Modular Multilevel Converter Leg

Modular multilevel converter leg with series-connected power submodules

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Description

The Modular Multilevel Converter Leg block models a modular multilevel converter leg as a two arms that are implemented with a number of series-connected power submodules.

Half-Bridge Topology

Full-Bridge Topology

This blocks allows you to select the level of model fidelity by choosing between a detailed model with switching devices or an equivalent model. You can choose from these 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.

Variables

Use the Variables settings to specify the priority and initial target values for the block variables before simulation. For more information, see Set Priority and Initial Target for Block Variables.

Ports

Input

G — Submodule gate control

vector of physical signals

Physical signal port associated with the gate signal for all submodules of the modular multilevel converter leg, specified as a vector of physical signals.

If you set the Converter topology parameter to Half-bridge, the output is a vector of length 4 * Nsm, where Nsm is the Number of power submodules.

If you set the Converter topology parameter to Full-bridge, the output is a vector of length 8 * Nsm.

Dependencies

To enable this port, set Fidelity level to Detailed model - switching devices or Equivalent model - PWM-controlled.

ref — Submodules reference waveform

vector of physical signals

Physical signal port associated with the reference waveforms, specified as a vector of physical signals of length 2.

Dependencies

To enable this port, set Fidelity level to Equivalent model - waveform-controlled.

Output

vc — Capacitor voltages

vector of physical signals

Physical signal port associated with the capacitor voltages for each submodule in the modular multilevel converter leg, specified as a vector of physical signals.

Dependencies

To enable this port, set Capacitor voltages to Instrumented.

Conserving

+ — Positive terminal

electrical

Electrical conserving port associated with the positive terminal of the modular multilevel converter leg.

- — Negative terminal

electrical

Electrical conserving port associated with the negative terminal of the modular multilevel converter leg.

a — Phase a terminal

electrical

Electrical conserving port associated with the single-phase terminal of the modular multilevel converter leg.

Parameters

Main

Converter topology — Converter topology

Half-bridge (default) | Full-bridge

Topology of the modular multilevel converter.

Fidelity level — Model fidelity

Detailed model - switching devices (default) | Equivalent model - PWM-controlled | Equivalent model - waveform-controlled

Level of fidelity of the model.

Capacitor voltages — Capacitor voltage instrumentation

Instrumented (default) | Uninstrumented

Whether to instrument the capacitor voltages.

Number of power submodules — Number of submodules

1 (default) | positive scalar

Number of power submodules of the modular multilevel converter.

Capacitance — Submodule capacitance

1e-7 F (default) | scalar | vector

Capacitance of a submodule. If you enter a vector, the vector must be of length 2 * Nsm, where Nsm is the Number of power submodules.

Capacitor effective series resistance — Capacitor effective series resistance

1e-6 Ohm (default) | scalar | vector

Capacitor effective series resistance. If you enter a vector, the vector must be of length 2 * Nsm, where Nsm is the Number of power submodules.

Dependencies

To enable this parameter, set Fidelity level to Detailed model - switching devices.

Arm inductance — Arm inductance

1e-6 H (default) | scalar

Inductance of the arm.

Arm inductance series resistance — Arm inductance series resistance

0 Ohm (default) | scalar

Arm inductance series resistance.

Capacitor initial voltage — Capacitor initial voltage

500 V (default) | scalar | vector

Initial voltage of the capacitor. If you enter a vector, the vector must be of length 2 * Nsm, where Nsm is the Number of power submodules.

Switching Devices

This table shows how enabled parameters in the Switching Devices settings depend on the Switching device that you select. To learn how to read the table, see Parameter Dependencies. To enable these settings, set Fidelity level to Detailed model - switching devices.

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			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 V (default) | scalar

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

• 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 the:

• GTO — Rate of change of the voltage versus the 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. The gate-to-source voltage also affects the Drain-source on resistance parameter.

Dependencies

See the Switching Devices Parameter Dependencies table.

Off-state conductance — Conductance when device is off

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 the:

• 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. The voltage threshold applies to different devices depending on the switching device used:

• 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 — Gate-cathode activation 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 — Gate-cathode deactivation 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 Diodes

For more information on these parameters, see Diode.

Model dynamics — Diode model

Diode with no dynamics (default) | Diode with charge dynamics | None

Diode type. The options are:

• None — The block does not model diode dynamics.

• 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 set Switching device to Averaged Switch in the Switching Device settings, the Diode with no dynamics setting is automatically selected.

Dependencies

To enable this parameter, set Switching device to GTO, Ideal Semiconductor Switch, IGBT, MOFSET, or Thyristor.

Forward voltage — Forward voltage

0.8 V (default) | scalar

Minimum voltage required across the + and - 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.

Dependencies

To enable this parameter, set Model dynamics to Diode with no dynamics or Diode with charge dynamics.

On resistance — On resistance

0.001 Ohm (default) | scalar

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

Dependencies

To enable this parameter, set Model dynamics to Diode with no dynamics or Diode with charge dynamics.

Off conductance — Off conductance

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

Conductance of the reverse-biased diode.

Dependencies

To enable this parameter, set Model dynamics to Diode with no dynamics or Diode with charge dynamics.

Junction capacitance — Junction capacitance

50 nF (default) | scalar

Diode junction capacitance.

Dependencies

To enable this parameter, set Model dynamics to Diode with charge dynamics.

Peak reverse current, iRM — Peak reverse current

-235 A (default) | negative scalar

Peak reverse current measured by an external test circuit. This value must be less than zero.

Dependencies

To enable this parameter, set Model dynamics to Diode with charge dynamics.

Initial forward current when measuring iRM — Initial forward current when measuring iRM

300 A (default) | positive scalar

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

Dependencies

To enable this parameter, set Model dynamics to Diode with charge dynamics.

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

-50 A/μs (default) | negative scalar

Rate of change of the current when measuring the peak reverse current. This value must be less than zero.

Dependencies

To enable this parameter, set Model dynamics to Diode with charge dynamics.

Reverse recovery time parameterization — Reverse recovery time option

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

Determines how you specify reverse recovery time.

If you select Specify stretch factor or Specify reverse recovery charge, you 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

To enable this parameter, set Model dynamics to Diode with charge dynamics.

Reverse recovery time, trr — Reverse recovery time

15 μs (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% 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

To enable this parameter, set Model dynamics to Diode with charge dynamics and Reverse recovery time parameterization to Specify reverse recovery time directly.

Reverse recovery time stretch factor — Reverse recovery time stretch factor

3 (default) | scalar

Value that the block uses to calculate Reverse recovery time, trr. This value must be greater than 1. 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

To enable this parameter, set Model dynamics to Diode with charge dynamics and Reverse recovery time parameterization to Specify stretch factor.

Reverse recovery charge, Qrr — Reverse recovery charge

1500 s*μA (default) | scalar

Value that the block uses to calculate Reverse recovery time, trr. Use this parameter if the data sheet for your diode 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

To enable this parameter, set Model dynamics to Diode with charge dynamics and Reverse recovery time parameterization to Specify reverse recovery charge.

Snubbers

To enable the Snubbers settings, set Fidelity level to Detailed model - switching devices and Switching device to GTO, Ideal Semiconductor Switch, IGBT, MOFSET, or Thyristor.

Snubber — Snubber

None (default) | RC snubber

Snubber for each switching device:

• None

• RC snubber

Snubber resistance — Snubber resistance

0.1 Ohm (default) | scalar

Snubber resistance.

Dependencies

To enable this parameter, set Snubber to RC snubber.

Snubber capacitance — Snubber capacitance

1e-7 F (default) | scalar

Snubber capacitance.

Dependencies

To enable this parameter, set Snubber to RC snubber.

References

[1] Saad, Hani, Sebastien Dennetiere, and Jean Mahseredjian. “On Modelling of MMC in EMT-Type Program.” 2016 IEEE 17th Workshop on Control and Modeling for Power Electronics (COMPEL), 1–7. Trondheim, Norway: IEEE, 2016. https://doi.org/10.1109/COMPEL.2016.7556717.

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