Electric motor drive control system and control method thereof

• US 7,701,156 B2
• Filed: 05/23/2007
• Issued: 04/20/2010
• Est. Priority Date: 05/30/2006
• Status: Active Grant

• Current Assignee: DENSO Corporation
• Original Assignee: Toyota Jidosha Kabushiki Kaisha (Toyota Motor Corporation)
• Inventors: Okamura, Masaki
• Primary Examiner(s): IP, SHIK LUEN PAUL
• Application Number:
  US11/802,523
• Publication Number:
  US 20070278986A1
• Time in Patent Office: 1,063 Days
• Field of Search: 318/245, 318/254, 318/139, 318/430, 318/400.21, 318/255, 318/798, 701/54, 701/55, 903/945, 903/947, 180/65.265, 180/65.275
• US Class Current: 318/255
• CPC Class Codes: B60K 6/365 with the gears having orbital motion
• CPC Class Codes: B60K 6/445 Differential gearing distribution type
• CPC Class Codes: B60K 6/547 the transmission being a stepped gearing
• CPC Class Codes: B60L 15/025 using field orientation; Vector control; Direct Torque Control [DTC]
• CPC Class Codes: B60L 2240/421 Speed
• CPC Class Codes: B60L 2240/423 Torque
• CPC Class Codes: B60W 10/08 including control of electric propulsion units, e.g. motors or generators
• CPC Class Codes: B60W 20/00 Control systems specially adapted for hybrid vehicles hybrid vehicle design, B60K6/00; electric vehicles B60L
• CPC Class Codes: B60W 20/15 Control strategies specially adapted for achieving a particular effect
• CPC Class Codes: B60W 2510/081 Speed
• CPC Class Codes: B60W 2510/083 Torque
• CPC Class Codes: B60W 2710/081 Speed
• CPC Class Codes: H02P 21/06 Rotor flux based control involving the use of rotor position or rotor speed sensors
• CPC Class Codes: H02P 2101/45 for motor vehicles, e.g. car alternators
• CPC Class Codes: H02P 2201/09 Boost converter, i.e. DC-DC step up converter increasing the voltage between the supply and the inverter driving the motor general aspects of plural converters in cascade H02M
• CPC Class Codes: H02P 2205/01 Current loop, i.e. comparison of the motor current with a current reference
• CPC Class Codes: H02P 2209/13 Different type of waveforms depending on the mode of operation
• CPC Class Codes: H02P 27/08 with pulse width modulation
• CPC Class Codes: H02P 5/74 controlling two or more ac dynamo-electric motors H02P5/46, H02P5/60 take precedence
• CPC Class Codes: Y02T 10/62 Hybrid vehicles
• CPC Class Codes: Y02T 10/64 : Electric machine technologies in electromobility

Abstract

A voltage command value of a converter is set by executing the step of determining a candidate voltage of a system voltage VH as a converter output voltage in a voltage range from the minimum necessary voltage corresponding to induction voltage of a motor generator and a maximum output voltage of the converter; the step of estimating power loss at the battery, converter, inverter and motor generator, at each candidate voltage, and calculating total sum of estimated power loss of the overall system; and the step of setting the voltage command value VH# based on the candidate voltage that minimizes the total sum of estimated power losses among the candidate voltages.

Claims

1. An electric motor drive control system, comprising:

a DC power source;

a converter configured to allow step up of an output voltage of said DC power source, for variably controlling the output voltage of said DC power source in accordance with a voltage command value and outputting to a DC power line;

an inverter performing power conversion between an AC power driving an electric motor and a DC power on said DC power line, by a plurality of switching elements, so that said electric motor operates in accordance with an operation command; and

a controller setting said voltage command value of said converter;

wherein

said controller includes

a first loss estimating unit for estimating power loss at said DC power source based on a preset loss characteristic,

a second loss estimating unit for estimating power loss at said converter based on a preset loss characteristic,

a third loss estimating unit for estimating power loss at said inverter based on a preset loss characteristic, and

a voltage command value generating unit calculating a minimum necessary voltage in correspondence with an induction voltage of said electric motor, based on a state of operation of said electric motor, establishing a DC voltage on said DC power line that minimizes total power loss including a sum of power losses estimated by said first to third loss estimating units, within a candidate voltage range not smaller than said minimum necessary voltage and not larger than an output upper limit voltage of said converter, and setting said voltage command value in accordance with the established DC voltage.

2. The electric motor drive control system according to claim 1, wherein

said controller further includes

a fourth loss estimating unit for estimating power loss at said electric motor based on a preset loss characteristic;

and

said voltage command value generating unit calculates said total power loss based on a sum of said power losses estimated by said first to fourth loss estimating units, establishes said DC voltage that minimizes said total power loss in said candidate voltage range and sets said voltage command value in accordance with the established DC voltage.

3. The electric motor drive control system according to claim 1, wherein

switching control of said inverter is executed by selecting one control method from a plurality of control methods;

and

said third loss estimating unit estimates power loss at said inverter, in accordance with rotation speed and torque of said electric motor and with the selected control method, based on said loss characteristic set for each of said control methods.

4. The electric motor drive control system according to claim 3, wherein

said plurality of control methods include

sinusoidal pulse width modulation control in which switching control on said inverter is executed such that voltage of each phase applied to said electric motor becomes a voltage with pulse-width-modulated waveform in accordance with said voltage command value,

overmodulation pulse width modulation control in which switching control on said inverter is executed such that voltage of each phase applied to said electric motor becomes a voltage with pulse-width-modulated waveform with higher modulation factor than in said sinusoidal pulse width modulation control, and

rectangular wave voltage control in which switching control on said inverter is executed such that voltage of each phase applied to said electric motor becomes a voltage with rectangular wave in accordance with said voltage command value.

5. The electric motor drive control system according to claim 1, wherein

said loss characteristic represents variation in said power loss with respect to at least one of rotation speed and torque of said electric motor and DC voltage on said DC power line.

6. A method of controlling an electric motor drive control system, wherein

said electric motor drive control system includes

a DC power source,

a converter configured to allow step up of an output voltage of said DC power source, for variably controlling the output voltage of said DC power source in accordance with a voltage command value and outputting to a DC power line, and

an inverter performing power conversion between an AC power driving an electric motor and a DC power on said DC power line, by a plurality of switching elements, so that said electric motor operates in accordance with an operation command;

said method of control comprising the steps of;

estimating power loss at said DC power source based on a preset loss characteristic;

estimating power loss at said converter based on a preset loss characteristic;

estimating power loss at said inverter based on a preset loss characteristic;

calculating a minimum necessary voltage in correspondence with an induction voltage of said electric motor, based on a state of operation of said electric motor;

establishing a DC voltage on said DC power line that minimizes total power loss including a sum of said estimated power losses, within a candidate voltage range not smaller than said minimum necessary voltage and not larger than an output upper limit voltage of said converter; and

setting said voltage command value in accordance with the established DC voltage.

7. The method of controlling an electric motor drive control system according to claim 6, further comprising the step of

estimating power loss at said electric motor based on a preset loss characteristic;

wherein

in said step of establishing, said total power loss is calculated based on a sum of estimated power loss at said DC power source, power loss at said converter, power loss at said inverter and power loss at said electric motor, and said DC voltage that minimizes said total power loss in said candidate voltage range is established.

8. The method of controlling an electric motor drive control system according to claim 6, wherein

switching control of said inverter is executed by selecting one control method from a plurality of control methods;

and

in said step of estimating power loss at said inverter, power loss at said inverter is estimated in accordance with rotation speed and torque of said electric motor and with the selected control method, based on said loss characteristic set for each of said control methods.

9. The method of controlling an electric motor drive control system according to claim 8, wherein

said plurality of control methods include

sinusoidal pulse width modulation control in which switching control on said inverter is executed such that voltage of each phase applied to said electric motor becomes a voltage with pulse-width-modulated waveform in accordance with said voltage command value,

overmodulation pulse width modulation control in which switching control on said inverter is executed such that voltage of each phase applied to said electric motor becomes a voltage with pulse-width-modulated waveform with higher modulation factor than in said sinusoidal pulse width modulation control, and

rectangular wave voltage control in which switching control on said inverter is executed such that voltage of each phase applied to said electric motor becomes a voltage with rectangular wave in accordance with said voltage command value.

10. The method of controlling an electric motor drive control system according to claim 6, wherein

said loss characteristic represents variation in said power loss with respect to at least one of rotation speed and torque of said electric motor and DC voltage on said DC power line.