DE102018209768A1 - Power electronic device and method for operating a power electronic device - Google Patents

Abstract

The invention provides a cooled power electronic device (10) and a method for operating such a device. The device is designed with: at least two converter units (12-i), which are each designed to switch with an adjustable switching frequency in order to influence an electrical current in a respective electrical line; wherein each converter unit (12-i) has a temperature sensor which is designed to detect a converter temperature (Ti) associated with the corresponding converter unit (12-i); a cooling device which is designed for sequential cooling of the at least two converter units (12-i); and a control device (22) which is designed to compare the measured converter temperatures (Ti) of at least two converter units (12-i) and to adapt a switching frequency of at least one converter unit (12-i) based on the result.

Description

The present invention relates to a power electronic device and a method for operating a power electronic device.

State of the art

Power electronic devices, for example converters, heat up during operation, in particular due to ohmic losses. Power converters that output an alternating current, i.e. Inverters and alternating current converters in particular often generate the alternating current using pulse-width modulation methods, with pulse-width modulation often also being abbreviated as PWM according to the English term “pulse-width modulation”.

In the PWM, an alternating current to be generated is approximated by a so-called modulation function. A switch is then controlled so that in respective switching periods (which are the inverse of a switching frequency, f _s , are), an output voltage corresponds on average to the modulation function. The modulation function can thus also be referred to as a short-term mean voltage value of an intermediate circuit voltage over a switching period.

Basic elements of power electronics are, for example, from Joachim Specovius: "Basic course in power electronics: components, circuits and systems"; Springer Vieweg; Edition: 8 (January 24, 2017); ISBN-10: 3658169109 known.

Frequently, several alternating currents are required which are out of phase with one another, for example for operating a multiphase electrical machine. It is desirable to make the electronics for operating such electrical machines compact so that they take up as little space as possible, for example in an electric vehicle with an electrical machine as the drive. The individual electronics converters are therefore often cooled by one and the same cooling circuit, i.e. through a coolant, which cools the individual converters in sequence.

A cooled power electronic device with three phases and an associated, cooled power converter is, for example, in the DE 10 2012 208 594 A1 described.

The coolant is inevitably the coolest immediately after leaving a heat sink (e.g. a heat exchanger) and gradually heats up, to the same extent as it gradually absorbs heat from the individual converters. For this reason, the first converter in the cooling circuit (i.e. the converter which is cooled by the coolant first after leaving the heat sink) is cooled more efficiently than the last converter in the cooling circuit (ie the converter which is last from the coolant before the re-entry of the Coolant is cooled in the heat sink). The same naturally also applies analogously to cooling devices without a circuit, where the coolant is not circulated, but is always supplied new (and cool).

Disclosure of the invention

The present invention discloses a power electronic device with the features of patent claim 1 and a method for operating a power electronic device with the features of patent claim 7.

Accordingly, a power electronic device is provided, with: at least two converter units, which are designed to switch in each case with an adjustable switching frequency in order to influence, in particular to generate, an electrical current in a respective electrical line; wherein each converter unit has a temperature sensor, which is designed to detect a converter temperature associated with the corresponding converter unit; a cooling device which is designed for sequential cooling of the at least two converter units; and a control device which is designed to compare the measured converter temperatures of at least second converter units with one another and to adapt a switching frequency of at least one converter unit based on the result.

In particular, it can be provided that the switching frequency is adapted to one of the converter units whose converter temperature was used in the comparison. The switching frequency is preferably adjusted based on a temperature difference and / or a temperature ratio between the at least two detected converter temperatures.

A converter unit is to be understood as a power electronic component which represents a converter, i.e. a rectifier, a direct current converter, an inverter, or an alternating current converter, and which generates or influences the electrical current in a line, or in a phase.

If the power electronic device comprises more than two converter units, each converter unit can have a separate power line for generating or adapting one electrical current may be formed thereon. Alternatively, two or more converter units for generating or adapting the electrical current can also be designed and arranged on one and the same power line.

Switching of a converter unit is to be understood to mean that the converter unit selectively produces or prevents a current flow in order to produce an average electrical current corresponding to the respective modulation function.

An associated converter temperature is to be understood in particular as a temperature of the converter unit itself. Alternatively, the associated converter temperature can also be a temperature of a coolant shortly before or shortly after reaching and cooling the respective converter temperature. In a variant, two or more of the above-mentioned temperatures can be measured, and an average value, for example a differently weighted or an equally weighted average value, a median or another derived variable from the measured temperatures, can be determined as the associated converter temperature. Sequential cooling of converter units is to be understood in particular to mean that the converter temperatures of the individual converter units act at least partially on one another. Sequential cooling can include, for example, that a common coolant flows successively around and / or around the individual converter units, as a result of which the converter temperature of each converter unit has an effect on the converter temperatures of the converter units located downstream in the coolant flow by means of the coolant.

• Steuern von mindestens zwei Stromrichtereinheiten zum Schalten mit einer jeweiligen anpassbaren Schaltfrequenz um einen elektrischen Strom in einer jeweiligen elektrischen Leitung zu beeinflussen, insbesondere zu erzeugen;
• Sequentielles Kühlen der mindestens zwei Stromrichtereinheiten; Erfassen einer ersten Stromrichtertemperatur einer ersten Stromrichtereinheit der mindestens zwei Stromrichtereinheiten; Erfassen einer zweiten Stromrichtertemperatur einer zweiten Stromrichtereinheit der mindestens zwei Stromrichtereinheiten;
• Vergleichen der erfassten ersten Stromrichtertemperatur und der erfassten zweiten Stromrichtertemperatur; und Anpassen der Schaltfrequenz einer Stromrichtereinheit, insbesondere der ersten und/oder der zweiten Stromrichtereinheit, basierend auf einem Ergebnis des Vergleichens, insbesondere auf einer Temperaturdifferenz und/oder einem Temperaturverhältnis zwischen der ersten und der zweiten erfassten Stromrichtertemperatur.

Furthermore, a method for operating a power electronic device is provided, with the steps:

• Controlling at least two converter units for switching with a respective adjustable switching frequency in order to influence, in particular to generate, an electrical current in a respective electrical line;
• Sequential cooling of the at least two converter units; Detecting a first converter temperature of a first converter unit of the at least two converter units; Detecting a second converter temperature of a second converter unit of the at least two converter units;
• Comparing the detected first converter temperature and the detected second converter temperature; and adapting the switching frequency of a converter unit, in particular the first and / or the second converter unit, based on a result of the comparison, in particular on a temperature difference and / or a temperature ratio between the first and the second detected converter temperature.

Advantages of the invention

The knowledge on which the present invention is based is that converter units can be controlled with a variable switching frequency in order to change their switching frequency as a function of temperature, as a result of which the overall service life of the power electronic device and / or the individual service life can be influenced positively by its components.

This means that the converter temperatures can be symmetrized to the same values, i.e. Several (preferably all) converter temperatures can be adjusted to the same converter temperature value, for example to prevent a different thermal degradation due to the temperature difference of the respective phase or the switch. In many power electronic devices, the total service life is based on the shortest life of one of the essential components, e.g. of the converter units, so that an overall extended service life can be achieved by symmetrizing the converter temperatures overall, even if the individual service lives of individual converter units may be reduced as a result.

By symmetrizing the converter temperatures and overall, a similar component load is achieved for all converter units, and the availability of the cooled power electronic device is maximized.

The basic idea can also be referred to as software-based control of the temperature difference depending on which phase is thermally overloaded.

An increase in the switching frequency in comparatively cool converter units increases the switching losses and thus leads to a symmetrization of the temperatures. A switching frequency of a converter unit can also be reduced in order to minimize the switching losses when the temperature of a converter unit rises. This also symmetrizes the temperature of the converter units.

Further advantageous embodiments and further developments result from the Subclaims and from the description with reference to the figures.

According to a preferred development, the control device is designed to reduce a switching frequency of a first converter unit and, essentially simultaneously or exactly simultaneously, to increase a switching frequency of a second converter unit. The control device is preferably designed to execute these control commands if the first converter unit is a converter unit with a first detected converter temperature which is higher than a second detected converter temperature of the second converter unit, or, in other words, if the first converter unit has a higher converter temperature than that second converter unit.

All converter units are particularly preferably controlled or regulated by the control device to adjust their switching frequency in such a way that the converter units all have the same converter temperature. In other words, the control device can be designed to regulate all of the individual converter units to the same converter temperature setpoint, the switching frequency of each individual converter unit serving as a manipulated variable.

According to a further preferred development, the cooling device comprises a coolant line, along which the at least two converter units are arranged for sequential cooling of the at least two converter units. In this way, the cooling device can advantageously be made particularly compact. It is preferred that the coolant line is designed as a circuit with a heat sink, e.g. with an active and / or a passive heat exchanger. The first converter unit is preferably a converter unit which is arranged such that it is cooled in the coolant circuit after the second converter unit.

According to a further preferred development, the device has at least three inverter units as converter units, each of which is designed to generate an alternating electrical current and / or an electrical direct current in the respective electrical line.

According to a further preferred development, at least one (or preferably all) of the converter units is an inverter, an AC converter, a rectifier and / or a DC converter.

According to a preferred development of the method according to the invention, the switching frequency is adjusted based on a temperature difference and / or a temperature ratio (or temperature quotient) between the first and the second detected converter temperature.

According to a further preferred development of the method according to the invention, the switching frequency of the first converter unit is reduced in one method step and, essentially or exactly at the same time, the switching frequency of the second converter unit is increased. According to a further preferred development, the first converter unit is a converter unit with a first detected converter temperature which is higher than a second detected converter temperature of the second converter unit. Which converter unit is referred to as the first and the second converter unit can change over time, so that, for example, the converter unit previously functioning as the first converter unit functions as the second converter unit in a subsequent process step and vice versa.

According to a further preferred development, the switching frequencies of at least two converter units, preferably of all converter units, are adapted and / or regulated in such a way that the converter temperatures of the converter units are the same, in particular taking into account the cooling effect of the cooling device, e.g. taking into account the changing temperature (coolant temperature) of a coolant of the cooling device.

list of figures

• 1 ein schematisches Blockdiagramm einer gekühlten leistungselektronischen Vorrichtung gemäß einer Ausführungsform der vorliegenden Erfindung; und
• 2 ein schematisches Flussdiagramm zum Erläutern eines Verfahrens zum Betreiben einer gekühlten leistungselektronischen Vorrichtung gemäß einer weiteren Ausführungsform der vorliegenden Erfindung.

The present invention is explained in more detail below with reference to the exemplary embodiments shown in the schematic figures of the drawings. Show it:

• 1 a schematic block diagram of a cooled power electronic device according to an embodiment of the present invention; and
• 2 a schematic flow diagram for explaining a method for operating a cooled power electronic device according to a further embodiment of the present invention.

In all the figures, elements and devices that are the same or have the same function are provided with the same reference symbols, unless stated otherwise. The numbering of procedural steps serves for clarity and, in particular, is not intended to imply a specific chronological order unless otherwise stated. In particular, several process steps can also be carried out simultaneously.

Description of the embodiments

1 shows a schematic block diagram of a cooled power electronic device 10 according to an embodiment of the present invention.

The device 10 comprises at least two converter units, with the aid of 1 an example of a cooled power electronic device 10 with three converter units 12 - 1 . 12 - 2 . 12 - 3 is described, which are also referred to collectively as 12-i. In the basis of 1 The example explained is for the three converter units 12-i around inverters, which are each designed to have an electrical phase of a multi-phase electrical machine 50 To provide, in the present example, a three-phase electrical machine 50 , The cooled power electronic device 10 can optionally be a multi-phase electrical machine 50 include and in this case can also be referred to as a cooled multi-phase electrical machine.

The individual converter units 12-i are designed to switch each with an adjustable switching frequency to an electrical current 11 . 12 . 13 in a respective electrical line 14 - 1 . 14 - 2 . 14 - 3 (in summary: 14-i). In the basis of 1 shown example leads each of the electrical lines 14-i an electrical phase for the three-phase electrical machine 50 ,

The cooled power electronic device 10 also includes a cooling device 16 which are used for sequential cooling of the converter units 12-i is designed. In the basis of 1 described example has the cooling device 16 plus a coolant 18 on, which gradually the individual converter units 12-i flows in and / or flows around, or in some other way heat from the converter units 12-i picks up and transported away. With the coolant 18 it can be, for example, a cooling fluid such as water, or a cooling gas such as air, nitrogen or the like.

Each of the at least two converter units 12-i has a temperature sensor 20-i , which is designed and set up, with the corresponding converter unit 12-i associated converter temperature Ti capture.

Below the associated converter temperature Ti each converter unit 12-i is in particular a temperature of the converter unit 12-i yourself to understand which the respective converter unit 12-i in particular due to the heat that arises from switching losses during switching. Alternatively, it may be the associated converter temperature Ti also a temperature of the coolant 18 shortly before or shortly after reaching and cooling the respective converter unit 12-i act.

In a variant, two or more of the above temperatures can be measured and as the associated converter temperature Ti For example, a mean value, for example a differently weighted or an equally weighted mean value, a median, or another derived variable can be determined from the measured temperatures. The respective temperature sensor 20-i may have a computing unit for these calculations, or for other purposes, for example a microcontroller, an application-specific integrated circuit (ASIC), an FPGA (field-programmable gate array) and / or the like more.

In addition, the cooled power electronic device includes 10 a control device 22 , which is designed or set up to measure the measured converter temperatures Ti . tj at least two converter units 12-i . 12-j to compare with one another and, based on the result, a switching frequency of at least one of the converter units 12-k adjust, the converter unit 12-k whose switching frequency is adjusted, not necessarily, but preferably one of the converter units 12-i . 12-j is whose converter temperatures Ti . tk were compared with each other. In other words, k can be equal to i or equal to j, but can also be different from both i and j.

The control device 22 can have a controller, for example a PI controller, and / or use a look-up table and / or a data model, for example using a processor and a non-volatile data memory of the control device 22 ,

The control device is preferred 22 designed to control the switching frequency of at least one converter unit 12-k based on a temperature difference ( Ti - tj ) and / or a temperature ratio (Ti / Tj) between at least two detected converter temperatures Ti . tj adapt. This is preferably done in such a way that the converter temperatures Ti of the converter units 12-i be synchronized, ie regulated to the same temperature value. The temperature value to which regulation is carried out can be adaptable, for example based on a single, or average, electrical variable (for example current strength) of the electrical currents which the Converter units 12-i influence, especially generate.

At the in 1 The example shown flows the coolant 18 lastly the converter unit 12-1 and first the converter unit 12-3 on. Accordingly, the converter unit 12-3 cooled more effectively than the converter unit 12-1 , so that, at originally the same switching frequencies, the converter temperature T-1 the converter unit 12-1 compared to the converter temperature of the converter unit 12-3 increases. This can be done by the control device 22 can be detected and compensated for by the switching frequency of the converter unit 12-1 reduced, and the switching frequency of the converter unit 12-3 is increased. The same procedure can be applied analogously to the ratios of the converter units 12-1 and 12-3 to the converter unit 12-3 transfer.

The control device is preferred 22 trained and set up the switching frequencies of all converter units 12-i using all converter temperatures Ti adjusted and / or regulated in such a way that the converter temperatures Ti all have the same, desired temperature value.

2 shows a schematic flow diagram for explaining a method for operating a cooled power electronic device according to a further embodiment of the present invention.

The procedure according to 2 can be carried out in particular with the cooled power electronic device according to the invention and is therefore adaptable according to all described variants and modifications of the cooled power electronic device according to the invention and vice versa.

If below to explain the procedure according to 2 isolated on elements of the cooled power electronic device 10 and the reference numerals of which are referred to, this illustrates the suitability of the cooled power electronic device 10 for the implementation of the method step mentioned, which, however, is not based on the implementation with the cooled power electronic device 10 are restricted.

In one step S10 are at least two converter units 12-i for switching with a respective adjustable switching frequency around a respective electrical current I1 . I2 . I3 in a respective electrical line 14-i to influence, especially according to a PWM method such as a SVPWM or a sine PWM method. Controlling the converter units 12-i can in particular by means of the control device 22 the cooled power electronic device 10 take place as described in the foregoing.

In one step S20 the at least two converter units are cooled sequentially, for example as described above with reference to the cooling device 16 the cooled power electronic device 10 described.

In one step S30 becomes a first converter temperature Ti a first converter unit 12-i the at least two converter units 12-i recorded, for example measured or calculated using several individual recorded or measured temperatures, as described in the foregoing. In one step S40 becomes a second converter temperature tj a first converter unit 12-j the at least two converter units 12-i recorded, for example measured or calculated using several individual recorded or measured temperatures, as described in the foregoing. Measuring the converter temperatures or temperatures used to calculate them can be done, for example, by temperature sensors 20-i take place as described in the foregoing.

In one step S50 become the recorded first converter temperature Ti and the detected second converter temperature tj compared with each other, for example by the control device 22 the cooled power electronic device 10 as described in the foregoing, in particular a temperature difference and / or a temperature quotient can be calculated and used as the basis for the comparison. The comparison can include comparing the calculated difference and / or the temperature coefficient with a respective threshold value.

In one step S60 becomes a switching frequency of at least one converter unit 12-i based on a result of the comparison S50 adapted, for example as in the preceding with reference to the control device 22 the cooled power electronic device 10 described.

In particular, a first switching frequency of the first converter unit can advantageously be used 12-i be reduced and / or a second switching frequency of the second converter unit 12-j be increased when the detected converter temperature Ti the first converter unit 12-i is higher than the detected converter temperature tj the second converter unit 12-j ,

This is particularly preferably done in such a way that the converter temperatures Ti all converter units 12-i can be regulated to the same temperature value.

Although the present invention has been described above on the basis of preferred exemplary embodiments, it is not restricted to these but can be modified in a variety of ways. In particular, the invention can be varied or modified in a variety of ways without departing from the essence of the invention.

QUOTES INCLUDE IN THE DESCRIPTION

This list of documents listed by the applicant has been generated automatically and is only included for the better information of the reader. The list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions.

Patent literature cited

• DE 102012208594 A1 [0006]

Claims (10)

Power electronic device (10), with: at least two converter units (12-i), which are each designed to switch with an adjustable switching frequency in order to influence an electrical current in a respective electrical line; wherein each converter unit (12-i) has a temperature sensor which is designed to detect a converter temperature (T-i) associated with the corresponding converter unit (12-i); a cooling device which is designed for sequential cooling of the at least two converter units (12-i); and a control device (22) which is designed to compare the measured converter temperatures (T-i) of at least two converter units (12-i) with one another and to adapt a switching frequency of at least one converter unit (12-i) based on the result. Device (10) after Claim 1 The control device (22) is designed to reduce a switching frequency of a first converter unit (12-1) and, essentially simultaneously, to increase a switching frequency of a second converter unit (12-2, 12-3). Device (10) after Claim 2 , wherein the first converter unit (12-1) is a converter unit with a first detected converter temperature (T-1) which is higher than a second detected converter temperature (T-2, T-3) of the second converter unit (12-2, 12 -3). Device (10) according to one of the Claims 1 to 3 , wherein the cooling device (16) comprises a coolant line, along which the at least two converter units (12-i) are arranged for sequential cooling of the at least two converter units (12-i). Device (10) according to one of the Claims 1 to 4 The device (10) has at least three inverter units as converter units (12-i), which are each designed to generate an alternating electrical current (11, 12, 13) in the respective electrical line (14-i). Device (10) according to one of the Claims 1 to 5 , wherein at least one of the converter units (12-i) is an inverter, an AC converter, a rectifier and / or a DC converter. Method for operating a power electronic device (10), comprising the steps: Controlling at least two converter units (12-i) for switching with a respective adjustable switching frequency in order to influence an electrical current in a respective electrical line; Sequential cooling of the at least two converter units (12-i); Detecting a first converter temperature (T-1) of a first converter unit (12-1) of the at least two converter units (12-i); Detecting a second converter temperature of a second converter unit (12-2, 12-3) of the at least two converter units (12-i); Comparing the detected first converter temperature (T-1) and the detected second converter temperature (T-2, T-3); and Adapting the switching frequency of at least one converter unit (12-i) based on a result of the comparison. Procedure according to Claim 7 , wherein the switching frequency is adjusted based on a temperature difference and / or a temperature ratio between the first and the second detected converter temperature (Ti). Procedure according to Claim 7 or 8th , wherein the switching frequency of the first converter unit (12-1) is reduced and, substantially simultaneously, the switching frequency of the second converter unit (12-2, 12-3) is increased if the first converter unit (12-1) has a converter unit with a first detected converter temperature (T-1), which is higher than a second detected converter temperature (T-2, T-3) of the second converter unit (12-2, 12-3). Procedure according to one of the Claims 7 to 9 , The switching frequencies of all converter units (12-i) being adapted and / or regulated in such a way that the converter temperatures (Ti) of the converter units (12-i) are the same.

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