Control and stability improvement of combined wind-battery system with permanent magnet synchronous generator supplying active load

This paper deals with the control and stability enhancement of a wind power generation system feeding active load with constant power characteristic. The under study system is a combined wind-battery generation system with permanent magnet synchronous generator (PMSG) supplying active load by using interfaced power electronics converters. The employed active load is indeed an active rectifier behaving such as a constant power load (CPL). Since CPLs from the small-signal point of view behave such as negative resistances, they result in stability margin reduction and even system instability at higher load power penetration. In this paper, as the novelty, a control approach is presented resulting in system stability at presence of active loads. In other words, by using the proposed control method, the output impedance of the load-side converter at low frequencies converge to zero, and this in turn results in system stability margin improvement under presence of active loads. At the end, performance of the study system with active loads is examined by time domain simulations and with/without proposed control method.