This paper presents a novel voltage-angle-based fieldweakening control scheme appropriate for the operation of permanent-magnet synchronous machines over a wide range of speed. At high rotational speed, the stator voltage is limited by the inverter dc bus voltage. To control the machine torque above the base speed, the proposed method controls the angle of the limited stator voltage by the integration of gain-scheduled q-axis current error. The stability of the drive is increased by a feedback loop, which compensates dynamic disturbances and smoothes the transition into field weakening. The proposed method can fully utilize the available dc bus voltage. Due to its simplicity, it is robust to the variation of machine parameters. Excellent performance of the proposed method is demonstrated through the experiments performed with and without speed and position sensors.
COBISS.SI-ID: 16458774
The work presents an in-depth comparative analysis of the variable speed drive (VSD) performance between an IEC frame size 90 four-pole three-phase induction motor (IM) and the equal line-start interior permanent magnet synchronous motor (LSIPMSM) by employing measurement data from no-load tests, load tests and temperature-rise tests. The motors’ no-load and load characteristics are firstly examined in detail and then the drives’ characteristics are analyzed in open-loop volts per hertz (V/f) control by using the same voltage-source inverter and the aforementioned IM or LSIPMSM in both constant torque and constant power operation. It has been established that especially the motors’ current and power factor characteristics have a distinct impact on the consequent VSD performance in terms of loss and efficiency. Furthermore, it has been shown that the lower loss of the LSIPMSM enables a significant increase of the VSD’s constant power range.
COBISS.SI-ID: 16458518
In this paper a three-dimensional non-holonomic integrator (NI) with drift terms is considered. For this type of plant, the question how to obtain desired piecewise constant output functions with minimum norm control inputs is explored. It is shown that this can be achieved by a nonlinear controller that provides simultaneous modulation of both the amplitude and the frequency of the harmonic input vector. The internal states are implicitly forced to follow natural periodic orbits satisfying the nonholonomic constraints of the plant. Global asymptotic stability and high dynamics in the output response are achieved. The problem of singularity at zero initial state is solved by a time optimal control scheme for the internal states. By combining the nonlinear controller and the time-optimal controller using an appropriate switching strategy, a powerful control concept can be established. The torque control of an induction machine is considered as an illustrative example for the application of the control scheme. Experimental results of the closed loop feedback control system are presented.
COBISS.SI-ID: 16326678
The independent scientific chapter in a monograph deals with magnetically nonlinear dynamic models of synchronous machines. Presented are procedures that can be applied to derive the magnetically nonlinear dynamic models written in the reference frame oriented with the rotor flux linkage vector or with the axis of lowest rotor reluctance. The descriptions of modeling procedures are completed by the descriptions of experimental procedures that can be applied to determine the parameters of derived models, and some descriptions related to the use of these models in synchronous machine control realizations. Discussed are linear and rotary permanent magnet machines and reluctance machines. Considered are the effects of saturation and cross-saturation, the interactions between the stator and rotor slots as well as the interactions between the slots and permanent magnets, and the end effects in the case of linear machines.
COBISS.SI-ID: 14658326
The paper proposes an IM torque control derived from the model in the stator current vector reference frame. The required torque is produced by simultaneously manipulating the magnitude and the rotation speed of the stator current vector thus forcing the rotor flux linkage vector to change implicitly in such a way that overall stability is preserved. Additional control features include maximal torque per ampere ratio in steady state and almost perfect command tracking even if the machine is magnetically saturated.The control adopts a cascaded structure and is based on a partial dynamic inversion of the reduced model that assures existence and uniqueness of the inverse mapping between the required torque, the rotor flux linkage vector and the stator current vector. Singularity at zero rotor flux linkage represents no restriction for the control performance in the admissible machine operating range. The implementation of the proposed control requires the estimation of the torque producing rotor flux component and cascaded stator current controllers. Experimental results confirm the key expectations and show the potential and benefits of the proposed control schemes.
COBISS.SI-ID: 16731414