JP2000134990A - Temperature protective controller of power converter - Google Patents

Abstract

PROBLEM TO BE SOLVED: To materialize the prevention of the overheat of a power converter while avoiding the problem accompanying the reduction of frequency such as motor noise, etc. to the utmost, in a temperature protective controller which prevents the overheat of the power converter such as an inverter or the like by reducing the switching frequency of a switching element at the time of motor lock. SOLUTION: A judgment line 300, which shows the criteria of judgment on whether to change the switching frequency from usual frequency α over to protective frequency β lower than it in what case the combination of an inverter temperature Tinv and a torque command value T* is, is obtained in advance, and it is stored in a temperature protective controller. When this temperature protective controller detects the lock of a motor, it gets Tinv and T* at that time, and based on which side, above or below the above- mentioned judgment line 300, those combinations are it judges whether to switch the switching frequency over to usual frequency α or to switch it over to protective frequency β.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a temperature protection control device for preventing overheating of a power converter used for supplying power to a motor.

[0002]

2. Description of the Related Art When an AC motor is driven by a DC power supply, a power converter, for example, an inverter, for converting a power supply output into AC is required. 2. Description of the Related Art In a power converter such as an inverter, power conversion is performed by switching with high frequency and high power. Such switching usually causes a switching element (for example, a high-power transistor such as an IGBT) to generate heat. Therefore, when controlling the power conversion device, it is necessary to consider how to deal with or protect the switching element from overheating. .

A particular problem arises when the rotation of the motor is locked by an external force when a permanent magnet excitation type synchronous motor (PM motor) or the like is driven by a power converter such as an inverter. . In this case, the current concentrates on only one phase of the windings provided in the motor, and as a result, among the plurality of switching elements provided in the power converter, the switching element corresponding to this phase suddenly changes. It may generate heat and be destroyed. In a motor such as an electric vehicle or a hybrid vehicle, when the wheels lock, the motor also locks. Therefore, it is necessary to design a power supply system for the motor in consideration of current concentration in one phase at the time of locking.

As a method for solving such a problem, while the motor is locked, the switching frequency of the switching element (that is, the carrier frequency of the pulse width modulation signal for controlling the on / off switching of the switching element) is temporarily set. There is known a method of reducing the temperature. Reducing the switching frequency leads to a reduction in the switching loss of the switching element and, consequently, a reduction in the heat generation of the switching element. For example, JP-A-9-70
Japanese Patent Publication No. 195 discloses this type of system.

[0005] However, such a temporary reduction of the switching frequency may cause a noise problem.
That is, the switching frequency of the switching element is
The electromagnetic resonance of the motor is also taken into consideration, and the switching frequency during normal operation is set to a high frequency so that the electromagnetic resonance does not fall within the audible range. However, the switching frequency at the time of locking is set low enough to reduce the heat generated by the switching element sufficiently, so that the electromagnetic resonance sound of the motor may be in the audible range and may cause noise. Therefore, if the switching frequency is reduced immediately after the lock is detected, there is a possibility that a noise problem may occur for passengers of the electric vehicle, for example.

Therefore, in a conventional electric vehicle, for example,
Even when the lock of the motor is detected, the switching frequency is not switched to a low value immediately, and the switching frequency is switched only when the locked state continues for a predetermined time.

[0007]

However, in this conventional method, switching is performed at a normal high frequency for a predetermined time after lock detection, so that the temperature of the switching element rises during that time. Therefore, when the lock is repeatedly generated in a short time, the temperature rise of the switching element until the frequency switching at the time of each lock is accumulated, and there is a possibility that the switching element is eventually damaged by heat.

However, if the switching frequency is immediately switched to a low value upon detection of lock, the above-mentioned problem of noise cannot be solved.

SUMMARY OF THE INVENTION The present invention has been made to solve such a problem, and it is an object of the present invention to provide a temperature protection control device capable of preventing heat damage to a power converter while minimizing generation of motor noise. With the goal.

[0010]

To achieve such an object, a first aspect of the present invention is to provide a temperature control device for preventing overheating of a power converter including a switching element corresponding to each winding of a motor. A protection control device for protecting a switching frequency of a switching element from a normal frequency in order to protect the switching element from a normal frequency when a combination of a command value relating to motor control when the motor is locked and a temperature of the switching element is any combination. A criterion storing means for storing a criterion for determining whether or not to reduce the frequency; a temperature detecting means for detecting a temperature of the switching element; a lock determining means for determining whether or not the rotation of the motor is locked; When it is determined that the temperature has been detected, a command value relating to the motor control at that time and the temperature detected by the temperature detecting means are used in advance. Frequency control means for determining whether to reduce the switching frequency from the normal frequency to the protection frequency with reference to a determination criterion, and controlling a switching frequency of the switching element according to a result of the determination. .

In this configuration, when the motor is locked, it is determined whether or not the switching frequency needs to be switched to the protection frequency based on the command value relating to the motor control and the temperature of the power converter at that time. The determination is made based on the criterion stored in the means. Therefore, according to the present configuration, when the command value relating to the temperature of the power converter or the motor control is small, the switching frequency cannot be immediately switched to the protection frequency even in the locked state, so that the switching frequency such as motor noise is reduced. Can be minimized. Conversely, if the temperature of the power converter or the command value related to motor control is large at the time of lock detection, the switching frequency is switched to the protection frequency without waiting for a certain period of time as in the conventional case, so that locking may occur repeatedly. However, the power converter can be protected from thermal damage. In this configuration and each of the following configurations, the command value related to motor control includes a torque command value indicating a torque to be output to the motor, a current command value indicating a current to be passed to the motor, and the like.

A second aspect of the present invention is a temperature protection control device for preventing overheating of a power converter including switching elements corresponding to each winding of a motor, wherein the temperature protection control device is provided when the motor is locked. A criterion in which a criterion for determining whether the switching frequency of the switching element is a normal frequency or a protection frequency for protecting the switching element is stored as a criterion for a combination of a command value for motor control and a temperature of the switching element at that time. Storage means;
When the lock of the motor is detected, a command value relating to the motor control at that time and the temperature of the power converter are obtained, a frequency corresponding to a combination thereof is determined based on the determination criterion, and a switching frequency of the switching element is determined. Frequency control means for setting the frequency.

In this configuration, when the motor is locked, whether the switching frequency appropriate for the motor control command value and the temperature of the power converter at that time is the normal frequency or the protection frequency is stored in the criterion storage means. Judge based on the judgment criteria. Therefore, also in this configuration, the same effect as the first configuration is obtained, and when the power converter is operated at the protection frequency, the temperature of the power converter decreases, the command value to the motor decreases, and the like. When the possibility of thermal damage to the power converter is reduced, the switching frequency is returned to the normal frequency, so that problems such as motor noise are reduced.

A third configuration of the present invention is a temperature protection control device for preventing overheating of a power converter including a switching element corresponding to each winding of a motor in a vehicle in which wheels are driven by a motor. A criterion for determining whether the switching frequency of the switching element at the time of wheel locking is a normal frequency or a protection frequency for protecting the switching element is determined based on a combination of a command value relating to motor control and a temperature of the switching element at that time. Criteria storage means stored as a reference, temperature detection means for detecting the temperature of the switching element, means for detecting wheel lock, a command value relating to motor control at that time when wheel lock is detected, and the temperature A frequency corresponding to a combination with the temperature detected by the detecting means is determined based on the determination criterion, and And having a frequency control means for setting the switching frequency of the quenching element to that frequency.

According to this configuration, when the lock of the wheel is detected, the same operation as in the second configuration is performed.
In an electric vehicle or the like, it is possible to effectively avoid heat damage to the power converter while minimizing problems such as motor noise due to switching frequency reduction control for preventing heat damage to the power converter.

A fourth configuration of the present invention is a temperature protection control device for preventing overheating of a power converter including a switching element corresponding to each winding of a motor in a vehicle in which wheels are driven by a motor. The appropriate switching frequency of the switching element from the viewpoint of preventing overheating of the power converter and avoiding motor noise during wheel lock is stored in association with the combination of the command value for motor control and the temperature of the switching element. Frequency condition storage means, temperature detection means for detecting the temperature of the switching element, means for detecting wheel lock, and when the wheel lock is detected, a command value relating to motor control at that time and the temperature detection means detect the value. The frequency corresponding to the combination with the set temperature is obtained from the frequency recording condition storage means, and the switching of the switching element is performed. And having a frequency control means for setting the frequency to the frequency.

According to this configuration, an appropriate switching frequency is selected from the viewpoint of preventing overheating of the power converter and avoiding motor noise, based on the combination of the command value relating to the motor control when the lock is detected and the temperature of the switching element. Therefore, the protection of the power converter and the avoidance of the motor noise can be realized in a well-balanced manner. If the switching frequency is provided not only with the normal frequency and the protection frequency but also with more steps, more fine-grained control becomes possible.

[0018]

Embodiments of the present invention (hereinafter referred to as embodiments) will be described below with reference to the drawings.

FIG. 1 shows the configuration of a drive system for an electric vehicle suitable for carrying out the present invention. In this system, a three-phase AC motor is used as the motor 10 for running the vehicle. An output shaft of the motor 10 is connected to driving wheels of the vehicle via a rotating shaft and a differential gear.
The motor 10 is driven by receiving power supply from the battery 14 via the inverter 12.

The inverter 12 converts the DC output of the battery 14 into a three-phase AC by PWM (pulse width modulation) control and supplies the three-phase AC to the U, V, and W windings of the motor 10. The inverter 12 is provided with a plurality of switching elements provided corresponding to the respective windings and connected to each other in a three-phase bridge. As the switching element, for example, IGBT,
Semiconductor elements such as bipolar transistors and thyristors are used. Each of these switching elements is an EV-EC
Switching is performed according to the PWM signal supplied from U20, whereby the DC output of the battery 14 is converted to three-phase AC.

The EV-ECU 20 generates the above-mentioned PWM signal for controlling the inverter 12 with the configuration shown in FIG. The torque command calculation unit 202 is configured to output a torque value to be output from the motor 10, that is, a torque command value T based on an input of an accelerator signal indicating a driver's accelerator pedal depression amount, a brake signal indicating a brake pedal depression amount, or the like. Calculate *. At this time, the torque command calculation unit 20
2 limits the torque command value according to a predetermined rule according to the temperature of the inverter 12 or the motor 10 obtained by the temperature sensor 16 or the like. The current command calculation unit 204 converts the torque command value into a current command value indicating a current to be supplied to the motor. The current control unit 206, based on the current command value, the current feedback from the inverter 12, and the like,
Calculate the control target of each phase current or the control target of each phase voltage,
The signal is input to the PWM modulator 208. PWM modulator 208
The PW is controlled by the carrier signal supplied from the carrier signal generation unit 210 by the control target signal from the current control unit 206.
The signal is M-modulated to generate a PWM signal and supplied to the inverter 12.

The EV-ECU 20 of this embodiment is provided with a temperature protection control unit 212 for preventing the inverter 12 from being damaged by heat when the driving wheels of the vehicle are locked. The temperature protection control unit 212 implements inverter protection by reducing the carrier frequency of the PWM signal, that is, the switching frequency of the switching element of the inverter 12 basically. Carrier signal generator 210
Is the carrier frequency during normal operation (for example, 10 kHz.
Carrier signals having two kinds of frequencies, that is, a normal frequency) and a carrier frequency (for example, 1.25 kHz; hereinafter, referred to as a protection frequency) for protecting the inverter can be generated.
Here, when the normal frequency is used, the electromagnetic resonance of the motor 10 becomes higher than the audible range, and the problem of vehicle interior noise is small, but the protection frequency is set to a low value so that the switching loss of the inverter 12 can be sufficiently reduced. Therefore, if a protection frequency is used, electromagnetic resonance sounds enter an audible range, and the problem of vehicle interior noise arises. Temperature protection controller 21
2 judges whether the carrier frequency should be the normal frequency or the protection frequency, and instructs the carrier signal generator 210.

The temperature protection control section 212 makes this determination based on the temperature Tinv of the inverter 12 and the torque command value T * to the motor 10. This determination processing will be described with reference to FIGS.

First, the temperature protection control section 212 determines whether or not the drive wheels are in a locked state with reference to the signal from the lock determination section 214 (S1). For this reason, the lock determination unit 214 always compares the motor speed input from the resolver provided in the motor 10 with a predetermined threshold value, and locks the motor while the motor speed is equal to or lower than the threshold value. And outputs a lock signal indicating that The temperature protection control unit 212 determines that the drive wheels are in the locked state while the lock signal is being input, and determines that the locked state is not set when there is no input of the lock signal.

If it is determined in step S1 that the locked state is not established, the temperature protection control section 212
0 to instruct carrier generation at the normal frequency (S
2).

If it is determined in S1 that the vehicle is in the locked state,
The temperature protection control unit 212 includes a frequency determination criterion storage unit 216
, An appropriate carrier frequency corresponding to a combination of the torque command value T * input from the torque command calculation unit 202 and the inverter temperature Tinv input from the temperature sensor 18 is determined.

The function f of the judgment line 300 shown in FIG. 4 is stored in the frequency judgment reference storage unit 216. The determination line 300 is a boundary line for determining whether the locked carrier frequency is the normal frequency α or the protection frequency β. The lower left area of the determination line 300 is the area of the normal frequency α (Hz). The area on the upper right side of the line 300 is the area of the protection frequency β (Hz). Here, this determination line 300 is

## EQU1 ## This function is represented by a function of T * = f (Tinv), and this function f is stored in the frequency determination reference storage unit 216. Specifically, the frequency determination criterion storage unit 216 stores, for example, a combination (Tin) of the inverter temperature and the torque command value at each point of the determination line 300.
v, T *). This function f
Is determined in advance based on experiments and the like. The experiment, for example,
At each inverter temperature Tinv, the torque command value T * is changed variously to drive the inverter 12 (and the motor 10),
Even if the carrier frequency is the normal frequency, it may be performed by a method such as obtaining an upper limit torque command value T * at which the inverter 12 does not suffer thermal damage. It is preferable that the obtained upper limit torque command value T * is adjusted by a method of multiplying the coefficient by 1 or less in consideration of safety, and then registered in the frequency determination criterion storage unit 216.

Here, if the torque command value T * is large, a large amount of power is supplied to the motor 10, so that the inverter 12 generates a large amount of heat and the risk of thermal damage increases. However, if the inverter temperature Tinv is low, the torque command value T * becomes large. The risk of thermal damage is small even at fairly high levels. If the inverter temperature Tinv is high, the temperature margin until the inverter thermal damage is small, but if the torque command value T * is small, the risk of thermal damage is small even if the inverter temperature Tinv is quite high. From such a thing,
The determination line 300 generally has a downward-sloping curve as shown in FIG.

The temperature protection control section 212 determines whether or not to switch the carrier frequency from the normal frequency to the protection frequency with reference to the determination line 300. That is, when it is determined in S1 that the locked state is established, the temperature protection control unit 212 determines which region in the map of FIG. 4 the combination of the torque command value T * and the inverter temperature Tinv is at that time. . Specifically, using the function f stored in the frequency determination criterion storage unit 216,

It is determined whether or not T *> f (Tinv) is satisfied (S3). If this determination is affirmative (Yes), the temperature protection control unit 212 determines that there is a high risk of thermal damage to the inverter 12, and sends a carrier signal of the protection frequency β to the carrier signal generation unit 210 for inverter protection. It is instructed to occur (S4).
On the other hand, if the determination result in S3 is negative (No), the temperature protection control unit 212 determines that the possibility of thermal damage to the inverter 12 is low, and instructs the carrier signal generation unit 210 to generate a carrier signal having the normal frequency α. Instruct (S5). After that, the process returns to S1, and the series of processes described above is periodically repeated. After switching to the protection frequency β in S4, if the release of the locked state is detected in the determination in S1, the switching frequency is returned to the normal frequency α.

According to such processing, even if the lock is detected, the carrier frequency is not reduced (switched to the protection frequency) if the inverter temperature or the torque command value is small. Only when the determination condition of S3 is satisfied due to an increase in the inverter temperature or the like, the carrier frequency is reduced and the inverter is protected. In such a general situation where locking is not frequent, the carrier frequency is not immediately reduced even when locking is detected, so that vehicle interior noise due to motor electromagnetic resonance can be minimized. On the other hand, if the lock is detected in a situation where the inverter temperature is considerably high due to the fact that the lock has been repeatedly repeated several times or the like, the protection frequency is easily selected in the above processing. Alternatively, the carrier frequency is reduced during a short period, and the inverter is protected.

As described above, according to the present embodiment, the carrier frequency of the PWM signal is determined based on the combination of the torque command value T * at the time of lock detection and the inverter temperature Tinv. In addition, the protection of the inverter can be reliably achieved.

The above embodiment is merely an example of the present invention, and various modifications can be considered within the scope of the present invention.
For example, in the above embodiment, the criterion for switching between the normal frequency α and the protection frequency β is represented by the relationship between the inverter temperature Tinv and the torque command value T *. Other command values related to the control of the motor 10, such as a current command value obtained by the unit 204, and a control target value may be used.

In the above embodiment, the information of the function f of the boundary line for switching between the normal frequency α and the protection frequency β (the determination line 300 in FIG. 4) is stored in the frequency determination criterion storage unit 216 as the criterion. This is just an example. In addition, for example, the inverter temperature Tin
A table indicating which of the protection frequency and the normal frequency is selected for each combination of v and the torque command value T * may be stored in the frequency determination reference storage unit 216 as a determination reference. In this case, the temperature protection control unit 212 searches the table for a frequency corresponding to the combination of the torque command value T * and the inverter temperature Tinv from the carrier signal generation unit 21.
0 may be supplied. If this method is developed, the carrier frequency is prepared not only in two stages of the normal frequency and the protection frequency but also in three or more stages, and an appropriate frequency is set for each combination of the torque command value T * and the inverter temperature Tinv. It is also possible to store it in the frequency determination reference storage unit 216. According to this, it is possible to perform finer control of the carrier frequency.

In the above embodiment, the lock state is detected based on the number of rotations of the motor 10. However, for example, in a vehicle or the like, the locked state is detected based on wheel rotation number information from a wheel speed sensor provided on wheels (particularly driving wheels). It is also possible to detect a locked state.

In the above description, an electric vehicle has been described as an example, but the present invention can be applied to a system other than the electric vehicle. Further, although a three-phase AC motor has been described as an example of the motor 10, the number of phases of the motor 10 is not limited at all.

[Brief description of the drawings]

FIG. 1 is a block diagram showing a configuration of a drive system of an electric vehicle suitable for carrying out the present invention.

FIG. 2 is a functional block diagram showing a functional configuration of an EV-ECU 20.

FIG. 3 is a flowchart illustrating a processing procedure of a temperature protection control unit 212;

FIG. 4 is a diagram showing a map for determining an appropriate carrier frequency based on a relationship between an inverter temperature and a torque command value.

[Explanation of symbols]

10 motors, 12 inverters, 14 batteries, 1
6 temperature sensor, 20 EV-ECU, 202 torque command calculation unit, 204 current command calculation unit, 206 current control unit, 208 PWM modulation unit, 210 carrier signal generation unit, 212 temperature protection control unit, 214 lock determination unit, 2
16 frequency judgment reference storage unit, 300 judgment lines.

 ────────────────────────────────────────────────── ─── Continuing on the front page (72) Inventor Kenichi Onishi 1 Toyota Town, Toyota City, Aichi Prefecture Toyota Motor Corporation F-term (reference) 5H007 BB06 CA01 CA03 CB02 CC23 DA05 DB03 DC02 DC08 EA02 5H115 PA00 PA01 PA08 PC06 PG04 PI13 PI29 PU10 PV09 PV22 PV25 QE09 QE20 QN09 RB22 SE03 TB01 TO05 TO12 TO21 TO23 TU12 5H576 AA15 BB04 BB10 CC02 DD02 DD07 EE11 FF03 GG04 HA02 HA04 HA05 HB02 JJ17 KK08 LL02 LL22 LL43 LL60 MM06

Claims (4)

[Claims] A temperature protection control device for preventing overheating of a power converter including a switching element corresponding to each winding of a motor, wherein a command value and a switching element relating to motor control when the motor is locked are provided. A reference criterion storing means for storing a criterion for determining whether or not to reduce the switching frequency of the switching element from the normal frequency to a protection frequency for protecting the switching element in any case in combination with the temperature of the switching element; Temperature detection means for detecting whether the motor is locked, lock determination means for determining whether or not the motor is locked, and when a determination is made that the motor is locked, a command value relating to motor control at that time and the temperature detection means Based on the detected temperature, the switching frequency is reduced from the normal frequency to the protection frequency with reference to the criterion. To decide whether to, temperature protection device for controlling a power converter having a frequency control means for controlling the switching frequency of the switching element in accordance with the determination result. 2. A temperature protection control device for preventing overheating of a power converter including a switching element corresponding to each winding of a motor, wherein the switching frequency of the switching element when the motor is locked is set to a normal frequency. And a protection frequency for protection of the switching element, a determination criterion storing means for storing a determination criterion as to a combination of a command value relating to motor control at that time and a temperature of the switching element, and a lock of the motor. Upon detection, a command value relating to motor control at that time and a temperature of the power converter are obtained, a frequency corresponding to a combination thereof is determined based on the determination criterion, and a switching frequency of the switching element is set to the frequency. A temperature control device for a power converter, comprising: 3. A temperature protection control device for preventing overheating of a power converter including a switching element corresponding to each winding of a motor in a vehicle in which wheels are driven by a motor, the switching element being used when a wheel is locked. A criterion storage means for storing a criterion as to which of the switching frequency of the normal frequency and the protection frequency for protecting the switching element as a criterion relating to a combination of a command value relating to motor control and a temperature of the switching element at that time. Temperature detection means for detecting the temperature of the switching element, means for detecting wheel lock, and, when wheel lock is detected, a command value relating to motor control at that time and a temperature detected by the temperature detection means. Determine the frequency corresponding to the combination based on the determination criteria,
A temperature control unit for setting a switching frequency of the switching element to the switching frequency; 4. A temperature protection control device for preventing overheating of a power converter including a switching element corresponding to each winding of a motor in a vehicle in which wheels are driven by a motor, comprising: Frequency condition storage means for storing an appropriate switching frequency of the switching element from the viewpoint of preventing overheating of the heater and avoiding motor noise in association with a combination of a command value for motor control and a temperature of the switching element; and a switching element. Temperature detection means for detecting the temperature of the vehicle, means for detecting the lock of the wheel, and when the lock of the wheel is detected, the temperature corresponds to a combination of a command value relating to motor control at that time and the temperature detected by the temperature detection means. The frequency is obtained from the frequency recording condition storage means, and the switching frequency of the switching element is set to the frequency. Temperature protection device for controlling a power converter having a constant frequency controlling means.