Permanent magnet wind generators: control strategies to manage voltage unbalances

Abstract

The paper presents four different control strategies for grid connected voltage source inverters, devoted to the interface of permanent magnet synchronous wind generators with the distribution network. A common dq-axes control is compared with two modified controls in the dq frame which take into account also negative sequence components of voltages, and currents and a control approach in the stationary αβ frame which reduces the computational complexity of the control itself. An ATPDraw model of a 2 MW wind generator has been developed and employed for simulating the responses of the four control schemes to voltage unbalances and voltage dips. The improved control strategies have shown better performances in terms of reduction of 100 Hz oscillating power components during network voltage unbalances.

Simulation model of a Permanent Magnet Synchronous Generator for grid studies

“…The PMSG is here represented through an ideal voltage three phase generator with leakage inductances and resistances connected in series to the outputs (Thevenin equivalent) [8]. Such a simplification in the generator representation, that should be validated, allows reducing the computational complexity of evaluating the solution of the equations (2) ÷ (5). In this way, it is possible to insert the simplified PMSG model within larger system in order to perform study of Distributed Generators (DG) integration within complex distribution grids [5].…”

“…Such a simplification in the generator representation, that should be validated, allows reducing the computational complexity of evaluating the solution of the equations (2) ÷ (5). In this way, it is possible to insert the simplified PMSG model within larger system in order to perform study of Distributed Generators (DG) integration within complex distribution grids [5]. The model validation is discussed in the next section.…”

“…The simplified model is then employed to assess the flicker emission of a 2,5 MVA wind generator for different grid conditions. Even though the study cases reported in this work are quite simple, the described modelling approach can be profitably employed for more complex studies [5].…”