Rotary electric machine controller and electric power steering device using the same

Patent metadata

Field	Value
Publication number	US-10404201-B2
Application number	US-201815910292-A
Country	US
Kind code	B2
Filing date	Mar 2, 2018
Priority date	Mar 6, 2017
Publication date	Sep 3, 2019
Grant date	Sep 3, 2019

Abstract

A capacitor current estimating unit estimates a capacitor current based on phase currents. A capacitor temperature estimating unit estimates a capacitor temperature based on the capacitor current. A motor controller can accurately estimate not only a temperature of a switching element but also the capacitor temperature based on the phase currents. As a result, the capacitor does not need to have excessive heat characteristics. Further, a current limiting unit limits a current flowing from a battery to an inverter based on the capacitor temperature. Therefore, an amount of temperature change is not over-estimated due to overheating of the capacitor. As a result, excessive current limitation can be avoided and the performance of the motor can be demonstrated.

First claim

The invention claimed is:

1. A rotary electric machine controller for controlling a rotary electric machine having three or more phase having at least one winding set, the rotary electric machine controller comprising:
an inverter provided for each winding set respectively and having a plurality of switching elements, electric power is supplied to the inverter from a power supply;
a capacitor connected to the power supply configured to smooth a voltage of the power supply;
a current detecting unit that detects a current flowing through at least one winding set of the rotary electric machine;
a capacitor current estimating unit that estimates a current flowing through the capacitor based on the current flowing through the at least one winding set of the rotary electric machine;
a capacitor temperature estimating unit that estimates a temperature of the capacitor based on the estimated current flowing through the capacitor;
a limiting current calculating unit that calculates a limiting current which is a limiting value of a current flowing from the power supply to the inverter based on the temperature of the capacitor; and
a current limiting unit that limits the current flowing from the power supply to the inverter based on the limiting current.

2. The rotary electric machine controller according to claim 1 , wherein
the limiting current is set so as to become smaller as the temperature of the capacitor increases.

3. The rotary electric machine controller according to claim 1 , wherein
when one set of ON and OFF states of the switching element is defined as a switching cycle and a ratio of an ON period with respect to the switching cycle is defined as a duty, and wherein
the rotary electric machine controller further comprises:
a PWM (pulse width modulation) command value calculation unit that calculates the duty; and
a drive circuit that controls the inverter based on the duty,

the capacitor current estimating unit estimates the current flowing through the capacitor based on the duty and the current flowing through the at least one winding set of the rotary electric machine.

4. The rotary electric machine controller according to claim 3 , wherein
the rotary electric machine controller further comprising:
a PWM reference signal generating unit that generates a reference signal corresponding to the duty; wherein
when an interval of one cycle of the reference signal is defined as a control cycle;
the plurality of switching elements include high-potential switching elements connected to a high potential line;
a ratio of a period when all the high-potential switching elements are on or when all the high-potential switching elements are off with respect to the control cycle is defined as an invalid period ratio; and
a ratio of a period when at least one of the high-potential switching elements is on and at least one of the high-potential switching elements is off with respect to the control cycle is defined as a valid period ratio;
the capacitor current estimating unit calculates the estimated current flowing through the capacitor based on the invalid period ratio and the valid period ratio.

5. The rotary electric machine controller according to claim 4 ,
wherein
when a ratio of a period when an odd number of the high-potential switching elements are on and at least one of the high-potential switching elements is off with respect to the control cycle is defined as an odd number period ratio; and
a ratio of a period when an even number of the high-potential switching elements are on and at least one of the high-potential switching elements is off with respect to the control cycle is defined as an even number period ratio,
the capacitor current estimating unit calculates the estimated current flowing through the capacitor based on the invalid period ratio, the odd number period ratio and the even number period ratio.

6. A rotary electric machine controller according to claim 1 , wherein
the rotary electric machine controller further comprising:
a circuit board on which the inverter and the capacitor are mounted;
a heat sink that dissipates heat of the switching elements; and
a temperature detecting unit that detects a temperature of the circuit board, a temperature of the heat sink or an outside air temperature; wherein
when a temperature detected by the temperature detecting unit is defined as a detected temperature,
the capacitor temperature estimating unit estimates a temperature change amount of the capacitor based on the estimated current flowing through the capacitor, and estimates the temperature of the capacitor based on the temperature change amount of the capacitor and the detected temperature.

7. The rotary electric machine controller according to claim 1 , wherein when a combination of the winding set and the inverter is defined as a system, the rotary electric machine controller includes a plurality of the systems.

8. The rotary electric machine controller according to claim 1 , wherein
the current detecting unit detects the current flowing through the rotary electric machine from the inverter, through the inverter from the rotary electric machine, or at a point therebetween.

9. An electric power steering device comprising:
a rotary electric machine that outputs an assist torque for assisting steering by a driver; and
a rotary electric machine controller for controlling a rotary electric machine having three or more phase having at least one winding set; wherein
the rotary electric machine controller includes:
an inverter provided for each winding set respectively and having a plurality of switching elements, electric power is supplied to the inverter from a power supply;
a capacitor connected to the power supply configured to smooth a voltage of the power supply;
a current detecting unit that detects a current flowing through at least one winding set of the rotary electric machine;
a capacitor current estimating unit that estimates a current flowing through the capacitor based on the current flowing through the at least one winding set of the rotary electric machine;
a capacitor temperature estimating unit that estimates a temperature of the capacitor based on the estimated current flowing through the capacitor;
a limiting current calculating unit that calculates a limiting current which is a limiting value of a current flowing from the power supply to the inverter based on the temperature of the capacitor; and
a current limiting unit that limits the current flowing from the power supply to the inverter based on the limiting current.

Assignees

• Denso Corp

Inventors

• Kano Ryo
• Suzuki Takashi

Classifications

• H02P29/032

  Preventing damage to the motor, e.g. setting individual current limits for different drive conditions · CPC title

• H02P21/22

  Current control, e.g. using a current control loop · CPC title

• B62D5/0463

  calculating assisting torque from the motor based on driver input · CPC title

• H02P29/02 Primary

  Providing protection against overload without automatic interruption of supply (protection against faults of stepper motors H02P8/36) · CPC title

• B62D5/0409

  Electric motor acting on the steering column · CPC title