POWER FACTOR CORRECTION AND REACTIVE POWER CON- TROL OF A SLIP SYNCHRONOUS PERMANENT MAGNET WIND TURBINE USING VARIABLE FLUX. A.S. Erasmus, L.L. Amuhaya and M.J. Kamper ∗ ∗ Department of Electric and Electronic Engineering, Stellenbosch, South Africa. Abstract: The slip-synchronous permanent magnet wind generator is a new concept wind generator that is able to directly connect to a power grid. In this paper the effect of implementing variable flux in the generator is investigated with regards to grid compliance of a Wind Energy Facility. The main focus of this paper will be the implementation of variable flux in the generator in order to achieve grid compliance in terms of power factor and reactive power control. Key words: Variable flux, power factor correction, reactive power control, Q-Point control, 1. INTRODUCTION There is a recent increase in electricity generated from wind turbines in the energy sector. Induction generators (IG) are popular choices among generator types for small scale wind farms. IGs however, have the disadvantage of requiring some form of power electronics to compensate for its power factor. Doubly Fed Induction Generator (DFIG) with a gearbox and a partially rated single stage converter (SSC) is the most common drivetrain technology used today [1]. The Slip-Synchronous Permanent Magnet Generator (SS-PMG) developed in [2] is an alternative, fixed speed wind turbine that doesn’t require a gearbox or power electronics in order to be grid connected. The absence of power electronics and gearboxes makes the SS-PMG a robust and affordable generator for low to medium voltage use. The SS-PMG in Figure 1 is a generator that originated from the PMIG concept of using multiple rotors and can be thought of as two separate PM generators linked by a freely rotating PM rotor. The SS-PMG’s IG rotor is short-circuited and mechanically connected to the turbine blades. The generator’s stator side directly connects to a 3-phase grid and is a synchronous generator (SG) operating at synchronous speed. The induction generator with its rotor connected to the turbine, operates at a slip speed relative to the synchronous rotor [3]. A performance evaluation of the SS-PMG with respect to the grid code in [4] shows that the voltage, frequency and low voltage ride through (LVRT) capability adheres to grid code standards. However, the SS-PMG doesn’t have the required power factor at low loads and has no form of reactive power control, and is thus not completely grid compliant. Due to the SS-PMG being a permanent magnet (PM) generator the flux is constant and cannot be used for power factor improvement. Hence, typical methods of improving the power factor is by either using an LC compensator or a static VAR compensator. These compensation techniques deliver or absorb reactive power depending on the power Figure 1: Cross section of SS-PMG output of the generator. The focus of this paper is to investigate a different approach to power factor correction with the use of variable flux in the PMSG side of the SS-PMG. Also investigated in this paper is if variable flux can be used as a reactive power control method to achieve complete grid code compliance of the SS-PMG. Important questions arising with the use of variable flux in the SS-PMG include: -Would the flux be adjusted physically in the generator? -If it is possible to implement variable flux, how much should the flux be adjusted in order to make the SS-PMG grid compliant? -How much reactive power would the variable flux compensate? -If there is need of control systems or power electronics, how robust and cost effective would it be?