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Position estimation at low/zero speed for permanent magnet synchronous machines is commonly achieved with the injection of high-frequency signals. This article presents a new sensorless scheme that accurately observe the rotor angle at low speeds, including standstill condition, without injecting high-frequency signals. The algorithm is built upon a previous sliding-mode current controller and uses the switching functions slopes inaccuracies produced by the saliency effect to determine the rotor position and speed. Thanks to the equivalent control concept and together with a sliding-mode-based phase-locked loop observer defined by a complex switching function, the algorithm provides both rotor position and speed in a compact form. This article includes the main working principle and defines the operational range of the proposed scheme. Finally, the feasibility of the method is corroborated through experimental results in sensorless configuration. [ABSTRACT FROM AUTHOR]

In this brief, a new control scheme is presented for the doubly fed induction machine (DFIM). The proposed control algorithm offers the advantages of proven stability and remarkable simplicity. In contrast to the classical vector control method, where the DFIM is represented in a stator-flux-oriented frame, a model with orientation of the stator voltage is adopted. This approach allows the decomposition of the active and reactive powers on the stator side and their regulation on the rotor side. A main contribution of this brief is the use of the Hurwitz test for polynomials with complex coefficients that has had little prior application in control theory. This results in a proof that a proportional-integral (PI) control regulating the stator currents ensures global stability for a feedback-linearized DFIM. The specific condition that the PI gains must satisfy is derived as a simple inequality. The PI controller has a particular structure that directly relates the d-component of the rotor voltages to the q-component of the stator currents and vice versa. The feedback linearization stage only uses the direct measurement of the rotor and stator currents and is thus easily implementable. Furthermore, it is also shown that the PI controller (without the feedback linearization terms) is also stable for a large range of control gains and does not require the knowledge of the machine parameters. Finally, the control system is validated in simulations and in experiments. [ABSTRACT FROM AUTHOR]

This paper presents a sliding mode control for a wound rotor synchronous machine acting as an isolated generator. The standard dq model of the machine is connected to a resistive load. A switching function is defined in order to fulfill control objectives, and the ideal sliding dynamics is proved to be stable. From the desired surface, the standard sliding methodology is applied to obtain a robust and very simple controller. Numerical simulations and experimental results validate the control law and show good performance and a fast response to load and reference changes. [ABSTRACT FROM AUTHOR]