Minoru Moteki

Stable startup of seamless controlled parallel bidirectional DC-DC converter

A smart control method for Bidirectional DC-DC Converter has been developed. Both charge and discharge with buck / boost mode transition are achieved by common control structure without mode judgment. This simple structure is also extended to a parallel system, and controls multiple output power for both directions. The function has some exceptional case at the period of start-up and stop, because introduced complementary switching flows unexpected reverse current. To avoid the unexpected reverse current, we introduced the selective disable function of complementary switching and achieved stable start and stop control. This improvement also equipped the system additional charge only operation. Improved control structure was evaluated at the four-parallel converter system.

Seamless controlled parallel bi-directional DC-DC converter for energy storage system

A scalable parallel bidirectional DC-DC converter system, which enables efficient seamless control using an H-bridge topology, was developed and evaluated. Although the unified control structure is simple, four drive-mode, both charge and discharge with buck/boost, can be handled. The proposed system was extended for use in simple parallel converter management. This scheme achieves high efficiency over a wide load range, especially for light loads. The only hardware required is a power line and communication cable connection. All other functions are provided by software and operate autonomously. A 5-kW prototype converter was constructed and evaluated, and a four-unit parallel converter system was tested and confirmed to work well, changing load between 20-kW discharge and 20-kW charge.

Low Insertion Loss Surface Acoustic Wave Matched Filter with Low Sidelobe Sequence and Its Application for Spread Spectrum Communication

For direct sequence (DS) spread spectrum communication systems with differential phase-shift keying (DPSK) modulation, we have calculated low autocorrelation sidelobe pseudo noise (PN) sequences. We constructed a matched filter comprising localized layered structure on a quartz crystal to obtain low matching loss. As a result of the sequences and the construction, 14 dB (6 dB improvement on that of the conventional sequences) peak vs sidelobe of correlated output signal and 9 dB lower loss than that of a conventional filter was achieved. We have applied these matched filters to SS rf-modem units for weak-power digital communications. In these modem units high data rate (1 Mbps), long communication distance (about 20 m) and low current (210 mA when received) performances are obtained.