Basic Study of a Circuit Configuration for Power Transformer-less A. C. Fed Electric Trains using High Withstand Voltage Property of SiC Power Devices

Experimental verification of isolation power circuit for transformer‐less AC fed electric vehicles

“…Using the same approach as shown in fig. 1 of Reference [11], AC power (voltage: 20 or 25 kV, frequency: 50 or 60 Hz) is collected by a pantograph, converted to DC by a non‐isolated AC‐DC converter 16 ; after that, the isolation circuit and inverter‐based motor drive circuits (Figure 3E) are cascade‐connected. Now, operation of the conventional circuit was verified with DC output voltage of the AC‐DC converter (Figure 3A) set to 12 kV and DC input voltage of the inverter modules (Figure 3F) set to 3 kV (fig.…”

“…As a first step, a flying capacitor circuit was proposed to transmit power between DC input and output without simultaneous conduction (below referred to as "conventional circuit"); the applicability of the circuit to AC trains was demonstrated via mini-model experiments. 11,12 As a second step, capacitive isolation 13 using a nesting capacitor structure was proposed, 14 and a similar circuit was incorporated into the conventional circuit to obtain a basic configuration for insolation between DC input and output 15 (below referred to as "isolation circuit"). In Reference [15], operation principle of the isolation circuit during powering and regeneration was demonstrated, and the feasibility of power transfer was confirmed via circuit response analysis in every mode.…”

“…One of the challenges is developing a new circuit to substitute the transformer's functions of isolation and voltage transformation. As a first step, a flying capacitor circuit was proposed to transmit power between DC input and output without simultaneous conduction (below referred to as “conventional circuit”); the applicability of the circuit to AC trains was demonstrated via mini‐model experiments 11,12 …”

“…As a second step, capacitive isolation 13 using a nesting capacitor structure was proposed, 14 and a similar circuit was incorporated into the conventional circuit to obtain a basic configuration for insolation between DC input and output 15 (below referred to as “isolation circuit”). In Reference [15], operation principle of the isolation circuit during powering and regeneration was demonstrated, and the feasibility of power transfer was confirmed via circuit response analysis in every mode.…”

“…Assuming that the 1-h rated output of the motor in Figure 3E is 150 kW, capacitance 11 of Reference [11]).…”