Description

Thermal loss feature is divided in two parts. There is the conducting losses and the switching losses. The energy dissipated in each power switch is computed on FPGA at the same sampling rate used by the eHS solver. These losses are for monitoring purposes only as they do not affect the simulation results of the eHS solver. Temperature elevation for each devices is computed in the CPU using either a Cauer model or a Foster model. The module only works with "Universal Bridge" block (1, 2, or 3 phases). The AC-current and the DC-voltage need to be measured. Current polarity should be considered positive when exiting the converter. The positive sign of the measurement should be on the converter side, and the negative sign of the measurement on the load side. In the picture below, Y01 is the DC-voltage measurement, Y02 is the current measurement associated with the switches 1 and 2 (phase A), Y03 is the current measurement associated with the switches 3 and 4 (phase B), and Y04 is the current measurement associated with the switches 5 and 6 (phase C).

Conducting losses are due to the forward voltage of the different devices, and the current flowing in the device. The foward voltage, or VCE, is function of the current and the temperature. In case of short-circuit of the DC-bus, by turning ON both the upper and lower switches, the current is computed using the DC-bus voltage, and the Ron value of the switches.

Switching losses, turn ON and turn OFF, are due to the transition of the voltage across the switch, and the current going through it. During a transition, voltage across the switch can be as high as the DC-bus, while the current is not zero yet, yielding large losses for a very short period of time. Since they can even last less than a simulation time-step, they are represented in Joule, and they need to be divided by the simulation time-step in order to get them in watts to compute the temperature variation of the device.

Parameters to configure the feature are grouped by Thermal model, 1 to 4, and by devices, switch and diode characteristics. The different lookup table and break point are explained below.

Conducting losses

VCE lookup table [V]: This parameter indicate the foward voltage when the component conducting. It is given by a 2-dimension lookup table. It is function of the device current and temperature. Temperature has a maximum of 4 break points and current a maximum of 16 break points. Therefore the lookup table has a maximum size of 4 lines, by 16 columns. (size(switchLosses.conductingVce) = [4, 16])

VCE lookup table when diode/switch conducting [V] : This parameter is only used in the case of a MOSFET, where the switch can conduct a reverse current. In this case, conducting losses will be decipated in both the switch and the diode, if the switch is conducting when the current is in reverse. The table is given by a 2-dimension lookup table. It is function of the device current and temperature. Temperature has a maximum of 4 break points and current a maximum of 16 break points. Therefore the lookup table has a maximum size of 4 lines, by 16 columns. (size(switchLosses.reverseConductingVce) = [4, 16])

Switch/Diode current axis breakpoints [Amps]: This parameter indicate the different break point for the current axis of the VCE lookup table. A minimum of 2 break points are required and a maximum of 16 break points is supported.

Temperature axis breakpoints [Degrees Celsius]: This parameter indicate the different break point for the temperature axis of the VCE lookup table. A minimum of 1 break points is required and a maximum of 4 break points is supported.

Switching losses

TurnOn lookup table [J]: This parameter indicate the number of joule dissipated during turn ON. It is given by a 3-dimension lookup table. It is function of the device current, voltage, and temperature. Temperature and Voltage have a maximum of 4 break points, and current a maximum of 16 break points. Therefore the lookup table has a maximum size of 4 lines for the voltages, by 16 columns for the currents, by 4 depth for the temperature. (size(switchLosses.turnOnTable) = [4, 16, 4])

TurnOff lookup table [J]: This parameter indicate the number of joule dissipated during turn OFF. It is given by a 3-dimension lookup table. It is function of the device current, voltage, and temperature. Temperature and Voltage have a maximum of 4 break points, and current a maximum of 16 break points. Therefore the lookup table has a maximum size of 4 lines for the voltages, by 16 columns for the currents, by 4 depth for the temperature. (size(switchLosses.turnOffTable) = [4, 16, 4])

Switch/Diode current axis breakpoints [Amps]: This parameter indicate the different break point for the current axis of the Turn ON/OFF lookup table. A minimum of 2 break points are required and a maximum of 16 break points is supported.

DC Voltage axis breakpoints [Volts]: This parameter indicate the different break point for the voltage axis of the Turn ON/OFF lookup table. A minimum of 1 break points is required and a maximum of 4 break points is supported.

Temperature axis breakpoints [Degrees Celsius]: This parameter indicate the different break point for the temperature axis of the Turn ON/OFF lookup table. A minimum of 1 break points is required and a maximum of 4 break points is supported.

Characteristics and limitations

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