Refrigerant abnormality determination device, electric power conversion system and refrigerant abnormality determination method

Abstract

To protect a switching element against a temperature on securely detecting abnormality of a refrigerant even when an inverter load varies.SOLUTION: In a refrigerant abnormality determination device 1 for an electric power conversion device that cools a switching element with a refrigerant and comprises a thermistor 6 for temperature protection, a thermistor-before-filter estimated temperature calculation unit 2 calculates a thermistor-before-filter estimated temperature based upon a thermistor temperature table 21 including a current command value or current detected value of the electric power conversion device as a parameter. The thermistor-before-filter estimated temperature is input to a filter 3. An addition unit 5 adds a value of a refrigerant temperature from a refrigerant temperature sensor 4 to a value output from the filter 3 to calculate a thermistor estimated temperature. An abnormality determination unit 8 determines that the refrigerant is abnormal if a continuance in which a difference between the gradient of a thermistor detected temperature from the thermistor 6 and the gradient of the thermistor estimated temperature from the addition unit 5 is equal to or larger than a threshold is longer than a determination time.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to a temperature protection technique for IGBTs (insulated gate bipolar transistors) in power conversion devices. [Background technology]

[0002] Some power conversion devices (motor drive inverters, etc.) equipped with switching elements include a thermistor in the IGBT module that mounts the switching element. Temperature protection for the switching element chip is performed based on the temperature detected by the thermistor.

[0003] In addition, as a cooling technique for the switching elements, the module is cooled by heat exchange using cooling water circulated as a refrigerant through a water-cooled case in contact with the IGBT module. The cooling effect of the switching elements increases with the flow rate of the cooling water.

[0004] When using a thermistor method to detect the temperature of an IGBT chip in a water-cooled inverter, the chip can only be measured indirectly, so it is necessary to limit the output according to the operating conditions or estimate the chip temperature to protect the chip from thermal damage by maintaining the rated temperature. In other words, there is a temperature difference between the temperature of the thermistor measurement part and the chip temperature based on the thermal resistance value between them.

[0005] A water-cooled case of a water-cooled inverter is usually supplied with cooling water at a flow rate equal to or greater than a reference value, so the protection value for the thermistor temperature is set on the assumption that the cooling water flow rate is equal to or greater than the reference value.

[0006] As described above, the protection based on the thermistor temperature does not directly measure the chip temperature as in the temperature sensor diode method. Therefore, it is not possible to detect a temperature rise caused by an abnormality in the cooling water (e.g., detachment of the cooling hose), which may damage the switching element. In particular, there is a risk that the IGBT will be damaged if an error detection of an operational abnormality in the cooling water pump or the like is not enough. In addition, since the thermistor has a time constant larger than the thermal time constant of the IGBT chip, it is not possible to protect the temperature of the chip during a transient caused by a reduction in the flow rate of the cooling water, etc.

[0007] Although a cooling abnormality can be detected by installing a cooling water flow sensor, this leads to increased costs and size of the equipment.

[0008] In order to solve these problems, a technique has been proposed for protecting the temperature of switching elements and detecting abnormalities in the cooling system based on the slope of the temperature change of the inverter (Patent Document 1). [Prior art documents] [Patent documents]

[0009] [Patent Document 1] Patent Application No. 2015-136217 Summary of the Invention [Problem to be solved by the invention]

[0010] The technology of detecting the abnormality based on the gradient of inverter temperature change as in Patent Document 1 is premised on the assumption that the loss generated by the switching element (i.e., the inverter load) is constant during temperature change. Under conditions where the inverter load fluctuates, it becomes difficult to detect an abnormality in the cooling system.

[0011] In view of the above circumstances, an object of the present invention is to reliably detect an abnormality in a refrigerant and protect a switching element from temperature fluctuations even under conditions in which the inverter load fluctuates. [Means for solving the problem]

[0012] Therefore, one aspect of the present invention is a refrigerant abnormality determination device for a power conversion device in which a switching element is cooled by a refrigerant and which is provided with a thermistor for temperature protection of the switching element, and which comprises: a pre-filter thermistor estimated temperature calculation unit that calculates a pre-filter thermistor estimated temperature based on a thermistor temperature table in which a current command value or a current detection value of the power conversion device is a parameter; a filter to which the pre-filter thermistor estimated temperature is input; an adder unit that calculates the thermistor estimated temperature by adding the refrigerant temperature value from a refrigerant temperature sensor to the value output from the filter; and an abnormality determination unit that determines that the refrigerant is abnormal if the continuous time during which the difference between the slope of the thermistor detected temperature from the thermistor and the slope of the thermistor estimated temperature from the adder unit is greater than or equal to a threshold value is greater than or equal to a determination time.

[0013] In one aspect of the present invention, in the refrigerant abnormality determination device, the thermistor is provided in a module of the switching element.

[0014] In one aspect of the present invention, in the refrigerant abnormality determination device, a carrier frequency of a gate on / off command for the switching element and a motor rotation speed command value or a motor rotation speed detection value are set as parameters of the thermistor temperature table.

[0015] In one aspect of the present invention, in the refrigerant abnormality determination device, the thermistor temperature table indicates the relationship between the thermistor temperature and the current command value or the current detection value, the carrier frequency, the motor rotation speed command value or the motor rotation speed detection value, and the reference flow rate, which are obtained based on an actual measurement value of the thermistor temperature when the power conversion device is operating under a predetermined current command value or the current detection value, a carrier frequency of a gate on / off command for the switching element, a motor rotation speed command value or the motor rotation speed detection value, and a reference flow rate of the refrigerant.

[0016] One aspect of the present invention is a power conversion device including the above-described refrigerant abnormality determination device.

[0017] One aspect of the present invention is a refrigerant abnormality determination method executed by a refrigerant abnormality determination device of a power conversion equipment in which switching elements are cooled by a refrigerant and which is equipped with a thermistor for temperature protection, the method comprising the steps of: calculating a pre-filter thermistor estimated temperature based on a thermistor temperature table having a current command value or a current detection value as a parameter; inputting the pre-filter thermistor estimated temperature into a filter; calculating a thermistor estimated temperature by adding a refrigerant temperature value from a refrigerant temperature sensor to the value output from the filter; and determining that the refrigerant is abnormal if the continuous time during which the difference between the slope of the thermistor detected temperature from the thermistor and the slope of the calculated thermistor estimated temperature is greater than or equal to a threshold value is greater than a determination time. Effect of the Invention

[0018] According to the present invention as described above, even under conditions in which the inverter load varies, it is possible to judge an abnormality in the refrigerant and to protect the switching elements from overheating. [Brief description of the drawings]

[0019] [Figure 1] 1 is a block diagram of a refrigerant abnormality determination device according to one embodiment of the present invention; [Diagram 2] Detected and estimated thermistor temperature over time. [Diagram 3] The slope of the detected and estimated thermistor temperatures in Figure 2. [Figure 4] FIG. 4 is an explanatory diagram of determining whether a refrigerant abnormality is detected based on the value of the slope in FIG. 3 . DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0020] Hereinafter, an embodiment of the present invention will be described with reference to the drawings.

[0021] A refrigerant abnormality determination device 1 according to one embodiment of the present invention shown in FIG. 1 determines an abnormality in a refrigerant that provides temperature protection for a switching element (IGBT) of a power conversion device that uses a thermistor temperature monitoring method.

[0022] The coolant may be a known cooling water, cooling oil, etc., used in the power conversion device. An abnormality in the coolant may be, for example, a loss of the coolant due to damage to a coolant supply path or detachment, etc. The switching element module is joined to a coolant case (not shown).

[0023] The refrigerant abnormality determination device 1 includes a pre-filter thermistor estimated temperature calculation unit 2, a filter 3, a refrigerant temperature sensor 4, an adder 5, a thermistor 6, a slope calculation unit 7, and an abnormality determination unit 8.

[0024] The pre-filter thermistor estimated temperature calculation unit 2 calculates the pre-filter thermistor estimated temperature based on a thermistor temperature table 21 that uses the current command value or the current detection value of the power conversion device as a parameter.

[0025] Thermistor temperature table 21 shows the relationship between the thermistor temperature and the current command value or the current detection value, the carrier frequency, the motor rotation speed command value or the motor rotation speed detection value, and the reference flow rate of the refrigerant, which is obtained based on the actual measurement value of the thermistor temperature when the power conversion device is operated under a predetermined current command value or the current detection value, the carrier frequency, the motor rotation speed command value or the motor rotation speed detection value, and the reference flow rate of the refrigerant.

[0026] Filter 3 has a function of outputting a delay corresponding to the thermistor thermal time constant with respect to the time change of the input value (a typical example is an RC filter), and receives the pre-filter thermistor estimated temperature from pre-filter thermistor estimated temperature calculation unit 2. The thermistor thermal time constant is determined based on the thermal time constant of the refrigerant case and the thermal time constant of the switching element.

[0027] The refrigerant temperature sensor 4 is provided at the input portion of a refrigerant case (not shown) that stores the refrigerant, and detects the refrigerant temperature.

[0028] Adder 5 adds the value of the detected refrigerant temperature from refrigerant temperature sensor 4 to the value output from filter 3 to calculate the thermistor estimated temperature.

[0029] The thermistor 6 is provided in the module of the switching element for temperature protection of the switching element, and outputs the detected temperature as a thermistor detected temperature.

[0030] The slope calculation unit 7 calculates the slope of the thermistor estimated temperature received from the addition unit 5 and the thermistor detected temperature received from the thermistor 6 .

[0031] An abnormality determination unit 8 determines that the refrigerant is abnormal when the continuous time during which the difference between the gradient of the thermistor detected temperature and the gradient of the thermistor estimated temperature is equal to or greater than a threshold value is equal to or greater than a determination time.

[0032] An example of the operation of the refrigerant abnormality determination device 1 will be described with reference to FIGS. 1-4.

[0033] First, in a preliminary test, for example, a current command value of a predetermined inverter (motor) related to the generated loss of the switching element, a carrier frequency of a gate on / off command of the switching element, a motor rotation speed, and a thermistor temperature (at saturation) when the power conversion device is operated with cooling water (refrigerant) of a reference flow rate are actually measured. The reference flow rate of the cooling water is set to a minimum value of a flow rate that allows actual load operation. Then, based on the actual measured value of the thermistor temperature, a thermistor temperature table 21 is created that shows the relationship between the current command value, the carrier frequency, the motor rotation speed detection value (or the motor rotation speed command value), the cooling water reference flow rate, and the thermistor temperature. This thermistor temperature table 21 is stored in the pre-filter thermistor estimated temperature calculation unit 2. Note that, when the carrier frequency is always constant or when a load other than a motor is used as the inverter load, only the current command value may be used as the parameter. Also, the current detection value may be used as the parameter instead of the current command value.

[0034] Next, during actual load operation, pre-filter thermistor estimated temperature calculation unit 2 calculates a pre-filter thermistor estimated temperature from the current command value, the carrier frequency, the motor rotation speed detection value or the motor rotation command value, and the reference flow rate of the cooling water based on a thermistor temperature table 21. This pre-filter thermistor estimated temperature is input to filter 3.

[0035] Adder 5 calculates the thermistor estimated temperature by adding the refrigerant temperature value from refrigerant temperature sensor 4 to the value output from filter 3. In this way, the pre-filter thermistor estimated temperature calculated by pre-filter thermistor estimated temperature calculation unit 2 is provided to adder 5 via filter 3 which takes into account the thermal time constant of the refrigerant case, thereby improving the accuracy of the thermistor estimated temperature when there is a sudden change in the loss generated by the switching element.

[0036] Next, the slope calculation unit 7 calculates the slope of the thermistor estimated temperature provided by the addition unit 5 and the slope of the thermistor detected temperature provided by the thermistor 6, respectively.

[0037] Then, the abnormality determination unit 8 performs the refrigerant abnormality determination process shown in FIG. 2-4, for example.

[0038] The thermistor detected temperature and thermistor estimated temperature during normal operation change from 0 to 5 s as shown in FIG. 2. The estimated temperature is higher than the detected temperature because it is estimated using the worst value taking into account the variation in detection. The slope of the detected temperature and the estimated temperature calculated by the slope calculation unit 7 is as shown in FIG. 3 (processing cycle 500 ms). At 0.5 s to 4 s in the figure, a temperature rise component due to normal operation of the inverter appears. Here, in order to remove the temperature rise component due to normal operation of the inverter, the difference between the slope of the thermistor detected temperature and the slope of the thermistor estimated temperature (slope of detected temperature - slope of estimated temperature) is calculated to extract only the temperature rise component due to an abnormality of the refrigerant (e.g., leakage of cooling water) as shown in FIG. 4. Then, if the continuous time during which the difference in slope is equal to or greater than the threshold value is equal to or greater than the judgment time, it is judged that the refrigerant is abnormal. The threshold value and the judgment time are set to values ​​that can protect the temperature of the switching element chip based on the pre-test.

[0039] When an abnormality is detected, the inverter is stopped by turning off all of the switching elements, and a fault signal indicating the occurrence of cooling water leakage is output to the outside, thereby preventing damage to the switching elements due to high temperatures.

[0040] Therefore, according to the refrigerant abnormality determination device 1 of this embodiment, it is possible to determine a refrigerant abnormality and protect the temperature of the switching element even when the inverter load fluctuates by using the thermistor temperature table 21 and filter 3. Also, it is possible to determine abnormalities such as cooling water leakage and protect the switching element without the need for a cooling water flow rate sensor, allowing the inverter device to be made smaller and less expensive.

[0041] The above embodiment utilizes the characteristic that the thermistor temperature rises suddenly when the cooling water is drained, but the present invention can also be applied to a configuration in which the thermistor is attached to a location other than the IGBT module (e.g., the surface of the cooling water case).Furthermore, a cooling medium other than cooling water (e.g., cooling oil) can also be used. [Explanation of symbols]

[0042] 1... Refrigerant abnormality determination device 2...Pre-filter thermistor estimated temperature calculation unit, 21...Thermistor temperature table 3. Filter 4...Refrigerant temperature sensor 5…Adder 6…Thermistor 7...Tilt calculation section 8...Abnormality determination section

Claims

1. A refrigerant anomaly determination device for a power conversion device that cools a switching element with a refrigerant and includes a thermistor for temperature protection of the switching element, a pre-filter thermistor estimated temperature calculation unit that calculates a pre-filter thermistor estimated temperature based on a thermistor temperature table having a current command value or a current detection value of the power conversion device as a parameter; a filter to which the pre-filter thermistor estimated temperature is input; an adder that adds a refrigerant temperature value from a refrigerant temperature sensor to a value output from the filter to calculate an estimated thermistor temperature; an abnormality determination unit that determines that the refrigerant is abnormal when a continuous time during which a difference between a slope of the thermistor detected temperature from the thermistor and a slope of the thermistor estimated temperature from the adder is equal to or greater than a threshold value is equal to or greater than a determination time; A refrigerant abnormality determination device comprising:

2. 2. The refrigerant abnormality determining device according to claim 1, wherein the thermistor is provided in a module of the switching element.

3. 2. The refrigerant abnormality determination device according to claim 1, wherein a carrier frequency of a gate on / off command for the switching element and a motor rotation speed command value or a motor rotation speed detection value are set as parameters of the thermistor temperature table.

4. 4. The refrigerant abnormality determination device according to claim 3, wherein the thermistor temperature table indicates a relationship between the thermistor temperature and the current command value or the current detection value, the carrier frequency, the motor rotation speed command value or the motor rotation speed detection value, and the reference flow rate, which is obtained based on an actual measurement value of the temperature of the thermistor when the power conversion device is operated under a predetermined current command value or the current detection value, a carrier frequency of a gate on / off command for the switching element, a motor rotation speed command value or the motor rotation speed detection value, and a reference flow rate of the refrigerant.

5. A power conversion device comprising the refrigerant abnormality determination device according to claim 1.

6. A refrigerant abnormality determination method for a power conversion device that cools a switching element with a refrigerant and includes a thermistor for temperature protection, the method comprising: calculating a pre-filter thermistor estimated temperature based on a thermistor temperature table having a current command value or a current detection value as a parameter; inputting the pre-filter thermistor temperature estimate into a filter; a step of calculating an estimated thermistor temperature by adding a refrigerant temperature value from a refrigerant temperature sensor to a value output from the filter; determining that the refrigerant is abnormal when a continuous time during which a difference between a slope of the thermistor detected temperature from the thermistor and a slope of the calculated thermistor estimated temperature is equal to or greater than a threshold value is equal to or greater than a determination time; A refrigerant abnormality determination method comprising:

Images