Delay-Dependent Stability Analysis of Modular Microgrid With Distributed Battery Power and SoC Consensus Tracking

The modular microgrid based on distributed battery storages is a simple and reliable power supply way for the islands. Modules are interconnected to the transmission network through the three-port converter. The three-port converter supplies the local ac bus voltage within the module and realizes the power exchange between the module and the transmission network. Distributed battery power and SoC consensus tracking model considering communication time delay is established on the leader-following multi-agent consensus tracking theory. By using the delay decomposition method, where the delay interval is discretized into two segmentations with an equal width, a modified Lyapunov-Krasovskii functional is constructed. A delay-dependent sufficient condition for the absolute stability of the battery power and SoC consensus tracking is derived in terms of linear matrix inequalities (LMIs) by using the free-weighting matrix method. The maximum delay margin corresponding to different controller parameters is calculated with the LMI toolbox of MATLAB. The case study is carried out based on the DongAo Island microgrid demonstration project. Simulations of battery power and SoC consensus tracking with constant time or time-varying delays verifies the effectiveness of the maximum delay margin determined by the stability criteria. Experiments reveal that the three-port converter can meet the requirements of the modular microgrid networking and operation control. The distributed battery power and SoC consensus tracking of the modular microgrid can be achieved when the communication time delay is less than the maximum delay margin.