This paper describes the randomized evolving Takagi–Sugeno (ReTSK)-adaptive neuro-fuzzy (ANF) estimation algorithm and optimized fractional-order proportional integral (FOPI) controller are integrated with parameter adaptive indirect vector control (PA-IVC) for induction motor drives performance enhancement. For appropriate slip-speed tuning and field orientation, the machine learning-based ReTSK-ANF approach is proposed for the estimation of induction motor parameters and sensorless speed. The optimized FOPI speed and current regulators are employed in PA-IVC to generate the reference signals with minimized error for encountering manual tuning and reduce the overshoot with less settling time. A metaheuristic algorithm of Gazelle optimization algorithm (GOA) is imposed to obtain the optimal weight, biases, membership functions (MFs), and MF rules in the predictive model of ReTSK-ANF for desired parameter estimation and optimal gains of FOPI for performance enhancement. Statistical metrics are carried out to examine the performance of ReTSK forecasting model. The metrics are mean square error (MSE), root mean square error (RMSE), mean error (ME), and error of standard deviation (ESD) as reported during the training stage were 3.33e-3, 3.41e-2, 1.92e-3, 3.37e-2, and during the testing stage 3.67e-3, 3.47e-2, 1.91e-3, 3.42e-2. This will confirm that the ReTSK-ANF estimator will achieve significant improvement in the estimation of parameters and closely follow the reference. Meanwhile, the optimized FOPI gains performance is analyzed using time response analysis.

Sensorless control technique is regarded as the enabler of the reliability improvements for interior permanent magnet synchronous motor (IPMSM) drives. However, the conventional estimation schemes by using the phase-locked loop (PLL) and the frequency-locked loop (FLL) may experience undesired accuracy under acceleration and deceleration cases (ADCs). To address this, a speed estimation scheme by combining a closed-loop active flux observer (CLAFO) with a tracking differentiator-based frequency-locked loop (TD-FLL) was proposed in this paper. Starting from a brief introduction of the conventional PLL and FLL performance analysis based on ADCs, a detailed analysis is provided. Accordingly, an estimation scheme based on the TD-FLL is elaborated. Considering the performance of the proposed TD-FLL scheme is adversely affected by various disturbances, a CLAFO is carefully designed to improve the disturbance immunity of the proposed TD-FLL scheme. Extensive experimental tests are conducted to verify the effectiveness of the proposed TD-FLL scheme under different test cases.

At radiated frequencies, common mode (CM) current is the dominant radiation source for isolated power converters with long cables attached. Based on the existing radiation noise model, this paper proposes a novel method to measure CM current using a current transformer (CT), which has a higher transfer impedance and can measure the radiation noise in a broader frequency range than the traditional high-frequency (HF) clamp-on current probe. According to the established CT model, the corresponding design methods are proposed to improve the bandwidth and transfer impedance, and the final CT that meets the requirements is determined after comparing different methods. The practicability and effectiveness of the designed CT are verified by comparing the measured CM current with the final anechoic chamber measurement results.

In response to the high cost and large size issues associated with traditional back-to-back three-level inverters, this paper proposes a novel dual-port three-level inverter (DP-TLI) that simplifies the system structure through the utilization of switch multiplexing. Based on the proposed inverter topology, a time-sharing coordination finite control set model predictive control (TSC-FCS-MPC) strategy is developed. The strategy, grounded in the concept of time-sharing control, incorporates a coordinated approach within a two-cycle control loop. During the first cycle, the primary control objective is to optimize the output current of the upper port, with the selection of the optimal vector centered around this goal. Subsequently, the lower port's output is coordinated through control, leveraging the unique aspects of switch multiplexing and the redundancy in switch states inherent in the proposed topology. In the second cycle, the emphasis is reversed, with the optimization of the lower port's output current taking precedence, while the upper port is subjected to coordinated control. The implementation of this method significantly enhances the quality of the output current and the overall efficiency of the system. The viability and effectiveness of both the proposed topology and the control strategy are confirmed through simulation and experimental results.

With the increasing popularity of new energy integration, the parallel operation of multiple inverters in power systems has become commonplace. Traditional theories and methods for analyzing power system stability face challenges in high-proportion new energy systems. Additionally, existing inverter analysis methods are inadequate for directly addressing multi-inverters paralleled system, resulting in unclear instability mechanisms and uncertain operational stability. To tackle these issues, this paper focuses on systems with multiple parallel LCL-type inverters and proposes an improved minor loop gain criterion (IMLG). Unlike traditional impedance ratio criteria, this improved criterion fully integrates considerations such as inverter capacity, short-circuit ratio, and other pertinent factors affecting system stability. Furthermore, treating each inverter as a subsystem by equivalenting the grid conductance to the inverter side, this criterion accurately identifies the primary inverter responsible for system instability. Finally, case and experimental studies are employed to verify the correctness of the theoretical analysis and demonstrate the effectiveness of the improved stability criterion.

This paper investigates the synchronization stability of hybrid power systems integrated with grid-forming (GFM) inverters and grid-following (GFL) inverters. In hybrid power systems, the interactions between GFM and GFL inverters bring about challenges for the synchronization stability analysis. To address this issue, a fourth-order synchronization model considering controller interactions is established. Then, the influence of interactions on the stable equilibrium point (SEP) and the synchronization process is fully clarified. It is found that interactions are detrimental to the SEP of GFM inverters but beneficial to the SEP of GFL inverters. For synchronization processes, the instability and stabilization caused by controller interactions are presented, indicating the important effect on the synchronization process. In addition, suggestions for controller design to improve synchronization dynamics through controller interactions are provided. Simulation results validate these findings.

High-permeability cores, such as ferrite, can increase power transfer efficiency and are often designed to be gapped to mitigate magnetic saturation. The fringing effect caused by the air-gap increases the winding loss of the gapped inductor. The key to accurately evaluating its winding loss is extracting that from the total loss. This paper introduces a method for measuring the winding loss of gapped inductors based on magnetic field equivalence. The gapless inductor with the winding for equivalent air-gap was constructed to characterize the magnetic field within the core window of the gapped inductor, and the auxiliary winding was used to replace the winding of the gapped inductor to generate the equivalent magnetizing magnetomotive force. Based on the transformer winding short-circuit method with the small-signal impedance test, the winding loss was separated from the core loss. After the resistance of auxiliary winding was measured by using an air-core inductor, the winding loss of the gapped inductor was consequently obtained. The proposed scheme was applied to inductors made of different sizes and structures, and the measured errors were within 20% in the range of 100 kHz to 1 MHz. The winding loss had a steeper growth tendency in this range than the lower frequency, so the proposed method is effective at high switching frequencies especially.

Control of shunt power active filter (SAPF) necessitates estimation of the fundamental active component (FAC) of load current and unit voltage templates (UVTs). In this paper, a frequency multiplier based FAC and UVT extractor is proposed, wherein the α−β quantities of load current and supply voltage undergo frequency multiplier action to obtain the respective components with fundamental frequency four times the power frequency. With the band pass filtering of these signals, the components corresponding to four times the power frequency are determined. Thus obtained current components are further processed to extract the FAC of load current. Similarly obtained voltage signals are used by the synchronous reference frame theory based phase locked loop for accurate UVT extraction with the help of the designed synchronizing logic. The comparative analysis performed using an experimental setup demonstrates faster dynamic response and accurate estimation with a developed extractor compared to earlier reported schemes. The performance of SAPF controlled with the proposed extraction algorithm is investigated in PSIM software. Further, experimental validation is also presented. The SAPF operation with the proposed control scheme ensures unity power-factor operation and adherence to total harmonic distortion (THD) limits by drawing sinusoidal currents from the grid.

This paper proposes a reduced switch modular multilevel inverter (RSM-MLI) requiring eight, thirteen, and fifteen switches per phase for 7-level, 15-level, and 31-level output voltages, respectively. For the generation of 7-level, 15-level, and 31-level output voltages, the proposed MLI employs two, three, and four designed modules, each comprising switches, diodes, and a DC source, respectively. The interconnection of modules results in the generation of unipolar staircase voltage. Further, an H-bridge inverter (HBI) facilitates DC-AC conversion. With modular construction, the levels can be easily increased in the proposed topology by adding extra modules. The merits of the proposed topology are highlighted through a comparative analysis. The higher switch count in MLI necessitates the use of multiple digital signal processors (DSPs), thereby complicating the gating circuitry. To simplify the gating requirements, this paper utilizes the digital output pins in a DSP, which are far higher in number than the PWM pins, for gate pulse generation. This negates the need of multiple DSPs. The operation of the developed experimental prototype of the proposed 7-level, 15-level, and 31-level RSM-MLI, controlled through the digital output pins of a DSP, is analyzed for steady-state and dynamic conditions.

The presented work demonstrates the three-port inverter configuration for a quadrupled reduction in the operating DC bus voltage compared to conventional inverter topology. Thus, the proposed configuration consists of the single inversion stage and operates with single or multiple sources. Irrespective of the source connected at input ports, the three inverters in the tri-inverter configuration synthesize the 512 switching combinations and spread across 61 voltage space locations to realize the load space vector. The switching states are segregated from the space spread not only to realize the maximum voltage gain but also to eliminate the common mode voltage during common DC source operations. In the case of common DC source operation, the CMV-eliminated switching combinations ensure the elimination of circulating current with minimum compromise of the voltage gain. The improved voltage gain and eliminated circulating current guarantee the maximum energy yield from source and improved reliability of the converter compared to the conventional inverter. The proposed converter’s efficacy and realized space vector switching states in terms of realizable four times voltage gain and the elimination of intra-inverter circulating currents are validated experimentally with single and multiple sources.