Electricity: motive power systems – Induction motor systems – Primary circuit control
Reexamination Certificate
1996-10-23
2001-07-03
Martin, David (Department: 2837)
Electricity: motive power systems
Induction motor systems
Primary circuit control
C318S722000, C318S724000, C318S432000, C318S809000, C318S811000
Reexamination Certificate
active
06255798
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to a control apparatus for controlling an electric vehicle, and in particular, it relates to a control apparatus for controlling power devices in a power converter which supplies power to an ac motor for driving the electric vehicle in which the power devices are driven by a digital actuating signal.
Many of the prior art control apparatuses for driving an ac motor, whether an induction motor or a synchronous motor which uses permanent magnets, in practice utilize the vector control method which divides a motor current into a torque current Iq and an exciting current Id in order to control the motor. Various control methods utilizing the vector control method have been proposed for the purpose of improving static and dynamic characteristic control performances and the like. For example, in JP-A-6-178575, timing control between an exciting current reference and a torque current reference is disclosed for improving such control characteristics.
For a drive unit including a motor and a power converter for driving an electric vehicle, it is essential that it be compact in size and light-weight in order to satisfy the requirement of improving the mileage per charge of a battery. In order to satisfy such a requirement for compactness and light-weight, it becomes necessary to increase its motor speed, for example, over several thousand revolutions per minute as well as frequencies of its power converter, for example, over several hundred Hz. As disclosed in the above-mentioned prior art JP-A-6-178575, it is a general practice to compute reference values of the torque current and exciting current using a microcomputer for motor current control in a control unit which produces a drive signal to drive power devices in the power converter which supplies power to the ac motor. However, since a number of electronic components are required such as logic circuits, operation amplifiers and the like, in addition to the microcomputer, increases in size and weight of the control unit cannot be avoided according to the prior art, thereby preventing realization of the requirements for compactness and light-weight of the drive unit.
SUMMARY OF THE INVENTION
An object of the present invention is to provide a compact and light-weight control apparatus which produces a drive signal to power devices in the power converter which supplies power to an ac motor for driving the electric vehicle.
The object of the invention can be accomplished by providing such a control apparatus for producing a drive signal to power devices in the power converter which supplies power to the ac motor for driving the electric vehicle that is comprised of: a current reference generator which calculates a d-axis exciting current reference value, according to which a magnetic flux of the ac motor is generated in response to a torque reference value which the ac motor desires to produce, and a q-axis torque current reference value, where the d-axis and the q-axis are orthogonal to each other; a current control unit which produces each ac voltage reference value on the basis of the d-axis exciting current reference value and the q-axis torque current reference value; and a PWM signal generation unit for driving the power devices in response to the ac voltage reference values, wherein the current reference generator and the current control unit are controlled by a single arithmetic unit in a digital mode.
The aforementioned current control unit of the invention includes: a three-to-two phase converter which obtains from a motor current each feedback value relative to the d-axis exciting current reference value and the q-axis torque current reference value; a d-axis exciting current control unit which calculates a d-axis exciting voltage reference value from a difference between the d-axis exciting current reference value and the d-axis exciting current actually obtained; a q-axis torque current control unit which calculates a q-axis torque voltage reference value from a difference between the q-axis torque current reference value and the q-axis torque current actually obtained; a two-to-three phase converter for converting the d-axis exciting voltage reference value and the q-axis torque voltage reference value into each ac voltage reference value; further a d-axis and q-axis voltage compensation unit for compensating the d-axis exciting voltage and the q-axis torque voltage reference value; and an ac voltage compensation unit for compensating the ac voltage reference value.
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IEEE Transactions on Industry Applications, vol. 30, No. 6, 1994, pp. 1632-1637 entitled “Effects and Compensation of Magnetic Saturation in Flux-Weakening Controlled Permanent Magnet Synchronous Motor Drives” by S. Morimoto et al.
Thesis 1982, TU Braunschweig, pp. 66-69, 86-89 entitled Feldorientierte Regelung einer Asynchronmaschine mit einem Mikrorechner by R. Gabriel.
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Masaki Ryoso
Obara Sanshiro
Ohtsu Eiichi
Takamoto Yuusuke
Yamada Hiroyuki
Crowell & Moring , L.L.P.
Hitachi , Ltd.
Martin David
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