ee_getEfficiency

Calculate efficiency as function of dissipated power losses

Syntax

efficiency = ee_getEfficiency('loadIdentifier',node)

efficiency = ee_getEfficiency('loadIdentifier',node,...
startTime,endTime)

[efficiency,lossesTable] = ee_getEfficiency('loadIdentifier',node)

Description

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.

Note

The power_dissipated internal variable does not report dynamic losses incurred from semiconductor switching or magnetic hysteresis.

Three different variables, lastTurnOnLoss, lastTurnOffLoss, and lastReverseRecoveryLoss report the switching losses.

Switching losses are losses associated with the transition of the semiconductor switch from its on-state to its off-state and viceversa, and also with the energy dissipated during a reverse recovery event. They are frequency dependent.

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.

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

• P_loss 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.

efficiency = ee_getEfficiency('loadIdentifier',node,...
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.

[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

Calculate Efficiency for Circuit

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 = 'ClassEDCDCConverter';
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_ClassEDCDCConverter is saved in your current workspace.

Calculate efficiency and display the results.

efficiency = ee_getEfficiency('Load',simlog_ClassEDCDCConverter)

efficiency =

   90.0213

Calculate Efficiency of Circuit for Specific Time Period

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 = 'ClassEDCDCConverter';
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_ClassEDCDCConverter 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 = ee_getEfficiency('Load',simlog_ClassEDCDCConverter,1e-4,1.25e-4)

efficiency =

   90.4771

Calculate Efficiency and Power-Loss Contributions

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 = 'ClassEDCDCConverter';
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_ClassEDCDCConverter is saved in your current workspace.

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

[efficiency,lossesTable] = ee_getEfficiency('Load',simlog_ClassEDCDCConverter)

efficiency =

   90.0213


lossesTable =

  7x2 table

                  LoggingNode                     Power   
    ________________________________________    __________

    {'ClassEDCDCConverter.LDMOS'           }        3.6583
    {'ClassEDCDCConverter.R_Trans.Resistor'}         2.911
    {'ClassEDCDCConverter.D2'              }        1.9516
    {'ClassEDCDCConverter.D1'              }        1.8436
    {'ClassEDCDCConverter.Cs'              }       0.27392
    {'ClassEDCDCConverter.Ls'              }       0.27099
    {'ClassEDCDCConverter.Cout'            }    0.00044574

Input Arguments

'loadIdentifier' — Identify load blocks in the circuit

case-sensitive string

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 Name in the Model		IGBT	IGBT1_Load	Diode	Diode1
Block Type		N-Channel IGBT	N-Channel IGBT	Diode	Diode
Block Role in the Model		Source	Load	Load	Load
'loadIdentifier'	'IGBT'	Yes	Yes	No	No
	'Diode'	No	No	Yes	Yes
	'Load'	No	Yes	No	No
	'1'	No	Yes	No	Yes
	'D'	No	No	Yes	Yes
	'd'	No	Yes	Yes	Yes

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 Name in the Model		IGBT	IGBT1_Load	Diode_Load	Diode1_Load
Block Type		N-Channel IGBT	N-Channel IGBT	Diode	Diode
Block Role in the Model		Source	Load	Load	Load
'loadIdentifier'	'IGBT'	Yes	Yes	No	No
	'Diode'	No	No	Yes	Yes
	'Load'	No	Yes	Yes	Yes

Example: 'Load'

Data Types: string

node — Simulation log variable, or a specific node within the simulation log variable

Node object

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

startTime — Start of the time interval for calculating the efficiency

0 (default) | real number

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

endTime — End of the time interval for calculating the efficiency

simulation stop time (default) | real number

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

efficiency — Efficiency of the circuit

percentage

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

lossesTable — Dissipated power losses and switching losses for each blocks

table

Dissipated power losses and switching losses for each 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. The third column lists the switching losses of each block, in watts. Switching losses comprise losses associated with the transition of the semiconductor switch from its on-state to its off-state and viceversa, and with the energy dissipated during a reverse recovery event.

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.

Version History

Introduced in R2017a