In the sliding-mode control of switched systems, the mode-dependent sliding surface is generally considered to fulfill performance requirements of different subsystems. However, in the mode-dependent sliding surface design, the system state may oscillate among subsliding surfaces, which affects both stability and robustness. To solve this issue, this article starts from ensuring the reachability of each subsliding surface and proposes the reachability-guaranteed sliding-mode control for asynchronously switched uncertain systems. First, a type of asynchronous mode-dependent sliding surface is designed. Then, the control law is novelly proposed upon the allowable maximum settling time based on the fixed-time theory, and a new criterion is given to address the reachability of each subsliding surface within the mode-running interval. Stability is analyzed for the closed-loop system under restricted switchings, and solvable inequalities are presented for the optimization of the controller gain. Finally, implementation to the Chua's circuit validates superiorities of the proposed method.

Modular multilevel converter (MMC) is an attractive topology in industrial applications such as high-voltage direct current (HVdc) transmission system where fast power control is required. The most conventional control method for MMC uses cascaded structures, where the power transmission and internal energy dynamic (outer loops) is limited by the “frequency separation” constraints since the dynamic choice of the currents (inner loops) must consider the tradeoff between rapidity and robustness. In this article, we present a new control method based on a differential flatness theory. The main interest of the proposed control is the possibility to obtain a very high dynamic performance of the MMC power flow, even under noisy measurements and parametric disturbances. Using the well-known average model of the MMC, a flat output is proposed, proving the differential flatness property of the MMC. Trajectory tracking controllers of ac grid active and reactive power are proposed using input-state full-order linearization. Simulation results, including losses corresponding to a realistic case of on-shore, point-to-point HVdc interconnection, are presented to show the performance of the proposed control scheme even with strong measurement noise.

Listening music with a headset is now a classical feature of mobile phones. A linear amplifier is still employed to drive the headset as the audio quality must challenge dedicated audio players with somewhat 100 dB of signal-to-noise ratio. This feature must also have the lowest impact on the platform autonomy, size, and cost. A symmetrical power supply is required by such audio amplifiers due to the standard jack connector of headsets. Using an inductive switch mode power supply (SMPS) is the most energy efficient solution to supply audio amplifiers from a battery. Classically, two dc/dc converters are employed to generate the required two symmetrical supply rails from a standard Lithium-Ion battery. It is at the cost of numerous bulky and expensive external components. A solution to reduce the number of external passive components is to consider a single-inductor, bipolar-outputs, (SIBO) dc/dc converter. An early prototype of such a converter has been realized on a 130-nm silicon process and offers primary results, nonoptimal but promising. The feedback control structure is studied based on a small signal model that serves to define the pairing of the loops for designing a decentralized controller. A set of controllers is designed by a pole placement technique and transient performances are demonstrated on audio patterns thanks to a piecewise linear model of the converter. Eighty percent peak efficiency is measured with the primary demonstrator but latter simulation results yield an expected improvement to 90%. The audio specifications appear very constraintful and the proposed SMPS does not meet entirely the latter figures. Limitations are detailed. However, many other applications can benefit from the proposed SIBO dc/dc converter.

This article considers a robust output set-point tracking problem for an $m$ -terminal power flow controller (PFC) for meshed dc micro-grids. The PFC is a power electronics device used to control the power flow at a node in the meshed grid and may act as a dc circuit breaker. The system is modeled by state-space bilinear dynamics coupled with a polynomial output. In the proposed design, the plant is first extended with an integral action processing the regulation error. The cascaded model composed of the plant and the integrator is then stabilized using a saturated state-feedback law, designed with a forwarding approach. An anti-windup function is added to cope with transient saturations. A tuning method is proposed to set the controller gains along the available degrees of freedom with respect to a cost function. The stability of the closed loop is guaranteed for any compact set of initial conditions and for small parametric variations around the nominal set point. Experiments have been carried out and these properties are successfully assessed on a tenth-scale experimental setup.

Considering the innately connected neutral point in a multifunctional converter system (MFCS) fed three-phase surface-mounted permanent magnet synchronous machine (SPMSM) drive, this article develops its fault self-tolerance toward open-phase faults (OPFs) without assisted hardware. First, the operating principle of the MFCS fed SPMSM drive is explained by building a zero-sequence model. Second, to achieve fault-tolerant operations, an unconventional current vector trajectory is proposed, aiming at maintaining the torque and average input power invariable. The shape of the proposed trajectory tends to be like a heart rather than a circle with the rise of motor speed. Moreover, $\boldsymbol{d}$ -axis and zero-sequence currents vary with the position of rotor. By considering the limits of inverter voltage and current, the postfault output capability of the drive is explicitly analyzed. Third, a new fault-tolerant control strategy is thus proposed, in which the OPF is detected by comparing the deviation between predictive and actual currents. To track the time-varying current references, a differential flatness-based current controller is further developed. Finally, experimental results are given to verify the effectiveness.

The existing fault-tolerant three-phase AC drives need split capacitors, auxiliary legs and triode for alternating current (TRIACs) upon a standard three-phase two-level voltage source inverter (VSI) to obtain the self-healing ability towards open-phase faults (OPFs). In order to reduce the cost, volume and weight, this paper proposes a novel fault-tolerant three-phase surface-mounted permanent magnet synchronous machine (SPMSM) drive without split capacitors, auxiliary legs or TRIACs. The proposed drive is still built upon a three-phase two-level VSI, while its DC-source is directly connected to the neutral point of the motor. First, mathematical model and equivalent circuit are established to reveal the existence of an equivalent DC/DC boost converter in the drive system. Second, the brand-new d-0 axes current references are proposed in order to preserve the motor's performance when an OPF occurs. In this case, both ${i_{d}}$ and ${i_{0}}$ are non-constant. Third, an overall control strategy including the healthy and fault-tolerant modes is presented. In the fault-tolerant mode, a deadbeat current controller is developed to track the non-constant current references. Finally, experiments are carried out on a SPMSM test-bench to verify the effectiveness of the proposed scheme.