JP2005124387A - Control method for synchronous motor driving gear - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a synchronous motor driving gear control method that performs appropriate control, even if a synchronous motor that is driven with variable speed via an inverter is stalled. <P>SOLUTION: The temperatures Tj at the junction portions of IGBTs that constitute the inverter 11 are obtained from an element loss operating circuit 28 and an element temperature operating circuit 30, that constitutes the synchronous motor driving gear 20. When stalling of a synchronous motor 3 is detected by a stall detecting circuit 31, the current from the inverter 11 to the synchronous motor 3 is made limited via an inverter control circuit 24 by either one of current limit commanding circuits 21 to 23, in such a way that the temperatures Tj at the junction portions do not exceed the permissible temperature. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a synchronous motor drive device including an inverter including a semiconductor power conversion circuit that supplies power to the synchronous motor, and a control device that performs variable speed control of the synchronous motor via the inverter, in particular, the synchronous motor is in a stalled state, That is, the present invention relates to a method for controlling the synchronous motor drive device when a drive current is continuously supplied from an inverter even when the rotor of the synchronous motor is stopped.

  A typical example of a device in which a synchronous motor driven at a variable speed via an inverter formed of a semiconductor power conversion circuit is in a stalled state is a synchronous motor for driving a vehicle.

  FIG. 10 is a configuration diagram of a power train of an electric vehicle using a synchronous motor for driving the vehicle. In this figure, 1 is a main power storage device including a storage battery and the like, 2 is a direct current power from the main power storage device 1. A synchronous motor drive device that converts to a desired AC power by PWM control and variable-speed-controls the permanent magnet type synchronous motor 3 by this AC power, 4 is a reduction gear, 5 is a differential gear, 6 is a wheel, and 7 is a vehicle control. Device.

  FIG. 11 is a configuration diagram of a power train of a hybrid electric vehicle using a synchronous motor for driving the vehicle. In this figure, components having the same functions as those in FIG. 10 are denoted by the same reference numerals.

  That is, in FIG. 11, 1a is a main power storage device made of a storage battery or the like, 2a is a converter that converts DC power from the main power storage device 1a into desired AC power by PWM control, and this AC power causes a permanent magnet type synchronous motor 3a to Synchronous motor drive device for variable speed control, 4a is a speed reducer, 5 is a differential gear, 6 is a wheel, 7 is a vehicle control device, 8 is an engine, 9 is power from the engine 8 and power from the synchronous motor 3a It is a power coupling / distributor that couples and distributes to the speed reducer 4a in accordance with the running state of the vehicle that does not.

  Further, FIG. 12 shows an inverter 11, a filter capacitor 12, and a synchronous motor 3, which are semiconductor power conversion circuits constituting the synchronous motor drive device 3 shown in FIG. 10 (or the synchronous motor drive device 3 a shown in FIG. 11). A position sensor 10 connected to the drive shaft for detecting the magnetic pole position is shown.

  FIG. 13 is a waveform diagram for explaining the normal operation of the inverter 11 shown in FIG. 12, and, as shown in FIG. 12, from the U phase consisting of an anti-parallel circuit of an IGBT and a diode, via the synchronous motor 3, This shows the state when current flows in the Y phase consisting of an anti-parallel circuit of IGBT and diode and the Z phase consisting of an anti-parallel circuit of IGBT and diode. In this state, it corresponds to the U-phase current iu of the sinusoidal synchronous motor 3 When the current iu is positive, the current flows alternately to the U-phase IGBT and the X-phase diode along with the PWM control. When the current iu is negative, the current iu is negative when the current iu is negative. The current flows alternately to the IGBT and the U-phase diode.

When the electric vehicle constituting the power train shown in FIG. 10 starts on a hill and rides on a curb, the synchronous motor 3 may fall into a stalled state. Damage to the components in the stalled state, for example, the burnout of the synchronous motor 3 may occur. In order to prevent this, the following patent documents are known.
Japanese Utility Model Publication No. 59-126599 (pages 4-5, FIG. 5 etc.)

  FIG. 14 is a waveform diagram for explaining the operation when the synchronous motor 3 fed from the inverter 11 shown in FIG. 12 is in a stalled state, and from the U phase composed of an anti-parallel circuit of an IGBT and a diode, as in FIG. When a current flows through the synchronous motor 3 to the Y phase composed of an antiparallel circuit of the IGBT and the diode and the Z phase composed of an antiparallel circuit of the IGBT and the diode, for example, the positive electrode of the U phase current iu of the synchronous motor 3 When the synchronous motor 3 falls into a stalled state near the stability peak value, the rotation of the position sensor 10 also stops, and as a result, the U-phase current iu is a DC current larger than the normal current while performing the PWM control. At this time, a current corresponding to the DC current Idc flows alternately to the U-phase IGBT and the X-phase diode as shown in the figure along with the PWM control.

As described above, when the synchronous motor 3 falls into a stalled state and this state continues, the current of the U-phase IGBT increases from the time t ₀ when the stalled state is reached, as shown in FIG. with it causes an increase also the switching loss of the IGBT, as a result, the junction temperature (Tj) Temp2 along with exceeding the allowable temperature Temp3 at time t ₁ of the IGBT, the not shown cooling body for cooling the inverter 11 temperature Temp1 Also rises. In order to prevent overheating damage of the U-phase IGBT in this state, for example, it is necessary to stop the operation of the inverter 11.

  However, for an electric vehicle, stopping the operation of the inverter 11 causes inability to travel. Conventionally, in order to avoid the stopping operation of the inverter 11 when the synchronous motor 3 falls into a stalled state, the output capacity of the inverter 11 is reduced. However, at least twice the rated capacity during normal driving has been set, but this countermeasure has a problem that the synchronous motor drive device 2 as a whole becomes large and expensive. .

  An object of the present invention is to solve the above-mentioned problems and to provide a control method for the drive device for making the synchronous motor drive device small and inexpensive.

The first aspect of the invention relates to a synchronous motor drive device comprising an inverter composed of a semiconductor power conversion circuit that supplies power to the synchronous motor, and a control device that performs variable speed control of the synchronous motor via the inverter.
When the synchronous motor is in a stalled state, a current limit value is calculated based on an internal temperature calculation value of the self-extinguishing element constituting the semiconductor power conversion circuit, and a current flowing from the inverter to the synchronous motor is calculated. A control method characterized by setting the current limit value or less is performed.

A second invention is a method for controlling a synchronous motor drive device according to the first invention, wherein:
The current limit value is made smaller corresponding to the passage of time in the stalled state.

A third invention is a method for controlling a synchronous motor drive device according to the first invention,
The current limit value is reduced corresponding to the passage of time based on a thermal time constant of a cooling body that cools the semiconductor power conversion circuit.

In a fourth aspect of the present invention, in the synchronous motor drive device,
When the synchronous motor is in a stalled state, a control method is performed that reduces a carrier frequency wave for PWM control of the semiconductor power conversion circuit.

According to a fifth aspect of the present invention, in the method for controlling a synchronous motor driving device according to the fourth aspect of the present invention,
The carrier frequency is reduced at a timing obtained based on the previous PWM control state.

  According to the control method of the synchronous motor drive device of the first to third aspects of the invention, when the stalled state of the synchronous motor continues, the internal temperature of the self-extinguishing element constituting the semiconductor power conversion circuit, that is, the junction temperature And the current flowing through the element is limited so that the junction temperature does not exceed an allowable value, so that the element can be prevented from being overheated and the operation of the inverter can be continued. .

  In the control methods of the fourth and fifth aspects of the invention, when the stall state of the synchronous motor continues, the self-extinguishing that constitutes the semiconductor power conversion circuit is achieved by reducing the carrier frequency of the PWM control of the semiconductor power conversion circuit. Since an increase in the junction temperature of the shape element is suppressed, overheating damage of the element can be prevented and the operation of the inverter can be continued.

  FIG. 1 is a circuit configuration diagram of a synchronous motor driving device showing a first embodiment of a control method of the synchronous motor driving device of the present invention. In FIG. 1, the same configuration as the conventional example shown in FIGS. Those having functions are given the same reference numerals.

  That is, in the synchronous motor drive device 20 shown in FIG. 1, in addition to the inverter 11 and the filter capacitor 12, any of current limit command circuits 21 to 23 described later, and torque corresponding to the current command from the vehicle control circuit 7 is usually used. Inverter control circuit 24 for controlling the AC voltage output from inverter 11 to a desired value by PWM control in order to generate synchronous motor 3 from the synchronous motor 3, and the ON / OFF signal from inverter control circuit 24 constitutes inverter 11 respectively. A switching element drive circuit 25 that converts the gate signal to the IGBT, a voltage detector 26 that detects the DC voltage Vd input to the inverter 11, and a current detector 27 that detects the current Im from the inverter 11 to the synchronous motor 3. And an IGBT switch constituting the inverter 11 from the voltage Vd, the current Im, etc. Element loss calculation circuit 28 for calculating loss Ps generated in accordance with the following equation (1), temperature sensor 29 for detecting temperature Tf of a cooling body (not shown) forming inverter 11, and the loss Pd, temperature An element temperature calculation circuit 30 that calculates the junction temperature Tj of the IGBT from Tf and the like according to the formula (2) described later, and the synchronous motor 3 from the position sensor 10 in a state where the current command is issued from the vehicle control device 7. When there is no rotation information, a stall detection circuit 31 that determines that the synchronous motor 3 is in a stalled state is provided.

  In the element loss calculation circuit 28 shown in FIG. 1, the calculation of the following formula (1) is performed.

Ps = Fs (P _ON + P _OFF ) + P _STD (1)
Here, Ps: generated loss, Fs: PWM control carrier frequency, P _ON : switching loss when on, P _OFF : switching loss when off, P _STD : loss when on.

That is, in the above formula (1), Fs is a known number, and P _STD can also be obtained from the current Im, the conduction rate during PWM control, and the like. Further, as shown in the waveform diagram of FIG. 2, for P _ON, and the element voltage v at the switching time Ts, the product of the device current i, this value is approximately from said voltage Vd and current Im Can be sought. Further, P _OFF can be obtained approximately from the voltage Vd and the current Im, similarly to P _ON .

  In the element temperature calculation circuit 30 shown in FIG. 1, the following equation (2) is calculated.

Tj = Tf + R _th · Ps (2)
Here, Tj: junction temperature, Tf: cooling body temperature, R _th : thermal resistance from the cooling body to the junction, Ps: generated loss represented by the above formula (1).

The thermal resistance _Rth of the above formula (2) will be described below with reference to FIGS.

FIG. 3 is a schematic conceptual block diagram of the inverter 11 constituting the synchronous motor drive device 20 shown in FIG. 1. The inverter 11 includes a cooling body 11a, an insulator 11b, an IGBT 11c, and a diode 11d. In this figure, “Circle 1” is the internal joint part of the IGBT 11c, “Circle 2” is the joint part between the insulator 11b and the cooling body 11a, and “Circle 3” is the joint between the cooling body 11a and the surroundings. The joint is shown. That is, the configuration shown in FIG. 3 is represented by the equivalent circuit of heat shown in FIG. 4, where R _{1 to} R ₃ indicate the saturation thermal resistance of the members from the internal junction of the IGBT 11c to the cooling body 11a, and C ₁ -C ₃ shows the heat capacity of the member.

  FIG. 5 is a waveform diagram for explaining the operation of the current limit command circuit 21 shown in FIG. 1 as a first embodiment of the control method for the synchronous motor drive device of the present invention.

That is, when the synchronous motor 3 falls into a stall state at time t ₀ , this is detected by the stall detection circuit 31 and transmitted to the current limit command circuit 21. As the stall state continues, the inverter 11 enters the operation state shown in the waveform diagram of FIG. 14 described above, and the generated loss Ps shown in the equation (1) increases. With this increase, the equation (2) ) Also increases, the current limit command circuit 21 outputs an allowable current value such that the junction temperature Tj does not exceed an allowable temperature, for example, 150 ° C. the current command value from the vehicle control device at time t ₂ in the example exceeds the allowable value, the time t ₂ later, inverter to generate torque inverter control circuit 24 corresponding to the allowable value from the synchronous motor 3 11 to control. At this time, since the inverter 11 has a thermal time constant as shown in the equivalent circuit diagram of heat shown in FIG. 4, the cooling body temperature Tf also increases with the continuation of the stall state, and accordingly, The current value also decreases, and as a result, the junction temperature Tj of the IGBT constituting the inverter 11 can be prevented from exceeding the allowable temperature of 150 ° C.

  FIG. 6 is a waveform diagram for explaining the operation of the current limit command circuit 22 shown in FIG. 1 as a second embodiment of the control method for the synchronous motor drive device of the present invention.

That is, when the synchronous motor 3 falls into a stall state at time t ₀ , this is detected by the stall detection circuit 31 and transmitted to the current limit command circuit 22. As the stall state continues, the inverter 11 enters the operation state shown in the waveform diagram of FIG. 14 described above, and the generated loss Ps shown in the equation (1) increases. With this increase, the equation (2) ) Also increases, the current limit command circuit 22 outputs an allowable current value such that the junction temperature Tj does not exceed an allowable temperature, for example, 150 ° C. The current limit command circuit 22 increases the limit rate for limiting the allowable current value as shown in FIG. 6 with the elapse of the stall state, so that the allowable current value also decreases. The junction temperature Tj of the IGBT constituting the inverter 11 can also be prevented from exceeding the allowable temperature 150 ° C.

  FIG. 7 is a waveform diagram for explaining the operation of the current limit command circuit 23 shown in FIG. 1 as a third embodiment of the control method for the synchronous motor drive device of the present invention.

That is, when the synchronous motor 3 falls into a stall state at time t ₀ , this is detected by the stall detection circuit 31 and transmitted to the current limit command circuit 23. As the stall state continues, the inverter 11 enters the operation state shown in the waveform diagram of FIG. 14 described above, and the generated loss Ps shown in the equation (1) increases. With this increase, the equation (2) ) Also increases, the current limit command circuit 22 outputs an allowable current value such that the junction temperature Tj does not exceed an allowable temperature, for example, 150 ° C. In the current limit command circuit 23, the limit rate for limiting the allowable current value with the elapse of the stall state time corresponds to the thermal time constant shown in FIG. 4 as shown in FIG. By increasing, the allowable current value also decreases, and as a result, the junction temperature Tj of the IGBT constituting the inverter 11 can also be prevented from exceeding the allowable temperature of 150 ° C.

Figure 8 is the synchronous motor driving device 20 is an operation waveform diagram when the synchronous motor 3 falls into stall state, when this state is continued, from time t ₀ became stall state, to form an inverter 11 The current of the IGBT increases, and as a result, the switching loss of the IGBT also increases. Thereafter, as described above, by limiting the current command value to the current limit value or less, the current and loss are reduced. Therefore, the junction temperature TjTemp2 of the IGBT can be reduced to the allowable temperature Temp3 or lower, and the temperature Temp1 of the cooling body (not shown) that cools the inverter 11 can be slightly increased.

  FIG. 9 is a circuit configuration diagram of a synchronous motor drive device showing a second embodiment of the control method of the synchronous motor drive device of the present invention, in which the same function as the circuit configuration shown in FIG. 1 is shown. Are denoted by the same reference numerals.

  That is, the synchronous motor drive device 40 includes an inverter control circuit 41 and an element loss calculation circuit 42 instead of the inverter control circuit 24 and the element loss calculation circuit 28 in the synchronous motor drive device 20 shown in FIG. Yes.

  In the synchronous motor drive device 40 shown in FIG. 9, when the synchronous motor 3 falls into a stalled state, this is detected by the stall detection circuit 31 and transmitted to the inverter control circuit 41 and the element loss calculation circuit 42. At this time, in the inverter control circuit 41, as a function added to the control function of the inverter control circuit 24, the carrier frequency in PWM control is reduced to about half of the normal value. That is, at this time, since the value of Fs in the calculation of the equation (1) performed by the element loss calculation circuit 42 is also halved, the loss Ps is also approximately halved. An increase in the junction temperature Tj obtained by the calculation of the expression (2) is also reduced, and as a result, the junction temperature Tj of the IGBT constituting the inverter 11 can be prevented from exceeding the allowable temperature of 150 ° C.

  FIG. 16 is a circuit configuration diagram of a synchronous motor driving device showing a third embodiment of the control method of the synchronous motor driving device of the present invention. In this figure, the same function as the circuit configuration shown in FIG. 9 is shown. Are denoted by the same reference numerals.

  That is, the synchronous motor drive device 50 includes an inverter control circuit 51 instead of the inverter control circuit 41 in the synchronous motor drive device 40 shown in FIG.

  17 to 19 are waveform diagrams and flowcharts for explaining the operation of the synchronous motor driving device 50 shown in FIG.

  In recent years, in this type of synchronous motor drive apparatus, it has become mainstream to use digital control technology such as a microcomputer, and a carrier wave for PWM control of the inverter 11 is also generated from an up / down counter. When changing the frequency, a method of changing the counter value is used. However, since the amplitude of the carrier wave changes with the change of the counter value of the carrier wave, it is necessary to simultaneously change the amplitude of the modulated wave.

  In the operation waveform diagram shown in FIG. 17, a change command for reducing the carrier frequency is issued while the counter value of the carrier wave in the up / down counter is increasing, and the counter value and the amplitude of the modulation wave are changed at this timing. doing. As a result, an unnecessary switching operation by PWM control is performed, and the motor current is also disturbed.

  Therefore, in the inverter control circuit 51 shown in FIG. 16, when a change command for reducing the carrier frequency is issued as shown in the flowchart of FIG. 17, first, the counter value of the carrier is read (step S1). It is checked whether or not it is “0”. If it is not “0” (step S2, branch N), it waits until the timing becomes zero, and if it is “0” (step S2, branch Y), the counter value and the modulated wave A process of changing the amplitude is performed (step S3).

  As a result, in the synchronous motor drive device 50 using the inverter control circuit 51, as shown in the operation waveform diagram of FIG. 18, when tw time elapses from when the change command for reducing the carrier frequency is issued, Since the counter value is “0”, the counter value and the amplitude of the modulated wave are simultaneously changed at this timing. Therefore, unnecessary switching operation by PWM control is avoided and no disturbance occurs in the motor current, so that the operation reliability of the synchronous motor driving device 50 is improved.

  In the above-described circuit configuration of the synchronous motor drive device 20 or the synchronous motor drive device 40, the example of the electric vehicle has been described.

The circuit block diagram of the synchronous motor drive device which shows 1st Embodiment of this invention Waveform diagram explaining the operation of FIG. Schematic conceptual diagram illustrating the configuration of FIG. Equivalent circuit diagram for explaining the operation of FIG. Waveform diagram for explaining the first embodiment of the present invention Waveform diagram for explaining the second embodiment of the present invention Waveform diagram illustrating the third embodiment of the present invention Waveform diagram explaining the operation of FIG. The circuit block diagram of the synchronous motor drive device which shows 2nd Embodiment of this invention Configuration diagram of electric vehicle powertrain Powertrain configuration diagram for hybrid electric vehicles Partial detailed circuit configuration diagram of FIG. Waveform diagram explaining the operation of FIG. Waveform diagram explaining the operation of FIG. Waveform diagram explaining the operation of FIG. The circuit block diagram of the synchronous motor drive device which shows 3rd Embodiment of this invention Waveform diagram explaining the operation of FIG. Flowchart for explaining the operation of FIG. Waveform diagram explaining the operation of FIG.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1, 1a ... Main electrical storage apparatus, 2, 2a ... Synchronous motor drive device, 3, 3a ... Synchronous motor, 4, 4a ... Reducer, 5 ... Differential gear, 6 ... Wheel, 7 ... Vehicle control apparatus, 8 ... Engine, DESCRIPTION OF SYMBOLS 9 ... Power coupling / distributor, 10 ... Position sensor, 11 ... Inverter, 12 ... Filter capacitor, 20 ... Synchronous motor drive device, 21-23 ... Current limit command circuit, 24 ... Inverter control circuit, 25 ... Switching element drive circuit , 26 ... voltage detector, 27 ... current detector, 28 ... element loss calculation circuit, 29 ... temperature sensor, 30 ... element temperature calculation circuit, 31 ... stall detection circuit, 40 ... synchronous motor drive device, 41 ... inverter control circuit 42 ... element loss calculation circuit, 50 ... synchronous motor drive device, 51 ... inverter control circuit.

Claims (5)

In a synchronous motor drive device comprising an inverter composed of a semiconductor power conversion circuit that supplies power to a synchronous motor, and a control device that performs variable speed control of the synchronous motor via the inverter,
When the synchronous motor is in a stalled state, a current limit value is calculated based on an internal temperature calculation value of the self-extinguishing element constituting the semiconductor power conversion circuit, and a current flowing from the inverter to the synchronous motor is calculated. A method for controlling a synchronous motor drive device, wherein the current limit value or less is set. In the control method of the synchronous motor drive device according to claim 1,
A control method for a synchronous motor drive device, wherein the current limit value is reduced corresponding to the passage of time in the stall state. In the control method of the synchronous motor drive device according to claim 1,
A method for controlling a synchronous motor drive device, wherein the current limit value is reduced corresponding to the passage of time based on a thermal time constant of a cooling body that cools the semiconductor power conversion circuit. In a synchronous motor drive device comprising an inverter composed of a semiconductor power conversion circuit that supplies power to a synchronous motor, and a control device that performs variable speed control of the synchronous motor via the inverter,
A method for controlling a synchronous motor drive device, comprising: reducing a carrier frequency for PWM control of the semiconductor power conversion circuit when the synchronous motor is in a stalled state. In the control method of the synchronous motor drive device according to claim 4,
A method for controlling a synchronous motor drive device, wherein the carrier frequency is reduced at a timing obtained based on the state of the previous PWM control.

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