Position sensorless and optimal torque control of reluctance and permanent magnet synchronous machines

[摘要] Keywords: position sensorless control, torque control, synchronous machinesThe work in this thesis deals with energy e cient torque control and rotor position estimationin the full speed range, for a family of synchronous machines that should be used more oftenin the near future. This family consists of the permanent magnet synchronous machine(PMSM), the reluctance synchronous machine (RSM), the interior-PMSM and the PMassisted-RSM.By designing and controlling these synchronous machines correctly, better performance andhigher energy e ciency can be expected compared to the performance and e ciency of anindustry standard induction machine. However, applications are limited to variable speeddrives (VSD) in a certain power range, e.g. below 100kW. With the growing concern andnecessity of a better utilization of energy, it is becoming standard to use electronicallycontrolled power converters between the electricity grid and electrical machines. Therefore,there is a very large scope for the implementation of this synchronous machine technology.For traction applications like electrical vehicles, the optimally controlled synchronous machinetechnology has a very strong position. Very compact and robust synchronous machineswith a very high power density can be designed that may out-perform the induction machineby far. However, one major requirement for most applications is position sensorless control,i.e. rotor position estimation in the whole speed range.To achieve energy e cient torque control, maximum torque per Ampere (MTPA) controlshould be implemented. It is possible to achieve MTPA control at low speed, but above therated speed of the machine,eld weakening needs to be performed. The question is how toimplement MTPA and e ectiveeld weakening for any value of speed and DC bus voltageand for any machine within this family of synchronous machines. In this thesis a method isexplained to achieve this goal using results fromnite element (FE) analysis directly. Thescheme may be implemented within a very short period of time.The contribution of this thesis is a general understanding of the problems at hand, withan in-depth view into the mathematical representation of synchronous machines, a genericmethod of energy e cient torque control and a thorough study of rotor position and speedestimation methods.

[发布机构] Stellenbosch University