Wind Generator Impedance Matching in Small-Scale Passive Wind Energy Systems

In this paper, the improved turbine power matching of passive wind energy systems for dc-connected battery storage applications with an impedance matching method is investigated. The passive system uses a direct-drive permanent magnet synchronous generator and is directly connected via a diode rectifier to the dc fixed-voltage battery storage. To improve power matching, an external inductance is added to the passive system between the generator and the diode rectifier. A static finite element based solution method is proposed to accurately calculate the necessary external inductance to achieve near maximum power point matching. It is shown that the proposed finite element based calculation method is computationally efficient and excellently suited for generator design optimization, which is critical for this application. It is also shown that by rewinding existing machines for the correct cut-in speed and adding the external inductance for improved power matching, existing machines can be effectively recycled for passive wind energy systems. The proposed static finite element solution method's accuracy and improved power matching are confirmed with measured results on a sub 5 kW power level.