Abstract
To solve the problem of the traditional quasi-Z-source inverters with low voltage gain, an enhanced half-quasi-Z-source inverter (E-HQZSI) is proposed and applied to direct-drive permanent-magnet wind power generation systems in this paper. The expression of the boosting factor is deduced, which shows that E-HQZSI has higher voltage gain compared with the QZSI and HQZSI. However, the higher voltage gain of the E-HQZSI will lead to the large distortion of the generator stator current necessarily. In this paper, a periodic shoot-through duty ratio control scheme is proposed to reduce the stator current harmonics for E-HQZSI. According to the change rule of the single-phase stator current, the shoot-through duty ratio is compromised to make that the three-phase stator currents are as close as possible to the sine wave. Finally, the correctness of the theoretical analysis is verified by simulation and experiment.
Highlights
In recent years, wind power generation has developed rapidly due to the advantages of green, clean, and pollutionfree [1,2,3,4,5]
(3) e adjustment of small- and medium-sized wind power generation system (WPGS) is more flexible, which is helpful for peak load shifting of the power grid e types of generators used in WPGS mainly include doubly fed induction generator (DFIG) and permanent-magnet synchronous generator (PMSG) [9,10,11,12]
It can be seen from equation (36) that the b-phase current is closer to the ideal sine wave when the shootthrough duty ratio of enhanced half-quasi-Z-source inverter (E-half-quasi-Zsource inverter (HQZSI)) is changed in accordance with equation (35)
Summary
Wind power generation has developed rapidly due to the advantages of green, clean, and pollutionfree [1,2,3,4,5]. Domestic wind power generation system (WPGS) is mainly developing towards large-scale, while the small- and medium-sized WPGS have been highly regarded in European and American countries at the same time [7, 8]. Compared with the DFIG, the PMSG has the advantages of light weight, small volume, high power factor, and good reliability and has become the mainstream choice of current WPGS gradually. An enhanced half-quasi-Z-source inverter (E-HQZSI) is proposed for direct-drive permanent-magnet wind power generation systems, which have higher voltage gain compared with the QZSI and HQZSI. 2. Proposed E-HQZSI e topology of E-HQZSI is shown, which includes DC power supply, impedance source network, and three-phase inverter bridge. In the shoot-through state, the inductor L1 is charged by DC power supply through the diodes D2 and D4 and the shoot-through loop; the inductor L2 is charged by the capacitor C1 through the diode D4 and the shoot-through loop, and the inductor L3 is charged by the capacitor C2 through the shoot-through loop
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