Sensor-less Vector Control of the Nine-phase Concentrated Wound Interior Permanent Magnet Motor Drive using A Unique Third Sequence High Frequency Injection Into the Stator Windings Olorunfemi Ojo Department of Electrical and Computer Engineering/ Centre for Energy Systems Research Tennessee Technological University, Cookeville, TN 38505, USA Mehdi Ramezani Department of Electrical and Computer Engineering/ Centre for Energy Systems Research Tennessee Technological University, Cookeville, TN 38505, USA Amrit Gautam Department of Electrical and Computer Engineering/ Centre for Energy Systems Research Tennessee Technological University, Cookeville, TN 38505, USA Abstract—This paper presents a sensor-less vector control method which estimates the rotor angle and speed of a nine- phase, Interior Permanent Magnet (IPM) machine with concentrated stator winding, especially for use at starting, zero and low speed operations. The injection of unique high frequency voltage signals into a non-torque producing third sequence circuit of the machine provides current information for the estimation of the rotor angle and speed without generating any high frequency torque ripple. The fundamental voltage component impressed on the motor by the converter, with the estimated rotor angle and rotor speed are used for the speed control of the motor drive under minimum stator copper loss operation. In order to computer simulate the complete controlled drive, including both the fundamental and high frequency components a full order model of the motor is utilized. The control and estimation strategies proposed have been implemented on a 2 hp, 36 slots, 4-pole concentrated stator wound interior permanent magnet motor drive. Some simulation based on a full order coupled machine model and experimental results validate the proposed vector control scheme for operation at both low and high speed operations. Keywords— sensor-less drive; position detection; high frequency voltage injection, minimum copper loss. I. INTRODUCTION To implement a precise vector control of an IPM motor drive, the rotor position of the machine should be accurately known. The mechanical sensors and extra components required for position measurement increase the price and complexity of the drive, motivating the development of several sensor-less methods [1-3]. These methods generally use the speed dependent back-EMF of the machine to estimate the rotor position, which is small at the low and zero rotor speeds. The methods yield poor position estimates at low and zero speed operations. Low and zero speed position angle estimation methods are generally now based on the relatively low magnitude, high frequency voltage or current injection into the stator windings, producing high frequency, rotor angle dependent current components. Using a heterodyne process and an observer the rotor angle can be estimated from the stator currents [4-5]. In all of these methods, the high frequency voltage or current signals generate high frequency ripple torques resulting in acoustic noise and mechanical damage to the bearings in addition to increasing motor losses. To reduce these detrimental effects, the magnitude of the high frequency injection signals are made small, which unfortunately leads to the reduction of the signal to noise ratio of the synthesized high frequency currents. This paper utilizes a new estimation method which utilizes the non-torque producing third sequence circuit of the nine- phase IPM machine to estimate the rotor angle and rotor speed especially at zero and low speeds [6]. The fundamental voltage component impressed on the motor by the converter, with the estimated rotor angle and rotor speed are used for the rotor speed control of the IPM motor drive under the minimum stator copper loss for a given torque strategy. The combined control and estimation algorithms are set forth in details. In order show by computer simulation the roles of the fundamental and third component voltages on the controlled drive, the control and estimation strategies are implemented on a full order coupled model of the motor which accounts for the winding distributions, effective air-gap variations and the dependence of the magnet flux linkage on the circumferential angle. The control and estimation strategies proposed have been experimentally implemented on a 2 hp, 36 slots, 4-pole concentrated stator wound interior permanent magnet motor drive. Some simulation and experimental results validating the proposed control and estimation methods are provided. This paper brings into focus another advantage of the concentrated wound multi-phase machines and their double, triple star variants, which is the possibility of using some of the stator higher non-torque producing MMF components for the estimation of the rotor speed and position, without the disadvantage of inducing a pulsating torque. Operation at low and possibly zero speeds are assured. II. THE MODEL OF THE NINE-PHASE IPM MACHINE To accurately predict the influence of high frequency voltage injections and possible interactions between the stator 978-1-4673-7151-3/15/$31.00 ©2015 IEEE 853