Power factor control and soft-start of a grid connected induction machine using floating bridge inverter

该项目将研究的技术是2013年1月14日提交的美国初步专利申请的主题，由TEC埃德蒙顿资助，标题为“具有可控功率因数的并网感应电机”。电机驱动系统消耗全球44%-46%的发电量，感应电机是许多工业应用中消耗电力的主要手段，如泵、压缩机和风扇负载。这些机器吸收的电流大于它们所提供的负载所需的电流。这种过大的电流称为无功电流，因此称为无功功率，并通过称为功率因数的性能进行监测：统一是理想的，小于统一，滞后是不理想的。众所周知，对于任何给定的电力系统，感应电机都是滞后功率因数的重要贡献者。并网感应电机以单位功率因数运行的想法被认为是非常可取的，甚至是领先的功率因数也是可取的，因为这样的机器将补偿其他连接到电网的机器的滞后功率因数。这将减轻工业工厂遇到的许多问题，并提高电力的有效传输和分配。在申请人开发的方法中，一个带有笼形转子的商用三相感应电机已在领先的功率因数下运行。与以前使用电流注入的方法不同，一种简单的电力电子转换器使用电压注入技术来实现机器电流相对于电网的相移。与目前使用的其他技术相比，这种电压注入使用低成本的电力电子设备和更少的组件实现。新技术还缓解了与感应电机相关的第二个重要技术问题，即降低启动电压以减少启动电流，从而减少公用事业电网电压的电压干扰。这种双重功能使该技术更具商业可行性。初步的实验结果证明，该技术如预期的那样有效，该计划将采取下一步措施，证明新技术的商业可行性。

This Project will investigate technology that was the subject of a preliminary US patent application, submitted 14th January 2013, financially supported by TEC Edmonton and entitled "Grid-connected induction machine with controllable power factor". Motor driven systems consume 44%-46% of global electrical energy generation, with induction machines being the prime means for consuming electrical power in many industrial applications, such as pumps, compressors and fan loads. These machines draw more current than is needed for the loads that they supply. This excessive current is known as reactive current, hence reactive power, and monitored by the performance known as power factor: unity being ideal and less than unity and lagging being less than ideal. Induction machines are known to be a significant contributor of lagging power factor for any given power system. The idea of a grid-connected induction machine operating at unity power factor is considered very desirable, and even leading power factor is desired as such a machine would compensate for the lagging power factor of other machines connected to the grid. This would alleviate many problems experienced in industrial plants and improve the efficient transmission and distribution of electrical power. In the approach developed by the applicants, a commercial three-phase induction machine with a cage rotor has been operated at a leading power factor. Unlike previous attempts that use a means of current injection, a simple power electronic converter uses a voltage injection technique to enable phase shifting of the machine current relative to the grid. This voltage injection is achieved using low cost power electronics with fewer components when compared with other technologies presently being used. The new technology also alleviates a second significant technical problem associated with induction machines, reduced voltage starting to reduce starting currents and hence reduce voltage disturbances of the utility grid voltage. This dual function makes the technology more commercially viable. Preliminary experimental results have proven that the technology works as predicted and this program will take the next step in proving the commercial viability of the new technology.