Development of a Permanent-Magnet Induction Generator for Wind Power and Small-Scale Hydropower Applications

近年来，风电和小型水电站被广泛引入，作为有助于环境保护的可再生能源。在这样的发电厂中，感应发电机(IGs)被广泛使用，因为它们可以直接接入电网，不需要太多额外的设备，同时在成本和维护方面具有优势。然而，IGS需要来自电网的磁化电流，这本质上会导致功率因数和效率的降低。在本研究项目中，研制了一种新型的永磁感应发电机，并对其电磁特性进行了分析。PMIG在松鼠笼形转子内有一个永磁体(PM)转子。分析结果表明：1.在永磁转子上加了阻尼器后，不能达到理想的IG运行；2.即使在不平衡电压或单相电网下运行，其效率也优于传统的IG3。由于鼠笼转子几乎消除了在不平衡运行模式下产生的负序旋转磁场，因此不存在PM退磁的风险。

Recently, wind power and small-scale hydropower plants have been extensively introduced as renewable energy sources that contribute to environmental protection. In such power plants, induction generators (IGs) are widely used because they can be directly connected to a power grid and do not require much additional equipment while being advantageous in terms of cost and maintenance. However, the IGs require a magnetizing current from the power grid, which essentially causes a decrease in power factor and efficiency. Therefore, the performance of the IGs needs further improvement.In this research project, a new type of IG termed the Permanent-Magnet Induction Generator (PMIG) was developed, and its electric and magnetic characteristics were analyzed. The PMIG has a permanent-magnet (PM) rotor inside a squirrel-cage rotor. The squin-el-cage rotor is linked to the shaft, and the PM rotor is free to rotate against the shaft.As a result of the analysis, the following new findings were obtained :1.The desired operation as an IG is not obtained when a damper function is added to the PM rotor.2.Even if the PMIG operates at unbalanced voltages or single-phase power grids, its efficiency is better than that of a conventional IG3.Since the negative-sequence rotating field, which is produced under unbalanced modes of operation, is almost canceled by the squirrel-cage rotor, there is no risk of PM's demagnetization.