Stability and Performance of an Autonomous Hybrid Wind-PV-Battery System

This paper presents small-signal stability, steady-state characteristics, and dynamic performance of an autonomous hybrid wind-PV-battery system feeding an isolated single-phase load. To improve the inherent variable frequency, variable voltage, and loading effects of the studied wind synchronous generator (SG) under random wind speeds, an AC-to-DC converter and a battery system are employed to combine distinct generated energies from the wind SG and a PV module. The stored energy in the battery is converted into a single-phase source with constant voltage and constant frequency to supply isolated single-phase loads by means of a DC-to-DC boost converter and a DC-to-AC inverter. The d-q axis equivalent-circuit models for the SG, AC-to-DC converter, DC-to-AC inverter, DC-to-DC boost converter, PV module, and battery system are respectively derived to establish the complete dynamic system equations of the studied hybrid system. Experimental results obtained from a laboratory 300 W SG, a 24 V, 1.5 kW PV module, and a 24 V, 250 Ah battery system are compared with the simulated results to validate the proposed system model. Small-signal stability of the studied system under various operating points and different disturbance conditions is also carried out by using eigenvalue analysis and dynamic simulations, respectively.