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Study on Control Strategy of Microgrid in Islanded Operation Mode

The droop control strategy is only considered the frequency stability during the islanded operation mode of microgrid. So a cooperative control strategy based on two-layer hierarchical control structure is proposed in this paper. In islanded operation mode, Single master operation (SMO) or multi master operation (MMO) is decided by microgrid management system (MMS). When power changes during islanded operation, the master unit (s) with v/f control can balance the energy production and consumption quickly. Based on detecting instantaneous power of master unit (s),The secondary control of MMS sets renewed reference values of instantaneous power of slave unit (s) with PQ control. After that the output power of master unit (s) will return into zero. The simulation studies demonstrate that the proposed cooperative control strategy not only implements no-error frequency control and voltage stability control, but also provides enough spinning reserve margin for master unit (s) to keep the system energy balance all the time.