200款Prius的升压转换器

Development of Hybrid Electric Drive System

Using a Boost Converter

Masaki Okamura

Eiji Sato

Shoichi Sasaki

TOYOTA MOTOR CORPORATION

1, Toyota-cho, Toyota, Aichi, 471-8572, Japan

Phone/ Fax : +81-565-72-9071/9147

Abstract

Toyota introduced a new generation of hybrid vehicle to the market in September of 2003. The new Prius, equipped with a new Toyota-developed inverter system, is capable of outputting more power than the conventional systems. One of the strong points of this new system is that a Boost Converter has been placed between the inverter and the battery. The Boost Converter is capable of raising the voltage from the battery, enabling the inverter to drive a high power output motor. The Toyota Hybrid System (THS), consists of a high power motor, generator, and a battery of relatively lower power. When the Boost Converter was adopted in the THS, it was possible to keep bulk and cost of the additional unit in the system to a minimum, by letting the Boost Converter function to the same power level as the battery. The control system of the Boost Converter consists simply of a PI controller. By using existing sensors and microprocessors, it was possible to develop a new system at no additional costs. The Boost Converter’s control system achieves high efficiency by optimizing its output voltage according to the relative state of the motor and the generator. Toyota was able to achieve a 50% improvement in the motor power output with the new Boost Converter, while keeping a similar complexity of the conventional system. As of now, Toyota plans to spread the development to other new hybrid vehicles.__

Keywords: Hybrid, Electric Drive, Converter, Inverter, Control System

Figure1: TOYOTA NEW PRIUS

1.Introduction

Toyota introduced the “Prius” in December 1997, the world’s first mass-produced hybrid vehicle, which is equipped with the Toyota Hybrid System (THS). The PRIUS has gained a reputation as a highly innovative vehicle, and its cumulative worldwide sales have exceeded 110,000 units. THS has continued to evolve, and Toyota has developed the concept of Hybrid Synergy Drive in 2003. Based on this concept, Toyota has developed a new-generation Toyota Hybrid System called THS I I. This system achieves a high level of compatibility between environmental performance and power thanks to an 1.5 times increase in the motor output, a boost of the power supply voltage, and significant advances in the control system. Toyota introduced the new PRI US in September 2003, equipped with THS I I. I n the following, we describe the Hybrid Electric Drive System using a Boost Converter, which is one of the new technologies of THSII.

2. Objective of THSII development

Automobiles in the future must increase both environmental and safety performances, while improving the all-important motor vehicle characteristic of being fun to drive. To achieve superior driving performance, which is the basis for driving enjoyment, the conventional approach has been to increase output and torque by increasing engine displacement or using supercharging. However, this approach decreases fuel efficiency, making it difficult to achieve compatibility of environmental performance and power. I n other words, fuel efficiency and power are in a trade-off relationship. By using the Toyota Hybrid System (THS) in the Prius, Toyota was able to find the solution to this problem. THS, which is a Series/Parallel Hybrid System, contains a power split device that splits power into two paths. In one path (Mechanical path), the power from the gasoline engine is directly transmitted to the vehicle's wheels. In the other path (Electrical path), the power from the engine is converted into electricity by a generator to drive an electric motor or to charge the battery. THS requires no external charging, unlike EVs (Electric Vehicles). I t is therefore usable with existing infrastructure. THS’s configuration, through the use of a motor having high low-speed torque and high output, manages idling stop, stopping of the gasoline engine while the vehicle is running, running of the vehicle using the electric motor, motor assist at any speed, and highly efficient energy regeneration, without using a clutch or transmission.

Mechanical path

Electrical path

Figure 2: System Configuration