Three-Phase) block models a standard three-leg, two-level inverter model (detailed mode) or an average-value inverter model (average mode). Average mode has multiple instances, depending on the AC motor drive type.
In detailed mode, the Inverter (Three-Phase) block is an instance of the Universal Bridge block configured as a three-arm (three-phase), forced-commutated converter.
In average mode, the Inverter (Three-Phase) block implements an average-value inverter model for a specific AC drive type. The average-value inverter model can be a current source type with AC current reference signal, voltage source type with an AC voltage reference signal, or voltage source type with AC current reference signal.
This model is used for an AC drive type based on field-oriented control, WFSM vector control, or PMSM vector control.
The inverter is represented by current sources on the AC side during normal operation. The AC current reference signal generates the three-phase currents at the inverter output. When the inverter is saturated, it operates in square-wave mode, and the current sources are replaced with voltage sources. The average-value inverter model of this type is shown in the figure.
The model is composed of one controlled current source on the DC side and of two controlled current sources and three controlled voltage sources on the AC side. The DC current source allows the representation of the average DC bus current behavior following the equation
Idc = (Pac + Plosses) / Vdc,
with Pac being the AC side instantaneous power, Plosses the losses in the power electronics devices, and Vdc the DC bus voltage.
On the AC side, the current sources represent the average phase currents fed to the motor. The current values are set equal to the current references sent by the current regulator. A small current is injected to compensate for the current drawn by the three-phase load (needed because of the inverter current sources in series with the inductive motor).
The currents are fed by three controlled voltage sources during loss of current tracking due to insufficient inverter voltage. These voltage sources represent the square wave mode and allow good representation of the phase currents during inverter saturation. Each voltage source outputs either Vin or 0, depending on the values of the pulses (1 or 0) send by the current controller. This mode of operation is detected from the Saturation detection block using the DC bus voltage and the counter electro-motive force generated by the AC machine.
This model is used for AC drive type based on space vector modulation.
The inverter is represented with voltage sources on the AC side. The AC voltage reference signal generates the three-phase voltage at the inverter output. The average-value inverter model of this type is shown in the figure.
The model is composed of one controlled current source on the DC side and three controlled voltage sources on the AC side. The DC current source allows the representation of the average DC bus current behavior, following the equation
Idc = αaIa + αbIb + αcIc,
with αa, αb, αc being the PWM duty cycles (or phase-voltage-to-DC-bus-voltage ratio) of the inverter legs A, B, and C respectively, and Ia, Ib, Ic the corresponding three-phase currents. The three AC voltage sources represent the average voltage values of the three-phase inverter voltages Va, Vb, Vc, following the equation
Va = αaVin
Vb = αbVin
Vc = αcVin,
with Vin being the input DC bus voltage value.
This average-value inverter model is used for the Brushless DC current control AC drive type.
The inverter is represented with voltage sources on the AC side. The AC machine parameters are required together with the AC current reference signal to generate the three-phase voltages at the inverter output. The figure shows the average-value inverter model of this type for a trapezoidal PMSM drive.
The model is composed of one controlled current source on the DC side and two controlled voltage sources on the AC side. The DC current source allows the representation of the DC bus current behavior described by the equation
Idc = (Pout + Plosses) / Vin,
with Pout being the output AC power, Plosses the losses in the power electronic devices, and Vin the DC bus voltage.
On the AC side, the voltage sources are fed by the instantaneous voltages provided by the Trapezoidal PMSM dynamic model (see the PMSM documentation for the machine model). This dynamic model takes the AC reference currents (the rate of these currents has been limited to represent the real-life currents), the measured BEMF voltages, and the machine speed to compute the terminal voltages to apply to the machine.
The dynamic rate limiter limits the rate of the reference currents when transitions occur. The rate depends on the inverter saturation degree.
During loss of current tracking due to insufficient inverter voltage, the dynamic rate limiter saturates the reference current according to this operation mode.
Specify the model detail level to use:
Detailed
(default)
Average
The sample time of the inverter, in seconds. The default value
is 2e-6
.
The snubber resistance, in ohms. Set the Snubber resistance
Rs parameter to inf
to eliminate the
snubbers from the model. The default value is 10e3
.
The snubber capacitance, in farads. Set the Snubber
capacitance Cs parameter to 0
to eliminate
the snubbers or to inf
to get a resistive snubber.
The default value is inf
.
Select the type of power electronic device to use in the bridge.
GTO / Diodes
(default)
MOSFET / Diodes
IGBT / Diodes
Specify the drive type to use. This parameter is visible only
when the Model detail level parameter is set
to Average
. Select one of these values:
Field-oriented control
(default)
Space vector modulation
WFSM vector control
PMSM vector control
Brushless DC
Internal resistance of the switch, in ohms. The default value
is 1e-3
.
Forward voltages, in volts, of the forced-commutated devices
(GTO, MOSFET, or IGBT) and of the antiparallel diodes. This parameter
is available when the selected Power electronic device is GTO/Diodes
or IGBT/Diodes
.
The default value is [1.2,1.2]
.
Fall time Tf and tail time Tt, in seconds, for the GTO or the
IGBT devices. The default value is [1e-6,2e-6]
.
The default value is[1e-6,2e-6]
.
Default is None
.
Select Device voltages
to measure
the voltages across the six power electronic device terminals.
Select Device currents
to measure
the currents flowing through the six power electronic devices. If
antiparallel diodes are used, the measured current is the total current
in the forced-commutated device (GTO, MOSFET, or IGBT) and in the
antiparallel diode. A positive current therefore indicates a current
flowing in the forced-commutated device and a negative current indicates
a current flowing in the diode. If snubber devices are defined, the
measured currents are the ones flowing through the power electronic
devices only.
Select UAB UBC UCA UDC voltages
to
measure the terminal voltages (AC and DC) of the Inverter (Three-Phase) block.
Select All voltages and currents
to
measure all voltages and currents defined for the Inverter
(Three-Phase) block.
Place a Multimeter block in your model to display the selected measurements during the simulation. In the Available Measurements menu of the Multimeter block, the measurement is identified by a label followed by the block name.
Measurement | Label |
---|---|
Device voltages |
|
Branch current |
|
Terminal voltages |
|
Synchronous frequency of the machine, in hertz. This parameter
is visible only when the Model detail level parameter
is set to Average
. The default value is 60
.
Specifies the reference frame that is used to convert input voltages (abc reference frame) to the dq reference frame, and output currents (dq reference frame) to the abc reference frame. You can choose from the following reference frame transformations:
Rotor
(default)
Stationary
Synchronous
This parameter is visible only when the Model detail
level parameter is set to Average
and
the Drive type parameter is set to Field-oriented
control
.
The stator resistance, in ohms, and leakage inductance, in henry,
of the motor. This parameter is visible only when the Model
detail level parameter is set to Average
and
the Drive type parameter is set to Field-oriented
control
.The default value is [14.85e-3,0.3027e-3]
.
The stator resistance, in ohms, leakage inductance, in henry,
and the d and q mutual inductances of the motor, in henry. This parameter
is visible only when the Model detail level parameter
is set to Average
and the Drive
type parameter is set to WFSM vector control
.
The default value is [2.01e-3,4.289e-4,4.477e-3,1.354e-3]
.
The rotor resistance, in ohms, and leakage inductance, in henry,
both referred to the stator. This parameter is visible only when the Model
detail level parameter is set to Average
and
the Drive type parameter is set to Field-oriented
control
. The default value is [9.295e-3,0.3027e-3]
.
The magnetizing inductance of the motor, in henry. This parameter
is visible only when the Model detail level parameter
is set to Average
and the Drive
type parameter is set to Field-oriented control
.
The default value is 10.46e-3
.
The default value is10.46e-3
.
The phase-to-neutral Ld and Lq inductances in the d-axis and
q-axis of the sinusoidal model with salient-pole rotor. This parameter
is visible only when the Model detail level parameter
is set to Average
and the Drive
type parameter is set to PMSM vector control
.
The default value is [8.5e-3,8.5e-3]
.
The armature inductance of the sinusoidal model with round rotor
(Ld is equal to Lq). This parameter is visible only when the Model
detail level parameter is set to Average
and
the Drive type parameter is set to Brushless
DC
. The default value is 8.5e-3
.
The stator phase resistance Rs, in ohms, of the motor. This
parameter is visible only when the Model detail level parameter
is set to Average
and the Drive
type parameter is set to PMSM vector control
.
The default value is 0.2
.
The constant flux, in weber, per pole pairs induced in the stator
windings by the magnets of the motor. This parameter is visible only
when the Model detail level parameter is set
to Average
and the Drive type parameter
is set to PMSM vector control
or Brushless
DC
. The default value is 0.175
.
The number of pole pairs of the machine controlled by the inverter.
This parameter is visible only when the Model detail level parameter
is set to Average
. The default value is 4
.
g
The gate input for the controlled switch devices. Pulses are
sent to upper and lower switches of inverter legs A, B, and C. This
input is visible only when the Model detail level parameter
is set to Detailed
.
ctrl
Control signals from the appropriate controller. In average
mode, the Inverter (Three-Phase) block no longer receives
pulses, but receives various types of other signals that are drive-type
specific. This input is visible only when the Model detail
level parameter is set to Average
and
the Drive type parameter is set to Field-oriented
control
, WFSM vector control
,
or PMSM vector control
.
Duty
The PWM duty cycles (or phase-voltage-to-DC-bus-voltage ratio)
of the inverter legs A, B, and C. This input is visible only when
the Model detail level parameter is set to Average
and
the Drive type parameter is set to Space
vector modulation
.
+
The positive terminal on the DC side.
-
The negative terminal on the DC side.
A, B, C
The three-phase terminals on the AC side.
The Inverter (Three-Phase) block is used in the AC1 to AC7 blocks of the Electric Drives library.
[1] Bose, B. K. Modern Power Electronics and AC Drives, NJ: Prentice-Hall, 2002.
[2] Erickson, R. W., and D. Maksimovic. Fundamentals of Power Electronics, Second Edition. NY: Kluwer Academic Publishers, 2004.