Aiming at the problems that fault diagnosis data of wind turbine gearboxes have time series and the single-channel model is difficult to effectively extract the composite fault feature information, a fault diagnosis method integrating an improved orthogonal convolutional capsule network (OCCN) and a bidirectional long short-term memory neural network (BiLSTM) is proposed. First, the original signals are preprocessed. Then, the preprocessed signals are fed into a constructed OCCN-BiLSTM dual-branch model to extract the spatial features and time domain features of composite faults, respectively. Finally, the extracted spatiotemporal features are fused through a cross-attention mechanism and input into a fully connected layer for signal classification, enabling intelligent fault diagnosis of wind turbine gearboxes. Experimental results show that the proposed diagnosis method can effectively achieve intelligent fault diagnosis for wind turbine gearboxes, with an accuracy of 99.53% on the test set. © (2026), (Power System Protection and Control Press). All rights reserved.

To diagnose single- and double-switch open-circuit faults in cascaded H-bridge (CHB) photovoltaic (PV) grid-connected inverters, an open-circuit fault diagnosis method based on an adaptive sliding mode observer is proposed. First, an adaptive sliding mode observer is designed using the mixed logic dynamic (MLD) model of the CHB PV inverter, and fault detection variables are constructed based on actual and estimated currents. Second, voltage thresholds derived from the DC-side capacitor voltage are used for fault module localization. Then, fault localization variables are constructed from current residuals, and the variations of current residuals of the adaptive sliding mode observer under fault conditions are compared to distinguish diagonal switch faults. Finally, double-switch open-circuit fault diagnosis is realized by designing an adaptive sliding mode observer based on the previous fault state. Experiment results show that the proposed method can accurately identify single- and double-switch faults at any position within one fundamental cycle, with fast diagnosis speed and strong robustness. © 2026, Power System Protection and Control Press. All rights reserved.

To address the weak dynamic performance of dual active bridge converters in DC microgrid systems, which are susceptible to external perturbations and circuit losses, this paper suggests a model-free non-singular fast terminal sliding mode control strategy that is combined with current stress optimization of adaptive super-twisting sliding mode observe. Initially, the output voltage state-space averaging equation is derived using the transmitted power model to create a novel ultra-local model of the converter. Secondly, a model-free non-singular fast terminal sliding mode controller is developed using a novel ultra-local model. An adaptive super-twisting sliding mode observer is introduced to achieve feed-forward compensation for accurately estimating the unknown part by dynamically adjusting the gain. Ultimately, the converter's output voltage is regulated by the two shift ratios that are calculated by combining the controller output results with the segmented current stress optimization calculated as D1 to invert the external phase shift angle D2. The experimental results confirm that the proposed strategy has a dynamic quality that ensures a smaller current stress optimization, reduces the reliance on the precise model of the system, and enhances control accuracy.

传统加权平均电流(weighted average current,WAC)控制策略下，并网电流中存在隐藏谐振，且开环增益受数字控制延时和电网阻抗的影响，导致无法实现降阶特性。为此，提出了一种改进型WAC控制策略。首先，通过引入电容电流反馈有源阻尼来抑制并网电流中的谐振，通过从反馈和前馈通道引入新的加权反馈系数，重新配置系统零极点，使开环系统可以实现降阶。然后，基于无源理论的稳定性设计要求，对闭环系统进行参数设计，使逆变器等效输出阻抗满足无源性稳定条件，改善并网电流质量，提高弱电网条件下并网逆变器系统的稳定性。最后进行了仿真实验，结果证实了所提方法有效性。

在极弱电网条件下,并网逆变器引入网压比例前馈控制策略来提升低频段幅值增益并抑制电网背景谐波干扰。但当电网阻抗参数增大时,系统的相位裕度会显著下降,出现失稳现象。对此,提出一种极弱电网下并网逆变器自适应改进前馈策略。先基于阻抗特性分析方法,分析系统相位裕度恶化的内在机理,提出在前馈通道上串联二阶低通滤波器来提高系统的相位裕度,并尽可能保留其在低频的增益效果的方法;再提出采用在线阻抗检测技术与结合遗传优化算法的自适应参数设计方法,提高参数设计效率,进而提高并网逆变器在极弱电网环境下的鲁棒性;最后,通过仿真与试验验证所提方法的可行性与有效性。

At present, the fault diagnosis methods of a dry reactor mainly focus on mechanical faults based on vibration signals. The fault type is singular, and there are problems such as difficulties with sensor installation. Thus, a dry reactor fault test platform based on an acoustic signal is built, and a variety of fault types are set up. To improve the accuracy of fault identification in small samples, a dry reactor fault diagnosis method based on a dual-channel feature fusion network is proposed. First, the one-dimensional time sequence is converted into two-dimensional image using Gramian angle field (GAF) encoding. Secondly, a two-channel parallel CNN-ResNet network structure is adopted, and an efficient channel attention (ECA) mechanism is introduced to obtain two-dimensional key information. Then the two-dimensional image features and one-dimensional time series features are extracted and fused. Finally, the source domain data is obtained based on finite element simulation, and the optimal network parameters of the target domain are obtained by the transfer learning method. Experimental comparison shows that the proposed method has stronger feature extraction ability than other methods, can significantly separate fault features, and the fault identification accuracy can reach 99.5% with small samples. It has good generalizability and convergence speed. © 2025 Power System Protection and Control Press. All rights reserved.

双向全桥DC-DC（DAB）变换器在直流微电网作为可再生能源与储能设备的能量传输环节，通过实现零电压开关（ZVS）和最小回流功率，可显著地提升DAB变换器的性能，从而提高直流微电网的稳定性。但同时实现ZVS和最小回流功率控制在理论上是相互制约的。针对这一问题，该文提出一种基于ZVS的最小回流功率双重移相分段控制策略。通过对双重移相下的传输功率进行分段，前段将ZVS作为约束条件，得到基于ZVS条件下的最小回流功率控制策略，后段通过KKT条件法实现在给定传输功率下的最小回流功率控制策略。通过将所提控制策略和传统的双重移相控制对比分析，发现所提控制策略具有更小的回流功率和电流应力，提高了变换器的性能。最后，基于所提控制策略搭建实验样机，验证了控制策略的正确性和有效性。

在弱电网条件下，数字控制延时会导致虚拟阻抗呈现负阻性，无法起到阻尼效果，因此并网逆变器在电网阻抗变化情况下不能稳定运行，鲁棒性受到严重威胁。针对上述问题，提出一种双线性正反馈有源阻尼策略，以扩大系统的有效阻尼区。为了节省传感器成本，将其优化为电容电压正反馈有源阻尼策略，在电容电压两端添加合适的正反馈阻尼环节，使得系统的有效阻尼区扩大为（0,0.477f3）。分析结果表明该策略使得并网逆变器在弱电网条件下始终具有良好的鲁棒性，即使谐振频率等于1/6采样频率时，系统也具有较好的稳定性。最后，以三相LCL型并网逆变器为例进行实验验证，实验结果验证了该策略的正确性。