Method for operating a power converter circuit, power converter control unit and power converter arrangement

Abstract

The invention relates to a method for operating a power converter circuit (1, 1') with a low side having a plurality of first controllable semiconductor switching elements (1a) connected in parallel between a first DC voltage terminal (3a) and a center terminal (3c) of the power converter circuit (1, 1'), a high side having a plurality of second controllable semiconductor switching elements (1b) connected in parallel between a second DC voltage terminal (3b) and the center terminal (3c) of the power converter circuit (1, 1'), a first temperature sensor (4a) arranged on one of the plurality of first controllable semiconductor switching elements (1a) and configured to measure a first temperature, a second temperature sensor (4b) arranged on one of the plurality of second controllable semiconductor switching elements (1b) and configured to measure a second temperature,comprising detecting (S100) the first temperature measured by the first temperature sensor (4a) and the second temperature measured by the second temperature sensor (4b), and determining (S110) that a fault exists in the power converter circuit (1, 1') if the first temperature and / or the second temperature deviates from a temperature expectation value by more than a temperature deviation threshold. The invention further relates to a power converter control unit (10) and a power converter arrangement (100, 100').

Description

The present invention relates to a method for operating a converter circuit, a converter control unit and a converter arrangement.BACKGROUND OF THE INVENTIONConverter circuits are electrical circuits for converting one type of electric current fed in into the other type of current, i.e. for example from a direct current into an alternating current or vice versa. For this purpose, in power converter circuits, for example, one or more half bridges connected in parallel with one another can be used, wherein one half bridge has a high side and a low side each having one or more parallel-connected semiconductor switching elements.However, in parallel-connected semiconductor switching elements, a so-called open circuit fault (i.e. permanently non-conductive) occurring in one of the parallel-connected semiconductor switching elements cannot be detected by a gate driver which switches over the semiconductor switching elements, since the individual semiconductor switching elements of one of the high side or the low side are driven with the same output of the gate driver. If one or more of the parallel-connected semiconductor switching elements of the high side or of the low side have an open circuit fault, that is to say are permanently open, the other semiconductor switching elements of the side can be thermally overloaded, which can ultimately cause the failure of all parallel-connected semiconductor switching elements.Disclosure of the InventionAccording to the invention, a method for operating a power converter circuit, a power converter control unit and a power converter arrangement having the features of the independent patent claims are proposed. Advantageous embodiments are the subject matter of the dependent claims and of the following description.The invention is based on a power converter circuit having a low side (low side) which has a plurality of first drivable semiconductor switching elements which are connected in parallel with one another between a first DC voltage connection and a central connection of the power converter circuit, and a high side (high side) which has a plurality of second drivable semiconductor switching elements which are connected in parallel with one another between a second DC voltage connection and the central connection. The converter circuit is configured in particular to supply a load, such as phase windings of an electric machine, with an output current via the central connection.The number of first drivable semiconductor switching elements of the low side and of second drivable semiconductor switching elements of the high side depends in particular on the maximum current conductivity and the heat resistance of the converter circuit.The invention makes use of the fact that, in normal operation, the parallel-connected semiconductor switching elements function normally and individual semiconductor switching elements do not overheat. By determining the temperature of one or more, in particular of all, semiconductor switching elements of the high and low sides, an open circuit fault can thus be determined if the temperature of one or more of the semiconductor switching elements deviates from a temperature expectation value by more than a temperature deviation threshold value. When an open circuit fault is thus determined, the converter circuit can be brought into a safe state. This makes it possible to prevent further semiconductor switching elements from being damaged in the presence of an open circuit fault.In detail, the converter circuit has a first temperature sensor which is arranged on one of the plurality of first drivable semiconductor switching elements and is configured to measure a first temperature, and a second temperature sensor which is arranged on one of the plurality of second drivable semiconductor switching elements and is configured to measure a second temperature.The temperature sensor can be arranged in direct contact with the semiconductor switching element, but it can also have a certain distance which, however, still enables sufficient heat conduction; a distance can be, for example, at most 1 cm. By arranging the temperature sensors on a semiconductor switching element, the measured temperature is associated with the temperature of the semiconductor switching element or depends on the latter and is thus an indicator for the latter. The closer the temperature sensor is to the semiconductor switching element, the closer the measured temperature is to the actual temperature.In the method, the first temperature measured by the first temperature sensor and the second temperature measured by the second temperature sensor are detected, and their deviation from the temperature expectation value is compared with a temperature deviation threshold value.In embodiments of the invention, the temperature expectation value is determined as a function of the first temperature and / or the second temperature. If in embodiments of the invention a plurality of first temperature sensors and a plurality of second temperature sensors are used and a plurality of first temperatures and / or a plurality of second temperatures are accordingly measured, the temperature expectation value is expediently determined as a function of all detected first temperatures and / or as a function of all detected second temperatures, in particular as an average value; or it is determined as a function of all other detected first temperatures and / or as a function of all other detected second temperatures, in particular as an average value. "As a function of all other", it means that that temperature value which is being compared is not used for determining the temperature expectation value.The temperature deviation threshold value is especially adaptable, for example to the region in which the converter circuit is used or to the ambient temperature of the converter circuit.It is then determined that there is a fault in the converter circuit if the first temperature and / or the second temperature deviates from the temperature expectation value by more than a temperature deviation threshold value. The temperature deviation threshold value may be 20 K, in particular. If the first temperature or the second temperature exceed the temperature expectation value by more than the temperature deviation threshold value, this indicates an open circuit fault, in particular on the side from which the increased temperature measurement value originates.If it is determined that a fault is present in the converter arrangement, the converter circuit can be transferred in particular into a safe state.The invention further relates to a converter control unit which is configured, in particular by programming, to carry out all method steps of a method according to the invention.The invention furthermore relates to a converter arrangement comprising a converter control unit according to the invention, and a converter circuit as set forth.This proposes a converter arrangement in which an open circuit fault can be determined in a simple and cost-effective manner and with which the advantages set out above in connection with the method can be achieved.In embodiments of the invention, all first drivable semiconductor switching elements can be closed (switched on) and all second drivable semiconductor switching elements can be opened (switched off) for the purpose of transferring into a safe state if the deviation of the second temperature from the temperature expectation value is above the temperature deviation threshold value. If, on the other hand, the deviation of the first temperature from the temperature expectation value is above the temperature deviation threshold value, in embodiments of the invention all second drivable semiconductor switching elements are closed and all first drivable semiconductor switching elements are opened. In particular, the side on which the open circuit fault is suspected is always opened and the other is closed.As a result, it is possible to prevent non-defective semiconductor switching elements from being damaged, as a result of which the repair of the power converter arrangement can be carried out more easily and economically. Furthermore, the method can be carried out cost-effectively with only one temperature sensor per side of the converter circuit.In one embodiment, a plurality of, in particular all, first controllable semiconductor switching elements have a first temperature sensor and / or a plurality of, in particular all, second controllable semiconductor switching elements have a second temperature sensor. At this time, in the detection, the first temperature measured by each of the first temperature sensors and the second temperature measured by each of the second temperature sensors are detected, and the deviation of each of the first temperatures and the second temperatures from the temperature expectation value is compared with the temperature deviation threshold value to determine whether it is above the temperature deviation threshold value. When using a plurality of first temperature sensors and / or a plurality of second temperature sensors, the temperature expectation value is determined in particular as an average of all (or all other, i.e. all except that which is compared with the temperature expectation value) first temperatures, all (or all other) second temperatures or all (or all other) first temperatures and all (or all other) second temperatures. For example, if the converter circuit has three first and three second drivable semiconductor switching elements, each of which is provided with a first and a second temperature sensor, respectively, the deviation of each of the first temperatures can be determined with the average of all three or only of the other two first temperatures as a temperature expectation value, and analogously each of the second temperatures can be determined with the average of all three or only of the other two second temperatures as a temperature expectation value. It is also conceivable that the deviation of each of the first temperatures is determined with the average of all second temperatures, or the average of all (or all other) first temperatures and all second temperatures as a temperature expectation value, in order to compare this with the temperature deviation threshold value and to determine whether a fault is present in the power converter circuit. The same applies analogously to the deviation of each of the second temperatures.By using a plurality of temperature sensors, in particular a temperature sensor on each semiconductor switching element, a location of an open circuit fault can be determined quickly and reliably, whereby one can carry out the method in an optimized manner and repair is simplified even more.In one embodiment, furthermore, for first drivable semiconductor switching elements which do not have a first temperature sensor, a first estimation temperature of the first drivable semiconductor switching element is determined as a function of the first temperature measured by the one first temperature sensor or, if a plurality of first temperature sensors are installed in the converter circuit, as a function of the first temperature measured by the plurality of first temperature sensors. Furthermore, for second drivable semiconductor switching elements which do not have a second temperature sensor, a second estimated temperature of the second drivable semiconductor switching element is determined as a function of the second temperature measured by the one second temperature sensor or, if a plurality of second temperature sensors are installed in the power converter circuit, as a function of the second temperature measured by the plurality of second temperature sensors. The first estimation temperature and / or the second estimation temperature are determined in particular by analytical equations which are obtained by thermal models, for example on the basis of a current flowing through the drivable semiconductor switching elements.The deviations of the first estimated temperature and / or the second estimated temperature from the temperature expectation value are also compared with the temperature deviation threshold value in embodiments of the invention in order to determine an error. This makes it possible to determine a temperature even for semiconductor switching elements which do not have a temperature sensor and thereby also to conclude that a fault has occurred, whereby the method can be carried out in an optimized manner.In this case, the temperature expectation value can be determined in particular as an average of all first temperatures and all (or all other) first estimation temperatures, all second temperatures and all (or all other) second estimation temperatures, or all first temperatures and all (or all other) first estimation temperatures and all second temperatures and all (or all other) second estimation temperatures. The procedure for determining the deviation is analogous to that which was presented for the embodiment with a plurality of first temperature sensors and / or a plurality of second temperature sensors.In one embodiment, the first drivable semiconductor switching elements and / or the second drivable semiconductor switching elements of the converter circuit are transistors, in particular metal oxide semiconductor field effect transistors or insulated gate bipolar transistors (IGB transistors).In one embodiment, a plurality of, in particular all, first controllable semiconductor switching elements have a first temperature sensor and / or a plurality of, in particular all, second controllable semiconductor switching elements have a second temperature sensor.Further advantages and embodiments of the invention will become apparent from the description and the accompanying drawing.The invention is schematically illustrated in the drawing on the basis of exemplary embodiments and is described below with reference to the drawing.Brief Description of the DrawingsFIG. 1 shows a block diagram of an embodiment of a power converter arrangement which is configured to carry out the method according to the invention, FIG. 2 shows a flow chart of an embodiment of the method according to the invention, and FIG. 3 shows a block diagram of a further embodiment of a power converter arrangement which is configured to carry out the method according to the invention.Embodiments of the InventionFIG. 1 shows a block diagram of a power converter arrangement 100 which is configured to carry out the method according to the invention. FIG. 2 shows a flow chart of an embodiment of the method according to the invention. In the further course, both figures will be described together.The converter arrangement 100 has a converter circuit 1 which has a high side and a low side and a central connection 3 cbetween the high side and the low side. A load, for example a phase winding of an electric machine 2, can be connected to the central connection 3 c. The present converter circuit 1 is designed as a half-bridge circuit, wherein a plurality of such converter circuits 1 can be part of the converter arrangement 100 in order to connect a polyphase alternating voltage load, for example a polyphase electric machine 2, to a direct voltage network.The low side here has two first drivable semiconductor switching elements 1 a, which are connected in parallel with one another between a first DC voltage connection 3 aand the central connection 3 cof the converter circuit 1. The first DC voltage connection 3 acan be in particular a ground connection. The high side here likewise has two second drivable semiconductor switching elements 1 b, which are connected in parallel with one another between a second DC voltage connection 3 band the central connection 3 c. The second DC voltage connection 3 bmay be connected in particular to a DC voltage potential.The first and second drivable semiconductor switching elements 1 a, 1 bare connected to a converter control unit 10 of the converter arrangement 100. The converter control unit 10 is configured to control the first and second drivable semiconductor switching elements 1 a, 1 b. It is understood that the high side and / or the low side can also have more than two controllable semiconductor switching elements connected in parallel, wherein the number depends in particular on the maximum current conductivity.The low side of the converter circuit 1 furthermore has, in a branch (here the left branch) of the parallel circuit, a first temperature sensor 4 awhich is arranged on the left first drivable semiconductor switching element 1 aand is configured to measure a temperature of the first drivable semiconductor switching element 1 aas a first temperature.Furthermore, the high side of the converter circuit 1 has, in one branch (here the left branch) of the parallel circuit, a second temperature sensor 4 b, which is arranged on the left second drivable semiconductor switching element 1 band is configured to measure a temperature of the second drivable semiconductor switching element 1 bas a second temperature.In the method, in step S 100, the first temperature measured by the first temperature sensor 4 aand the second temperature measured by the second temperature sensor 4 bare detected.In an optional step S 101, a first estimation temperature is determined as a function of the detected first temperature for the other first drivable semiconductor switching element 1 aof the low side (shown here on the right), which does not have a first temperature sensor 4 a. Furthermore, a second estimated temperature is determined as a function of the detected second temperature for the other second drivable semiconductor switching element 1 bof the high side (shown here on the right). In particular, analytical equations based on a thermal model that estimates the temperatures, for example, on the basis of measured currents flowing through the drivable semiconductor switching elements, can be used to determine the estimation temperature.Subsequently, in step S 110, it is determined that a fault is present in the converter circuit 1 if the first temperature of one or more of the plurality of first drivable semiconductor switching elements 1 aand / or the second temperature of one or more of the plurality of second drivable semiconductor switching elements 1 bare above a temperature expectation value by more than a temperature deviation threshold value. For example, in this case, as the temperature expectation value, an average value of the other measured temperatures (i.e., all but that compared with the temperature expectation value) and all the estimated temperatures may be used. According to another example, the estimation temperature of the same page can also be used as the temperature expectation value.Likewise, in step S 111, it is determined that a fault is present in the converter circuit 1 if the first estimation temperature of one or more of the plurality of first drivable semiconductor switching elements 1 aand / or the second estimation temperature of one or more of the plurality of second drivable semiconductor switching elements 1 bare above the temperature expectation value by more than a temperature deviation threshold value, which can be 20 K, for example. For example, in this case, an average value of the other estimated temperature and all the measured temperatures may be used as the temperature expectation value. According to another example, the measured temperature of the same page can also be used as the temperature expectation value.If it is determined that there is a fault in the converter circuit 1, this indicates that there is an open circuit fault in the low side or the high side, and the converter circuit 1 is transferred to a safe state in block S 120.For this purpose, if one or more of the first drivable semiconductor switching elements 1 aexhibit a deviation of the first temperature or estimated temperature from the temperature expectation value that is greater than the temperature deviation threshold value, all first drivable semiconductor switching elements 1 aare opened in step S 121 aand all second drivable semiconductor switching elements 1 bare closed in step S 122 a.If it is determined that one or more of the second drivable semiconductor switching elements 1 bhave a deviation of the second temperature or estimated temperature from the temperature expectation value that is greater than the temperature deviation threshold value, all second drivable semiconductor switching elements 1 bare opened in step S 121 band all first drivable semiconductor switching elements 1 aare closed in step S 122 b.Thereby, the remaining semiconductor switching elements can be protected.FIG. 3 shows a further embodiment of the converter arrangement 100' which is configured to carry out the method according to the invention.In contrast to the converter arrangement 100 shown in FIG. 1, both the low side and the high side of the converter circuit 1' in FIG. 3 have three first and second drivable semiconductor switching elements 1 a, 1 b. Each of the first and second drivable semiconductor switching elements 1 a, 1 bis connected to the converter control unit 10 and is controlled by the latter.Furthermore, a first or second temperature sensor 4a, 4b is arranged on each of the first and second semiconductor switching elements 1a, 1b of the converter circuit 1' of the converter arrangement 100', said first or second temperature sensor measuring the first or second temperature of the corresponding first or second semiconductor switching element 1a, 1b.The method in the converter arrangement 100' proceeds analogously to the method described above with reference to the converter arrangement 100 of FIG. 1, so that only the differences will be shown in the further course.Since a first or second temperature sensor 4 a, 4 bis arranged on each of the first and second drivable semiconductor switching elements 1 a, 1 b, a first or second temperature is detected for each of the first and second drivable semiconductor switching elements 1 a, 1 bin step S 100. Therefore, no first or second temperatures need to be estimated by step S101 either.The remaining course of the process corresponds to the process as described with reference to FIG. 1. In step S 110, for example, an average of all measured temperatures of the same side, or of the other measured temperatures of the same side, or of both sides may be used as the temperature expectation value.FIGS. 1 and 3 show, by way of example, converter circuits 1, 1' having two or three drivable semiconductor switching elements per side. The application is not intended to be limited to these examples, i.e. each of the high and low sides of the converter circuit 1, 1' can also have more than three semiconductor switching elements. Furthermore, in converter circuits 1, 1' with more than three first or second semiconductor switching elements, not all semiconductor switching elements 1a, 1b can have a corresponding temperature sensor 4a, 4b, but only a part of semiconductor switching elements 1a, 1b. It is also possible for different numbers of first and second temperature sensors 4 a, 4 bto have a temperature sensor in the low and high sides, respectively.

Claims

Method for operating a power converter circuit (1, 1') having - a low side which has a plurality of first drivable semiconductor switching elements (1a) which are connected in parallel with one another between a first DC voltage connection (3a) and a central connection (3c) of the power converter circuit (1, 1'), - a high side which has a plurality of second drivable semiconductor switching elements (1b) which are connected in parallel with one another between a second DC voltage connection (3b) and the central connection (3c) of the power converter circuit (1, 1'), - a first temperature sensor (4a) which is arranged on one of the plurality of first drivable semiconductor switching elements (1a) and is configured to measure a first temperature, - a second temperature sensor (4b) which is arranged on one of the plurality of second drivable semiconductor switching elements (1b) and is configured to measure a second temperature, wherein the method comprises: detecting (S100) the first temperature measured by the first temperature sensor (4a) and the second temperature measured by the second temperature sensor (4b), and determining (S110) that a fault is present in the converter circuit (1, 1') if the first temperature and / or the second temperature deviates from a temperature expectation value by more than a temperature deviation threshold value.Method according to claim 1, wherein the temperature expectation value is determined depending on the first and / or the second temperature.The method according to claim 1 or 2, wherein the method further comprises: transitioning (S120) the power converter circuit (1, 1') to a safe state when it is determined that there is a fault in the power converter circuit (1, 1').Method according to Claim 3, wherein the conversion (S120) of the power converter circuit into the safe state comprises: closing (S121a) all first drivable semiconductor switching elements (1a) and opening (S122a) all second drivable semiconductor switching elements (1b), and / or closing (S121b) all second drivable semiconductor switching elements (1b) and opening (S122b) all first drivable semiconductor switching elements (1a).Method according to one of the preceding claims, wherein a plurality of, in particular all, first drivable semiconductor switching elements (1a) have a first temperature sensor (4a) and / or a plurality of, in particular all, second drivable semiconductor switching elements (1b) have a second temperature sensor (4b), wherein the first temperature measured by each of the first temperature sensors (4a) and the second temperature measured by each of the second temperature sensors (4b) are detected during the detection (S100) and the temperature expectation value is compared during the determination (S110) whether a fault is present in the power converter circuit (1, 1').Method according to claim 5, wherein the temperature expectation value is determined as a function of all detected first temperatures and / or as a function of all detected second temperatures, in particular as an average value.Method according to claim 5, wherein the temperature expectation value is determined depending on all detected first temperatures other than that compared with the temperature expectation value and / or depending on all detected second temperatures other than that compared with the temperature expectation value, in particular as an average value.Method according to one of the preceding claims, further comprising: determining (S101) for first drivable semiconductor switching elements (1a) which do not have a first temperature sensor (4a), a first estimated temperature of the first drivable semiconductor switching element (1a) as a function of the first temperature, and determining (S101) for second drivable semiconductor switching elements (1b) which do not have a second temperature sensor (4b), a second estimated temperature of the second drivable semiconductor switching element (1b) as a function of the second temperature.The method of claim 8, wherein the first estimation temperature and / or the second estimation temperature are determined by analytical equations obtained by thermal models.The method according to claim 8 or 9, further comprising: determining (S111) that there is a fault in the converter circuit (1, 1') if the first estimation temperature and / or the second estimation temperature deviate from the temperature expectation value by more than the temperature deviation threshold value.The method according to any of claims 8 to 10, wherein the temperature expectation value is determined as an average - of all first temperatures and estimation temperatures, - of all first temperatures and estimation temperatures other than that compared to the temperature expectation value, - of all second temperatures and estimation temperatures, - of all second temperatures and estimation temperatures other than that compared to the temperature expectation value, - of all first and second temperatures and estimation temperatures, or - of all first and second temperatures and estimation temperatures other than that compared to the temperature expectation value.Converter control unit (10) which is configured to carry out all method steps of a method according to one of the preceding claims.Converter arrangement (100, 100') comprising a converter control unit (10) according to claim 12 and at least one converter circuit (1, 1') comprising at least one converter circuit (1, 1'): - a low side having a plurality of first drivable semiconductor switching elements (1a) which are connected in parallel with one another between a first DC voltage connection (3a) and a central connection (3c) of the converter circuit (1, 1'), - a high side having a plurality of second drivable semiconductor switching elements (1b) which are connected in parallel with one another between a second DC voltage connection (3b) and the central connection (3c) of the converter circuit (1, 1'), - a first temperature sensor (4a) which is arranged on one of the plurality of first drivable semiconductor switching elements (1a) and is configured to measure a first temperature, - a second temperature sensor (4b), which is arranged on one of the plurality of second drivable semiconductor switching elements (1b) and is configured to measure a second temperature.Converter arrangement (100, 100') according to Claim 13, wherein the first drivable semiconductor switching elements (1a) and / or the second drivable semiconductor switching elements (1b) are transistors, in particular metal oxide semiconductor field effect transistors or IGB transistors.Converter arrangement (100') according to Claim 13 or 14, wherein a plurality of, in particular all, first drivable semiconductor switching elements (1a) have a first temperature sensor (4a) and / or a plurality of, in particular all, second drivable semiconductor switching elements (1b) have a second temperature sensor (4b).

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