## 1 Introduction
Indeed, a three-phase diode bridge guarantees less power loss and the DC/DC converter is still more robust and simpler compared to the controlled rectifier. When the WT system is connected to the grid, it generally operates at maximum power point tracking (MPPT) which allows for extracting the maximum power from the wind energy system in all environmental conditions [11]. However, for distributed generation systems, there may be constraints where WT systems are not supposed to generate maximum power. Indeed, taking into account some constraints in terms of economy and system security of the MG, e.g., when the storage device is fully charged or there is low demand, a technique able to function below MPPT must be used instead. This technique, called limited power point tracking (LPPT), allows for more flexible operation of the system [8]. Consequently, a general control strategy which can deal with both MPPT and LPPT is very important for WT systems. Several power control strategies, especially MPPT algorithms, have been suggested in the literature with the main objective of extracting the desired power, reducing power oscillation, using excess power and improving the quality of the power injected into the grid. They are classified into three categories: direct power controllers (DPCs) [12; 13], indirect power controllers (IPCs) [14; 15; 16] and advanced power controllers (APCs) [14; 15; 17]. The main DPC methods are the perturb and observe (P&O) method or its derived version called hill-climb search (HCS) and the incremental conductance (IC). Regarding IPCs, three algorithm methods are mostly considered: the tip speed ratio (TSR), the power signal feedback (PSF) and the optimal torque (OT). APCs are characterized by using soft computing techniques like fuzzy logic (FL) and artificial neural networks (ANNs). These techniques could work independently or combined with other methods to reach the operating point [17]. An overview and details about these techniques are provided in Section 2. Some of these algorithms have already been modified to allow the possibility of operating in LPPT mode. However, the change from one operating point to another still represents the most critical situation for the system stability. In addition, the sudden variation of some conditions, such as power required by the user or climatic changes, e.g., wind velocity, can have an impact on power output [18]. Therefore, the purpose of this paper is split into three objectives:* To propose a strategy in order to limit the power provided from an SSWT that will be integrated in a DC MG.
* To propose two LPPT algorithms based on the P&O principle to overcome drawbacks of the conventional P&O method. * To test the impact of a sudden variation of the power and the wind speed on the performances of the selected LPPT methods. Firstly, this paper presents an overview of control power strategies found in the literature. Secondly, a description of the MG, the experimental test bench and the proposed power control strategies are given in Section 3. Finally, the strategies are validated by experimental tests and the performances of the proposed methods are investigated in Section 4.