In this paper, a novel LLC-asymmetric half-bridge flyback converter (AHB) that can realize a wide range of voltage gains is proposed. This type of topology utilizes the idea of topology morphing to realize the mode transition between LLC mode and AHB mode by adding a switch. The sharing of the same set of resonant tank parameters for both LLC and AHB can be realized by suitable resonant tank parameter design, which allows this topology to use the AHB mode at low voltage gains and the full-bridge LLC mode (FBLLC) and half-bridge LLC (HBLLC) modes at higher voltage gains, and each topology operates in its more suitable operating range. The design considerations, design ideas of this topology are discussed in this paper. Finally, the performance and realizability of the proposed topology are confirmed by simulation results.

This paper proposes a novel single-stage single-phase transformerless topology based on a buck-boost converter for grid-connected photovoltaic (PV) inverters. The proposed inverter has a wide input voltage range, low total harmonic distortion of current, and effective suppression of common-mode leakage current. The single-input structure ensures that it does not suffer from energy imbalance problems. The new inverter utilizes dead beat control and refines the method of controlling the inverter when the input energy is insufficient. The simulation results verify that the proposed grid-connected PV inverter maintains high grid-connected power quality both during normal operation under conventional conditions and when operating under discontinuous conduction mode (DCM) during energy insufficiency. The simulation models the operating mode of the inverter under abnormal environments, such as load changes and grid voltage transients, which proves that the proposed inverter under dead beat control has a better dynamic performance.

As the search for sustainable, environmentally friendly energy sources continues, DC devices such as new energy-electric vehicles and energy-saving LED lights have been actively promoted. Consequently, the necessity for the DC microgrid in grid system development will become increasingly apparent, and the research on three-terminal output converters is increasing. Besides, double-frequency ripple power is an inherent problem in single-phase power electronic systems. This paper proposes a three-terminal output AC/DC converter with automatic power decoupling and common ground for the DC microgrid as a solution to the issues above. The equivalent circuit has been subjected to a detailed analysis to elucidate its underlying operating principles. Due to the structure of the common ground, the common mode leakage current can be eliminated in this converter. In addition, the implementation of automatic power decoupling enables the replacement of electrolytic capacitors with film capacitors, leading to higher power density and longer lifespan. Furthermore, the employed deadbeat control has a fast dynamic response capability. Finally, the simulation results are presented to verify the theoretical analysis and the performance of this converter.

This article presents a novel transformer-less single-stage buck-boost inverter (SSBBI) utilizing coupled inductors and its dual-mode time-sharing control method. The leakage current can be completely suppressed by connecting the neutral of the electrolytic capacitors to the common ground of the power grid. Besides, only one MOSFET operates at high-frequency in Buck and Boost mode. As a result, in theory, high conversion efficiency can be guaranteed for the proposed inverter. Moreover, compared with conventional Aalborg inverters, the number of switches, diodes, and inductors is further reduced to reduce cost and increase power density. In addition, the operating principle based on equivalent circuits and the control strategy of the proposed inverter are given in this article. As a proof of concept, the simulation results based on PSIM of the proposed SSBBI with different input voltages and output powers and a 110 V power grid are provided.

Virtual oscillator control (VOC) is a grid-forming controller designed for microgrids, where inverters are regulated to mimic the dynamics of weakly nonlinear oscillators. VOC operates in the time domain and offers a faster transient response compared to the virtual synchronous generator. However, conventional VOC implementations often result in reduced power system inertia, which poses a risk to frequency stability due to the lack of inertia. The inertial response is introduced into VOC by integrating the swing equation of a synchronous generator to represent virtual inertia and damping. Unlike real synchronous generators, the parameters of the swing equation can be adjusted in real time to support frequency stability. By employing varying levels of virtual inertia and damping during frequency deviation and recovery, improvements of 10.4% in frequency nadir and 4.9% in the rate of change of frequency are achieved compared to fixed inertia setups. Simulation results confirm the effectiveness of the proposed approach.

In DC microgrid, the uncontrollable DC link short-circuit current seriously shortens the life of the electrolytic capacitors in conventional AC/DC converters. To solve the issue, a new AC/DC converter with controllable DC link short-circuit current is proposed. Simulation results have verified the performance of the proposed converter.

In order to mitigate the negative effect of multi-frequency ripple power, a non-isolated micro-inverter with active power decoupling has been proposed in recent years, which shows some potential advantages, in terms of low cost, fewer switches, high efficiency, and a brief system control strategy. However, it has two independent PV panel input dc sources, which may be asymmetrical in realistic PV systems, resulting in a decrease in the power generation capacity of the whole system. To address this problem, an improved non-isolated micro-inverter topology with active power decoupling is proposed in this paper. Similar to the conventional micro-inverter, it can effectively suppress the common-mode leakage current. Different from the conventional micro-inverter topology, it uses a single PV panel input dc source and achieves positive and negative half-line cycle equivalent dc sources through two split-bus capacitors. The simulation has validated the effectiveness of the proposed non-isolated micro-inverter.

Today, a predictive controller becomes one of the state of the art in power electronics control techniques. The performance of this powerful control approach will be pushed forward by simplifying the main control criterion and objective function, and decreasing the number of calculations per sampling time. Recently, predictive control has been incorporated in the Z-source inverter (ZSI) family. For example, in quasi ZSI, the inverter capacitor voltage, inductor current, and output load currents are controlled to their setting points through deciding the required state; active or shoot through. The proposed algorithm reduces the number of calculations, where it decides the shoot-through (ST) case without checking the other possible states. The ST case is roughly optimized every two sampling periods. Through the proposed strategy, about 50% improvement in the computational power has been achieved as compared with the previous algorithm. Also, the objective function for the proposed algorithm consists of one weighting factor for the capacitor voltage without involving the inductor current term in the main objective function. The proposed algorithm is investigated with the simulation results based on MATLAB/SIMULINK software. A prototype of qZSI is constructed in the laboratory to obtain the experimental results using the Digital Signal Processor F28335.