Power management and second-order sliding mode control for standalone hybrid wind energy with battery energy storage system

Abstract

The purpose of this article is to provide a high performance control of a renewable distributed generator to guarantee an electric power quality and jointly reduce the mechanical stress despite any possible uncertainties such as the random nature of wind speed, the presence of parameters uncertainties, and external perturbations acting on the system (sudden load variation). The renewable distributed generator integrating a wind generator associated with a batteries module is considered as an energy storage device and a variable load. The proposed method is designed by a power management supervisor and a sliding mode control technique. First, the power management supervisor is used to monitor the power flows transferred between the different system devices depending on the load variation and on the intermittency of wind production. In fact, it enables to ensure the balance at the continuous, Direct Current (DC) bus between the powers supplied by the renewable distributed generator and those demanded by the load. In addition, it prevents batteries from exceeding its maximum or minimum state of charge ( SOCbat) by keeping it at an acceptable level [30%, 90%]. Second, a second-order sliding mode control based on the super-twisting algorithm is suggested to control the two subsystems (generator side and load side converters). The main target of the first one is to extract the maximum wind power taking into account the parameter variations and the fluctuating nature of wind. The second one is to investigate a second-order sliding mode control of active and reactive load power quantities, which provides better results in terms of attenuation of the harmonics present in the load voltage and current while considering the sudden load variations. In addition, a proportional–integral controller is also designed and simulated to establish a comparison framework. According to the simulation results, the second-order sliding mode control successfully deals with the nonlinearity of the renewable distributed generator compared with the proportional–integral performance.