In this paper, we address the problem of state observation for sensorless control of switched reluctance motors (SRMs), that is, the regulation of the motor measuring only the voltage and the current of the electrical supply. Instrumental for the construction of the observer is the derivation of algebraic relations, which define regression models, between the unknown rotor flux and the measured quantities. With the knowledge of the flux, it is shown that the mechanical coordinates can be estimated with suitably tailored adaptive nonlinear observers. Replacing the observed states, in a certainty equivalent manner, with a full information stabilizing law completes the sensorless controller design. In contrast with other motors, there is no universally accepted mathematical model to describe the dynamics of SRMs. To widen our target audience, we present the results for four different mathematical models reported in the literature. Simulation results with a precise (finite element) model of the SRM are used to illustrate the performance of the proposed observer and sensorless control.
This paper presents the control of a Switched Reluctance Generator (SRG) for low voltage DC grid with the objective of efficiency maximizing. Analysis of the energy conversion, including electrical machine losses (Joule, magnetic, mechanical) and power converter losses (switching and conduction), has shown that there is an optimal combination of control variables (turn-on and conduction angles, phase current reference), which maximizes the drive efficiency. The control variables are derived from a Finite Element Analysis and parametric optimization algorithm for all of the operating points in the torque-speed plane and stored in lookup tables. The performances are evaluated with intensive numerical simulations and experimental tests with a 8/6 SRG feeding a DC resistive load for different rotational speeds. The results show good performances of the output DC voltage control with low ripples, even in the presence of speed and load variations. Thanks to the optimization, simulation results show that beyond 1500 rpm, drive efficiency is higher than 60 % and almost reaches 70 % at nominal speed. The experimental results show that, for light loads and beyond rated speed, the drive efficiency lies in the range between 60 % and 80 % .
The Switched Reluctance Machine is one of the most promising electrical machine in variable speed applications because of its intrinsic robustness and its fault tolerant capability. However, the performances of the machine are deteriorated when a defect affects the position sensor. This paper describes a sensorless control for the switched reluctance machine: two methods based on the characteristics of the machine are proposed to eliminate the requirement of the position sensor. The first one utilizes the phase inductance characteristic to determine the rotor position by injecting a test signal while the phase winding is non-energized. The second one utilizes the flux characteristic to estimate the position by measuring the phase voltage and current. Both methods are evaluated through intensive simulation and the results show their good performance respectively in low speed and high speed region. The flux-based method, implemented in a FPGA, has been evaluated on a test bed. The experimental results confirm the simulation ones with an average position estimation error of around 2° mechanical in the range between 1/3 and the rated speed.
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