Distributed Secondary Control for Island Microgrids With Expected Dynamic Performance Under Communication Delays

Abstract

In island microgrids, the increasing integration of inverter-interfaced distributed generators (DGs) degrades the dynamic performance of the control system. The operation voltage and frequency may appear unacceptable overshoots and fluctuations under disturbances. To achieve rapid convergence while efficiently suppressing overshoot, this paper develops a distributed control method for island microgrids with expected dynamic performance. In addition to the typical distributed consensus design, an auxiliary dynamic reshaping function is introduced into the algorithm to increase the control degree of freedom of the operation dynamics. Thus, the proposed method can realize independent and flexible configurations of the damping ratio and natural frequency of the control system, and obtain the expected state convergence and overshoot suppression performance according to the actual requirements of microgrids. Besides, different delays between DGs are also considered. Instead of simply adopting the conventional global fixed delay time, we preserve the difference of delays to the greatest extent. Such processing can effectively reduce the conservatism of control and improve the response rate. A nonlinear programming problem is also established for DGs to calculate the allowable delays under the specific performance. Finally, several case studies and an RT-Lab experiment evaluate the effectiveness of the method.