Hybrid Modulation Method of PWM and Square-Wave Operation for Single-Phase Solid-State Transformer with ISOP Connection

Abstract

This paper proposes a hybrid modulation for a solid-state transformer (SST) with an input-series output-parallel (ISOP) connected cells. One of the cells on the high-voltage side for power factor correction (PFC) is driven using pulse width modulation (PWM) to compensate for the harmonic components of the input current, whereas the other cells are driven using square-wave operation. The square-wave operation cell enables the use of low-cost Si devices instead of expensive SiC devices, which reduces the cost of the SST. Moreover, this paper proposes the balancing control of the conduction loss in each square-wave cell. The experimental results demonstrate that the total harmonic distortion of the input current is 2.91%, and the conduction loss of each square-wave cell is well-balanced.