Documentation

# ee_getEfficiency

Calculate efficiency as function of dissipated power losses

## Description

example

efficiency = ee_getEfficiency('loadIdentifier',node) returns the efficiency of a circuit based on the data extracted from a Simscape™ logging node.

Before you call this function, you must have the simulation log variable in your current workspace. Create the simulation log variable by simulating the model with data logging turned on, or load a previously saved variable from a file. If node is the name of the simulation log variable, then the table contains the data for all semiconductor blocks in the model. If node is the name of a node in the simulation data tree, then the table contains the data only for the blocks within that node.

Checking efficiency allows you to determine if circuit components are operating within their requirements. All blocks in the Semiconductor Devices library, as well as some other blocks, have an internal variable called power_dissipated, which represents the instantaneous power dissipated by the block. This instantaneous dissipated power includes only the real power (not the reactive or apparent power) that the block dissipates. When you log simulation data, the time-value series for this variable represents the power dissipated by the block over time. You can view and plot this data using the Simscape Results Explorer. The ee_getPowerLossTimeSeries function also allows you to access this data.

The ee_getEfficiency function calculates the efficiency of the circuit based on the losses for blocks that have a power_dissipated variable and that you identify as a load block. The equation for efficiency is

$Eff=100\cdot \frac{{P}_{load}}{{P}_{loss}+{P}_{load}},$

where:

• Eff is the efficiency of the circuit.

• Pload is the output power, that is, the power dissipated by load blocks.

• Ploss is the power dissipated by nonload blocks.

This equation assumes that all loss mechanisms are captured by blocks containing at least one power_dissipated variable. If the model contains any lossy blocks that do not have this variable, the efficiency calculation gives incorrect results.

Some blocks have more than one power_dissipated variable, depending on their configuration. For example, the N-Channel MOSFET block has separate power_dissipated logging nodes for the MOSFET, the gate resistor, and for the source and drain resistors if they have nonzero resistance values. The function sums all these losses to provide the total power loss for the block, averaged over simulation time. The function uses the loss data to calculate the efficiency of the circuit.

example

startTime,endTime)
returns the efficiency of a circuit based on the power_dissipated data extracted from a Simscape logging node within a time interval. startTime and endTime represent the start and end of the time interval for calculating the efficiency. If you omit these two input arguments, the function calculates the efficiency over the whole simulation time.

example

[efficiency,lossesTable] = ee_getEfficiency('loadIdentifier',node) returns the efficiency of a circuit and the power loss contributions of the nonload blocks in a circuit based on the data extracted from a Simscape logging node.

## Examples

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This example shows how to calculate efficiency based on the power dissipated by blocks in a circuit using the ee_getEfficiency function.

Open the model. At the MATLAB® command prompt, enter:

model = 'ee_converter_dcdc_class_e';
open_system(model)

The load in the model is represented by the R Load resistor. No other blocks with power_dissipated variables contain Load in their names. Therefore, you can use the string Load as the loadIdentifier argument.

If no string at least partially matches the names of all load blocks in your circuit, rename the load blocks using a schema that satisfies the matching criteria for the loadIdentifier argument.

This example model has data logging enabled. Run the simulation and create the simulation log variable.

sim(model)

The simulation log variable simlog_ee_converter_dcdc_class_e is saved in your current workspace.

Calculate efficiency and display the results.

efficiency =

90.0324

This example shows how to calculate efficiency based on the power dissipated for a specific time period using the ee_getEfficiency function.

Open the model. At the MATLAB® command prompt, enter:

model = 'ee_converter_dcdc_class_e';
open_system(model)

The load in the model is represented by the R Load resistor. No other blocks with power_dissipated variables contain Load in their names. Therefore, you can use the string Load as the loadIdentifier argument.

If no string at least partially matches the names of all load blocks in your circuit, rename the load blocks using a schema that satisfies the matching criteria for the loadIdentifier argument.

This example model has data logging enabled. Run the simulation and create the simulation log variable.

sim(model)

The simulation log variable simlog_ee_converter_dcdc_class_e is saved in your current workspace.

The model simulation time (t) is 1.25e-4 seconds. Calculate efficiency for the interval when t is between 1e-4 and 1.25e-4 seconds.

efficiency =

90.4879

This example shows how using the ee_getEfficiency function allows you to calculate both the efficiency of the circuit and the power-loss contributions of the nonload blocks based on the power that they dissipate.

Open the model. At the MATLAB® command prompt, enter:

model = 'ee_converter_dcdc_class_e';
open_system(model)

The load in the model is represented by the R Load resistor. No other blocks with power_dissipated variables contain Load in their names. Therefore, you can use the string Load as the loadIdentifier argument.

If no string at least partially matches the names of all load blocks in your circuit, rename the load blocks using a schema that satisfies the matching criteria for the loadIdentifier argument.

This example model has data logging enabled. Run the simulation and create the simulation log variable.

sim(model)

The simulation log variable simlog_ee_converter_dcdc_class_e is saved in your current workspace.

Calculate the efficiency and power-loss contributions due to dissipated power.

efficiency =

90.0324

lossesTable =

7x2 table

LoggingNode                        Power
______________________________________________    __________

{'ee_converter_dcdc_class_e.LDMOS'           }        3.6584
{'ee_converter_dcdc_class_e.R_Trans.Resistor'}         2.911
{'ee_converter_dcdc_class_e.D2'              }        1.9446
{'ee_converter_dcdc_class_e.D1'              }        1.8371
{'ee_converter_dcdc_class_e.Cs'              }       0.27392
{'ee_converter_dcdc_class_e.Ls'              }       0.27098
{'ee_converter_dcdc_class_e.Cout'            }    0.00044579

## Input Arguments

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String that is a complete or partial match for the names of load blocks in the circuit. For example, consider a circuit that contains the four semiconductor blocks shown in the table.

Block TypeN-Channel IGBTN-Channel IGBTDiodeDiode
'Diode'NoNoYesYes
'1'NoYesNoYes
'D'NoNoYesYes
'd'NoYesYesYes

The ee_getEfficiency function returns data just for the three load blocks only when the 'loadIdentifier' is 'd'.

A load-block naming schema that gives you better control over the output of the ee_getEfficiency function is shown in this table.

Block TypeN-Channel IGBTN-Channel IGBTDiodeDiode
'Diode'NoNoYesYes

Data Types: string

Simulation log workspace variable, or a node within this variable, that contains the logged model simulation data, specified as a Node object. You specify the name of the simulation log variable by using the Workspace variable name parameter on the Simscape pane of the Configuration Parameters dialog box. To specify a node within the simulation log variable, provide the complete path to that node through the simulation data tree, starting with the top-level variable name.

If node is the name of the simulation log variable, then the table contains the data for all blocks in the model that contain power_dissipated variables. If node is the name of a node in the simulation data tree, then the table contains the data only for:

• Blocks or variables within that node

• Blocks or variables within subnodes at all levels of the hierarchy beneath that node

Example: simlog.Cell1.MOS1

Start of the time interval for calculating the efficiency, specified as a real number, in seconds. startTime must be greater than or equal to the simulation Start time and less than endTime.

Data Types: double

End of the time interval for calculating the efficiency, specified as a real number, in seconds. endTime must be greater than startTime and less than or equal to the simulation Stop time.

Data Types: double

## Output Arguments

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Efficiency of the circuit based on data extracted from a Simscape logging node.

Dissipated power losses for each nonload block, returned as a table. The first column lists logging nodes for all blocks that have at least one power_dissipated variable. The second column lists the corresponding losses in watts.

## Assumptions

• The output power equals the total power dissipated by blocks that you identify as load blocks.

• The input power equals the output power plus the total power dissipated by blocks that you do not identify as load blocks.

• The power_dissipated variables capture all loss contributions.