Implement universal power converter with selectable topologies and power electronic devices
Fundamental Blocks/Power Electronics
The Universal Bridge block implements a universal three-phase power converter that consists of up to six power switches connected in a bridge configuration. The type of power switch and converter configuration are selectable from the dialog box.
The Universal Bridge block allows simulation of converters using both naturally commutated (or line-commutated) power electronic devices (diodes or thyristors) and forced-commutated devices (GTO, IGBT, MOSFET).
The Universal Bridge block is the basic block for building two-level voltage-sourced converters (VSC).
The device numbering is different if the power electronic devices are naturally commutated or forced-commutated. For a naturally commutated three-phase converter (diode and thyristor), numbering follows the natural order of commutation:
For the case of a two-phase diode or thyristor bridge, and for any other bridge configuration, the order of commutation is the following:
MOSFET-Diode and Ideal Switch bridges:
2 to get a
single-phase converter (two or four switching devices). Set to
get a three-phase converter connected in Graetz bridge configuration
(six switching devices). Default is
The snubber resistance, in ohms (Ω). Default is
Set the Snubber resistance Rs parameter
inf to eliminate the snubbers from the model.
The snubber capacitance, in farads (F). Default is
Set the Snubber capacitance Cs parameter
0 to eliminate the snubbers, or to
get a resistive snubber.
When you are using the continuous solver you can eliminate snubbers in all power electronic devices if you select the Disable snubbers in switching devices option in the Preference tab of the Powergui block
When your system is discretized, you can simulate power electronic devices with virtually no snubbers by specifying purely resistive snubbers with a very large resistance, thus producing negligible leakage currents. The bridge operates satisfactorily with purely resistive snubbers.
Select the type of power electronic device to use in the bridge.
When you select
Switching-function based VSC,
a switching-function voltage source converter type equivalent model
is used, where switches are replaced by two voltage sources on the
AC side and a current source on the DC side. This model uses the same
firing pulses as for other power electronic devices and it correctly
represents harmonics normally generated by the bridge.
When you select
Average-model based VSC,
an average-model type of voltage source converter is used to represent
the power-electronic switches. Unlike the other power electronic devices,
this model uses the reference signals (uref) representing the average
voltages generated at the ABC terminals of the bridge. This model
does not represent harmonics. It can be used with larger sample times
while preserving the average voltage dynamics.
an example comparing these two models to an Universal Bridge block
using IGBT/Diode device.
Internal resistance of the selected device, in ohms (Ω).
Internal inductance, in henries (H), for the diode or the thyristor
device. Default is
0. When the bridge is discretized,
the Lon parameter must be set to zero.
This parameter is available only when the selected Power electronic device is
Forward voltage, in volts (V), across the device when it is
conducting. Default is
This parameter is available when the selected Power
electronic device is
Forward voltages, in volts (V), of the forced-commutated devices
(GTO, MOSFET, or IGBT) and of the antiparallel diodes. Default is
0 0 ].
Device voltages to measure
the voltages across the six power electronic device terminals.
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
UAB UBC UCA UDC voltages to
measure the terminal voltages (AC and DC) of the Universal Bridge
All voltages and currents to
measure all voltages and currents defined for the Universal Bridge
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.
The gate input for the controlled switch devices. The pulse ordering in the vector of the gate signals corresponds to the switch number indicated in the six circuits shown in the Description section. For the diode and thyristor bridges, the pulse ordering corresponds to the natural order of commutation. For all other forced-commutated switches, pulses are sent to upper and lower switches of phases A, B, and C.
Pulse Vector of Input g
illustrates the use of one Universal Bridge block in
an ac/dc/ac converter to model a diode rectifier feeding an IGBT inverter
through a DC link.