Xiaoqiang Li

Permanent magnet synchronous motors (PMSMs) are widely used in various fields due to their advantages. However, mechanical position sensor failures will cause various serious safety issues. High-frequency square-wave injection (HF-SWI) enables sensorless control of PMSMs at low speeds; yet, the fixed-frequency nature of conventional methods results in narrow current power spectral density (PSD), causing harsh noise and limiting the widespread application of sensorless control, especially in household appliances. To address this, this paper proposes a pseudo-random coding (PRC) injection strategy. First, a 2³ PRC-injection method (2³ PRC-IN) is introduced, which disrupts the signal periodicity by varying the injection frequency and amplitude, thereby significantly expanding the current PSD. To further suppress residual peaks in the 2³ PRC-IN, an improved 2^(3&1) PRC-IN method is developed. By optimizing the code transition logic, this approach can completely eliminate the sharp noise. Experiments on a 5.5 kW PMSM platform validate that the proposed methods effectively broaden the current PSD and reduce the noise without compromising position observation accuracy.

As the power conversion device between new energy generation systems and the power grid, the high‐frequency resonance self‐stability of the current loop of grid‐following (GFL) converters has been widely researched. However, this paper finds that, in addition to the current loop, the power loop of GFL converters also has high‐frequency resonance self‐stability issues when adopting a closed‐loop control strategy. Therefore, this paper researches the high‐frequency resonance mechanism in the power loop first, and the research results show that the resonance in the power loop is induced by power‐current loop interaction, which results from the mismatched control parameters between the power loop and the current loop. Based on this, a self‐stability design method is proposed in this paper. This method reduces power‐current loop interaction by designing the power loop control parameters based on existing current loop constraints, thereby suppressing the high‐frequency resonance in the power loop. Finally, the experimental results validate the feasibility and effectiveness of the theoretical analysis and the proposed design method.

Under weakly supported power grids or islanded microgrids, the fundamental frequency dynamic is gradually highlighted and has been incorporated into dq impedance modelling. However, since dq impedance modelling lacks a clear physical interpretation, in practical applications, it is difficult to verify the influence of this dynamic and the accuracy of established models. In contrast, this paper finds that the P/Q‐ω/U modelling also contains this dynamic but changes system terminal characterisation, which has clearer physical interpretation and is more convenient for system analysis and verification. Considering the existing P/Q‐ω/U is only suitable for grid‐forming (GFM) converters, a P/Q‐ω/U characteristics modelling for grid‐following (GFL) converters is proposed in this paper, which is established at a unified PCC terminal benchmark to be consistent with the P/Q‐ω/U model of GFM converters for the convenience of system integration. Furthermore, the self‐stability of GFL converters is analysed in this paper based on the proposed P/Q‐ω/U model, and the stability design of the PLL and the power loop are presented. Experimental results are finally provided to verify the feasibility and effectiveness of the proposed model and the stability design.

Under severe symmetrical grid faults, grid‐forming (GFM) converters may suffer from excessive fault currents and transient stability issues. To restrict fault current, current limiters provide a simple and effective solution. However, they convert GFM control into grid‐following control, leading to the loss of voltage‐source characteristics. Virtual impedance–based methods can preserve the voltage‐source behaviour of GFM converters during faults. However, the commonly used resistive–inductive virtual impedance introduces power coupling, surplus capacity requirements, and small‐signal stability issues. Therefore, an adaptive virtual inductor (AVI)‐based current‐limiting control strategy is proposed. This strategy introduces an output current amplitude control loop to dynamically adjust the virtual inductance, thereby limiting the fault current while enhancing reactive current injection capability. In addition, the small‐signal stability and virtual inductance gains are investigated by establishing a small‐signal model of the output current amplitude control loop. The AVI control strategy proposed in this paper not only achieves power decoupling but also ensures that the fault current accurately tracks the current limit reference under any symmetrical fault conditions. Consequently, precise reactive current injection is guaranteed, thereby satisfying national grid code requirements. A large‐signal model is further developed to analyse transient stability using P–δ curves and phase portraits. Based on this analysis, an enhanced transient stability design method is proposed, in which a power‐reference regulation term is incorporated into the active power reference to ensure transient stability while expanding the critical power angle. Finally, simulation and experimental results are presented to validate the feasibility and effectiveness of the proposed method.

The performance of large-scale photovoltaic (PV) power plants is strongly influenced by array layout parameters including module tilt angle, azimuth angle, and row spacing. These geometric variables jointly determine solar irradiance geometry, shading losses, and land-use efficiency, affecting annual energy yield and levelized cost of electricity. To achieve multi-objective comprehensive optimization of array layout parameters for a PV power generation system, a collaborative optimization strategy for PV array layout based on the lemur optimization (LO) algorithm is proposed in this paper. The method couples the Perez anisotropic irradiance model with a dynamic shading irradiance geometric model to simulate the effective insolation, incorporating land availability, shading thresholds, and maintenance access requirements. In addition, the LO algorithm is employed to solve resulting nonlinear and constrained problems, enabling an efficient global search across large parameter spaces. The case studies in Lianyungang, Dalian, and Fuzhou City show that the proposed scheme based on the LO algorithm improves annual energy yield compared with the existing optimization schemes, providing new theoretical methods and engineering application paths for the optimal layout of PV arrays.

The fundamental frequency of high speed permanent magnet synchronous motor (HSPMSM) is relatively high (possibly exceeding 1 kHz), which can lead to low carrier ratio. Model predictive control (MPC) has the advantages of simple principles, easy implementation, and the ability to handle nonlinear systems. Therefore, adopting MPC in HSPMSM drivers can bring better control performance. Dual-vector model predictive current control (DV-MPCC) manipulates two voltage vectors in one control cycle, which can have higher control accuracy than that of single-vector model predictive current control (SV-MPCC). However, for HSPMSM, the stator inductance of HSPMSM is minimal (10-4 H). Therefore, during start-up and low-speed operation, the stator current ripple is relatively large, which would exacerbate torque ripple. Therefore, this paper proposes an adaptive dutycycle adjustment-based dual-vector MPCC (AD-MPCC), which can reduce stator current and torque ripple during start-up and low-speed operation. Meanwhile, an improved error-correction Smith (IEC-Smith) structure compensator is adopted, providing better delay compensation characteristics and reducing the statice error. Finally, the experimental results validate the effectiveness and feasibility of the proposed method.

Featuring high control flexibility, high efficiency, and fast dynamic response, modular dual active bridge (DAB) dc–dc converters have been frequently employed for energy conversion and management. However, DAB converters are also susceptible to open-circuit faults, primarily attributed to the vulnerability of the power switches. Therefore, a fault detection, localization, and tolerance control method is proposed in this work, based on frequency-domain analysis of far-end or remote voltage. The frequency characteristics of DAB converters in normal and faulty operations are analyzed. From the perspective of remote fault monitoring and diagnosis, the output voltage is used as the characteristic variable for fault feature extraction. The detection and localization of an open-circuit fault involve an analysis of the fundamental and second harmonic components of the output voltage. The associated fault tolerance control method is implemented by isolating a specific secondary-side switch. The realization of the proposed method is straightforward and cost-effective, requiring no additional devices and sensors. The feasibility and effectiveness of this approach are validated through simulation and experimental results.