The sync_ctrl class is being developed as a controller for the sync_check class, which enables the paralleling of two separated systems (e.g., microgrids, feeders, bulk power systems, etc.). A hierarchical structure is adopted for flexibility and future expansion.
Both sync_ctrl and sync_check are mainly developed for enabling the paralleling capability, which can be utilized and/or improved in further simulations of several projects. For instance, the advanced synchronization controls (e.g., optimization and redispatch) are not included, but can be developed based on the basic implementations of sync_ctrl and sync_check.
This paralleling controller is not designed for the full secondary control, while its initial version will incorporate the functionality for the secondary control of both frequency and voltage. It will provide very basic functionalities for paralleling. Users are expected to model the system, scenario, switch, and controller properly.
The PI (Proportional Integral) control will be implemented. Parameters of the controller can be set by the users.
The controller does not check the system topology for verifying the connectivity of controlled generation resources.
The initial implementation of sync_ctrl will allow one controlled generation unit (e.g., a diesel generator or a grid-forming inverter) only, which can be specified by the user as a property of the sync_ctrl object. In future, the updated version will involve the control of two or more generation units for improving the paralleling capability.
The bounds are defined by the user. The controller checks the measurements of both sides and decides the frequency and voltage values within the user defined limits for matching.
The user specifies upper and lower limits for chekcing the absoulte vaule of the difference between the frequency measurements of the 'from' and 'to' node of the switch in Hz (e.g., 0.2 – 0.6 Hz).
The user specifies a tolerance (i.e., the upper limit) for checking the magnitude of the difference of voltage magnitudes in per unit (e.g., 0.01 pu). Note that there is no need for the user to specify a lower limit, which should always be set as zero.
The controller may pop up warnings with respect to the settings and system conditions.
If the step size is too large for the constraints on “frequency difference”, a warning should be displayed to indicate that the synchronization may not be achievable.
If the frequency difference between two systems are too small or are the same, another warning would be triggered because it might take too much time to close the switch.