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Background: Focusing on the stability problems brought by integrated wind power and fuel cell, the objective of this paper is to analyze small-signal stability and improvement of a hybrid renewable energy system connected with doubly-fed induction generators (DFIGs) and solid oxide fuel cells (SOFCs) energy with the static series synchronous compensator (SSSC) and power-oscillation damper (POD). Methods: For this purpose, a SSSC-POD controller is designed and the state-space representation of such a hybrid power system for modal analysis is developed. Then an approach of coordination and optimization of SSSC-POD parameters based on genetic algorithm (GA) and modal analysis is proposed to further improve the power system small-signal stability. Results: Several designed scenarios, including changing the tie-line power, POD input signal and SOFC power output, are considered in IEEE two-area system to test the proposed method through small-disturbance eigenvalue analysis and time-domain simulations. Conclusion: Simulation results demonstrate that the proposed approach can effectively suppress the local and inter-area oscillations and improve power system stability.

The new energy represented by strong random wind power connecting to the power system may make the problem of inter-area low-frequency oscillation more serious. In this paper, a DFIG-PSS controller based on virtual impedance is constructed to solve the low-frequency oscillation problem in the wind power system. The step response of PSS-VI was carried out to test the effect of the controller to verify the advantages of PSS-VI than traditional PSS. The input signal of PSS-VI which is a controller based on PSS installed virtual impedance is the active power of DFIG. The output signal of PSS-VI is added to the reactive power control loop of rotor side controller of DFIG. DFIG-PSS-VI was built in Digsilent/Powerfactory software, and the simulation was carried out on the system of 4 machines and 2 regions. It is verified that PSS-VI can improve the low-frequency oscillation of wind power system.