This paper investigates a control approach for achieving reliable zero-voltage switching transitions within the entire operating range of a conventional nonisolated bidirectional dc-dc converter that utilizes synchronous rectification. The approach is based on operation in the discontinuous conduction mode with a constant reversed current of sufficient amplitude, which is achieved by load-dependent variation of the switching frequency. This paper focuses on the obtained resonant voltage transitions and provides analytical models for determining the reversed current and timing parameters that would ensure safe, reliable and highly efficient operation of the converter. In addition, the proposed approach solves the synchronous transistor's spurious turn-on and body diode reverse recovery induced issues, does not require any additional components or circuitry for its realization, and can be entirely implemented within a digital signal controller. The effectiveness and performance of the presented control approach was confirmed in a 1-kW experimental bidirectional dc-dc converter that achieved 97% efficiency over a wide range of output powers at switching frequencies above 100 kHz.

A pulse-density-modulated (PDM) flyback-based microinverter with a high-frequency AC (HFAC) link and an active decoupling circuit is proposed. The converter's structure and basic operating principle are analysed. The advantages of utilising an active decoupling circuit and the demand for using pulse-density modulation are explained. The operation of the proposed microinverter has been verified by experiment.

This study proposes a new control method for a pulse-density modulated microinverter and its implementation within a field programmable gate array circuit. The structure and operating principle of the studied microinverter demand implementation of a pulse-density modulation-based control method with two independent control loops. The first one ensures a constant input current from the source while the second one provides a sinusoidal voltage at the converter's output. At the same time the implemented control method ensures zero-current switching of the utilised power transistors in decoupling and output stages which allows operation at high switching frequency. The performance of the proposed control method for a microinverter operating in island mode was experimentally verified in steady-state operation, as well as during load transients.

This article presents a single-shunt measurement of a three-level inverter using a modified space-vector modulation to reconstruct the three-phase load current. The proposed method was implemented on a digital signal processor (DSP), and the algorithm was verified in the laboratory experiment. Through the work, it was proven that the single-shunt three-phase current measurement could be performed using the space-vector modulation for three-level inverters in an analogous way to ordinary three-phase inverters. Three-phase current reconstruction for ordinary three-phase inverters was performed using the ordinary space-vector modulation with eight vectors, but for three-level inverters, 21 vectors were available. When the inverter was working on the edges between two vectors, the modulation disturbances appeared as current spikes. This problem was solved using the modified SVM performed by shifting the SVM signals. Carefully designed signal shifting (vector injection) demonstrated an excellent reconstruction of the three-phase load currents that were single-shunt measured.

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