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elec_getNodeDvDtTimeSeries

Calculate rates-of-change of voltage variables

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Syntax

seriesTable = elec_getNodeDvDtTimeSeries(node,tau)

Description

seriesTable = elec_getNodeDvDtTimeSeries(node,tau) calculates rates-of-change of voltage variables for nodes that are based on the foundation.electrical.electrical domain, based on logged simulation data. The function returns the data for each terminal in a table. The data in the table appears in descending order according to the maximum absolute value of the rate-of-change of voltage variables with respect to the ground, over the whole simulation time. The table does not contain data for terminals that are held fixed.

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 the blocks in the model that have nodes based on the foundation.electrical.electrical domain. If node is the name of a node in the simulation data tree, then the table contains the data only for the children of that node.

Examining rates-of-change of voltage variables in power electronics circuits is useful for determining the potential for unwanted conducted or radiated emissions. The rate-of-change data also helps you to identify unwanted turn-on of switching devices. All nodes that are based on the foundation.electrical.electrical domain store the potential with respect to electrical ground as the variable v. When you log simulation data, the time-value series for this variable represents the trend of the potential over time. You can view and plot this data using the Simscape™ Results Explorer.

To evaluate the rates-of-change of voltage variables, the elec_getNodeDvDtTimeSeries function employs finite difference approximation of the first derivative with respect to time. It performs 1-D data linear interpolation of voltage variables using a uniform grid with the time step, tau. The function then applies the central differencing scheme to the interpolated data.

Tip

For small time steps, finite differencing may lead to inaccurate results. The time step tau should be small enough to capture waveforms, but not so small that the finite differencing error becomes large. For example, for power transistors with an expected limit of 50 V/ns for their voltage rate-of-change, a reasonable guess for tau is 1e-9 s.

Input Arguments

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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.

Example: simlog_ee_converter_dcdc_class_e.LDMOS

Time step for numerical differentiation, specified as a real number, in seconds. tau determines the interpolation grid as startTime:tau:endTime.

Example: 1e-9

Data Types: double

Output Arguments

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Time series of the voltage rates-of-change for each block, returned as a table. The first column lists all the logging nodes in node that are based on the foundation.electrical.electrical domain. The second column lists the terminal names. The third column lists the corresponding interpolated voltage values, in volts. The fourth column lists the corresponding numerically differentiated values of voltage rates-of-change, in volts per second. The table does not contain data for terminals that are held fixed.

Version History

Introduced in R2018b

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See Also

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