Analysis of Dynamic Frequency Performance Among Voltage-Controlled Inverters Considering Virtual Inertia Interaction in Microgrid

Inertia emulation in inverter control strategies benefits in improving dynamic frequency performance in a microgrid. Therefore, some inverter control strategies introduce virtual inertia, and the corresponding performance is investigated. These strategies mainly focus on improving frequency dynamics from the perspective of an inverter, whereas their dynamic influence on ac bus and the interaction among different inverters are still unclear. This paper aims to investigate the dynamic frequency performance of multiple generation units in both grid-connected and islanded modes considering inertia interaction. A transfer function model of paralleled inverters with emulated inertia is set up for theoretical analysis. With this model, frequency and phase response of ac bus is studied under several cases, which reveals the interactive frequency performance of voltage-controlled inverters. Furthermore, inertia interaction among different inverters is analyzed in detail, which indicates the reaction from the grid to the inverter. Consequently, the effectiveness and ineffectiveness of virtual inertia in improving frequency dynamics are demonstrated, which is practical and helpful for virtual inertia imitation in a microgrid. Simulation and experimental results are provided to validate its effectiveness.