A new technique for optimum excitation of switched reluctance motor drives over a wide speed range

Abstract

Optimum performance of switched reluctance motors (SRMs) over a wide range of speed control is an essential approach for many industrial applications. However, the doubly salient structure and deep magnetic saturation make magnetization characteristics of SRMs a highly nonlinear function of rotor position and current magnitude. This, in turn, makes the control of SRM drives a challenging task. As the control of SRMs depends on the inductance profile, it requires an adaptive control technique for optimum operation over a wide range of operating speeds. This paper presents an adaptive control technique for optimum excitation of SRM drives. The proposed control technique accurately considers the effect of back-emf voltage for high-and even low-speed operation. It determines the most efficient switch-on angle as a function of motor speed and current magnitude. Moreover, the optimum switch-off angle is defined to enhance motor output torque/power without negative torque production. The proposed technique simplifies the SRM control in order to cut down the complexity and cost; it offers easy implementation and can be used for sensor and sensorless operation of SRM drives. It also provides an eligible candidate for industrial applications as the optimization strategy uses an analytical solution. For adequate modeling, the nonlinear magnetization characteristics of the SRM are obtained using finite element analysis. The SRM, converter, and control algorithm are modeled using the MATLAB/Simulink environment. The simulation results are compared with a closed-loop switch-on angle controller in order to show the feasibility of the proposed control technique. In addition, experimental results are obtained to prove the promising performance and simplicity of the proposed controller.

Optimum Control Parameters of Switched Reluctance Motor for Torque Production Improvement over the Entire Speed Range

“…In order to consider the effect of back-emf voltage, the inductance profile is analyzed and fitted accurately over the minimum inductance zone [18], [19]. After that the optimum θ on is calculated as follows [18]:…”

“…The highest torque/ampere ratio over the possible range of operating speeds is an essential approach for many applications [16]- [19]. The develop torque of SRMs can be optimized by machine design and/or applying appropriate control parameters [18]- [22]. The control parameters are reference current, turn-on (θ on ) angle and turn-off (θ off ) angle.…”

“…The control parameters are reference current, turn-on (θ on ) angle and turn-off (θ off ) angle. As the reference current is determined by outer loop controller, switching-angles (θ on , θ off ) are the main control parameters for SRM torque optimization [18], [23]. For single-phase excitation, the conduction angle (θ c ) is set to a constant value.…”

“…In this method, the control strategy is affected by energizing switching angle and requires a complicated process to shorten its searching time. Analytical solutions are used for turn-on angle optimization [18], [28]. They mainly introduce the turn-on angle as a function of multiple variables.…”

“…On the contrary, for high speeds, the phase current can't rise or decay quickly enough to reach its reference commanded level. For that reason, the motor phase winding is turned-on early in order to allow phase current to reach its commanded level as shown in Figure 1(b) [18], [28]. Regarding the observation and analysis of static magnetization characteristics of SRM, for a given current, the maximum torque occurs as rotor begins to move out from minimum inductance zone [24]- [28].…”