Abstract
This paper proposes a synchronous reference frame (SRF) control strategy for a single-phase, three-level, dual-buck photovoltaic (PV) inverter. The concept of virtual d-q transformation is adapted to the current control of the inverter, and the repetitive controller is implemented in the SRF. With the proposed control strategy, the memory allocation quantity for the repetitive controller is decreased and the capability of the current reference tracking is maximized. Thus, the proposed method significantly reduces the total harmonic distortion (THD) of the output current in both the continuous conduction mode (CCM) and the discontinuous conduction mode (DCM). In addition, the distortion of the output current is mostly composed of odd harmonics. Odd harmonic expressed to the even harmonic in SRF can be calculated using Park’s transformation. Therefore, a repetitive controller can improve dynamics by considering only even harmonic components in SRF rather than including all harmonics. The simulation and the experimental results verify the effectiveness of the proposed control strategy. The proposed method not only reduces the THD of the output current in both the CCM operation and the DCM operation, but also improves the dynamics of the current controller.
Highlights
Greenhouse effects and atmosphere pollution problems caused by conventional power generation are becoming severe [1,2]
This paper proposes the synchronous reference frame (SRF) proportional integral (PI) controller with repetitive current control strategy for dual-buck PV inverters
This means errors at the even harmonics in the SRF are effectively mitigated with the proposed control repetitive control scheme
Summary
Greenhouse effects and atmosphere pollution problems caused by conventional power generation are becoming severe [1,2]. The leakage current can be increased compared with the PV inverters with a decoupling transformer because of the stray capacitor between the PV module and the utility grid. The distortion caused by unidirectional and control performance of the current is highly dependent on the controller structure Regarding this issue, many control strategies have been studied including predictive controllers and modulations. This paper proposes the synchronous reference frame (SRF) PI controller with repetitive current control strategy for dual-buck PV inverters. The current distortion caused by the discontinuous conduction mode (DCM) operation of the inverter under light load conditions can be dramatically compensated.
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