Two-Quadrant Chopper

Two-quadrant controlled DC-DC chopper

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• Simscape / Electrical / Semiconductors & Converters / Converters

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Description

The Two-Quadrant Chopper block represents a two-quadrant controlled chopper for converting a fixed DC input to a variable DC output. The block contains two switching devices. Options for the type of switching devices are:

• GTO — Gate turn-off thyristor. For information about the I-V characteristic of the device, see GTO.

• Ideal semiconductor switch — For information about the I-V characteristic of the device, see Ideal Semiconductor Switch.

• IGBT — Insulated-gate bipolar transistor. For information about the I-V characteristic of the device, see IGBT (Ideal, Switching).

• MOSFET — N-channel metal-oxide-semiconductor field-effect transistor. For information about the I-V characteristic of the device, see MOSFET (Ideal, Switching).

• Thyristor — For information about the I-V characteristic of the device, see Thyristor (Piecewise Linear).

• Averaged Switch.

Model

There are two model variants for the block. To access the model variants, in the model window, right-click the block. From the context menu, select Simscape > Block choices.

The model variants are:

• First- and second- quadrant chopper. This block choice is the default. The figures show the equivalent circuit and the operation for the first- and second- quadrant model.

  

  

• First- and fourth- quadrant chopper. The figures show the equivalent circuit and the operation for the first- and fourth- quadrant model.

  

  

Protection

The block contains an integral protection diode for each switching device. The integral diode protects the semiconductor device by providing a conduction path for reverse current. An inductive load can produce a high reverse-voltage spike when the semiconductor device suddenly switches off the voltage supply to the load.

To configure the internal protection diode block, use the Diode parameters. This table shows how to set the Model dynamics parameter based on your goals.

Goals	Value to Select	Integral Protection Diode
Prioritize simulation speed.	Diode with no dynamics	The Diode block
Prioritize model fidelity by precisely specifying reverse-mode charge dynamics.	Diode with charge dynamics	The dynamic model of the Diode block

You can also include a snubber circuit for each switching device. Snubber circuits contain a series-connected resistor and capacitor. They protect switching devices against high voltages that inductive loads produce when the device turns off the voltage supply to the load. Snubber circuits also prevent excessive rates of current change when a switching device turns on.

To include and configure a snubber circuit for each switching device, use the Snubbers parameters.

Gate Control

To connect Simulink^® gate-control voltage signals to the gate ports of the internal switching devices:

1. Convert each voltage signal using a Simulink-PS Converter block.

2. Multiplex the converted gate signals into a single vector using a Two-Pulse Gate Multiplexer block.

3. Connect the vector signal to the G port.

Ports

Conserving

G — Switching device gate control

electrical | vector

Electrical conserving port associated with the gate terminals of the switching devices.

Data Types: double

1+ — Positive DC voltage 1

electrical | scalar

Electrical conserving port associated with the positive terminal of the first DC voltage.

Data Types: double

1- — Negative DC voltage 1

electrical | scalar

Electrical conserving port associated with the negative terminal of the first DC voltage.

Data Types: double

2+ — Positive DC voltage 2

electrical | scalar

Electrical conserving port associated with the positive terminal of the second DC voltage.

Data Types: double

2- — Negative DC voltage 2

electrical | scalar

Electrical conserving port associated with the negative terminal of the second DC voltage.

Data Types: double

Parameters

Switching Devices

This table shows how the visibility of Switching Devices parameters depends on the Switching device that you select. To learn how to read the table, see Parameter Dependencies.

Switching Devices Parameter Dependencies

Parameters and Options
Switching device
Ideal Semiconductor Switch	GTO	IGBT	MOSFET	Thyristor	Averaged Switch
On-state resistance	Forward voltage	Forward voltage	Drain-source on resistance	Forward voltage	On-state resistance
Off-state conductance	On-state resistance	On-state resistance	Off-state conductance	On-state resistance
Threshold voltage	Off-state conductance	Off-state conductance	Threshold voltage	Off-state conductance
	Gate trigger voltage, Vgt	Threshold voltage		Gate trigger voltage, Vgt
	Gate turn-off voltage, Vgt_off			Gate turn-off voltage, Vgt_off
	Holding current			Holding current

Switching device — Switch type

Ideal Semiconductor Switch (default) | GTO | IGBT | MOSFET | Thyristor | Averaged Switch

Switching device type for the converter.

Dependencies

See the Switching Devices Parameter Dependencies table.

Forward voltage — Voltage

0.8 Ohm (default) | scalar

For the different switching device types, the Forward voltage is taken as:

• GTO — Minimum voltage required across the anode and cathode block ports for the gradient of the device I-V characteristic to be 1/R_on, where R_on is the value of On-state resistance

• IGBT — Minimum voltage required across the collector and emitter block ports for the gradient of the diode I-V characteristic to be 1/R_on, where R_on is the value of On-state resistance

• Thyristor — Minimum voltage required for the device to turn on

Dependencies

See the Switching Devices Parameter Dependencies table.

On-state resistance — Resistance

0.001 Ohm (default) | scalar

For the different switching device types, the On-state resistance is taken as:

• GTO — Rate of change of voltage versus current above the forward voltage

• Ideal semiconductor switch — Anode-cathode resistance when the device is on

• IGBT — Collector-emitter resistance when the device is on

• Thyristor — Anode-cathode resistance when the device is on

• Averaged switch — Anode-cathode resistance when the device is on

Dependencies

See the Switching Devices Parameter Dependencies table.

Drain-source on resistance — Resistance

0.001 Ohm (default) | scalar

Resistance between the drain and the source, which also depends on the gate-to-source voltage.

Dependencies

See the Switching Devices Parameter Dependencies table.

Off-state conductance — Conductance

1e-5 1/Ohm (default) | scalar

Conductance when the device is off. The value must be less than 1/R, where R is the value of On-state resistance.

For the different switching device types, the On-state resistance is taken as:

• GTO — Anode-cathode conductance

• Ideal semiconductor switch — Anode-cathode conductance

• IGBT — Collector-emitter conductance

• MOSFET — Drain-source conductance

• Thyristor — Anode-cathode conductance

Dependencies

See the Switching Devices Parameter Dependencies table.

Threshold voltage — Voltage threshold

6 V (default) | scalar

Gate voltage threshold. The device turns on when the gate voltage is above this value. For the different switching device types, the device voltage of interest is:

• Ideal semiconductor switch — Gate-emitter voltage

• IGBT — Gate-cathode voltage

• MOSFET — Gate-source voltage

Dependencies

See the Switching Devices Parameter Dependencies table.

Gate trigger voltage, Vgt — Voltage threshold

1 V (default) | scalar

Gate-cathode voltage threshold. The device turns on when the gate-cathode voltage is above this value.

Dependencies

See the Switching Devices Parameter Dependencies table.

Gate turn-off voltage, Vgt_off — Voltage threshold

-1 V (default) | scalar

Gate-cathode voltage threshold. The device turns off when the gate-cathode voltage is below this value.

Dependencies

See the Switching Devices Parameter Dependencies table.

Holding current — Current threshold

1 A (default) | scalar

Gate current threshold. The device stays on when the current is above this value, even when the gate-cathode voltage falls below the gate trigger voltage.

Dependencies

See the Switching Devices Parameter Dependencies table.

Protection Diode

The visibility of Diode parameters depends on how you configure the protection diode Model dynamics and Reverse recovery time parameterization parameters. To learn how to read this table, see Parameter Dependencies.

Protection Diode Parameter Dependencies

Parameters and Options
Model dynamics
Diode with no dynamics	Diode with charge dynamics
Forward voltage	Forward voltage
On resistance	On resistance
Off conductance	Off conductance
	Junction capacitance
	Peak reverse current, iRM
	Initial forward current when measuring iRM
	Rate of change of current when measuring iRM
	Reverse recovery time parameterization
	Specify stretch factor	Specify reverse recovery time directly	Specify reverse recovery charge
	Reverse recovery time stretch factor	Reverse recovery time, trr	Reverse recovery charge, Qrr

Model dynamics — Diode model

Diode with no dynamics (default) | Diode with charge dynamics

Diode type. The options are:

• Diode with no dynamics — Select this option to prioritize simulation speed using the Diode block.

• Diode with charge dynamics — Select this option to prioritize model fidelity in terms of reverse mode charge dynamics using the commutation diode model of the Diode block.

Note

If you select Averaged Switch for the Switching Device parameter in the Switching Device setting, this parameter is not visible and Diode with no dynamics is automatically selected.

Dependencies

See the Protection Diode Parameter Dependencies table.

Forward voltage — Voltage

0.8 V (default) | scalar

Minimum voltage required across the positive and negative block ports for the gradient of the diode I-V characteristic to be 1/R_on, where R_on is the value of On resistance.

On resistance — Resistance

0.001 Ohm (default) | scalar

Rate of change of voltage versus current above the Forward voltage.

Off conductance — Conductance

1e-5 1/Ohm (default) | scalar

Conductance of the reverse-biased diode.

Junction capacitance — Capacitance

50 nF (default) | scalar

Diode junction capacitance.

Dependencies

See the Protection Diode Parameter Dependencies table.

Peak reverse current, iRM — Current

-235 A (default) | scalar less than 0

Peak reverse current measured by an external test circuit.

Dependencies

See the Protection Diode Parameter Dependencies table.

Initial forward current when measuring iRM — Current

300 A (default) | scalar greater than 0

Initial forward current when measuring peak reverse current. This value must be greater than zero.

Dependencies

See the Protection Diode Parameter Dependencies table.

Rate of change of current when measuring iRM — Current change rate

-50 A/us (default) | scalar

Rate of change of current when measuring peak reverse current.

Dependencies

See the Protection Diode Parameter Dependencies table.

Reverse recovery time parameterization — Recovery-time model

Specify stretch factor (default) | Specify reverse recovery time directly | Specify reverse recovery charge

Model for parameterizing the recovery time. When you select Specify stretch factor or Specify reverse recovery charge, you can specify a value that the block uses to derive the reverse recovery time. For more information on these options, see How the Block Calculates TM and Tau.

Dependencies

See the Protection Diode Parameter Dependencies table.

Reverse recovery time stretch factor — Stretch factor

3 (default) | scalar greater than 1

Value that the block uses to calculate Reverse recovery time, trr. Specifying the stretch factor is an easier way to parameterize the reverse recovery time than specifying the reverse recovery charge. The larger the value of the stretch factor, the longer it takes for the reverse recovery current to dissipate.

Dependencies

See the Protection Diode Parameter Dependencies table.

Reverse recovery time, trr — Time

15 us (default) | scalar

Interval between the time when the current initially goes to zero (when the diode turns off) and the time when the current falls to less than 10 percent of the peak reverse current.

The value of the Reverse recovery time, trr parameter must be greater than the value of the Peak reverse current, iRM parameter divided by the value of the Rate of change of current when measuring iRM parameter.

Dependencies

See the Protection Diode Parameter Dependencies table.

Reverse recovery charge, Qrr — Charge

1500 s*uA (default) | scalar

Value that the block uses to calculate Reverse recovery time, trr. Use this parameter if the data sheet for your diode device specifies a value for the reverse recovery charge instead of a value for the reverse recovery time.

The reverse recovery charge is the total charge that continues to dissipate when the diode turns off. The value must be less than $$-\frac{i^2{}_{RM}}{2a}$$,

where:

• i_RM is the value specified for Peak reverse current, iRM.

• a is the value specified for Rate of change of current when measuring iRM.

Dependencies

See the Protection Diode Parameter Dependencies table.

Snubbers

The Snubbers parameters tab is not visible if you set Switching device to Averaged Switch.

The table summarizes the Snubbers parameter dependencies. To learn how to read the table, see Parameter Dependencies.

Snubbers Parameter Dependencies

Snubbers Parameter Dependencies
Snubber
None	RC Snubber
	Snubber resistance
	Snubber capacitance

Snubber — Snubber model

None (default) | RC snubber

Switching device snubber.

Dependencies

See the Snubbers Parameter Dependencies table.

Snubber resistance — Resistance

0.1 Ohm (default) | scalar

Resistance of the switching device snubber.

Dependencies

See the Snubbers Parameter Dependencies table.

Snubber capacitance — Capacitance

1e-7 (default) | F | scalar

Capacitance of the switching device snubber.

Dependencies

See the Snubbers Parameter Dependencies table.

Model Examples

First and Fourth Quadrant Chopper Control

Control a two-quadrant chopper. The two-quadrant chopper operates in the first and fourth quadrants, allowing positive and negative output voltage. The Control subsystem implements a simple PI-based control algorithm for controlling the output current. The total simulation time (t) is 0.5 seconds. At t = 0.25 seconds, the polarity of the load DC source E is changed.

First and Second Quadrant Chopper Control

Control a two-quadrant chopper. The two-quadrant chopper operates in the first and second quadrants, allowing positive and negative output current. The Control subsystem implements a simple PI-based control algorithm for controlling the output current. The load of the system is considered constant throughout the simulation.

Synchronous Machine State-Space Control

Control currents in a synchronous machine (SM) based traction drive using state-space control. A high-voltage battery feeds the SM through a controlled three-phase converter for the stator windings and through a controlled two-quadrant chopper for the rotor winding. An ideal angular velocity source provides the load. The SM operates below the base speed. At each sample instant, the torque request is converted to relevant current references using the zero d-axis control approach. A state-feedback controller controls the currents in the rotor reference frame. A Luenberger observer obtains the velocity-dependent feedforward pre-control terms. The simulation uses several torque steps in both motor and generator modes. The task scheduling is implemented as a Stateflow® state machine. The Scopes subsystem contains scopes that allow you to see the simulation results.

Three-Phase Synchronous Machine Drive

Control the rotor speed in a Synchronous Machine (SM) based electrical drive. A high-voltage battery feeds the SM through a controlled three-phase converter for the stator windings and through a controlled two-quadrant chopper for the rotor winding. Use the model to design the SM controller, selecting architecture and gains to achieve desired performance. The Scopes subsystem contains scopes that allow you to see the simulation results.

References

[1] Trzynadlowski, A. M. Introduction to Modern Power Electronics, 2nd Edition. Hoboken, NJ: John Wiley & Sons Inc., 2010.

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