Comparative study of series and parallel schemes for stabilization of a microgrid integrated with a solar thermal cogeneration system using virtual synchronous generator control

When a solar thermal cogeneration system is located close to energy consumers, the electricity loss caused by transportation can be largely reduced and the low-temperature thermal energy can be utilized for air conditioning. In this case, a microgrid is introduced to connect a solar thermal cogeneration system and a conventional grid to switch between islanded and grid-connected modes. A new technology for stabilizing the system is required to handle the relatively slow response of the solar thermal cogeneration system for this configuration. Virtual synchronous generator (VSG) control can enhance the power system stability by mimicking steady-state and transient behaviors of synchronous generators (SGs). A swing equation in the VSG control identifies the virtual inertial property of SGs to rapidly adjust to a steady-state frequency. In this work, the transient responses of the VSG series and parallel configurations incorporated into a microgrid are compared. The transient behaviors of rotor angular speed and voltage are simulated for loading and tripping operations. The analysis results suggest that the VSG series configuration suppresses fluctuations better than the parallel configuration and enables stable network operation.