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The vanadium redox flow battery (VRB) is a large stationary energy storage system; which presents high-speed response and overload capacity characteristics. The VRB produces a dc voltage between two terminals; so a power conditioning system composed principally by a dc/ac flexible ac transmission system (FACTS), is required in order to connect the battery to the power system. In this regard, this study proposes a new FACTS compensator for controlling the VRB based on a 12-pulse thyristor converter with commutated capacitors on the ac side. This type of compensator offers a good transient response with low-power converter losses. Simulations of the FACTS compensator employing Matlab/Simulink software validate the proposal and show the good performance of the proposed device.

The variable speed double-feed induction generator wind turbine (DFIG) is today the most widely used concept, owing to its high performance, its capability to capture the maximum wind energy, and the low cost of the induction machine. These features contribute to the continuous installation of the DFIG power generation in several countries [1]. As a consequence, in the near future, this type of wind turbines may start to influence the behavior of electric power systems by interacting with conventional generation and loads. Therefore, DFIG turbine models that can be integrated into power system simulation software are needed.The DFIG is a standard, wound rotor induction machine with its stator winding connected directly to the grid and its rotor windings connected to the grid trough an ac/dc/ac PWM converter. The ac/dc/ac converter normally consists of a machine-side converter and a grid-side converter, both of which are controlled by decoupled d-q control approaches. The detailed model of the DFIG demands high computational requirement, which increases when a wind farm is considered. The aim of this paper is, therefore, to propose a new simplified model of the DFIG appropriate for bulk power system dynamic studies.

Wind generation (WG) is the most widespread renewable energy resource in the world. However, this implementation inevitably leads to an increase in the problems caused by WG, e.g. frequency oscillations, power fluctuations or voltage variations. To overcome these problems, the use of a power conditioning system (PCS) coupled with a vanadium redox flow battery (VRFB) is proposed in this study. The PCS is composed of a distribution static synchronous compensator connected to a dc/dc chopper. The PCS/VRFB detailed model is presented and a three-level control system is developed. This control system allows the PCS/VRFB to perform a decoupled reactive and active power flow control. The dynamic response of the PCS/VRFB is evaluated through simulation tests, and performance characteristics of the device are obtained by means of the variation of the power references. The results obtained demonstrate that the PCS/VRFB offers a good transient response and the control system proposed allows mitigating the problems caused by wind power generation.

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The penetration of wind generation into AC micro-grids (MGs) has been increasing in recent years. Wind generation is uncontrollable, variable in nature, and uncertain. If the penetration level is high, the random variations of the wind power generation could cause problems for MGs to maintain the nominal system frequency. A typical solution is to employ energy storage systems (ESS) into the MG in order to compensate the wind power fluctuations. In this chapter, the use of a vanadium redox flow battery (VRFB) coupled with a power conditioning system (PCS) is suggested to enhance the frequency stability of a MG with high wind power penetration. A new control system is developed for the PCS/VRFB. The control system performs the load leveling of the wind generation and carries out the primary and secondary frequency control of the MG. Dynamic simulations of the proposed device are performed and demonstrate that the new control system improves the transient responses of the PCS/VRFB and the MG, during minor and/or severe disturbances.