Modular Multilevel Converter Leg

Modular multilevel converter leg with series-connected power submodules

Since R2020b

Libraries:
Simscape / Electrical / Semiconductors & Converters / Converters

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 — Semiconductor switch with an antiparallel diode. The control signal port G accepts values in the interval [0,1]. When G is equal to 0 or 1, the averaged switch is fully opened or fully closed respectively. The switch behaves similarly to the Ideal Semiconductor Switch block with an antiparallel diode. When G is between 0 and 1, the averaged switch is partly opened. You can average the pulse-width modulation (PWM) signal over a specified period. You can then undersample the model and use modulation waveforms instead of PWM signals.

Piecewise Constant Approximation in Averaged Switch for FPGA Deployment

If you set the Switching device parameter to Averaged switch and your model uses a partitioning solver, this block produces nonlinear partitions because the average mode equations include modes, G_sat that are functions of the input G. To make these equations compatible with hardware description language (HDL) code generation, and therefore FPGA deployment, set the Integer for piecewise constant approximation of gate input (0 for disabled) parameter to a value greater than 0. This block then treats the G_sat mode as a piecewise constant integer with a fixed range. This turns the previously nonlinear partitions to linear time varying partitions.

An integer value in the range [0,K], where K is the value of the Integer for piecewise constant approximation of gate input (0 for disabled), is now associated with each real value mode in the range [0,1]. The block computes the piecewise constant mode by dividing the original mode by K to normalize it back to the range [0,1]:

$\begin{array}{l} u_{I} = (f l o o r (u \cdot K)) \\ \hat{u} = \frac{u_{I}}{K} \end{array}$

Variables

To set the priority and initial target values for the block variables before simulation, use the Initial Targets section in the block dialog box or Property Inspector. For more information, see Set Priority and Initial Target for Block Variables.

Nominal values provide a way to specify the expected magnitude of a variable in a model. Using system scaling based on nominal values increases the simulation robustness. You can specify nominal values using different sources, including the Nominal Values section in the block dialog box or Property Inspector. For more information, see System Scaling by Nominal Values.

Ports

Input

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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

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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

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+ — 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

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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	Integer for piecewise constant approximation of gate input (0 for disabled)
	Gate turn-off voltage, Vgt_off			Holding current
	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-cathode voltage
IGBT — Gate-emitter 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.

Integer for piecewise constant approximation of gate input (0 for disabled) — Integer mode for FPGA deployment
`0` (default) | nonnegative scalar

Integer used to perform piecewise constant approximation of the gate input for FPGA deployment.

Dependencies

To enable this parameter, set Switching device to Averaged Switch.

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.