No abstract

Microgrids can be operated in a utility‐connected mode or an islanded mode in separation with the transmission or distribution system. As major disasters occur, intentional islanding of a microgrid is a possible solution to serve critical loads, within or outside the microgrids, until the utility service is restored. Through a field test, the technical feasibility to utilize microgrids as a resiliency resource is evaluated. Waveforms of the system dynamics are recorded, and the acquired data and measurements are analyzed and compared with simulation results. Technical issues arising from the starting of an islanded microgrid have been identified. The parallel operation of distributed generators is a major issue in the field test. With different droop characteristics, the dispatch rule of real and reactive power between the DGs is established. Based on the field test experience, a control scheme integrating droop control and feedback control is designed for proper power dispatch among DGs and frequency/voltage control in a microgrid. During the parallel operation, regulation of the frequency and voltage within an acceptable range is provided by the proposed control method. The proposed dispatch and control capabilities would significantly improve the dynamic performance of the microgrid. Simulation results based on a modified IEEE 13‐node test feeder validate the performance of the control strategy.

An islanded microgrid is cyber-physical system, and the control relies on the communication system significantly. Improper parameters of the cyber system can result in instability of a microgrid system. To evaluate the impact of a networked control system on control performance, a cyber model is developed to represent data acquisition periods and communication delays. Simplification of the networked control system model is proposed to enhance the computational performance, making the analytical method applicable for large-scale systems. Based on the analysis, a two-dimensional stability region of a microgrid in the space of cyber parameters can be obtained. To validate the proposed method, a microgrid control scheme is proposed for power dispatch and regulation based on the droop and proportional-integral (PI) feedback control. The analytical method is compared to the time-domain simulation, and it is shown that the stability regions are nearly identical. The critical values of cyber parameters are determined based on the analytical results. The proposed control strategy with the given cyber parameters is validated for transient stability following dynamic events. Simulation results indicate that the design of a microgrid as a cyber-physical system needs to be guided by critical values for cyber parameters to prevent system instability.

No abstract

No abstract