Model Predictive Direct Power Control of Grid-connected Converters Considering Unbalanced Filter Inductance and Grid Conditions

The grid-connected converter(GCC) is widely used as the interface between various distributed generations and the utility grid. To achieve precise power control for GCC, this paper presents a model predictive direct power control(MPDPC)with consideration of the unbalanced filter inductance and grid conditions. First, the characteristics of GCC with unbalanced filter inductance are analyzed and a modified voltage control function is derived. On this basis, to compensate for the power oscillation caused by unbalanced filter inductance, a novel power compensation method is proposed for MPDPC to eliminate the DC-side current ripple while maintaining sinusoidal grid current. Besides, to improve the control robustness against mismatched filter inductance, a filter inductance identification scheme is proposed. Through this scheme, the estimated value of filter inductance is updated in each control period and applied in the proposed MPDPC. Finally, simulation results in PSCAD/EMTDC confirm the validity of the proposed MPDPC and the filter inductance identification scheme.

High-power Tm^(3+)-doped all-fiber laser operating at1908 nm by a master oscillator power amplifier configuration with narrow spectral linewidth

We demonstrate a diode-pump Tm^（3＋）t-doped all-fiber laser operating at 1908 nm based on a master oscillator power amplifier（MOPA） configuration. In our work, 152 W of laser output power is generated by a total incident pump power of 434 W at 790 nm, corresponding to the total optical efficiency of 35%. The laser wavelength is1908.29 nm. To the best of our knowledge, it is the highest output power reached around 1908 nm with such a narrow linewidth of 0.18 nm based on a MOPA configuration.