Three-Level Converter (Three-Phase)

Twelve-pulse three-phase three-level neutral-point clamped controlled converter

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Libraries:
Simscape / Electrical / Semiconductors & Converters / Converters

Description

The Three-Level Converter (Three-Phase) block models a twelve-pulse three-phase three-level neutral-point clamped controlled converter. You can use this block to connect a three-phase AC network to a three-level DC network.

Model

The block contains three bridge arms, each of which has four switching devices and the associated anti-parallel diodes. 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).

• Averaged Switch — Semiconductor switch with an anti-parallel diode. The control signal port, G, accepts values in the [0,1] interval. When the value at port G is equal to 0 or 1, the averaged switch is either fully opened or fully closed, and it behaves similarly to the Ideal Semiconductor Switch block with an anti-parallel diode. When the value at port G is between 0 and 1, the averaged switch is partly opened. You can then average the PWM signal over a specified period. This allows for undersampling of the model or using modulation waveforms instead of PWM signals.

Each component in the three-arm circuit is the same switching device that you specify. The switching devices are the same as the devices in the Semiconductors > Fundamental Components sublibrary.

The figure shows the equivalent circuit for the block using an Ideal Semiconductor block as the switching device.

You control the gate ports of the 12 switching devices via an input to the Three-Level Converter (Three-Phase) block G port.

1. Use a Twelve-Pulse Gate Multiplexer block to multiplex all 12 gate signals into a single vector.

2. Connect the output of the Twelve-Pulse Gate Multiplexer block to the Three-Level Converter (Three-Phase) block G port.

You use the Diodes tab of the block dialog box to include an integral protection diode for each switching device. An 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.

The table shows how to set the Integral protection diode 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 use the Snubbers tab of the block dialog box to include a snubber circuit for each switching device. Each snubber consists of a resistor and capacitor connected in series. Typically, a snubber circuit protects a switching device against very high voltages produced by an inductive load when the device turns off the voltage supply to the load. Snubber circuits also prevent excessive rates of change of current when a switching device turns on.

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]:

$$\begin{array}{l}{u}_I=\left(floor\left(u\cdot K\right)\right)\\ \widehat{u}=\frac{u_I}{K}\end{array}$$

Examples

Three-Phase Three-Level PWM Generator

Use the PWM Generator (Three-phase, Three-level) to control a Three-Level Converter. The upper and lower supply voltages are input to a Neutral point controller, which balances the DC-link capacitor voltages. Reference AC waveforms are used as inputs to the PWM Generator. There is one time scope for the controller waveforms.

• Open Model

Ports

Conserving

G — Gate terminals

electrical

Vector input port associated with the gate terminals of the switching devices. Connect this port to a Twelve-Pulse Gate Multiplexer block.

~ — Three-phase port

electrical

Expandable three-phase port.

Dependencies

To enable this port, set Electrical connection to Composite three-phase ports.

a — a-phase

electrical

Electrical conserving port associated with a-phase.

Dependencies

To enable this port, set Electrical connection to Expanded three-phase ports.

b — b-phase

electrical

Electrical conserving port associated with b-phase.

Dependencies

To enable this port, set Electrical connection to Expanded three-phase ports.

c — c-phase

electrical

Electrical conserving port associated with c-phase.

Dependencies

To enable this port, set Electrical connection to Expanded three-phase ports.

+ — Positive terminal

electrical

Electrical conserving port associated with the DC positive terminal.

0 — Neutral terminal

electrical

Electrical conserving port associated with the DC neutral terminal.

- — Negative terminal

electrical

Electrical conserving port associated with the DC negative terminal.

Parameters

Electrical connection — Electrical connection

Composite three-phase ports (default) | Expanded three-phase ports

Whether to have composite or expanded three-phase ports.

Switching device — Switching device

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

Converter switching device. The default value is Ideal Semiconductor Switch.

The switching devices you can select are:

• Switching Devices: GTO

• Switching Devices: Ideal Semiconductor Switch

• Switching Devices: IGBT

• Switching Devices: MOSFET

• Switching Devices: Averaged Switch

Dependencies

Multiple additional parameters will become visible depending on the choice of the specific switching device.

Switching Devices: GTO

For more information, see GTO.

The parameters for this switching device will be visible only if you select it in the Switching device parameter.

Forward voltage, Vf — Forward voltage

0.8 V (default)

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.

On-state resistance — On-state resistance

0.001 Ohm (default)

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

Off-state Conductance — Off-state conductance

1e-6 1/Ohm (default)

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

Gate trigger voltage, Vgt — Gate trigger voltage

1 V (default)

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

Gate turn-off voltage, Vgt_off — Gate turn-off voltage

-1 V (default)

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

Holding current — Holding current

1 A (default)

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.

Switching Devices: Ideal Semiconductor Switch

For more information, see Ideal Semiconductor Switch.

The parameters for this switching device will be visible only if you select it in the Switching device parameter.

On-state resistance — On-state resistance

0.001 Ohm (default)

Anode-cathode resistance when the device is on.

Off-state Conductance — Off-state conductance

1e-6 1/Ohm (default)

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

Threshold voltage, Vth — Threshold voltage

6 V (default)

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

Switching Devices: IGBT

For more information, see IGBT (Ideal, Switching).

The parameters for this switching device will be visible only if you select it in the Switching device parameter.

Forward voltage, Vf — Forward voltage

0.8 V (default)

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.

On-state resistance — On-state resistance

0.001 Ohm (default)

Collector-emitter resistance when the device is on.

Off-state Conductance — Off-state conductance

1e-6 1/Ohm (default)

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

Threshold voltage, Vth — Threshold voltage

6 V (default)

Gate-emitter voltage at which the device turns on.

Switching Devices: MOSFET

For more information, see MOSFET (Ideal, Switching).

The parameters for this switching device will be visible only if you select it in the Switching device parameter.

Drain-source on resistance, R_DS(on) — Drain-source on resistance

0.001 Ohm (default)

Drain-source resistance when the device is on.

Off-state Conductance — Off-state conductance

1e-6 1/Ohm (default)

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

Threshold voltage, Vth — Threshold voltage

6 V (default)

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

Switching Devices: Averaged Switch

The parameters for this switching device will be visible only if you select it in the Switching device parameter.

On-state resistance — On-state resistance

0.001 Ohm (default)

Anode-cathode resistance when the device is on.

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.

Integral Diodes

Integral protection diode — Integral protection diode

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

Integral protection diode for each switching device.

The diodes you can select are:

• Diode with no dynamics

• Diode with charge dynamics

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.

Forward voltage — Forward voltage

0.8 V (default)

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.

On resistance — On resistance

0.001 Ohm (default)

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

Off conductance — Off conductance

1e-5 1/Ohm (default)

Conductance of the reverse-biased diode.

Junction capacitance — Junction capacitance

50e-9 F (default)

Diode junction capacitance.

Dependencies

To enable this parameter, set Integral protection diode 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. The default value is -235 A.

Dependencies

To enable this parameter, set Integral protection diode 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 Integral protection diode to Diode with charge dynamics.

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

-50A/μs (default) | negative scalar

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

Dependencies

To enable this parameter, set Integral protection diode to Diode with charge dynamics.

Reverse recovery time parameterization — Reverse recovery time parameterization

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

Determines how you specify reverse recovery time in the block. The default value is Specify reverse recovery time directly.

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 Integral protection diode to Diode with charge dynamics.

Reverse recovery time, trr — Reverse recovery time

15 μs (default)

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 Integral protection diode 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)

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 Integral protection diode to Diode with charge dynamics and Reverse recovery time parameterization to Specify stretch factor.

Reverse recovery charge, Qrr — Reverse recovery charge

1500 μAs (default)

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

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

For more information on these parameters, see Diode.

Snubbers

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

Snubber — Snubber

None (default) | RC snubber

Snubber for each switching device:

• None - This is the default value.

• RC snubber

Snubber resistance — Snubber resistance

0.1 Ohm (default)

Snubber resistance.

Dependencies

This parameter is visible only when the Snubber parameter is set to RC snubber.

Snubber capacitance — Snubber capacitance

1e-7 F (default)

Snubber capacitance.

Dependencies

This parameter is visible only when the Snubber parameter is set to RC snubber.

Extended Capabilities

C/C++ Code Generation
Generate C and C++ code using Simulink® Coder™.

Version History

Introduced in R2014b

R2021b: Electrical connection ports update

From R2021b forward, to switch between composite and expanded ports, set the Electrical connection parameter to either Composite three-phase ports or Expanded three-phase ports.

As a result of these changes, inside a model saved in an earlier release, review the Electrical connection parameter of this block.