Req:Microgrids

= Application concept =

The purpose of the microgrids capability in GridLAB-D is to facilitate studying the effects of various technologies on a smaller power system. These studies will be conducted with a newly added dynamic solver capability for GridLAB-D.

GridLAB-D simulations of microgrids will model the power system at the point of the disconnect (as an isolated grid). Islanding and reconnection of the system are not expected to be part of the GridLAB-D functionality at this time. Furthermore, non-rotating generators, such as solar inverter models, shall not be part of the initial expectation, but will be implemented in the future.

= Use Case =

The microgrids capability will be used to simulate the reduced grid of a specific utility's project, or a representative equivalent. Initial plans are to model a representation of San Diego Gas and Electric's Beach Cities Microgrid. This will include simulating the dynamics of diesel generators (1.8 MW units) and utility-connected storage (~3.3 kW). The microgrids capability will use this simple system to provide the basis for testing new grid control strategies aimed at microgrid environments. As per the Application Concept section, this modeling will only encompass the time from which the microgrid has disconnected from the main system to its reconnection (only simulating while it is operating as a microgrid).

= General Requirements =

The microgrids capability shall represent a full three-phase unbalanced power system and model changes in frequency and voltage associated with the operation of microgrids. This capability will require the development on one new object in the powerflow module, dynamic_solver.

Analysis and control of microgrids with the dynamic solver will require the following capabilities:

R1
The dynamic solver shall represent the influences on dynamic effects from objects.

R1.1
Static loads and powerflow devices shall ignore dynamics effects represented by the dynamic solver.


 * Note : The initial implementation will neglect frequency dependencies in loads. Furthermore, frequency dependent components like distribution lines will still only compute their impedance based on the nominal_frequency parameter of the powerflow module.  These capabilities may be added to the microgrids solution at a later date.

R1.2
Rotating machine, synchronous generators shall represent the dynamics affected by the dynamic solver.

R1.2.1
Rotating machine generators shall initially implement the classical synchronous machine model.

R1.2.2
Rotating machine generators shall initially implement the simple speed-droop governor

R1.2.3
Rotating machine generators shall initially implement a simple DC exciter

R1.2.4
Framework for various generators shall support implementations of subtransient models, PSS units, and more complicated exciter and governor models.

R1.2.5
Contributing portions of the rotating machine (exciter, governor, etc.) shall be modeled within that specific device, not as separate devices in the generators module.

R1.3
Non-rotating generators, such as solar inverter models, shall not be part of the initial expectation, but will be implemented in the future.

R1.4
Cogeneration and combined heat-power (CHP) models shall be framed out as part of the initial expectation, but the behavioral model within the objects will not be implemented as part of the initial microgrid solution.

R2
The dynamic solver shall allow objects in other modules to interface with objects it supports.

R2.1
The dynamic solver shall provide a common interface for objects to interface with the dynamic simulation.

R2.2
The dynamic solver shall allow objects to access data for the frequency and voltage dependent dynamic capabilities.

R2.3
The dynamic solver shall allow objects to access data for mechanical and control dynamics.

R2.4
The dynamic solver shall allow a single object to centrally aggregate and solve all relevant influences.

R2.4.1
The dynamic solver shall be part of the powerflow module.

R2.4.2
The dynamic solver shall aggregate and solve the equations necessary to compute the dynamic influences on the system.

R2.4.3
objects with dynamic influences on the system shall manage all parameter and secondary equations within themselves or support objects attached to them.

R3
The dynamic solver shall allow calculate dynamic updates for timesteps down to 1 ms

R3.1
The dynamic solver shall allow user specifiable timesteps not less than 1 ms.

R3.2
The dynamic solver shall allow represent the timesteps in a manner compliant with GridLAB-D time management conventions.

R3.3
Time progress shall be displayed if requested by the user.

R3.4
The dynamic solver shall represent synchronous grid frequency.

R3.5
The dynamic solver shall represent transient voltage values.

= See also =


 * User's manual
 * Specifications
 * Implementation