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A 1500 V three-level forward converter with phase-shifted control is proposed to meet the requirements on mediumand high-voltage DC bus of photovoltaic grid-connected system. The architecture of 1500 V DC bus is established by filtering the phase-shifted outputs in series centrally, in which the internal filters of each DC/DC converter are removed. The three-level voltage is superimposed by phase-shifting the rectified output voltages in series, which is beneficial to decrease the inductor current pulsation, diminish the ripple of output voltage and improve the system efficiency. The centralised filter contributes to downsizing the filter and reducing the system cost. With the introduction of parallel-series structure, the characteristics of lowvoltage stress are retained and the power transmission is improved. Meanwhile, the minimum value of total harmonic distortion (THD) with phase-shifted control is obtained through the Fourier decomposition of three-level voltage waveform. By analysing the variation rule of THD with the change of conduction angle, the optimal steady-state operating point of the converter is achieved. The operating principle of the proposed system is presented minutely in this study and a prototype has been established. The experimental results verify the validity of the proposed converter.

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