Improvement in Two Adjacent Microgrids Frequency Using the AC-to-AC Converter Based on Sugeno Fuzzy Control Scheme

Microgrid and multi-microgrid are solution for integrating DGs into a system and are components of future power systems. Exploitation and frequency control in islanding mode is of special importance due to the lack of sufficient spinning reserve. Almost, DGs are connected to the microgrid through inverters and frequency deviation from an allowed threshold makes their removal from the main grid which is not acceptable for consumers and producers of the electrical power. One way for frequency control and optimized exploitation of the entire system is to connect the adjacent microgrids. Indeed, the microgrids cooperate together through exchanging their power surplus and power shortage. In this paper, a new hybrid control method based on Sugeno- and Mamdani-type fuzzy inference system to control an AC-to-AC converter connector of two adjacent microgrids has been proposed. An analytical method for controlling the converter was developed using the Sugeno. The proposed method is simple and practical and can be easily implemented. Moreover, to eliminate the steady-state error and to modify the performance of the control system, it is proposed to use a PI fuzzy controller in its outer loop. Simulation results show that the AC-to-AC converter with the proposed controlling strategy has prevented the intensive frequency deviations and has improved the frequency control in both microgrids.