Fault diagnosis is currently considered a crucial method to enhance the reliability of permanent magnet synchronous motor (PMSM) drives. In this article, an open-circuit fault (OCF) diagnosis method of a voltage source inverter-fed PMSM with model predictive control is proposed. The developed approach mainly consists of fault detection and localization. Besides, the normalized cost function variation is designed as a fault detection indicator according to the impact of OCFs on current signatures. It can not only monitor drive system conditions, but also discriminate fault categories. Afterward, the polarities of normalized αβ -current average values and phase angles of residual current vectors are utilized to locate the exact faulty switch in each fault type. Consequently, a total of 21 possible combinations of faulty switches can be correctly detected and located. Finally, the effectiveness in fault diagnoses and the robustness against operating point variations are verified by the experimental results.

Conventional planar coils in an asymmetric structure cannot provide stable mutual inductance over a wide range. To address this issue, a novel asymmetric flat cross -shaped solenoid magnetic coupler (FCSMC) with high lateral misalignment tolerance for a multiple-receiver wireless power transfer (WPT) system is proposed in this article, which can achieve freer charging positions for multiple automated guided vehicles (AGVs) at a single wireless charging station. Moreover, the analytical model of FCSMC is analyzed to simplify the design process based on the air-core mutual inductance equations. Then, a general design process is proposed for larger-scale FCSMC, which greatly reduces the workload of finite-element analysis (FEA) simulations. Finally, a 200/400 W prototype is built to verify the validity of the system within a $\pm$ 90-mm misalignment. In single-receiver cases with a 10 mm air gap, the comparisons with conventional planar square coils show that FCSMC's (planner square coils') output power fluctuates within 5% (27%) with maximum efficiency of 88.55% (92.01%), indicating that FCSMC sacrifices about 3% efficiency for 22% improvement in power stability. At the highest $\pm$ 90-mm misalignments, the output power fluctuates within 1% (19%), improving about 18%. In multiple-receiver cases for FCSMC, the charging positions are free with maximum efficiency of 87.96% when the shortest distance between ferrites of receivers is 20 mm or more.

This article presents a parallel structure digital repetitive control (PSDRC) scheme, where the internal models of all harmonics are decomposed into multiple parallel connected groups. Compared with conventional repetitive controller, the proposed parallel structure enables repetitive controller to regulate the error convergence rate at each group of harmonic frequencies independently and offers faster total error convergence rate. Moreover, PSDRC can achieve zero-error tracking or perfect disturbance rejection for all harmonics without occupying more data memory. A stability criterion with rigorous proof for PSDRC system is addressed, which is compatible with those existing stability criteria for existing RC schemes. An application example of three-phase pulse-width modulation inverter is provided to demonstrate the effectiveness of the proposed PSDRC scheme.

This paper proposes an improved SOC balancing strategy for the modular energy storage system (ESS) based on low bandwidth communication (LBC) technology, aiming at solving the drawbacks of the conventional balancing strategy based on droop control. The proposed control scheme can improve the SOC balancing efficiency and remove the current deviation by using the SOC slope-adjusting and current-shifting approaches simultaneously. The average value of SOC can be derived through the LBC line, and the droop coefficient based on SOC can be controlled in the local control layer. Thus, the SOC of each sub-module can converge to the average SOC value in system dynamic process, and the balancing speed under the condition of low SOC difference between sub-modules can be improved. Furthermore, the current regulation performance in steady and transient states can be enhanced by using the proposed method. At last the effectiveness of the proposed strategy is verified by experimental results.

A generic multifrequency repetitive control (GMFRC) scheme, is proposed to perfectly compensate for all kinds of periodic signals including multifrequency signals, where multiple selective harmonic repetitive controllers in parallel are added into a stable instantaneous feedback control loop to achieve overall satisfactory performance. The GMFRC scheme provides a general framework for housing various repetitive control and even resonant control schemes in power electronic conversion and other extensive engineering applications. A universal approach to the analysis and synthesis of the digital GMFRC scheme has been developed, which includes the stability criteria and control gain rules. More important, the digital GMFRC controller is transformed into a general fractional-order one for exact compensation of multifrequency signals and other fractional-order periodic signals in practice. An application example of a 5 kVA three-phase pulsewidth modulation nverter under a fractional-order GMFRC scheme is provided. Experimental results demonstrated that the proposed GMFRC scheme can force the inverter to produce required mono-frequency or multifrequency voltages with high accuracy, fast response and good robustness.

In this article, a general high-order selective harmonic repetitive control (HO-SHRC) scheme is proposed, which is composed of a standard high-order repetitive controller structure and a new order-expandable SHRC. Different from conventional SHRC, the proposed new SHRC is capable of being applied into the standard high-order repetitive control (HORC) structure for generating any high-order SHRC. The proposed HO-SHRC can be used to improve the steady-state tracking accuracy of the pulsewidth modulation (PWM) converter systems and is robust to system frequency variations without changing the controller parameters online. The order expansion of the controller will lead to the increase of the implementation complexity, but it will bring the overall improvement of the controller performance, such as the improvement of frequency adaptability, steady-state tracking accuracy, and dynamic performance. Therefore, HO-SHRC can achieve a good compromise between the controller performance and the implementation complexity. Moreover, the proposed HO-SHRC provides a general structure for various repetitive controls (RCs), such as conventional RC (CRC), odd-harmonic RC (OHRC), high-order CRC (HO-CRC), and HO-odd-harmonic RC (HO-OHRC). Application examples of second-order (SO)- $6k~\pm $ 1 RC-controlled three-phase PWM inverter show the effectiveness and advantages of the proposed control scheme.