Req:SubsecondInverter

= Application Concept =

The SubsecondInverter will serve as a higher order model (as compared to the standard inverter class) for use in transient time scale studies in the millisecond range. This will enable the inclusion of inverters in subsecond (delta mode) simulations, where the controller dynamics are accurately reflected.

= Use Case =

The SubsecondInverter capability will be used to model and study inverter behavior for microgrids applications. Inverter field tests carried out in Oak Ridge National Laboratory's (ORNL) DECC facility will be used for validation of the class's functionality.

= General Requirements =

The SubsecondInverter shall model the transient behavior of a three phase voltage-sourced inverter. Initially single level (6 switch) PWM-configured inverters with four-quadrant power control will be supported.

R1
The overall SubsecondInverter object will be modeled using a state space-type approach for solution of the differential equations.

R1.1
Millisecond-level transient dynamics (e.g. those relating to voltage and angle stability) will be accurately represented.

R1.2
The inverter will be modeled as a controllable voltage source with saturation limits.


 * R1.2.1
 * Switching transients will be neglected.


 * R1.2.2
 * The reference AC voltage signals for the inverter will be generated by one of several control modes.


 * R1.2.2.1
 * Each specific control mode will be modeled separately.


 * R1.2.2.2
 * There will be capability to specify more than one control mode, as well as criteria for switching between them (e.g., islanding detection).


 * R1.2.2.3
 * There will be support for a constant real and reactive power control mode.


 * R1.2.2.3.1
 * Controls will work to maintain reference values for P and Q.


 * R1.2.2.3.2
 * AC voltage angle will be controlled by tracking the P error.


 * R1.2.2.3.3
 * AC voltage magnitude will be controlled by tracking the Q error.


 * R1.2.2.4
 * There will be support for a voltage magnitude/frequency droop control mode.


 * R1.2.2.4.1
 * The reference P signal will be derived from a P vs. frequency droop curve.


 * R1.2.2.4.2
 * The P error will be tracked to control AC voltage angle.


 * R1.2.2.4.3
 * The reference Q signal will be derived from a Q vs. |V| droop curve.


 * R1.2.2.4.4
 * The Q error will then be tracked to control AC voltage magnitude.


 * R1.2.2.5
 * The implementation will be flexible enough that later modes can be added (e.g., maximum power-point tracking).

R1.3
There will be capability to include the coupling reactance in the state space-type model.


 * R1.3.1
 * There will be capability to model the coupling reactance as a simple series inductance.


 * R1.3.2
 * There will be capability to model the coupling reactance as a common LCL filter:



= See also =


 * User's manual
 * Specifications
 * Implementation