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This paper presents a novel approach for modeling Boost converters using the Caputo–Fabrizio (C-F) definition-based fractional-order model to address singular characteristics in fractional-order definitions and enhance model accuracy. A small signal modeling method is proposed to improve the accuracy of circuit parameter design and to derive state-averaged models, state-space equations, and transfer functions. The influence of capacitor and inductor orders on steady-state characteristics is analyzed and the influence of fractional-order on ripple characteristics is investigated through simulation. When the fractional-order approaches 1, the output voltage increases and the inductance current decreases, with waveform jitter mitigation. Moreover, boundary conditions for continuous conduction mode operation are established based on ripple characteristics. The numerical and circuit-oriented simulations verify the correctness of the proposed model. Finally, the orders and accurate parameters of capacitors and inductors based on the C-F definition are determined and the experiments are conducted. The comparison between the experimental and simulation results demonstrates that the proposed model can accurately describe the steady-state characteristics of the practical circuit systems, which further validates the accuracy of the proposed method. [ABSTRACT FROM AUTHOR]

Unexpected faults that occur in the sensors of the single-phase grid-connected converter (SGC) may deteriorate the control performance ofthe grid current and dc-link voltage and pose risks to the connected distributed generation system. This article proposes an unknown input sliding mode observer (UI-SMO) based sensor fault identification and remediation strategy. Therein, an UI-SMO is established that integrates the observations of the grid current and dc-link voltage with the reconstruction of the unknown input (i.e., load condition of the SGC). Such an observer-based analytical redundancy generates the residuals that indicate the abnormalities of the sensors for fault identification. An adaptive fault-tolerant control (AFTC) strategy for the SGC is developed, where an automated control system reconfiguration with unknown input adaptation is seamlessly implemented by substituting the data reported by the faulty sensors with their observed values. Extensive simulation and experimental studies validate the effectiveness of the proposed UI-SMO-based sensor fault identification and AFTC strategy of the SGC. [ABSTRACT FROM AUTHOR]

The Caputo–Fabrizio (C–F) definition, which solves the singularity problem in the Caputo definition, has been preliminarily applied in the field of circuit system modeling. However, the complex characteristics of the C–F definition-based circuit systems are still understudied. Therefore, this paper proposes a C–F definition-based fractional-order RLC (CF-FORLC) circuit model and analyzes its basic characteristics. First, the effects of different component orders on the performance parameters including the impedance, quality factor, and bandwidth are analyzed, which gives insights into the design of CF-FORLC. Then, the analytical solutions and the frequency-domain characteristics of CF-FORLC with different capacitance and inductance orders under arbitrary input are derived. Finally, the data of actual circuits are fitted to obtain the parameters of the CF-FORLC model, and the orders of the C–F definition-based capacitors and inductors are estimated. The results of the comparative experiments show that the proposed modeling scheme can improve the consistency of the dynamic performance of the model with that of the actual circuit. In addition, the proposed CF-FORLC model shows higher accuracy and flexibility with more adjustable parameters. [ABSTRACT FROM AUTHOR]

The high common-mode voltage (CMV) generated by conventional synchronized space vector pulsewidth modulation (SVPWM) strategies may lead to bearing failure and electromagnetic interference problems. However, existing CMV reduction methods are based on asynchronized SVPWM, which will cause unacceptable harmonic distortion at low switching frequency. In this article, four modified synchronized SVPWM (MS-SVPWM) strategies are presented to reduce the CMV and improve the output performance of three-phase voltage source inverters (VSIs) at low switching frequency. In the proposed methods, only nonzero vectors are employed to reduce CMV, and the constraint conditions of preserving three-phase, half-wave, and quarter-wave symmetries of PWM waveforms in terms of active vectors are established. A precorrection scheme is proposed and applied to the presented MS-SVPWM strategies to achieve an accurate output voltage of inverters. Moreover, the linearity characteristics of the output voltage, the harmonic performance of line-line voltage and CMV, and the stator flux trajectories of the proposed strategies are investigated and compared. Experimental results for a 2.2-kW induction motor fed by a two-level VSI are presented to illustrate the effectiveness of the proposed MS-SVPWM strategies. [ABSTRACT FROM AUTHOR]

In some applications of inverter-fed induction motor drive systems, a fast and smooth restarting of free-running motors may be required when their inverters are faced with short-term power interruptions. In this article, a novel restarting strategy is proposed, consisting of three steps. First, during the restarting process, the initial step requires the machine's speed estimation. To achieve this, a dc current injection-based method is used to estimate the rotor flux and subsequently the speed of the rotating machine. In this step, a filtering and a phase-locked loop are used to extract speed information. Next, to further improve the speed estimation accuracy, the speed-sensorless vector control with zero torque command is used. Finally, a full-order adaptive observer is utilized for speed estimation in the restored normal operation of the induction motor. Compared to existing/alternative methods, the proposed strategy much faster estimates the initial speed and is able to restore the normal smooth operation within 0.5 s. The effectiveness of the proposed method is demonstrated by simulation and experimental studies. [ABSTRACT FROM AUTHOR]

In various applications that utilize maximum torque per ampere (MTPA) operation of interior permanent magnet synchronous machines (IPMSMs), there exist unexpected perturbations in electrical parameters and operating environment, which deteriorate the accuracy and efficiency of the MTPA operation. This paper establishes a step-signal-injection-based robust MTPA operation strategy for the IPMSM drives. The method works by injecting a step signal into the current vector angle and observing the response in the current magnitude, followed by a proportional-integral controller which returns the system to optimal operation. The stability of the proposed algorithm is established using the Lyapunov theory. A speed-servo control system of IPMSM is considered, where a disturbance detection unit is designed to switch operation between optimal current angle updating mode and steady-state MTPA operation mode. Since the optimal current angle updating is independent of machine parameters, the impact of system perturbations on the MTPA operation can be effectively suppressed. Extensive experimental results for IPMSM and hardware-in-the-loop-based machine are presented to validate the effectiveness and robustness of the proposed method. [ABSTRACT FROM AUTHOR]

In single-phase grid-connected converters, unexpected perturbations and variations of system parameters can deteriorate the performance of grid current and dc-link voltage control and even jeopardize the stability and operation of loads. In this paper, a robust control strategy for the single-phase grid-connected converter operating under multiple system perturbations is proposed. An adaptive quasi-proportional-resonant (AQ-PR) controller for the grid current is adopted in combination with an equivalent inductance identification algorithm, which assures that the parameters of the AQ-PR controller can be online calibrated to attain accurate current regulation under ac-side inductance uncertainties. A super-twisting sliding mode (ST-SM) controller for the dc-link voltage is proposed to enhance system behavior under both internal and external disturbances. The convergence of the controller is ensured by utilizing Lyapunov theory. Experimental prototype and rigorous tests are presented to validate the feasibility and robustness of the proposed approach under various perturbations. [ABSTRACT FROM AUTHOR]

Single-phase pulse-width modulation (PWM) rectifier is commonly used in a high-speed railway electric traction system. Occurrence of unexpected failure in the sensors of the detection system may lead to feedback values deviation and system degradation, which can be extremely detrimental to the operation safety of the electric locomotive. This paper presents a fast and reliable fault diagnosis and fault resilient control strategy for catenary current and dc-link voltage sensor faults in the control system for an electric traction single-phase PWM rectifier. Sliding mode observers are designed to produce analytical redundancy. In order to avoid unobservable states and fluctuation introduced by discrete dynamics in observer design, a novel description for switching variables is presented in system modeling. Normalized residuals are generated using measured and observed values. The fault diagnosis unit proposed can detect and isolate three types of sensor faults online by comparing residuals with thresholds. System reconfiguration is realized by substituting the observed values for the information of faulty sensors. Simulation and experimental results are demonstrated to validate the effectiveness of the strategy. [ABSTRACT FROM AUTHOR]