PERFORMANCE CONVERSION UNIT DIAGNOSTIC SYSTEM

Abstract

This power conversion unit diagnostic system 100 has an input section that receives AC power from an AC power supply 1 and an output section that converts the AC power into DC power and outputs the DC power. The power conversion unit diagnostic system 100 comprises: several power conversion units 10 that supply DC power to at least one load and are connected in series, a control unit 20 that controls the several power conversion units 10, and an output-side switching unit 40 that allows the output sections of at least some of the several power conversion units 10 to be connected in parallel to a load.If the output sections of at least some of the multiple power conversion units 10 are connected in parallel to the single load, the control unit 20 determines the state of each of the multiple power conversion units 10 and, based on the state, determines whether the characteristics of each of the multiple power conversion units 10 have deteriorated.

Description

Technical area

[0001] The present invention relates to a system for diagnosing a condition of a power conversion unit. Technical background

[0002] In recent years, power conversion units that convert alternating current (AC) to direct current (DC) or direct current to alternating current (AC) have been widely used. In addition, multi-port power conversion technology has been developed for applications involving high-voltage drives, EV chargers, and electric motors, where multiple power conversion units are connected and operated with multiple loads.

[0003] In a system using multiple power conversion units, the status of each power conversion unit must be determined to ensure stable output power and to respond quickly when a fault occurs in some power conversion units.

[0004] Patent Application Publication No. 1 relates to a system using multiple power conversion units. Patent Application Publication No. 1 describes that the emergency prevention system disclosed therein includes a switching unit capable of switching a power supply path from a voltage conversion unit to a power supply path from an external power supply device via an external connection unit when a failure occurs in the voltage conversion unit, thereby performing rapid temporary recovery from a failure in a power supply unit. Citation listPatent literature

[0005] PTL 1: JP 2021-168593 A Summary of the inventionTechnical problem

[0006] However, the technique described in PTL 1 refers to a measure after the occurrence of a malfunction in the power supply unit and does not describe the prior prevention of the malfunction of the power supply unit and the extension of its service life.

[0007] Specifically, with the multi-port power conversion technology described above, when used in a charger, for example, the number of parallel connections of the units is switched according to the number of power sources to be charged simultaneously and the capacity of each of the power sources. The service life of the unit depends on each load condition (load current / current fluctuation and ambient temperature). If biases occur in the number of load fluctuations or operating time, or if there are initial manufacturing variations in some units, the service life of the unit will be shortened. Therefore, to extend the service life of the unit, a deterioration state of the unit must be determined and operation control must be performed to suppress deterioration. Solution to the problem

[0008] To solve the above problems, a power conversion unit diagnostic system according to the present invention comprises: a plurality of power conversion units, each having an input unit that receives alternating current (AC) power from an AC power supply, and an output unit that converts the AC power into direct current (DC) power and outputs the DC power and supplies the DC power to at least one load, wherein each of the plurality of power conversion units is connected in series to the AC power supply, a control unit that controls the plurality of power conversion units, and an output-side switching unit that is capable of connecting the output units of at least some of the plurality of power conversion units in parallel to one of the loads, wherein the control unit determines a state of each of the plurality of power conversion units,when the output units of at least some of the plurality of power conversion units are connected in parallel to the one load, and compares the determined states of the plurality of power conversion units to determine whether the characteristics of the respective plurality of power conversion units have deteriorated. Advantageous effects of the invention

[0009] According to the present invention, when multiple power conversion units are operated simultaneously, respective changes in characteristics can be individually determined. Therefore, the control of the deteriorated unit can be appropriately adjusted based on the characteristic change, and the service life of the unit can be extended.

[0010] Further features related to the present invention will become apparent from the description of the present specification and the accompanying drawings. Problems, configurations, and effects other than those described above will become clear from the following description of embodiments. Brief description of the drawings

[0011] They show: Fig. 1 is a block diagram of an overview of a power conversion unit diagnostic system according to an embodiment of the present invention, Fig. 2 is a flowchart of a power conversion unit diagnostic processing executed using a power conversion unit diagnostic system, Fig. 3 is a diagram of an example of a method executed by a control unit for controlling a power conversion unit, Fig. 4 is a block diagram of an overview of a power conversion unit diagnostic system according to another embodiment of the present invention; and Fig. 5 is a flowchart showing another example of diagnostic processing executed using the power conversion unit diagnostic system. Description of embodiments

[0012] Embodiments will be described below with reference to the drawings.

[0013] Fig. 1 is a block diagram showing an overview of a power conversion unit diagnostic system 100 (hereinafter referred to simply as “system 100”) according to an embodiment of the present invention.

[0014] The system 100 includes a plurality of power conversion units 10a to 10c whose inputs are connected to the AC power supply 1 and connected in series with each other; a power conversion unit controller 20 that determines a state of each power conversion unit and diagnoses the deterioration state of the power conversion unit based on the state; DC buses 30a to 30c connected between an output of each power conversion unit and each load; and an output-side switching unit 40 that switches the connection of the DC buses. Note that, for convenience of description, the power conversion units 10a to 10c are collectively referred to as power conversion unit 10 hereinafter unless otherwise specified. The same applies to other components.

[0015] An AC reactor 2 for power supply coordination, power factor improvement, and harmonic suppression and a switching element 3 for switching the connection between the AC power supply 1 and the power conversion unit 10 are provided between the AC power supply 1 and the power conversion unit 10.

[0016] Furthermore, the output of the power conversion unit 10 is connected to loads 51 and 53 via the output-side switching unit 40. Loads 51 and 53 are, for example, EV chargers or electric motors, and they each output a specific load power. Note that reference numerals 52 and 54 also represent smoothing capacitors.

[0017] Each of the power conversion units 10 includes a power semiconductor element 11 and a smoothing capacitor 12. The power semiconductor element 11 includes, for example, a metal oxide semiconductor field-effect transistor (MOSFET), an insulated gate bipolar transistor (IGBT), a bipolar transistor, a diode, and the like, and converts AC power input from the AC power supply 1 into DC power. The smoothing capacitor 12 converts the fluctuating DC voltage converted by the power semiconductor element 11 into a stable DC voltage.

[0018] The power conversion unit controller 20 is implemented, for example, in a computer that is wired or wirelessly connected to the power conversion unit 10, and executes the processing described below using a CPU and a memory built into the computer.

[0019] The DC bus 30 provided between the output of the power conversion unit 10 and the loads 51 and 53 is switched by the output-side switching unit 40. Any mechanical switch, semiconductor switch, or the like can be used as the switching elements 41 and 42 constituting the output-side switching unit 40.

[0020] According to the present embodiment, the switching elements 41 and 42 constituting the output-side switching unit 40 are configured to switch the connection between one of the power conversion units 10 and one of the loads 51 and 53 by turning the switching elements 41 and 42 on / off.

[0021] Specifically, the connections between the power conversion units 10a to 10c and the load 51 are switched by turning on / off the respective switching elements 42a to 42c, and the connections between the power conversion units 10a to 10c and the load 53 are switched by turning on / off the respective switching elements 41a to 41c.

[0022] Because the switching elements 42a, 42b and 41c in Fig. 1 are switched on, the power conversion units 10a and 10b are connected to the same load 51 (see currents 13a and 13b). The power conversion unit 10c is connected to the load 53.

[0023] That is, according to the present embodiment, because the power conversion units 10a and 10b are connected to the same load 51, the load powers supplied to the power semiconductor elements 11a and 11b and the smoothing capacitors 12a and 12b are also the same. Therefore, the deterioration state of each power conversion unit can be diagnosed by determining the states of these elements and comparing and analyzing the states between the units. Then, if a deviation occurs between the operating conditions of the power conversion units, the operating state of the power conversion unit can also be adjusted in a direction to eliminate the deviation.

[0024] The conditions addressed in the present invention are the thermal resistance of the power semiconductor element and the temperature of the smoothing capacitor. These characteristics are directly related to the deterioration of the power conversion unit and can be easily measured using an existing temperature sensor or the like, and are therefore suitable as parameters for determining a deterioration state of the power conversion unit.

[0025] Fig. Fig. 2 is a flowchart showing the processing performed by the power conversion unit diagnostic system 100 according to the present embodiment. First, in step S201, as shown in Fig. 1, a plurality of power conversion units 10 are connected in parallel to a load, and their operation is controlled. At the same time, the power conversion unit controller 20 acquires state values ​​indicating the states of the plurality of power conversion units 10 connected and operated in parallel. Note that the power conversion unit controller 20 may acquire the state value, for example, when the power conversion unit 10 to be diagnosed is connected in parallel to the load, or may continue to acquire the state value during operation.

[0026] Then, in step S202, it is determined whether an incremental value of the thermal resistance of the power module (PM: power semiconductor element) and / or an incremental value of the temperature of the capacitor (CAP: smoothing capacitor) of a unit has reached or exceeded a specific value.

[0027] If "No" is selected in step S202, the process returns to step S201 to continue parallel operation. If "Yes" is selected in step S202, the process continues to step S203, and it is determined which element of which unit has deteriorated.

[0028] If the deteriorated element is the power semiconductor element 11 of one of the power conversion units 10 (step S204), the process proceeds to step S205, and control is executed to suppress deterioration of the power semiconductor element 11. If the deteriorated element is the smoothing capacitor 12 of one of the power conversion units 10 (step S206), the process proceeds to step S207, and control is executed to suppress deterioration of the smoothing capacitor 12. Note that in a case where the control is executed once, this control is continuously executed until the operation of the power conversion unit 10 is terminated.

[0029] The processing to suppress the deterioration of the element is carried out with reference to Fig. 3 described. Fig. Figure 3(a) shows the load of several processing Fig. 2 power conversion units to be diagnosed are connected in parallel, output load power.

[0030] In step S205 in Fig. 2, namely, in a case where the deteriorated element is the power semiconductor element 11, the control of a Fig. 3(b) is executed. Specifically, a signal to be supplied to the power semiconductor element 11 is controlled so that the power output from the power conversion unit 10 including the power semiconductor element 11 detected to have deteriorated becomes constant (in order to reduce the range of power fluctuation). This is because the deterioration of the thermal resistance characteristics of the power semiconductor element 11 is caused by the fluctuation in the output voltage.

[0031] In step S207 in Fig. 2, namely, when the deteriorated element is the smoothing capacitor 12, the control of a Fig. Control Mode 2 shown in Figure 3(c) is executed. Specifically, a time during which the power conversion unit 10 including the smoothing capacitor 12 detected to have deteriorated is not operated and a time during which no power is output from the unit are set. This is because the deterioration in the temperature of the smoothing capacitor 12 is caused by the power output.

[0032] According to the present embodiment, the plurality of power conversion units 10 are connected in parallel to a single load so that they are in the same operating state, and then control is performed as described above, so that the state changes of the elements between the power conversion units 10 can be compared, and the deterioration state of each power conversion unit 10 can be determined based on the comparison. In addition, the control signal is adjusted according to the deterioration state to suppress the thermal resistance deterioration of the power semiconductor element 11 and / or the temperature deterioration of the smoothing capacitor 12, and the operating environment imbalance occurring between the power conversion units 10 can also be resolved.

[0033] Next, a power conversion unit diagnostic system according to another embodiment of the present invention will be described with reference to Fig. 4. The Fig. The system 100 shown in Figure 4 differs in this respect from the system shown in Fig. 1, that the system 100 shown in Fig. 4, the system 100 shown has on the input side of each power conversion unit 10 an input-side switching unit 60 for switching the parallel connection between the inputs of each power conversion unit 10.

[0034] The input-side switching unit 60 has switching elements 61a and 61b. When the switching element 61a is in the ON state, the power conversion units 10a and 10b are connected in parallel. When the switching element 61b is in the ON state, the power conversion units 10b and 10c are connected in parallel. When both switching elements 61a and 61b are in the ON state, all the power conversion units 10a, 10b, and 10c are connected in parallel.

[0035] In Fig. 4, only switching element 61b is in the ON state, so that the power conversion units 10b and 10c are connected in parallel. Switching element 3 in the AC circuit is in the OFF state, so that the AC power supply 1 is not connected to the power conversion unit. Additionally, in the output-side switching unit 40, switching elements 41b and 41c are in an ON state, so that the outputs of the power conversion units 10b and 10c are connected in parallel to the load 53.

[0036] According to the present embodiment, the load 53 is a storage battery.

[0037] In the above configuration, a Fig. 4 Current indicated by an arrow 14 using the storage battery 53 as a power supply between the parallel-connected power conversion units 10b and 10c.

[0038] Here too, by performing a similar procedure as in Fig. 2 the deterioration state of each power conversion unit 10 can be determined and the operation can be controlled to suppress the deterioration of the element.

[0039] Furthermore, in the system 100 according to the present embodiment, the Fig. 5 is executed. First, in step S501, the power supply is adjusted to set the output of the load (storage battery) to which the power conversion unit 10 is connected to a range suitable for diagnosing the power conversion unit 10.

[0040] After completing the setting, the process proceeds to step S502, the power conversion units 10 to be diagnosed are connected in parallel, and the diagnosis is initiated. Then, the power conversion unit controller 20 acquires the status value of each power conversion unit 10 (step S503). Afterward, processing similar to that in Fig. 2 to diagnose a deterioration condition of the power conversion unit 10.

[0041] As described above, according to the present embodiment, since the AC power supply 1 need not be operated, the state of the unit can be independently diagnosed when power need not be supplied to another load (for example, at night when a factory in which the load 51 is installed is not operating, or the like), which is advantageous in terms of efficiency and cost.

[0042] In addition, according to the present embodiment, unlike the example of Fig.1 The power conversion units to be diagnosed can be combined in any way. Therefore, the completeness of a diagnosis can be ensured, for example, by diagnosing a unit that could not be diagnosed during factory operation (during the day) at night.

[0043] According to the above-described embodiment of the present invention, the following effects are obtained in operation.

[0044] (1) A power conversion unit diagnostic system according to the present invention comprises: a plurality of power conversion units, each having an input unit that receives alternating current (AC) power from an AC power supply, and an output unit that converts the AC power into direct current (DC) power and outputs the DC power and supplies the DC power to at least one load, wherein each of the plurality of power conversion units is connected in series to the AC power supply, a control unit that controls the plurality of power conversion units, and an output-side switching unit capable of connecting the output units of at least some of the plurality of power conversion units in parallel to one of the loads, wherein the control unit determines a state of each of the plurality of power conversion units,when the output units of at least some of the plurality of power conversion units are connected in parallel to the one load, and compares the determined states of the plurality of power conversion units to determine whether the characteristics of the respective plurality of power conversion units have deteriorated.

[0045] With the above configuration, when multiple power conversion units are operated simultaneously, the respective changes in characteristics can be individually determined. Therefore, the control of the deteriorated unit can be appropriately adjusted based on the characteristic change, and the service life of the unit can be extended.

[0046] (2) The power conversion unit includes a power semiconductor element and a capacitor, and a condition of the power conversion unit is a change in the thermal resistance of the power semiconductor element and a change in the temperature of the capacitor. These conditions directly lead to deterioration of the power conversion unit, but can be easily measured by an existing temperature sensor or the like, so the degree of deterioration of the power conversion unit can also be easily determined.

[0047] (3) The control unit controls the power conversion unit to suppress the change in the thermal resistance of the power semiconductor element and / or the change in the temperature of the capacitor with respect to the power conversion unit whose characteristics are determined to have deteriorated. Specifically, the control unit reduces the fluctuation range of the power output from the power conversion unit to suppress the change in the thermal resistance of the power semiconductor element and sets a time during which no power is output from the power conversion unit to suppress the change in the temperature of the capacitor. Thereby, for example, the effect of the present invention can be easily obtained merely by adjusting the control signal supplied to the power conversion unit.

[0048] (4) The power conversion unit diagnostic system further includes an input-side switching unit that switches the parallel connection between the input units of the plurality of power conversion units. When the plurality of power conversion units are connected in parallel by the input-side switching unit, the output units of the plurality of power conversion units are connected to a single DC power supply. As described above, since it is not necessary to drive the AC power supply, the state of the unit can be independently diagnosed when no power needs to be supplied to another load (for example, at night when a factory in which the load is installed is not operating, or the like), which is advantageous in terms of efficiency and cost.

[0049] It should be noted that the present invention is not limited to the above embodiments, and various modifications are possible. For example, the above embodiments have been described in detail in order to easily explain the present invention, and the present invention is not necessarily limited to an aspect having all of the described configurations. Furthermore, part of the configuration of one embodiment may be replaced with the configuration of another embodiment. In addition, the configuration of another embodiment may be added to the configuration of a particular embodiment. In addition, part of the configuration of each embodiment may be removed, or another configuration may be added or replaced. List of reference symbols 1 AC power supply 10a to 10c power conversion unit 11 a to 11 c power semiconductor element 12a to 12c smoothing capacitor 20 Power conversion unit control device (control unit) 40 output-side switching unit 51, 53 Last 60 input-side switching unit 100 Power Conversion Unit Diagnostic System QUOTES CONTAINED IN THE DESCRIPTION

[0000] This list of documents submitted by the applicant was generated automatically and is included solely for the convenience of the reader. This list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions. Cited patent literature

[0000] JP 2021-168593 A

[0005]

Claims

[1] Power conversion unit diagnostic system, comprising: a plurality of power conversion units, each having an input unit that receives alternating current (AC) power from an AC power supply, and an output unit that converts the AC power into direct current (DC) power and outputs the DC power and supplies the DC power to at least one load, wherein each of the plurality of power conversion units is connected in series to the AC power supply, a control unit that controls the plurality of power conversion units, and an output-side switching unit capable of connecting the output units of at least some of the plurality of power conversion units in parallel with one of the loads, wherein the control unit determines a state of each of the plurality of power conversion units when the output units of at least some of the plurality of power conversion units are connected in parallel to the one load, and compares the determined states of the plurality of power conversion units to determine whether the characteristics of the respective plurality of power conversion units have deteriorated. [2] Power conversion unit diagnostic system according to claim 1, wherein the power conversion unit comprises a power semiconductor element and a capacitor and a state of the power conversion unit is a change in the thermal resistance of the power semiconductor element and a change in the temperature of the capacitor. [3] The power conversion unit diagnostic system according to claim 2, wherein the control unit controls the power conversion unit to suppress the change in the thermal resistance of the power semiconductor element and / or the change in the temperature of the capacitor with respect to the power conversion unit which is determined to have deteriorated in its characteristics. [4] The power conversion unit diagnostic system according to claim 3, wherein the control unit reduces the fluctuation range of the power output from the power conversion unit to suppress the change in the thermal resistance of the power semiconductor element, and sets a time during which no power is output from the power conversion unit to suppress the change in the temperature of the capacitor. [5] The power conversion unit diagnostic system of claim 1, further comprising: an input-side switching unit which switches the parallel connection between the input units of the plurality of power conversion units, wherein, when the plurality of power conversion units are connected in parallel by the input-side switching unit, the output units of the plurality of power conversion units are connected to a single DC power supply.

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