Linearized Modeling of Switched Reluctance Motor for Closed-Loop Current Control

Current control of a switched reluctance motor (SRM) is challenging due to nonlinearity and double saliency of the machine. A linear proportional-integral (PI)-based current controller, which is popular in other electrical machines, cannot be directly applied, as this requires a linearized machine model. This paper examines different small-signal linearized models for an SRM and identifies the model best suited for the purpose of current controller design. This paper then utilizes this linearized model to propose a fixed proportional-integral (PI)-based current controller, the parameters of which can be selected directly from the machine parameters. This paper also proposes a simple method to evaluate back-electromotive force (EMF) for the purpose of disturbance rejection during current control. The performance of the proposed fixed-PI-based control with back-EMF compensation is better than that of delta modulation in terms of current ripple; it is comparable to that of variable-gain PI with back-EMF compensation in terms of current ripple and current reference tracking. While variable-gain PI requires knowledge of the entire flux-linkage characteristics and involves calculation of controller gains in every sampling interval, the proposed method requires only limited details of the motor characteristics and is much simpler to implement.