| Summary: | Hybrid AC/DC microgrids are an appealing choice for future building networks due to benefits such as flexibility, high efficiency, low cost of loads, and green sources. The construction of a building hybrid AC/DC microgrid differs from that of a typical microgrid. In addition, when the typical load in the building microgrid undergoes a step change, it may affect the transient stability and power quality of the system. When the MVS (Main Voltage Source) in the subgrid is disconnected, it will cause voltage sag, frequency variation, and even affect the balance of energy transmission. If the voltage and frequency cannot be stabilized in a short period of time, it will cause the decline of power quality and even the transient imbalance of the power system. Aiming at the above problems, this dissertation proposes a building hybrid AC/DC microgrid architecture that uses renewable energy as MVS and includes the typical load of the building microgrid. It also uses the coordination control approach to the hybrid building microgrid and a uniform control for bidirectional ac/dc interlinking converter (BIC), which includes both centralized and decentralized control. The control method can ensure system stability and maintain power balance when the building microgrid has a sudden load change and MVS disconnection. It has the capacity to transmit power via BIC in order to preserve stability and achieve fast and smooth changeover between modes. The voltage and frequency are also adjusted to swiftly restore to the permitted range, resolving the voltage stability and power quality issues created by the building hybrid microgrid's voltage sag. This dissertation also includes a simulation verification of the control approach. Under specific scenarios such as step changes in building microgrid load and MVS disconnection, voltage and frequency can also recover to a safe level rapidly and remain relatively constant. Voltage sag-related voltage stability and power quality issues can be effectively controlled.
It's worth noting that this dissertation also verifies the efficacy of centralized control. When the system is operating regularly, BIC can transmit the appropriate power flow. What’s more, BIC can still receive the instructions from the energy management system (EMS) and transmit the prescribed power when the load has a step change. In certain instances, such as MVS disconnection, the system will prioritize guaranteeing stability, particularly for voltage and frequency parameters. This dissertation proposes a possible solution to the transient voltage stability and power quality challenges of building hybrid AC/DC microgrids.
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