A new low-cost sensorless MPPT algorithm for small wind turbines René Aubrée 1,2 , François Auger 1 and Ping Dai 1 1 LUNAM Université, IREENA, Saint-Nazaire, France 2 LUNAM Université, ICAM, Nantes, France E-mail: rene.aubree@icam.fr, francois.auger@univ-nantes.fr, daipinghere@gmail.com ABSTRACT This paper presents an original method for the sensorless Maximum Power Point Tracking (MPPT) of a small power wind turbine using a permanent magnet synchronous generator to supply a DC load. This method does neither require the knowledge of the wind speed nor the turbine parameters. After a presentation of the energy conversion chain (wind turbine, PMSM generator, rectifier and boost circuit), we first derive an analysis of its energy efficiency. This analysis shows that the highest power at the output of the turbine and the highest power supplied to the load are not obtained at the same rotor speed. This clearly shows the interest to maximize the power supplied to the load rather than to track the maximum power at the output of the turbine deduced from its theoretical power coefficient ܥ ௣ . We then describe the proposed MPPT algorithm and the speed estimator used to design a sensorless MPPT. Simulation results demonstrate the feasibility of the proposed approach. Index Terms— Small Wind Turbines, Permanent Magnet Synchronous Generator, MPPT, Angle Tracking Observer 1. INTRODUCTION For centuries, man converts wind into mechanical energy for its own needs. This is especially true today with the depletion of fossil fuels and the emergence of environmental issues. Increasingly large wind turbines, which are becoming more and more efficient, are now appearing. These wind turbines are grouped into large wind farms and are connected to the grid. On the other hand, there is also a need for small wind turbines (SWTs), designed to produce energy close to its consumer (remote sites, “off-grid” homes, relocatable equipment buildings, road signs, street lighting...) [6,12]. The optimal operation of a SWT is a key issue because of its low efficiency and its high initial cost. As shown in [11], the efficiency of a SWT depends on many factors. One of them is the power converter. For economic reasons, low-cost power converters are usually integrated, leading to a poor efficiency which deteriorates the reputation of SWTs. Another factor is the electric power generator. Compared to other possible generators, permanent magnet synchronous generators (PMSGs) have a higher efficiency, as the copper losses in the rotor are weak, and a larger energy density. Moreover, PMSGs may be used at low varying speeds, allowing the generator to be directly coupled to the wind turbine, without using a gearbox which would decrease the availability of the system, increase its weight and the need for maintenance [7]. However, since PMSGs are AC machines, a controlled AC/DC converter is necessary to efficiently supply a DC load. A last factor is the operating conditions. Indeed, SWTs are usually installed at a low height (below 12 meters). At this altitude, the wind is often quickly varying both in direction and force [1]. High power horizontal axis wind turbines, which are located at an altitude where the wind is constant, are controlled by powerful computers with all the necessary sensors. On the other hand, low-cost small wind turbines must be controlled by inexpensive microcontrollers which must embed complex algorithms to get the maximum efficiency of the system. Moreover, to decrease the cost and the encumbrance of the generator, and to increase the system reliability [3], one may wish that these control algorithms do not require any mechanical sensor [17]. The aim of this paper is to present a new sensorless algorithm that can provide the highest power to a DC load. To this aim, the studied energy conversion chain is introduced in Section 2. Section 3 then presents an analysis of the performance of this chain. The proposed MPPT algorithm and the speed estimator used to provide a sensorless algorithm are presented in Sections 4 and 5 respectively. Simulation results are finally presented in Section 6 to demonstrate the feasibility of the proposed approach. 2. THE ENERGY CONVERSION CHAIN The wind energy conversion system studied here is made of a turbine, a direct coupled permanent magnet generator, a 6 diode rectifier and a boost circuit.