## 1 Introduction
However, MPPT control is also used in this region to smooth out abrupt changes in wind speed, where the mechanical restrictions of the pitch system do not allow for a rapid response. Finally, there is region IV, where the wind turbine must be stopped, even with a mechanical brake [11; 12]. To operate in variable speed conditions a wind power system needs a generator that can work in these conditions. The first wind turbines did not have torque control and used a squirrel-cage induction generator (SCIG) connected directly to the grid, so the torque of the generator was not controllable and the speed of the generator was linked to the frequency of the net. Currently, most generators use variable speed operations, namely the Dual Feed Induction Generator (DFIG) and the Permanent Magnet Synchronous Generator (PMSG) [7]. Among the electric generators, the PMSG is preferred due to its high efficiency, reliability, power density, gearless construction, and light weight and self-excitation characteristics. Among various types of gear train coupling, the gearless or directly allied permanent magnet type wind generators are more popular nowadays in the wind energy market in on-shore application [13]. The control of the PMSG to achieve the maximum power point can be done by varying its load using an electronic power interface circuit. The interconnection can be done through a back-to-back converter or through a three-phase diode rectifier connected to a boost converter [14]. The objective of this work is to perform an analysis of the MPPT control systems with PMSG generators. According to the reviewed literature, it is stated that an MPPT controller is the most important part of the control in a wind turbine, since the turbines are designed to work most of the time in regions II and III and in both regions an MPPT controller it is required. On the other hand, the PMSG is the most used. The MPPT algorithms have been classified according to the maximization of the captured power, the MPPT algorithms are categorized into Indirect Power Controllers (IPC) and Direct Power Controllers (DPC). The IPC maximizes the captured mechanical wind energy while the DPC directly maximizes the electrical power output [15]. The main MPPT algorithms that are widely used include the tip speed ratio (TSR), power signal feedback control (PSF), optimal torque (OPC), Search for slope ascent (HCS), perturbation and observation method (P&O), incremental conductance and optimal base relation (ORB), as well as computer techniques developed with expert systems, such as fuzzy logic and neural networks [10]. Energy storage too can control and reduce power fluctuations, enhances the electric system flexibility, and enables the storage and dispatching of the electricity generated. Different storage technologies are used in electric power systems. They can be electrochemical (Batteries), mechanical (Flywheel energy storage) or electrical (Super capacitor energy storage). Several types of batteries can be used: NickeleCadmium (NieCd), NickeleZinc (NieZn) or lead acid. The battery must have some important characteristics such as high charge or discharge efficiency, low self-discharge and long cycle life. The flywheel includes a cylinder with a shaft connected to an electrical generator and helps to maintain the power generation constant, as long as the wind power is sufficient. Inertial energy is stored to cushion power changes of the wind generator; it is necessary to know the reference speed, which ensures that the system transfers the required energy by the load at any time. Super capacitors are used to suppress fast wind power fluctuations but at a minor scale. Thus, they can be considered only as a support for wind turbines systems and are generally combined with a battery system [16]. The analysis carried out in the literature indicates a trend in the use of MPPT controllers with ECS for wind turbines, due to the complexity of the mathematical models and the non-linearity of the system.