A fixed switching period sliding mode control (SMC) for Permanent Magnet Synchronous Machines (PMSMs) is presented. The aim of the paper is to design a SMC that improves the traditional PI based Field Oriented Control (FOC) transient response, as well as to reduce the switching frequency variations of the Direct Torque Control (DTC). Such SMC requires a decoupling method of the control actions, which also brings constant switching functions slopes. These constant slopes allow to calculate the required hysteresis band value to control the switching frequency. The digital implementation degrades the performance of the hysteresis comparator and as a consequence, the previously calculated band becomes inaccurate to regulate the switching frequency. In order to recover the analogue hysteresis band comparator performance, a predictive algorithm is proposed. Finally, a set of experimental results with constant switching frequency during a torque reversal and speed control tests are provided.

Abstract-Fixing the switching frequency is a key issue in sliding mode control implementations. This paper presents a hysteresis band controller capable of setting a constant value for the steady state switching frequency of a sliding mode controller in regulation and tracking tasks. The proposed architecture relies on a piecewise linear modeling of the switching function behavior within the hysteresis band, and consists of a discrete-time integraltype controller that modifies the amplitude of the hysteresis band of the comparator in accordance with the error between the desired and the actually measured switching period. For tracking purposes an additional feedforward action is introduced to compensate the time variation of the switching function derivatives at either sides of the switching hyperplane in the steady state. Stability proofs are provided, and a design criterion for the control parameters to guarantee closed-loop stability is subsequently derived. Numerical simulations and experimental results validate the proposal.

This paper describes the design of an interleaved sliding mode control for a multiphase synchronous buck converter, which inherits the properties of the sliding mode control, operates with fixed switching frequency at steady-state and ensures current equalization among the phases. Moreover, a power management algorithm is added in order to decide the number of active phases as function of the power load demand, thus optimizing the converter efficiency. The systems uses a Master-Slave structure where each phase can actuate as the Master one in such a way that the overall system reliability is improved. Experimental results in a 1.5 kW 8-phase synchronous buck converter show that interleaving operation, robust output voltage regulation, phase current equalization, switching frequency regulation and power management are achieved.

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This work presents a nonlinear control strategy for a magnetically coupled multiport dc-dc converter aimed at automotive applications. First, a behavioural dynamic model, based on averaging the power flowing among the ports, is derived. Then, a control algorithm, based on feedback linearization techniques, is proposed. Essentially, the controller ensures decoupling and a linear dynamic behaviour thanks to a transformation of control and state variables, and a conventional PI action is devised to render asymptotic stability, as well as robustness to load uncertainties. The inversion of the control transformation, which involves nonlinear terms, is carried out using linear approximations with no significant performance decay. Hence, simplicity and efficiency are the main features of the control design. The proposed controller is validated via experimental results.INDEX TERMS Isolated multiport dc-dc converter, bidirectional power flow, nonlinear control, feedback linearization, decoupling, phase-shifted pulse width modulation, automotive applications.

This paper presents a hysteresis band controller in charge of fixing the switching frequency of a sliding mode controller. The proposed control measures the switching period of the control signal and modifies the hysteresis band of the comparator to regulate the switching frequency of the sliding motion. The switching frequency control system is modelled and a design criterion of the control parameters is derived to guarantee the closed loop stability.Postprint (published version

Position estimation at low/zero speed for permanent magnet synchronous machines is commonly achieved with the injection of high frequency signals. This paper 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 PLL observer defined by a complex switching function, the algorithm provides both rotor position and speed in a compact form. The paper 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.

An alternative to the linear control techniques, which are based on small signal averaged models, is the sliding mode control. That method uses instantaneous models of the switched power converter to design robust controllers. The large signal modelling allows not only to control the system behaviour around the steady-state, but also the start-up transient. This paper presents the design of two sliding mode controllers that regulate the output voltage of a synchronous buck converter and limit the start-up peak current. A terminal sliding mode control is designed and compared with a first order sliding mode control, which is called here as a conventional sliding mode control. The study shows that the terminal sliding mode control presents lower transient time to reach the final value as compared to the conventional one because of its finite time convergence property. It also achieves better performance in terms of line and load regulation. A power converter prototype of 150 W / 100 kHz is assembled and both sliding mode controllers are digitalized and implemented in a microcontroller. Numerical simulations and experimental results validate the proposal. Index Terms-Sliding mode control, terminal dynamics, synchronous buck converter.