Kazuyoshi Obayashi

Concept of Vehicle Electric Power Flow Management System (VEF)

Increasing electric loads in a vehicle causes over-discharge of a battery and drag torque due to an alternator. This paper gives a system concept of vehicle electric power flow management to solve these issues. Its primary function includes preserving electricity in a battery, stabilizing electric bus voltage, interfacing with vehicle torque control system, and improving fuel economy. The key point to realize such a system is a unified structure. It offers ‘Plug and Play’ function for electric power management components. Newly developed Vehicle Electric Power Flow Management System (VEF) totally controls electric power flow in a vehicle. VEF contains an Electric Power Manager and its functional sub-systems, and controls them with the key parameter ‘electric power’. The sub-system includes Generation, Storage, Conversion, and Distribution to the loads. While sum of power required by electric loads exceeds a capacity of Generation and discharge of Storage, some electric loads are forced to reduce. These loads are selected according to the sum of required electric power and priority based on the load operating conditions. As VEF has a unified structure, it can be extensively applied for newcomer generators, batteries and loads in various categories of vehicles. VEF is evaluated with a test vehicle, and the results show that overall experiments are positive, including bus voltage stability and loads limitation with acceptable driver’s feeling.

Wireless power transfer system for delivery truck connected to energy management system / smart grid

Wireless power transfer (WPT) system for delivery truck is newly developed and evaluated at smart grid field test in Toyota city [1]. The truck is equipped with electrical refrigerator and on board battery to keep frozen foods, which is operated at idling stop mode. In order to keep capacity of on board battery small, driver must charge the battery occasionally when the truck stops at several delivery places. WPT, which transfers 4.5kW electricity over 300mm, reduces drivers effort for charging, such as plug in, plug out and put cables in order. WPT also allows misalignment at parking 100mm in longitudinal direction and 200mm in lateral direction. Therefore its easy for drivers to park the truck at an appropriate position. Field test proves that WPT also saves more than 80% of drivers operation time for charging preparation. Concept and experimental results of WPT for delivery truck are shown in this paper.

Z-matched active common-mode canceller for the suppression of common-mode current in an inverter system

In a vehicle, radiational noise generated by the common-mode current in an inverter system is the cause of electromagnetic problems of in-vehicle radio antennas. This paper proposes a new method ”Z-matched ACC” for suppressing the common-mode current at AM band. With this method, the freewheel current, which reduces the common-mode current suppression effect at AM band in conventional voltage-cancellation ACC, does not flow by setting the phase of the Z-matched circuit equal to that of the motor common line. Therefore, the Z-matched ACC can suppress the common-mode current at AM band. The suppression effect of the Z-matched ACC is superior to the conventional ACC from 100 kHz to 10MHz. In addition, the Z-matched ACC can reduce the size of the common-mode transformer over that for the conventional ACC by reducing the ET product applied to the common-mode transformer.