Introduction

This block estimates the power loss and junction temperature of the half-bridge or full-bridge submodules. It performs power loss estimation using lookup tables containing device switching and conduction loss characteristics. The lookup table for conduction loss requires information on current through the device and its junction temperature, while the lookup table for switching loss requires both current and temperature plus the voltage across the device. A switching logic block is also created to determine which device/s are incurring losses. The actual power losses are passed to a state-space model-based Foster Network to compute the junction temperature.

Figure 1: Schematic drawing of OPAL-RT Thermal Loss Model block

There are two types of Thermal Loss block available in the MMC Blockset. The main difference is the data size of the ‘Pulse’ port, where full-bridge expects 4 gating pulses, and half-bridge expects 2 gating pulses for each submodule.

Figure 2: Half and full-bridge submodules

Mask and Parameters

General tab

Name	Description	Unit
Number of SM	Number of submodules	None
Switching frequency	Carrier frequency or estimated switching frequency	Hz
Ambient temperature	Air temperature of environment where device is located.	°C
Time step	Simulation time step in seconds (default).	Seconds

Lookup table - Losses tab

Tabs:

Don - Diode turn-on loss, Doff - Diode turn-off loss, Dcond - Diode conduction loss

Ton - IGBT turn-on loss, Toff - IGBT turn-off loss, Tcond - IGBT conduction loss

Name	Description	Unit
Table data	Data value of the look-up table	J or V
Voltage axis	Breakpoints along voltage axis	V
Current axis	Breakpoints along current axis	A
Temperature axis	Breakpoints along Temperature axis	°C

Lookup table - Foster Network

Name	Description		Unit
Foster Network parameter Resistance vector	The thermal resistances used in the Foster network, positioning from outer layer to inner layer.		°C/W
Foster Network parameter Time Constant vector	The thermal time constant used in the Foster Network, positioning from outer layer to inner layer.		Seconds

Inputs, Outputs and Signals Available for Monitoring

Inputs

Name

Description

Unit

Size

Range

Vdc

the measured dc voltage at each submodule

[VdcSM1, VdcSM2, …, VdcSMN]

V

[1xN]

None

Iac

the measured ac current flows through each submodule

[IacSM1, IacSM2, …, IacSMN]

A

[1xN]

None

Pulse

the controlled gate pulses to full-bridge submodules. Refer to Figure 1 for the relevant position of switch index.

[Pulse_s1SM1, Pulse_s1SM2, …, Pulse_s1SMN]

[Pulse_s2SM1, Pulse_s2SM2, …, Pulse_s2SMN]…

pu

[1xN]

-1 to 1

Outputs

Name

Description

Unit

Size

Range

Power Loss

The switching (Sw) and conduction (Cond) power loss at each IGBT (T) and diode (D). Refer to Figure 1 for the relevant position of switch index.

[lossD1SwSM1, lossD1SwSM2,…, lossD1SwSMN]

[lossD2SwSM1, lossD1SwSM2,…, lossD2SwSMN]

W

[16xN]

0 to Inf

Switch Logic

The switching logic that determines the state of the device.

Logic

[24xN]

0 to 1

TjuncOut

The junction temperatures at each switching device.

°C

[8xN]

0 to Inf

Validation

Description

The following example demonstrates the advantage of the Thermal Loss Model block. The example model is based on a three-phase two-level converter test system at 10µs. The test system is modeled in both PLECS [2] and RT-LAB platforms as shown in the following figures:

Figure 3: Two-level converter in PLECS

Figures 4: Two-level converter with Opal Thermal Loss Model block in Simulink

Result Comparison

PLECS: Power loss and junction temperature measured in PLECS.

SPS: Power loss and junction temperature measured using OPAL-RT VSC Thermal Loss Block.

Figures 5: Estimation switching and conducting power loss at upper and lower switches

Figures 6: Measured junction temperature at upper and lower switches

Figures 7: Measured junction temperature at upper and lower switch (Zoom-in)

Limitations

The Thermal Loss Model block supports multi-dimensional junction temperature measuring. However, if the data characteristic is different between submodules, two or more blocks are required.

References

[1] ABB, “5SNA 1300K450300 StakPak IGBT Module,” Data Sheet, Doc. No. 5SYA 1432-02 01-2018, Jan. 2008, Accessed on: July. 23, 2021. [Online]. Available: https://new.abb.com/products/5SNA1300K450300/stakpak-igbt-module.

[2] PLEXIM, “Thermal Simulation Accounting for Switching and Conduction Losses”, Accessed on: July. 23, 2021. [Online]. Available: https://www.plexim.com/products/plecs/thermal.

See Also

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