Sensorless Vector Control of AC Drives

In the recent years the numbers of electric drives in the automotive and other industries have drastically increased, which leads to the obvious recognition that appropriate control method must be chosen based on the application. The vector control theory itself was described by Hasse and Blaschke in the early ’70s, but the implementation of these methods are still a challenging task for the developer engineers. In most cases, the shaft angle encoder cannot be omitted, since the safety level of the application. But in these cases a sensorless vector control method can be used as backup algorithm, with which the drive systems can be stopped without damaging the drive or the users. This paper summarizes some of the available sensorless vector control methods, which have been successfully implemented in the industry. Comprehensive analysis of the main sensorless techniques, such as Model Reference Adaptive System (MRAS), Natural Field Orientation (NFO) and High Frequency Signal injection methods will be presented with their control structure, possible field of application and simulation results.