power_steadystate
Compute steady-state values of voltages and currents of model
Syntax
power_steadystate('sys')
sps = power_steadystate('sys')
Description
power_steadystate('sys') opens the Steady-State
Voltages and Currents Tool dialog box that allows you to view steady-state
values of the inductor currents and capacitor voltages (electrical
state variables), steady-state voltages and currents of measurement
blocks and sources, as well as steady-state voltages and currents
of nonlinear blocks of a model. This tool can also be activated from
the Powergui block dialog box by selecting Steady-State
Voltages and Currents.
If the model contains power electronic switches (diodes, thyristors, IGBTs, and so on) the steady-state values are computed considering them as open-circuit. If the model contains breakers (Breaker, Three-Phase Breaker, Three-Phase Fault blocks) the steady-state values are computed considering their initial status (open-circuit or short-circuit).
sps = power_steadystate('sys') returns
a structure with the fields:
| Field | Description |
|---|---|
circuit | The name of the model |
Frequencies | Vector listing the source frequencies in the model |
States | The names of the electrical states of the model |
Xss | The steady-state values of electrical states of the model |
DependentStates | The names of the dependent states, if any |
Measurements | The names of the Measurement blocks of the model |
Yss_Measurements | The steady-state values of measurement blocks of the model |
Sources | The names of the electrical source blocks of the model |
Uss_Sources | The steady-state values of the electrical sources of the model |
NonlinearOutputs | The names of the outputs corresponding to the nonlinear blocks (current-source injection based models). It consist of the measured terminal voltages used by the nonlinear models to compute the corresponding current sources |
Yss_NonlinearOutputs | The steady-state values of outputs used by the nonlinear blocks |
NonlinearInputs | The names of the inputs corresponding to the nonlinear blocks of the model |
Uss_NonlinearInputs | The steady-state values of current inputs defined by the nonlinear blocks (current-source injection based models) |
Note
When the model contains more that one source frequency, the Xss, Yss_Measurements, Uss_Sources, Yss_NonlinearOutputs,
and Uss_NonlinearInputs fields return a matrix
of steady-state values. For every source frequency listed in the Frequencies field,
there is a corresponding column of steady-states values in the matrix.
Dialog Box
- Steady state values
Display measurements of steady-state voltages and currents in the model.
- Units
Set the Units parameter to
Peak valuesto display the peak values of the selected values. Set the Units parameter toRMSto display the root-mean-square (RMS) values of the selected values.- Frequency
Allows you to choose the frequency, in hertz (Hz), that you want for display of the voltage and current phasors. The Frequency parameter lists all the different frequencies of the electrical sources of the model.
- States
If selected, the window displays the steady-state phasors of the capacitor voltages and inductor currents of the circuit. The default is unselected.
- Measurements
If selected, the window displays the steady-state voltage and current phasors of the measurement blocks of the circuit. The default is selected.
- Sources
If selected, the window displays the steady-state voltage and current phasors of the electrical sources of the circuit. The default is unselected.
- Nonlinear elements
If selected, the window displays the steady-state voltages and currents of the nonlinear blocks of the circuit. The default is unselected.
- Format
In the pull-down menu, choose the format in which you want your measurements displayed. The
floating pointoption is displayed in mantissa-exponent form with five significant figures. Thebest ofoption displays with four significant figures and uses mantissa-exponent form only for numbers larger than 9999. The final option is displayed in plain numbers with two figures to the right of the decimal point. The default isfloating point.- Ordering
In the pull-down menu, choose the ordering in which you want your measurements displayed. The V
alue then nameoption displays the steady-state values in the first column followed by the names of the states variables. TheName then valueoption displays the name of the states variables in the first column followed by the steady-state values.- Update Steady State Values
Recompute and display the steady-state measurements.
Sign Conventions for Voltages and Currents
Unlike Simulink® signal lines and input and output ports,
the Physical Modeling connection lines and terminal ports 
lack intrinsic
directionality. The voltage and current polarities are determined,
not by line direction, but instead by block orientation. To find out
a block orientation, first click on the block to select it. Then enter
the following command:
get_param(gcb,'Orientation')
The following table indicates the polarities of the currents and voltages for single-phase and three-phase RLC elements (branches or loads), surge arresters, and single-phase and three-phase breakers. The table also indicates the polarities of their state variables (inductor currents and capacitor voltages).
Block | Positive Current | Measured |
|---|---|---|
| left —> right | Vleft – Vright |
| right —> left | Vright – Vleft |
| top —> bottom | Vtop – Vbottom |
| bottom —> top | Vbottom – Vtop |
The natural orientation of the blocks (that is, their orientation in the Element library) is right for horizontal blocks and down for vertical blocks.
For single-phase transformers (linear or saturable), with the winding connectors appearing on the left and right sides, the winding voltages are the voltages of the top connector with respect to the bottom connector whatever the block orientation (right or left). The winding currents are the currents entering the top connector. For three-phase transformers, the voltage polarities and positive current directions are indicated by the signal labels used in the Multimeter block.