Due to several reasons, the three-phase voltages of power grids cannot be balanced. The performance of AC-DC converters using dq0-based controls can be severely affected by the presence of unbalanced input AC voltages. Different to these proposals, this study presents a new easy-to-implement control scheme based on a single PI loop algorithm for VSC-PFC rectifiers using a phasorial approach. This new scheme has various significant advantages: (i) fast counteracting of large unbalanced voltage and current conditions; (ii) power factor = 1 at any unbalanced sag operating conditions; (iii) negligible current harmonic distortion and (iv) low-ripple DC voltage. All these features are concurrently obtained. The proposed single-PI loop VSC-PFC rectifier control strategy is theoretically and experimentally validated. A revision of the main results and characteristics of various proposed techniques that are similar to the one proposed in this study is also carried out, qualitatively indicating the main advantages featured by the proposed control strategy for VSC-PFC rectifiers.
This paper proposes a single‐phase transformerless photovoltaic (PV) microinverter for low and medium‐voltage applications. The proposed approach comprises a suitable combination of multilevel boost/buck and H‐bridge topologies with a current‐sensorless control scheme, where the system controller only needs a straightforward‐to‐implement control loop to reach the desired attributes in solar PV conversion systems. Compared with other microinverters, this proposal significantly reduces the number of hardware components and required software resources, considerably attaining industrial and production advantages; guaranteeing: (i) a high DC elevation factor; (ii) an extraction of maximum power from solar PV panels; (iii) a multilevel output voltage; (iv) a low total harmonic distortion; and (v) a power factor close to unity. The multilevel microinverter's feasibility and effectiveness are assessed by a comprehensive mathematical model, whose simulation results are evaluated using MATLAB‐Simulink, and the experimental results are validated by means of an on‐grid low‐scale prototype, generating a power capacity of 1.5 kW.
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