The operational stability of grid‐connected converters is affected by unbalanced grid voltage, which often leads to overcurrent. The traditional control method maintains the grid‐into current within the rated limit by adjusting the current reference value. However, this method limits the output active power of the converters and affects their reliability, which can cause active power shortage or even disconnection of the power grid. To deal with this issue, this paper proposes an effective control strategy. First, the interaction between AC and DC sides of the converters under unbalanced voltage conditions is analysed. Second, the resilience is defined and elaborated. Third, considering various constraints such as the grid‐into current harmonics, power fluctuations and DC side voltage fluctuations, the operation resilience range of the converters is calculated. Based on the resilience range, an optimal operating point is selected and an optimal strategy is developed. Compared with the traditional strategy, the proposed strategy allows improving the maximum active power output capacity and resilience of the grid‐connected converters under unbalanced grid conditions, while simultaneously limiting the power fluctuations and grid‐into current distortions within an allowable range. Last, simulation and experimental results show the effectiveness and feasibility of the proposed strategy.

In low‐voltage distribution systems, the increased penetration of power electronic devices leads to the decentralization of harmonic sources, which puts the sensitive loads or communication systems in the risk status. The conventional methods of point‐to‐point harmonic control are not applicable. In order to solve this problem without increasing additional investments, this paper focuses on mitigating the harmonic interference through the power factor correction (PFC) converter. Hence, a critical conduction mode (CRM) single‐phase boost PFC converter with adaptive harmonic compensation (AHC) control is proposed to reduce the harmonic interference at user side. Firstly, the feed‐forward control loop of a PFC converter is decoupled into the fundamental branch and harmonic branch to trace the harmonic interference and generate the compensation current. Then the compensation gain is designed by the compensation loop gain and compensation capacity of PFC converter. Meanwhile, the characteristics of the PFC converter are analyzed to study the effect of the AHC control on the active power transmission and output load, which can provide important support for the proposed method in application. Finally, a 160‐W experimental prototype is built to verify the effectiveness of the proposed AHC control.

This paper focuses on mitigating the harmonic interference through power factor correction (PFC) converter. Based on this, the compensation characteristics of the single‐stage and multi‐stage compensation structures are analyzed in the low‐voltage distribution system.image

This research proposes a novel multilevel inverter based on a new capacitor basic unit. Four capacitors are deployed in this unit to provide both even and odd voltage levels. Two‐cell proposed cascaded multilevel inverters and developed cascaded multilevel inverters are evaluated in order to improve the number of output levels generated. Calculations are made for all associated equations after determining the value of the necessary DC voltage source. Additionally, both inverters' switching tables and capacitor charge and discharge modes are fully explained. The merits and disadvantages of the proposed topology are then assessed by contrasting the cascaded multilevel inverter under consideration with a number of widely used multilevel inverters. The key benefit of the suggested architecture is the increase in the number of output levels produced while using fewer power electronic devices and DC voltage sources overall. The proposed one‐cell cascaded inverter is then utilized to evaluate the performance of the proposed topology using the relevant equations, simulations, and experimental data. The simulation is carried out using the EMTDC/PSCAD software, and a lab prototype yields the experimental data.

A new multilevel inverter based on new capacitor basic unit is proposed. To generate all voltage levels, four capacitors are used. To increase the number of generated output levels, developed cascaded multilevel inverter are analyzed. The main advantage this inverter is increasing the number of generated output levels with lower number of required power electronic devices and DC voltage sources.image

Direct torque control (DTC) is one of the most prominent control techniques used by permanent magnet synchronous motor (PMSM) drives in industry applications. Nevertheless, the presence of hysteresis controllers and inaccurate voltage switching table in traditional DTC results in higher torque and flux ripple. This study proposes an enhanced DTC functioned Surface‐mounted PMSM (S‐PMSM) drive with mitigation of torque and flux ripple. The operation relies on generating the reference voltage vector (VV) in a stationary reference frame, which supports control of torque and flux without hysteresis controllers. The reference VV generation is simple and does not affect control robustness. The position of reference VV in a sector is used to build the voltage vector (VV) switching table. As a result, the application of nearest discrete VV to reference VV produces optimal torque and flux control. Moreover, redundant switching combinations of null VV are effectively used for possible minimization of switching frequency of two‐level voltage source inverter (VSI) supplied S‐PMSM drive. Therefore, proposed DTC gains improved S‐PMSM drive response along with switching frequency reduction. In dSPACE‐RTI 1104 platform, experimental response of S‐PMSM drive under various operating conditions have been depicted to highlight the proficiency of proposed DTC in comparison with existing DTC.

Enhanced DTC‐functioned PMSM drive with mitigation of torque and flux ripple. The operations rely on generating the reference voltage vector (VV) in stationary reference frame, which supports control of torque and flux without hysteresis controllers. The reference VV generation is simple and does not affect control robustness. Redundant switching combinations of null VV are used for possible minimization of switching frequency of two‐level voltage source inverter (VSI) supplied PMSM drive.image

The real‐time monitoring technology of power line is an important guarantee for the digitization and intelligence of the modern power system. Traditional current transformers cannot provide continuous and stable energy when the power line current fluctuates in a large range. This paper proposes a comprehensive design method of an active electronic current transformer (AECT) based on a single‐phase full‐bridge voltage‐type PWM rectifier (VSR), which can acquire continuous and stable energy from the power line with a minimum magnetic core. The control of the AECT is divided into four different operation modes to adapt the fluctuation of primary current. Maximum power point tracking (MPPT) mode and minimum loss (ML) mode is designed to harvest the maximum power with lower iron core loss when the primary current is relatively low. Excitation mode and demagnetization mode are designed to harvest stable power when the primary current is higher than a certain current. The specific mode operation principles and control strategies are analysed in detail. Besides, the calculation method of the primary current is also presented for the primary current measurement. Finally, simulations and experiments verify that the iron core can obtain power steadily (9.91 W/kg) when the current fluctuation between 50 and 600 A.

This paper describes a kind of harvester for high‐voltage transmission lines. It mainly includes the structure of power harvester and automatic control strategy.image