Search

The single-phase isolated quasi-single-stage AC-DC converter has many virtues, such as high power density and efficiency; however, its grid current closed-loop control has not been solved. This paper aims to solve the remaining gap based on a large-signal model. In this paper, the large-signal model of this converter under triple-phase-shift modulation is built for the first time. It is verified that the built model is a zero-order linear system. Based on this built model, the effect of grid harmonics on this converter grid current is analyzed. The theoretical analysis reveals that the grid voltage low-order harmonics will cause the same order grid current harmonics and only varying the parameters of the filter is not an effective method to solve this problem. For the purpose of eliminating the effect of grid voltage harmonics on the grid current and realizing the zero-error control of the fundamental component of the grid current, a grid current closed-loop control strategy based on the proportional-resonant compound odd-mode repetitive controller is proposed. The operation principle, parameter constraint, and design rule of the proposed compound control strategy are analyzed comprehensively. The theoretical analysis and the compound control strategy put forward in this paper are tested, with detailed experimental results. [ABSTRACT FROM AUTHOR]

In this paper, a triple-active-bridge resonant dc-dc converter with the ability of topology-level power decoupling is proposed. The power coupling between the two dc ports is eliminated by adding a resonant capacitor to the common port. The operation principle and the steady-state power characteristics are analyzed. On this basis, a multi-phase-shift-based global optimization modulation is proposed to minimize the RMS values of the transformer currents in the entire power and voltage range, thus increasing the global efficiency. An experimental prototype is built to verify the correctness and availability of the proposed power decoupling topology and optimized modulation. [ABSTRACT FROM AUTHOR]

Power electronics technology is playing an increasingly important role in modern energy utilization systems. In order to improve the power quality and power conversion efficiency, various power electronics technologies are being researched. This Special Issue aimed to collect and present breakthrough research on various kinds of the power electronics converters, including topologies and modulations, modeling and control, fault diagnosis, and power-conversion technologies for wireless power transmission in emerging power-conversion technologies. [Extracted from the article]

Insufficient frequency regulation capability and system inertia reduction are common problems encountered in a power grid with high wind power penetration, mainly due to the reason that the rotor energy in doubly fed induction generators (DFIGs) is isolated by the grid side converters (GSCs), and also due to the randomness and intermittence of wind power which are not as stable as traditional thermal power sources. In this paper, the frequency inertia response control of a DFIG system under variable wind speeds was investigated. First, a DFIG system topology with rotor-side supercapacitor energy storage system (SCESS-DFIG) was introduced. Then a control strategy for frequency inertia response of SCESS-DFIG power grid under fluctuating wind speed was designed, with two extended state observers (ESOs) which estimate the mechanical power captured by the DFIG and the required inertia response power at the grid frequency drops, respectively. Based on one inconstant wind speed model and the SCESS-DFIG system model adopting the control strategy established, one power grid system consisting of three SCESS-DFIGs with different wind speed trends and a synchronous generator was simulated. The simulation results verified the effectiveness of the SCESS-DFIG system structure and the control strategy proposed. [ABSTRACT FROM AUTHOR]