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Operating Voltage and Loss Analysis of a Bi-Directional Isolated DC/DC Converter
| Content Provider | Semantic Scholar |
|---|---|
| Author | Inoue, Shigenori Akagi, Hirofumi |
| Copyright Year | 2007 |
| Abstract | This paper describes the bi-directional isolated dc/dc converter shown in Fig. 1 having a high-frequency transformer with a unity turn ratio, where the input and output dc voltages are different from each other. Few technical papers have dealt with the dc/dc converter under different dc voltages. Besides, no technical paper has demonstrated the operation of the dc/dc converter rated around 10 kW under different dc voltages. However, voltage-adjusting capability may bring about a significant expansion of the application fields of the dc/dc converter. Thus, this paper analyzes the relationship between operating dc voltages, transfered power, and power loss to determine how different the two dc voltages can be from each other without excessively increasing power loss. Then, experiments are conducted on the dc/dc converter rated at 360 V, 10 kW, and 20 kHz, demonstrating bi-directional power flow under different dc voltages stably. The effect of the so-called “dead time” on the operating performance is also discussed in this paper. Fig. 2 shows the calculated relationship between transfered power PDC and the theoretical loss when one dc voltage is fixed at 320 V and the other is adjusted between 180 V and 360 V. Note that Fig. 2 assumes the power transfer PDC to be positive, and the theoretical loss consists of a snubber loss and an IGBT conducting loss excluding an IGBT switching loss and magnetic-component losses. The calculation was carried out under the condition where the snubber capacitor Csnub = 0.01 μF and the voltage drop across each IGBT and diode is 1.5 V regardless of the current. Difference between E1 and E2 narrows the range of transfered power where ZVS (zerovoltage switching) operation is possible, resulting in an increased snubber loss. The lower E2 becomes, the higher current is needed to transfer a given power, causing larger power loss than that at E1 = E2 = 320 V. Thermal limit of 212 W is drawn as a dashed line in Fig. 2 based on the theoretical loss at E1 = E2 = 320 V. When E1 = 320 V and E2 = 180 V, the theoretical loss reaches the thermal limit at PDC = 5.6 kW. The power loss or the thermal design of the dc/dc converter determines the possible range of power transfer and the difference between the two dc voltages. As is mentioned in this paper, the peak value of the current i1 also imposes limitation on the possible voltage difference. Despite the above-mentioned increased power loss, the operation under different dc voltages is useful and may expand the application field of the dc/dc converter. Experiments were conducted with E1 fixed to 320 V and E2 changed to be 320 V, 360 V, 260 V, and 180 V. Fig. 3 shows experimental waveforms of the dc/dc converter when a power of 5 kW is transfered from Bridge 2 to Bridge 1 (PDC = −5 kW) at E1 = 320 V and E2 = 180 V. The peak value of i1 was 60 A while its theoretical value was 66 A. Although Bridge 2 was operated in hard switching Fig. 1. A bi-directional isolated DC/DC converter |
| Starting Page | 189 |
| Ending Page | 197 |
| Page Count | 9 |
| File Format | PDF HTM / HTML |
| DOI | 10.1541/ieejias.127.189 |
| Volume Number | 127 |
| Alternate Webpage(s) | https://www.jstage.jst.go.jp/article/ieejias/127/2/127_2_189/_pdf |
| Alternate Webpage(s) | https://doi.org/10.1541/ieejias.127.189 |
| Language | English |
| Access Restriction | Open |
| Content Type | Text |
| Resource Type | Article |
