Bidirectional DC-DC

DC-to-DC converter that supports bidirectional boost and buck

• 

Libraries:
Powertrain Blockset / Energy Storage and Auxiliary Drive / DC-DC

Description

The Bidirectional DC-DC block implements a DC-to-DC converter that supports bidirectional boost and buck (lower) operation. Unless the DC-to-DC conversion limits the power, the output voltage tracks the voltage command. You can specify electrical losses or measured efficiency.

Depending on your battery system configuration, the voltage might not be at a potential that is required by electrical system components such has inverters and motors. You can use the block to boost or buck the voltage. Connect the block to the battery and one of these blocks:

• Mapped Motor

• IM Controller

• Interior PM Controller

• Surface Mount PM Controller

To calculate the electrical loss during the DC-to-DC conversion, use Parameterize losses by.

Parameter Option	Description
Single efficiency measurement	Electrical loss calculated using a constant value for conversion efficiency.
Tabulated loss data	Electrical loss calculated as a function of load current and voltage. DC-to-DC converter data sheets typically provide loss data in this format. When you use this option, provide data for all the operating quadrants in which the simulation will run. If you provide partial data, the block assumes the same loss pattern for other quadrants. The block does not extrapolate loss that is outside the range voltage and current that you provide. The block allows you to account for fixed losses that are still present for zero voltage or current. If you have Model-Based Calibration Toolbox™, click Calibrate Maps to virtually calibrate the 2-D lookup table using measured data.
Tabulated efficiency data	Electrical loss calculated using conversion efficiency that is a function of load current and voltage. When you use this option, provide data for all the operating quadrants in which the simulation will run. If you provide partial data, the block assumes the same efficiency pattern for other quadrants. The block: Assumes zero loss when either the voltage or current is zero. Uses linear interpolation to determine the loss. At lower power conditions, for calculation accuracy, provide efficiency at low voltage and low current.

Note

The block does not support inversion. The polarity of the input voltage matches the polarity of the output voltage.

Theory

The Bidirectional DC-DC block uses the commanded voltage and the actual voltage to determine whether to boost or buck (lower) the voltage. You can specify a time constant for the voltage response.

If	Then
Voltcmd > SrcVolt	Boost
Voltcmd < SrcVolt	Buck

The Bidirectional DC-DC block uses a time constant-based regulator to provide a fixed output voltage that is independent of load current. Using the output voltage and current, the block determines the losses of the DC-to-DC conversion. The block uses the conversion losses to calculate the input current. The block accounts for:

• Bidirectional current flow

  • Source to load — Battery discharge

  • Load to source — Battery charge

• Rated power limits

The block provides voltage control that is power limited based on these equations. The voltage is fixed. The block does not implement a voltage drop because the load current approximates DC-to-DC conversion with a bandwidth that is greater than the load current draw.

DC-to-DC converter load voltage	$$\begin{array}{l}LdVol{t}_{Cmd}=\min (Vol{t}_{Cmd},\frac{P_{limit}}{L{d}_{Amp}},0)\\ LdVolt=LdVol{t}_{Cmd}\cdot \frac{1}{\tau s+1}\end{array}$$
Power loss for single efficiency source to load	$$Pw{r}_{Loss}=\frac{100-Eff}{Eff}\cdot L{d}_{Volt}\cdot L{d}_{Amp}$$
Power loss for single efficiency load to source	$$Pw{r}_{Loss}=\frac{100-Eff}{Eff}\cdot \left|L{d}_{Volt}\cdot L{d}_{Amp}\right|$$
Power loss for tabulated efficiency	$$Pr{w}_{Loss}=f\left(L{d}_{Volt},L{d}_{Amp}\right)$$
Source current draw from DC-to-DC converter	$$Sr{c}_{Amp}=\frac{L{d}_{Pwr}+Pr{w}_{Loss}}{Sr{c}_{Volt}}$$
Source power from DC-to-DC converter	$$Sr{c}_{Pwr}=Sr{c}_{Amp}\cdot Sr{c}_{Volt}$$

Virtual Calibration

If you have Model-Based Calibration Toolbox, click Calibrate Maps to virtually calibrate the lookup table using measured data. The dialog box steps through these tasks.

Task	Description
Import data	Import this loss data from a file. For example, open <matlabroot>/toolbox/autoblks/autoblksutilities/mbctemplates/MappedDCDCConverterDataset.xlsx. For more information, see Using Data (Model-Based Calibration Toolbox). Required data: Current, A Voltage, V Power loss, W Collect data at steady-state operating conditions. To filter or edit the data, select Edit in Application. The Model-Based Calibration Toolbox Data Editor opens.
Generate response models	The Model-Based Calibration Toolbox uses test plans to fit data to Gaussian process models (GPMs). To assess or adjust the response model fit, select Edit in Application. The Model-Based Calibration Toolbox Model Browser opens. For more information, see Model Assessment (Model-Based Calibration Toolbox).
Generate calibration	Model-Based Calibration Toolbox calibrates the response models and generates calibrated table. To assess or adjust the calibration, select Edit in Application. The Model-Based Calibration Toolbox CAGE Browser opens. For more information, see Calibration Lookup Tables (Model-Based Calibration Toolbox).
Update block parameters	Update these block lookup table and breakpoint parameters with the calibration. Vector of voltages (v) for tabulated loss, v_loss_bp Vector of currents (i) for tabulated loss, i_loss_bp Corresponding losses, losses_table

Power Accounting

For the power accounting, the block implements these equations.

Bus Signal			Description	Variable	Equations
PwrInfo	PwrTrnsfrd — Power transferred between blocks Positive signals indicate flow into block Negative signals indicate flow out of block	PwrBusSrc	Source power to DC-to-DC converter	Psrc	$P_{src}= SrcPwr$
		PwrBusLd	Load power from DC-to-DC converter	Pbus	$P_{bus}= -LdVolt$
	PwrNotTrnsfrd — Power crossing the block boundary, but not transferred Positive signals indicate an input Negative signals indicate a loss	PwrLoss	Converter power loss	Ploss	$P_{loss}= PwrLoss$
	PwrStored — Stored energy rate of change Positive signals indicate an increase Negative signals indicate a decrease		Not used

The equations use these variables.

VoltCmd	DC-to-DC converter commanded output voltage
SrcVolt	Source input voltage to DC-to-DC converter
LdAmp	Load current of DC-to-DC converter
LdVolt	Load voltage of DC-to-DC converter
SrcAmp	Source current draw from DC-to-DC converter
τ	Conversion time constant
Vinit	Initial load voltage of the DC-to-DC converter
Plimit	Output power limit for DC-to-DC converter
Eff	Input to output efficiency
SrcPwr	Source power to DC-to-DC converter
LdPwr	Load power from DC-to-DC converter
PwrLoss	Power loss
LdVoltCmd	Commanded load voltage of DC-to-DC converter before application of time constant

Examples

Build Full Electric Vehicle Model

Build a vehicle with a motor-generator, battery, direct-drive transmission, and powertrain control algorithms using the electric vehicle (EV) reference application.

Ports

Inputs

VoltCmd — Commanded voltage

scalar

DC-to-DC converter commanded output voltage, Volt_Cmd, in V.

SrcVolt — Input voltage

scalar

Source input voltage to DC-to-DC converter, Src_Volt, in V.

LdCurr — Load current

scalar

Load current of DC-to-DC converter, Ld_Amp, in A.

Output

Info — Bus signal

bus

Bus signal containing these block calculations.

Signal			Description	Variable	Units
SrcPwr			Source power to DC-to-DC converter	SrcPwr	W
LdPwr			Load power from DC-to-DC converter	LdPwr	W
PwrLoss			Power loss	PwrLoss	W
LdVoltCmd			Commanded load voltage of DC-to-DC converter before application of time constant	LdVoltCmd	V
PwrInfo	PwrTrnsfrd	PwrBusSrc	Source power to DC-to-DC converter	Psrc	W
		PwrBusLd	Load power from DC-to-DC converter	Pbus	W
	PwrNotTrnsfrd	PwrLoss	Converter power loss	Ploss	W
	PwrStored	Not used

LdVolt — Load voltage

scalar

Load voltage of DC-to-DC converter, Ld_Volt, in V.

SrcCurr — Source current

scalar

Source current draw from DC-to-DC converter, Src_Amp, in A.

Parameters

Electrical Control

Converter response time constant, Tc — Constant

1/1000 (default) | scalar

Converter response time, τ, in s.

Programmatic Use

To set the block parameter value programmatically, use the set_param function.

To get the block parameter value programmatically, use the get_param function.

Parameter:	Tc
Values:	1/1000 (default) | scalar
Data Types:	double

Converter response initial voltage, Vinit — Voltage

0 (default) | scalar

Initial load voltage of the DC-to-DC converter, V_init, in V.

Programmatic Use

To set the block parameter value programmatically, use the set_param function.

To get the block parameter value programmatically, use the get_param function.

Parameter:	Vinit
Values:	0 (default) | scalar
Data Types:	double

Converter power limit, Plimit — Power

100000 (default) | scalar

Initial load voltage of the DC-to-DC converter, P_limit, in W.

Programmatic Use

To set the block parameter value programmatically, use the set_param function.

To get the block parameter value programmatically, use the get_param function.

Parameter:	Plimit
Values:	100000 (default) | scalar
Data Types:	double

Electrical Losses

Parameterize losses by — Loss calculation

Single efficiency measurement (default) | Tabulated loss data | Tabulated efficiency data

This table summarizes the loss options used to calculate electrical options.

Parameter Option	Description
Single efficiency measurement	Electrical loss calculated using a constant value for conversion efficiency.
Tabulated loss data	Electrical loss calculated as a function of load current and voltage. DC-to-DC converter data sheets typically provide loss data in this format. When you use this option, provide data for all the operating quadrants in which the simulation will run. If you provide partial data, the block assumes the same loss pattern for other quadrants. The block does not extrapolate loss that is outside the range voltage and current that you provide. The block allows you to account for fixed losses that are still present for zero voltage or current. If you have Model-Based Calibration Toolbox, click Calibrate Maps to virtually calibrate the 2-D lookup table using measured data.
Tabulated efficiency data	Electrical loss calculated using conversion efficiency that is a function of load current and voltage. When you use this option, provide data for all the operating quadrants in which the simulation will run. If you provide partial data, the block assumes the same efficiency pattern for other quadrants. The block: Assumes zero loss when either the voltage or current is zero. Uses linear interpolation to determine the loss. At lower power conditions, for calculation accuracy, provide efficiency at low voltage and low current.

Programmatic Use

To set the block parameter value programmatically, use the set_param function.

To get the block parameter value programmatically, use the get_param function.

Parameter:	param_loss
Values:	Single efficiency measurement (default) | Tabulated loss data | Tabulated efficiency data
Data Types:	character vector

Overall DC to DC converter efficiency, eff — Constant

98 (default) | scalar

Overall conversion efficiency, Eff, in %.

Programmatic Use

To set the block parameter value programmatically, use the set_param function.

To get the block parameter value programmatically, use the get_param function.

Parameter:	eff
Values:	98 (default) | scalar
Data Types:	double

Dependencies

To enable this parameter, for Parameterize losses by, select Single efficiency measurement.

Vector of voltages (v) for tabulated loss, v_loss_bp — Breakpoints

[0 200 400 600 800 1000] (default) | 1-by-M vector

Tabulated loss breakpoints for M load voltages, in V.

Programmatic Use

To set the block parameter value programmatically, use the set_param function.

To get the block parameter value programmatically, use the get_param function.

Parameter:	v_loss_bp
Values:	[0 200 400 600 800 1000] (default) | 1-by-M vector
Data Types:	double

Dependencies

To enable this parameter, for Parameterize losses by, select Tabulated loss data.

Vector of currents (i) for tabulated loss, i_loss_bp — Breakpoints

[0 25 50 75 100] (default) | 1-by-N vector

Tabulated loss breakpoints for N load currents, in A.

Programmatic Use

To set the block parameter value programmatically, use the set_param function.

To get the block parameter value programmatically, use the get_param function.

Parameter:	i_loss_bp
Values:	[0 25 50 75 100] (default) | 1-by-N vector
Data Types:	double

Dependencies

To enable this parameter, for Parameterize losses by, select Tabulated loss data.

Corresponding losses, losses_table — 2-D lookup table

N-by-M matrix

Electrical loss map, as a function of N load currents and M load voltages, in W.

Programmatic Use

To set the block parameter value programmatically, use the set_param function.

To get the block parameter value programmatically, use the get_param function.

Parameter:	losses_table
Values:	N-by-M matrix
Data Types:	double

Dependencies

To enable this parameter, for Parameterize losses by, select Tabulated loss data.

Vector of voltages (v) for tabulated efficiency, v_eff_bp — Breakpoints

[200 400 600 800 1000] (default) | 1-by-M vector

Tabulated efficiency breakpoints for M load voltages, in V.

Programmatic Use

To set the block parameter value programmatically, use the set_param function.

To get the block parameter value programmatically, use the get_param function.

Parameter:	v_eff_bp
Values:	[200 400 600 800 1000] (default) | 1-by-M vector
Data Types:	double

Dependencies

To enable this parameter, for Parameterize losses by, select Tabulated efficiency data.

Vector of currents (i) for tabulated efficiency, i_eff_bp — Breakpoints

[25 50 75 100] (default) | 1-by-N vector

Tabulated efficiency breakpoints for N load currents, in A.

Programmatic Use

To set the block parameter value programmatically, use the set_param function.

To get the block parameter value programmatically, use the get_param function.

Parameter:	i_eff_bp
Values:	[25 50 75 100] (default) | 1-by-N vector
Data Types:	double

Dependencies

To enable this parameter, for Parameterize losses by, select Tabulated efficiency data.

Corresponding efficiency, efficiency_table — 2-D lookup table

N-by-M matrix

Electrical efficiency map, as a function of N load currents and M load voltages, in %.

Programmatic Use

To set the block parameter value programmatically, use the set_param function.

To get the block parameter value programmatically, use the get_param function.

Parameter:	efficiency_table
Values:	N-by-M matrix
Data Types:	double

Dependencies

To enable this parameter, for Parameterize losses by, select Tabulated efficiency data.

Calibrate Maps — Calibrate tables with measured data

selection

If you have Model-Based Calibration Toolbox, click Calibrate Maps to virtually calibrate the lookup table using measured data. The dialog box steps through these tasks.

Task	Description
Import data	Import this loss data from a file. For example, open <matlabroot>/toolbox/autoblks/autoblksutilities/mbctemplates/MappedDCDCConverterDataset.xlsx. For more information, see Using Data (Model-Based Calibration Toolbox). Required data: Current, A Voltage, V Power loss, W Collect data at steady-state operating conditions. To filter or edit the data, select Edit in Application. The Model-Based Calibration Toolbox Data Editor opens.
Generate response models	The Model-Based Calibration Toolbox uses test plans to fit data to Gaussian process models (GPMs). To assess or adjust the response model fit, select Edit in Application. The Model-Based Calibration Toolbox Model Browser opens. For more information, see Model Assessment (Model-Based Calibration Toolbox).
Generate calibration	Model-Based Calibration Toolbox calibrates the response models and generates calibrated table. To assess or adjust the calibration, select Edit in Application. The Model-Based Calibration Toolbox CAGE Browser opens. For more information, see Calibration Lookup Tables (Model-Based Calibration Toolbox).
Update block parameters	Update these block lookup table and breakpoint parameters with the calibration. Vector of voltages (v) for tabulated loss, v_loss_bp Vector of currents (i) for tabulated loss, i_loss_bp Corresponding losses, losses_table

Programmatic Use

To set the block parameter value programmatically, use the set_param function.

To get the block parameter value programmatically, use the get_param function.

Parameter:	CalLossMapsButton
Values:	selection
Data Types:	character vector

Dependencies

To enable this parameter, for Parameterize losses by, select Tabulated loss data.

Extended Capabilities

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

Version History

Introduced in R2017b