Inverter - Power Flow Tab

Option Descriptions
Option	Description
Model	Describes the way the output of the inverter is controlled for IGBT type. The options are: Stand Alone: The inverter will supply any amount of required load, just like an AC grid Swing Bus. The specified voltage magnitude (Ctrl kV PU) and angle (Ctrl Angle) will be maintained. You should carefully check the capability (limits) of the inverter. Voltage Controlled: This model supplies the specified amount of kW to connected system, keeping the voltage magnitude at specified value (Ctrl kV PU) on the load side bus. There must be a Stand Alone system present when an inverter is operating in Voltage Controlled mode. Specify the kVAR Min and kVAR Max limits for the inverter. Const PQ Output: This model supplies the specified amount of kW and kVAR to connected system. There must be a Stand Alone system present when an inverter is operating in Const PQ Output mode. Specify the kVAR Min and kVAR Max limits for the inverter.
Ctrl kV PU	The per unit magnitude of Inverter output voltage. This is maintained at the specified value for a Stand Alone model, and is maintained at the specified value while within var limits for a Voltage Controlled model.
Ctrl Angle	The angle in degrees of the controlled output voltage for Stand Alone model.
Eff	Efficiency of the inverter. This is the ratio between output and input power in percent.
kW	Specified controlled output active power in kW for Voltage Controlled and Const PQ Output models.
kVAR	Specified controlled output reactive power in kVAR for Const PQ Output models.
kVAR Min	Minimum kVAR capability of the inverter in voltage controlled mode.
kVAR Max	Maximum kVAR capability of the inverter in voltage controlled mode.
Min Voltage Threshold	For an IGBT inverter only, if the DC voltage on the input to the inverter drops below this value, then the inverter begins stepping its specified kW loading down until the input voltage rises above Min Voltage Threshold. Note: The power flow will not solve when loading on photovoltaics causes them to experience a severe terminal under-voltage. Therefore, this special control was added so that inverters fed by photovoltaics reduce load when voltage drops below VMP so that photovoltaics are required to supply less power, thus helping the DC voltage on the photovoltaics increase into a range where a power flow solution can be reached.
Gamma Min	Minimum inverter margin angle in degrees for thyristor type inverter.
Gamma Max	Maximum inverter margin angle in degrees for thyristor type inverter.
Commutation Impedance	Commutation impedance used to calculate the power flow using Kimbark’s equations with Thyristor type. The inverter must feed a dedicated transformer that matches these same values one-for-one. Z1: Commutation impedance in percent on kVA base specified below. This must correspond to the downstream transformer. X/R: X/R ratio of the commutation impedance. This must correspond to the downstream transformer. kVA: kVA rating base for Z1. This must correspond to the downstream transformer.

Model

Describes the way the output of the inverter is controlled for IGBT type. The options are:

Stand Alone: The inverter will supply any amount of required load, just like an AC grid Swing Bus. The specified voltage magnitude (Ctrl kV PU) and angle (Ctrl Angle) will be maintained. You should carefully check the capability (limits) of the inverter.
Voltage Controlled: This model supplies the specified amount of kW to connected system, keeping the voltage magnitude at specified value (Ctrl kV PU) on the load side bus. There must be a Stand Alone system present when an inverter is operating in Voltage Controlled mode. Specify the kVAR Min and kVAR Max limits for the inverter.
Const PQ Output: This model supplies the specified amount of kW and kVAR to connected system. There must be a Stand Alone system present when an inverter is operating in Const PQ Output mode. Specify the kVAR Min and kVAR Max limits for the inverter.

Ctrl kV PU

The per unit magnitude of Inverter output voltage. This is maintained at the specified value for a Stand Alone model, and is maintained at the specified value while within var limits for a Voltage Controlled model.

Ctrl Angle

The angle in degrees of the controlled output voltage for Stand Alone model.

Eff

Efficiency of the inverter. This is the ratio between output and input power in percent.

kW

Specified controlled output active power in kW for Voltage Controlled and Const PQ Output models.

kVAR

Specified controlled output reactive power in kVAR for Const PQ Output models.

kVAR Min

Minimum kVAR capability of the inverter in voltage controlled mode.

kVAR Max

Maximum kVAR capability of the inverter in voltage controlled mode.

Min Voltage Threshold

For an IGBT inverter only, if the DC voltage on the input to the inverter drops below this value, then the inverter begins stepping its specified kW loading down until the input voltage rises above Min Voltage Threshold.

Note: The power flow will not solve when loading on photovoltaics causes them to experience a severe terminal under-voltage. Therefore, this special control was added so that inverters fed by photovoltaics reduce load when voltage drops below VMP so that photovoltaics are required to supply less power, thus helping the DC voltage on the photovoltaics increase into a range where a power flow solution can be reached.

Gamma Min

Minimum inverter margin angle in degrees for thyristor type inverter.

Gamma Max

Maximum inverter margin angle in degrees for thyristor type inverter.

Commutation Impedance

Commutation impedance used to calculate the power flow using Kimbark’s equations with Thyristor type. The inverter must feed a dedicated transformer that matches these same values one-for-one.

Z1: Commutation impedance in percent on kVA base specified below. This must correspond to the downstream transformer.
X/R: X/R ratio of the commutation impedance. This must correspond to the downstream transformer.
kVA: kVA rating base for Z1. This must correspond to the downstream transformer.

Inverter - Power Flow Tab

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