Abstract
In a small-to-medium-scale wind energy conversion system (WECS), diode rectifiers rather than pulse-width modulated (PWM) rectifiers are widely adopted due to the features of high reliability and low cost. However, large current harmonics are induced in the generator phase current by commutations of diode rectifier, eventually causing large torque ripple on the drive-train of the WECS and making it more likely to be fatigue breakdown. In this paper, a 12-pulse autotransformer rectifier unit (ATRU) with reduced volume and weight is proposed for WECS application. By analyzing the characteristics of the input current and output voltage of the ATRU within the entire operation range of WECS, the method to properly design its parameters is proposed. A 1.2 kW direct-drive WECS demonstration platform using ATRU is built in the lab. A modified sensorless overall power control strategy is adopted to control the WECS. Experimental tests are carried out and the results not only validate the feasibility of implementing ATRU in WECS applications, but also prove its high torque ripple reduction ability.
Highlights
Small-to-medium-scale (1–100 kW) wind energy conversion system (WECS) is developing very rapidly recently, because it is one of the major ways to meet the electricity needs of users in remote areas, and it is one of the key micro generators (MGs) in microgrids
On the other hand, comparing with the delta-polygon auto-transformer rectifier unit (ATRU) proposed in [20], which is more superior in reducing the system volume and weight as the magnetic rating is only 16.4% of the conventional ATRU, the proposed ATRU is better at reducing the shaft torque ripple because its current total harmonic distortions (THDs) is lesser
When wind speed varies between vcut-in and vΩN, the WECS operates in the maximum power point tracking (MPPT) region, in which the generated power and the direct current (DC)-link voltage reference satisfy the following equation, which is
Summary
Small-to-medium-scale (1–100 kW) wind energy conversion system (WECS) is developing very rapidly recently, because it is one of the major ways to meet the electricity needs of users in remote areas, and it is one of the key micro generators (MGs) in microgrids. Taking the WECS in [13] as an example, if the most commonly used 12-pulse rectifier in industry is adopted, which requires two six-pulse converters connected through Y-∆ and Y-Y isolation transformers, the volume and weight of the transformer should be very large considering the low electric frequency (maximum 33.3 Hz) and high magnetic rating of the transformer (1.03 times of the maximum output power [18]). This inevitably would increase the system’s cost.
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