Contemporary sensorless AC drives require the use of electromechanical quantities estimation. The skin effect occurring in AC machines with solid secondary or with solid secondary elements causes machines of this type to be represented by equivalent circuits containing distributed elements, which makes the analysis of machine electrodynamic states more complicated and hinders the construction of relatively simple and effective estimators of electromechanical quantities. The variability of rotor parameters is modelled, with a good approximation, by the machine secondary multi-loop equivalent circuit with lumped elements. In this paper the construction procedure of electromechanical state variable estimators basing on this type of equivalent circuit will be presented. The simulation investigations of the created electromechanical quantities estimators, performed for the selected states of solid iron rotor AC machine operation will be shown as well.

A lot of methods for sensorless drive control have been published last years for synchronous and asynchronous machines. One of the approaches uses high frequency carrier injection for position control. The injected high frequency signal is controlled to remain in alignment with the saliency produced by the saturation of the main flux. Due to the fact that it does not use the fundamental machine model which fails at standstill of the magnetic field it is possible to control the drive even at zero speed. In spite of this obvious advantage industry does not apply sensorless control in their products. This is due to the dependency of many published methods on physical parameters of the machine. The high frequency carrier injection method, presented in this paper, does not need to have exact machine parameters and it can be used for machines where there is only a very small rotor anisotropy like in Surface Mounted Permanent Magnet Synchronous Machines (SMPMSM) [1]. Standard drives usually are supplied by a 6-pulse diode rectifier. Due to new European directives concerning the harmonic content in the mains it is expected that the use of controlled pulse-width modulated PWM rectifiers will be enforced in the future [2]. An important advantage of this type of rectifiers is the regeneration of the energy back to the grid. Another benefit are low harmonics in comparison to diode rectifiers. Using one of many control methods published so far it is also possible to achieve almost unity power factor. However, in these methods voltage sensors are necessary to synchronize PWM rectifiers with the mains. Therefore they are not very popular in the industry with respect to the cost and the lack of reliability. Recently a control method was proposed which is based on a tracking scheme. It does not need any voltage sensor on the ac-side of the rectifier and it does not need to know accurate parameters of the system. This paper presents the control solution for a cheap, industry friendly (no additional hardware and installation effort) drive system. The phase tracking method for control of electrical drive and PWM rectifier is described. Encouraging experimental results are shown.

This paper presents a position sensorless drive of non salient pole PM synchronous motors for all speeds including zero speed. Using adaptive Lyapunov design a new approach for the design of an observer is developed. The resulting scheme leads to a nonlinear full order observer for the motor states including the rotor speed. Assuming motor parameters known the design achieves stability with guaranteed region of attraction even at zero speed. The control method is made robust at zero and low speed by changing the direct vector current component to a value different from zero. In order to verify the applicability of the method the controller has been implemented and tested on a 800 W motor.

The paper presents a sensorless control approach for a five-phase induction motor drive with third harmonic injection and inverter output filter. In the case of the third harmonic injection being utilised in the control, the physical machine has to be divided into two virtual machines that are controlled separately and independently. The control system structure is presented in conjunction with speed and rotor flux observers that are required for a speed sensorless implementation of the drive. The last section is dedicated to experimental results of the drive system in sensorless operation, and the uninterrupted drive operation for two open-phase faults

The paper presents a novel model predictive flux control (MPFC) scheme for three-level inverter-fed sensorless induction motor drive operated in a wide speed region, including field weakening. The novelty of the proposed drive lies in combining in one system a number of new solutions providing important features, among which are: very high dynamics, constant switching frequency, no need to adjust weighting factors in the predictive cost function, adaptive speed and parameter (stator resistance, main inductance) estimation. The theoretical principles of the optimal switching sequence predictive stator flux control (OSS-MPFC) method used are also discussed. The method guarantees constant switching frequency operation of a three-level inverter. For speed estimation, a compensated model reference adaptive system (C-MRAS) was adopted while for IM parameters estimation a Q-MRAS was developed. Simulation and experimental results measured on a 50 kW drive that illustrates operation and performances of the system are presented. The proposed novel solution of a predictive controlled IM drive presents an attractive and complete algorithm/system which only requires the knowledge of nominal IM parameters for proper operation.