DVM - Design Verification Module

LineDropout() Test Objective

The purpose of the LineDropout() test is to determine the converter response to a sudden interruption of line voltage. The input is configured as a AC Line Dropout Input Source, and the output is configured as a Resistive Load. The initial conditions for the simulation are typically found with a FindAcSteadyState() test, which runs a long transient simulation and saves the initial conditions using the GenerateInitFile testplan entry.

This test captures the output voltage and current waveforms and measures the minimum output voltage during the line dropout event.

The LineDropout() test objective runs a transient simulation on the converter with the timing based on values entered in the Line Dropout tab, which is shown below and accessed from the Full Power Assist DVM control symbol.

This test objective measures the following scalar values:

Minimum Output Voltage during the Line Dropout Event
Frequency of Input Source
Per Line Cycle Average of each output load voltage at:

The start of the simulation
The last line cycle of the simulation
The second-to-the-last line cycle

Percentage change in output load voltages over the final two line cycles

In this Topic ShowHide

Testplan Syntax
Simulation Timing
Source and Load Subcircuit Configuration
Measured Scalar Values
Measured Specification Values
Testplan Example
Optional Parameter String
Test Report

Testplan Syntax

The LineDropout() function has the following syntax with the arguments described in the table below:

LineDropout(REF, LINE_RANGE, NOMINAL_VOLTAGE, NUMBER_OF_CYCLES, FREQUENCY)
LineDropout(REF, LINE_RANGE, NOMINAL_VOLTAGE, NUMBER_OF_CYCLES, FREQUENCY, OPTIONAL_PARAMETER_STRING)

Argument	Range	Description
REF	n/a	The actual reference designator of the DVM Source or the generic syntax of INPUT:n where n is an integer indicating a position in the list of managed DVM sources.
LINE_RANGE	LL or HL	The line range to select the correct symbolic voltage value. This can only be the two strings LL or HL.
NOMINAL_VOLTAGE	min:0	The RMS voltage for the input source during the normal operating conditions. The voltage can be a numeric value or a symbolic value, such as a percentage of nominal input voltage. Symbolic values use the LINE_RANGE parameter to find the correct symbolic value.
FREQUENCY	min: > 0	The AC line frequency of the input source. This is used to both set the frequency of the input source and to set the simulation timing. The frequency can be a numeric or a symbolic value, such as F_High or F_Low.
NUMBER_OF_CYCLES	min: > 0	The number of line cycles to dropout the line voltage. The dropout vent starts a the line phase angle entered in the DVM Control symbol. This number can be any floating point number greater than zero. It is not restricted to integers.
OPTIONAL_PARAMETER_STRING	n/a	Parameter string with a combination of one or more timing parameters: NCYCLES_STOP* NCYCLES_DELAY PHASE_ANGLE* LINE_PHASEANGLE*

* If more than one parameter is specified, join the parameter key-value pairs with a space, as shown in the example below. The order of the parameter names does not matter.

Simulation Timing

DVM sets the timing parameters for the LineDropout() test objective based on values that you enter on the Line Surge/Sag tab of the DVM Full Power Assist control symbol:

Delay before Dropout, Duration of Surge/Sag, Time to Recover, and Dropout Phase Angle.

In the OPTIONAL_PARAMETER_STRING and in the calculations below, these values are renamed as follows:

NCYCLES1 = Delay Before Dropout
NCYCLES3 = Time to Recover
PHASE_ANGLE = Dropout Phase Angle

The duration of the Line Dropout is determined by the test objective argument NUMBER_OF_CYCLES.

The time delay is based on the following conditions and calculations. Typically the LINE_PHASEANGLE is set to 0, although in a 3 phase system only one of the three line sources will have a zero LINE_PHASEANGLE.

If LINE_PHASEANGLE is greater than 0, then

\[ \text{TIME_DELAY} = \frac{360 - \text{LINE_PHASEANGLE}}{360 * \text{FREQUENCY}} + \frac{\text{NCYLES1}}{\text{FREQUENCY}} + \frac{\text{PHASE_ANGLE}}{360 * \text{ FREQUENCY}} \]

If LINE_PHASEANGLE is less than or equal to 0, then

\[ \text{TIME_DELAY} = \frac{\text{NCYLES1}}{\text{FREQUENCY}} + \frac{\text{PHASE_ANGLE}}{\text{360} * \text{FREQUENCY}} \]

The pulse width and stop time are based on these calculations:

\[ \text{PULSE_WIDTH} = \frac{\text{NUMBER_OF_CYCLES}}{\text{FREQUENCY}} \]

\[ \text{STOP_TIME} = \frac{\text{NCYCLES1} + \text{NUMBER_OF_CYCLES} + \text{NCYCLES3}}{\text{FREQUENCY}}\]

A special note about the input voltage source used for this test objective. The slew rate of the input line voltage during the line transitions is limited by the input source. Each AC source has a programmable filter and slew rate limiter - the combination of these two circuits will limit the rate of change of the input line voltage. Of course, if the surge phase angle is set to 0, 180 or 360, there is no instantaneous change in the input voltage, as the line source changes when the line voltage is zero.

Source and Load Subcircuit Configuration

The LineDropout() test objective sets the source and load subcircuits to the following:

Source	Control Source (if used)	Load
AC Line Dropout Input Source	DC Auxiliary Source	Resistive Load

Loads other than the output under test are set to the Resistive Load. All other sources are set to either the DC Input Source for DC sources or the AC Fixed Input Source for the AC input sources.

Measured Scalar Values

The LineDropout() test objective measures the following scalar values where {load_name} is the name assigned to each load, and {source_name} is the name assigned to each source.

Scalar Name	Description
Frequency({source_name})	A number which represents the line frequency.
V{load_name}%_diff_last_2_linecycles	The percent change in the output voltage when averaged over the last two line cycles.
vout{n}_recovery_time	The time required for the output voltage to reach the output voltage regulation band after the line surge event.
I{source_name}	Minimum, Maximum, and RMS values of the source current during the entire simulation time.
I{source_name} Inrush Current	The maximum current for the input source during the dropout event.
I{load_name}	Minimum and Maximum values of the load current.
I{load_name} in Reg.	Average, Minimum, Maximum, and RMS values of the load current when the converter is in regulation.
V{source_name}	Minimum and Maximum values of the source voltage.
V{source_name} After Surge	The RMS voltage of the source after the dropout event.
V{load_name}	Minimum and Maximum values of the load voltage during the entire simulation time.
V{load_name} At Simulation Start Time	The output voltage taken at time=0.
V{load_name} During Dropout	Minimum value of the load voltage during the line dropout event.
V{load_name} Last LineCycle	The average value of the output voltage during the last line cycle in the simulation. Used for the V{load_name}%_diff_last_2_linecycles calculation.
V{load_name} Previous LineCycle	The average value of the output voltage during the second to the last line cycle in the simulation. Used for the V{load_name}%_diff_last_2_linecycles calculation.
V{load_name} in Reg.	Average, Minimum, Maximum, and RMS values of the load voltage when the converter is in regulation.
V{load_name} overshoot	Maximum value of the load voltage after the line dropout event.

Measured Specification Values

In the following table, {load_name} is the name assigned to each load, and {source_name} is the name assigned to each source.

Scalar Name	PASS/FAIL Criteria
AC_Settling({load_name})	The percentage change in the output load voltage over the final two line frequency cycles is less than the maximum specification value.
Min_V{load_name}_during_Dropout	The minimum value of the output during the dropout event is greater than the minimum specification value entered on the Output tab.
Max_I{load_name}_Inrush	The converter passes if the maximum source current is less than the maximum source current inrush specification.
Max_V{load_name}	The maximum value of the output during the simulation time is less than the maximum specification value.
Max_V{load_name}_overshoot	The maximum overshoot value of the output during the simulation time is less than the overshoot specification value.
Min_V{load_name}_reg	The minimum value of the output at the end of the simulation time is greater than the minimum specification value.
Max_V{load_name}_reg	The maximum value of the output at the end of the simulation time is less than the maximum specification value.

Testplan Example

An example of the LineDropout() test objective taken from the AC/DC (1-input/1-output) testplan is shown below. This test objective configures the line to dropout for one line cycle with timing values set on the Line Dropout tab of the Full Power Assist DVM control symbol. The Line Dropout duration (in line cycles) is the fifth argument to the LineDropout test objective.

*?@ Analysis	Objective	Source	Load	Label	GenerateInitFile	IncludeInitFile
Transient	LineDropout(INPUT:1, HL, Nominal, F_Low, 1)		Load(OUTPUT:1, 100%)	Transient\|LineDropout\|HL_Nominal\|F_Low\|1Cycles\|100% Load		INITFILE_HL_Nominal_F_Low_100% Load

Optional Parameter String

The following LineDropout() test objective uses the OPTIONAL_PARAMETER_STRING argument to set the line voltage to dropout for one line cycle, and sets the time delay before the dropout (NCYLES1) to 2 line cycles.

LineDropout(INPUT:1, HL, Nominal, F_Low, 1, NCYCLES1=2)

Test Report

You can view the complete test report in a new browser window here: LineDropout() Test Report. Below is an interactive link to the same test report.