Message from Editors

POWER electronics is a key technology that enables the revolution of electric power generation,transmission,and distribution in modern power systems for improved energy security,efficiency,and sustainability.In distribution systems,power electronic converters not only serve as the critical interfaces between the utility grid and distributed energy resources such as solar,wind,and energy storage,but also play a pivotal role in power quality control and management.In transmission systems,high voltage high power electronic converters are the ideal candidate for achieving flexible and efficient power flow in bulk interconnected power systems.On one hand,it is no doubt that more electronic apparatus will be integrated into future power systems to further reduce carbon emissions.

Stability of interacting grid-connected power converters

The power grid in a typical micro distribution system is non-ideal,presenting itself as a voltage source with significant impedance.Thus,grid-connected converters interact with each other via the non-ideal grid.In this study,we consider the practical scenario of voltage-source converters connected to a three-phase voltage source with significant impedance.We show that stability can be compromised in the interacting converters.Specifically,the stable operating regions in selected parameter space may be reduced when grid-connected converters interact under certain conditions.In this paper,we develop bifurcation boundaries in the parameter space with respect to Hopftype instability.A small-signal model in the dq-frame is adopted to analyze the system using an impedance-based approach.Moreover,results are presented in design-oriented forms so as to facilitate the identification of variation trends of the parameter ranges that guarantee stable operation.

Non-isolated high step-up DC–DC converter adopting auxiliary capacitor and coupled inductor

For grid-connected power system based on photovoltaic(PV) source and fuel cells, high step-up and high-efficiency DC–DC converters are needed, due to the bus voltage of the grid-connected inverter is much higher than the output voltage of PV and fuel cells. In this paper, a novel high step-up converter is proposed. An auxiliary capacitor is introduced into the boost converter, which serves as a voltage source. It is in series with the input voltage source with the same voltage polarities. Thus, the input voltage is increased equivalently and the voltage gain is increased accordingly. To reduce the voltage stresses of the switch and the diode, multiple output capacitors are introduced. The voltage of each output capacitor is degraded leading to the reduced voltage stress. To replenish energy for the multiple output capacitors, a coupled inductor is adopted. Based on this, high step-up converter adopting auxiliary capacitor and coupled inductor is derived. The operating principles and voltage gain of the proposed converters are analyzed in this paper. In theend, experiment results are given to verify the theoretical analysis.

Guest Editorial:Special Section on Applications of Power Electronics in Power Systems

Power transformers and steam turbines were the key drivers in the development of the AC power system paradigm at the dawn of the 20 th century, characterized by huge synchronous generators feeding millions of passive loads through large interconnected systems, all of them supervised and controlled from a centralized energy management system(EMS). In the same way, thyristor valves and IGBTs, introduced

Editorial for the Special Issue on Switched-Capacitor Circuits and Partial Processing Techniques

Switched-capacitor circuits are gaining renewed interests for its capability of processing unregulated power with 99% duty ratio,ultra-high efficiency and ultra-high power density.Among various techniques,half-resonance circuits are most promising because of its lab demonstrated efficiency(>98.5%)and power density(>1000 W/in^(3)).