Power conversion unit diagnostic system

Abstract

To prolong a lifespan of a power conversion unit.SOLUTION: A power conversion unit diagnosis system 100 includes: a plurality of power conversion units 10 connected in series each of which includes an input section for receiving AC power from an AC power supply 1 and an output section for converting the AC power to DC power and outputting it and supplies the DC power to at least one load; a control section 20 for controlling the plurality of power conversion units 10; and an output side switching unit 40 that can connect output sections of at least some of the plurality of power conversion units 10 in parallel with one load. In the case that the output sections of the at least some of the plurality of power conversion units 10 are connected in parallel with the one load, the control unit 20 determines a state of each of the plurality of power conversion units 10 and diagnoses whether a characteristic of each of the plurality of power conversion units 10 has been deteriorated or not on the basis of the state.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a system for diagnosing the condition of a power conversion unit. [Background technology]

[0002] In recent years, power conversion units that convert AC to DC or DC to AC have become increasingly common. Multi-port power conversion technology, which allows multiple power conversion units to be connected to multiple loads, is being developed for applications such as high-voltage drives, EV chargers, and electric motors.

[0003] In a system using multiple power conversion units, it is necessary to understand the status of each individual power conversion unit in order to ensure stable output and to be able to respond quickly if a failure occurs in one of the power conversion units.

[0004] Patent Document 1 is an example of a system using multiple power conversion units. The disaster prevention system described in Patent Document 1 describes that, for the purpose of quickly temporarily restoring power supply units from a failure in the power supply unit, a switching unit is provided that can switch the power supply path from the voltage conversion unit to a power supply path from an external power supply device via an external connection unit when the voltage conversion unit fails. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Japanese Patent Publication No. 2021-168593 Summary of the Invention [Problem to be solved by the invention]

[0006] However, the technology described in Patent Document 1 relates to measures to be taken after a failure occurs in the power supply unit, and does not describe how to prevent failures in the power supply unit before they occur or how to extend the life of the power supply unit.

[0007] In particular, when using the above-mentioned multi-port power conversion technology as a charger, the number of parallel connections of units is changed depending on the number of power sources to be charged simultaneously and their respective capacities. The lifespan of a unit depends on each load condition (load current, current fluctuation, ambient temperature). If some units have uneven load fluctuations or operating times, or if there are initial manufacturing variations, the unit's lifespan will be shortened. Therefore, to extend the lifespan of a unit, it is necessary to understand the unit's deterioration state and control its operation to suppress deterioration. [Means for solving the problem]

[0008] In order to solve the above problem, the power conversion unit diagnostic system of the present invention has an input section that receives AC power from an AC power source and an output section that converts the AC power into DC power and outputs it, and has a plurality of power conversion units that supply DC power to at least one load and are each connected in series to the AC power source, a control section that controls the plurality of power conversion units, and an output-side switching unit that is capable of connecting the output sections of at least some of the plurality of power conversion units in parallel to one load, and the control section determines the state of each of the plurality of power conversion units when the output sections of at least some of the plurality of power conversion units are connected in parallel to one load, and by comparing the determined states of each of the plurality of power conversion units, diagnoses whether the characteristics of each of the plurality of power conversion units have deteriorated. [Effects of the Invention]

[0009] According to the present invention, when multiple power conversion units are operated simultaneously, it is possible to individually determine changes in the characteristics of each unit, thereby making it possible to appropriately adjust the control of a deteriorated unit based on the changes in the characteristics, thereby extending the life of the unit. Further features related to the present invention will become apparent from the description of the present specification and the accompanying drawings. Furthermore, problems, configurations, and effects other than those described above will become apparent from the following description of the embodiments. [Brief explanation of the drawings]

[0010] [Figure 1] 1 is a block diagram showing an overview of a power conversion unit diagnostic system according to an embodiment of the present invention; [Figure 2] 4 is a flowchart showing a diagnostic process for a power conversion unit performed using the power conversion unit diagnostic system. [Figure 3] FIG. 4 is a diagram showing an example of a control method for the power conversion unit performed by a control unit. [Figure 4] FIG. 10 is a block diagram showing an overview of a power conversion unit diagnostic system according to another embodiment of the present invention. [Figure 5] 10 is a flowchart showing another example of diagnostic processing performed using the power conversion unit diagnostic system. DETAILED DESCRIPTION OF THE INVENTION

[0011] Hereinafter, an embodiment will be described with reference to the drawings. FIG. 1 is a block diagram showing an overview of a power conversion unit diagnostic system 100 (hereinafter simply referred to as "system 100") according to one embodiment of the present invention.

[0012] The system 100 includes a plurality of power conversion units 10a-10c connected in series with their inputs connected to an AC power source 1, a power conversion unit controller 20 that determines the state of each power conversion unit and diagnoses the deterioration state of the power conversion units based on that state, serial buses 30a-30c connected between the output of each power conversion unit and each load, and an output-side switching unit 40 that switches the connection of the serial bus. Note that, for simplicity of explanation, the power conversion units 10a-10c will be collectively referred to as power conversion units 10 below unless they are individually mentioned. The same applies to the other components.

[0013] Between the AC power supply 1 and the power conversion unit 10, there are provided an AC reactor 2 for power supply coordination, power factor correction, and harmonic suppression, and a switching element 3 for switching the connection between the AC power supply 1 and the power conversion unit 10.

[0014] The output of the power conversion unit 10 is selectively connected to loads 51 and 53 by the output-side switching unit 40. The loads 51 and 53 are, for example, an EV charger or an electric motor, and each load outputs a specific load power. Note that reference numerals 52 and 54 are also smoothing capacitors.

[0015] Each power conversion unit 10 has a power semiconductor element 11 and a smoothing capacitor 12. The power semiconductor element 11 is configured by, for example, a metal-oxide-semiconductor field-effect transistor (MOSFET), an insulated gate bipolar transistor (IGBT), a bipolar transistor, a diode, or the like, and converts AC power input from the AC power source 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.

[0016] The power conversion unit controller 20 is implemented in a computer connected to the power conversion unit 10, for example, by wire or wirelessly, and executes the processes described below using a CPU and memory built into the computer.

[0017] The DC bus 30 provided between the output of the power conversion unit 10 and the loads 51 and 53 has its connection switched by an output-side switching unit 40. The switching elements 41 and 42 constituting the output-side switching unit 40 can be any type of mechanical switch, semiconductor switch, or the like.

[0018] In this 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 them on and off.

[0019] Specifically, the connection between the power conversion units 10a to 10c and the load 51 is switched by turning on / off the switching elements 42a to 42c, respectively, and the connection between the power conversion units 10a to 10c and the load 53 is switched by turning on / off the switching elements 41a to 41c, respectively.

[0020] 1, since the switching elements 41b, 41c, and 42a are in the ON state, the power conversion units 10a and 10b are connected to the same load 51 (see currents 13a and 13b). Also, the power conversion unit 10c is connected to a load 53.

[0021] That is, in this embodiment, since the power conversion units 10a and 10b are connected to the same load 51, the load power applied to the internal power semiconductor elements 11a and 11b and smoothing capacitors 12a and 12b is also the same. Therefore, by determining the states of these elements and comparing and analyzing them between the units, it is possible to diagnose the deterioration state of each power conversion unit. Furthermore, if there is a bias in the operating conditions between the power conversion units, it is also possible to adjust the operating conditions of the power conversion units in a direction that eliminates the bias.

[0022] The conditions addressed in this invention are the thermal resistance of the power semiconductor elements 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, etc., so they are suitable as parameters for determining the deterioration state of the power conversion unit.

[0023] 2 is a flowchart showing the processing performed by the power conversion unit diagnostic system 100 according to this embodiment. First, in step S201, as shown in FIG. 1, a plurality of power conversion units 10 are connected in parallel to one 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 in parallel and operating. Note that the power conversion unit controller 20 may acquire the state values, 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 values ​​during operation.

[0024] Then, in step S202, it is determined whether the increment in the thermal resistance of a PM (Power Module: power semiconductor element) of any unit and / or the increment in the temperature of a CAP (Capacitor: smoothing capacitor) has reached a specified value or more.

[0025] If the answer is "No" in step S202, the process returns to step S201 and parallel operation continues. If the answer is "Yes" in step S202, the process proceeds to step S203 and it is determined which element in which unit has deteriorated.

[0026] If the deteriorated element is the power semiconductor element 11 of any of the power conversion units 10 (step S204), the process proceeds to step S205, where control is performed to suppress deterioration of the power semiconductor element 11. If the deteriorated element is the smoothing capacitor 12 of any of the power conversion units 10 (step S206), the process proceeds to step S207, where control is performed to suppress deterioration of the smoothing capacitor 12. Note that once this control is performed, it continues to be performed until the operation of the power conversion unit 10 is terminated.

[0027] The process for suppressing the deterioration of these elements will be explained using Fig. 3. Fig. 3(a) shows the load power output from a load to which multiple power conversion units, which were the measurement targets in the process of Fig. 2, are connected in parallel.

[0028] In step S205 in Fig. 2, that is, when the degraded element is the power semiconductor element 11, control in control mode 1 shown in Fig. 3(b) is performed. Specifically, the signal supplied to the power semiconductor element 11 is controlled so that the power output from the power conversion unit 10 having the power semiconductor element 11 determined to be degraded is kept constant (so that the fluctuation range of the power is reduced). This is because the degradation of the thermal resistance characteristics of the power semiconductor element 11 is caused by fluctuations in output voltage.

[0029] In step S207 in Fig. 2, that is, when the deteriorated element is the smoothing capacitor 12, control in control mode 2 shown in Fig. 3(c) is performed. Specifically, a period of time is set during which the power conversion unit 10 having the smoothing capacitor 12 determined to be deteriorated is not operated, and a period of time is set during which power is not output from the unit. This is because the temperature deterioration of the smoothing capacitor 12 is caused by the power output.

[0030] In this embodiment, by connecting a plurality of power conversion units 10 in parallel to a single load and setting them under the same operating conditions, and then performing the above-described control, it becomes possible to compare changes in the state of elements between the power conversion units 10, and based on this comparison, it becomes possible to determine the deterioration state of each power conversion unit 10. Furthermore, the control signal is adjusted to suppress thermal resistance deterioration of the power semiconductor elements 11 and / or temperature deterioration of the smoothing capacitor 12 according to the deterioration state, and it becomes possible to eliminate imbalances in the operating environments that occur between the power conversion units 10.

[0031] Next, a power conversion unit diagnostic system according to another embodiment of the present invention will be described with reference to Fig. 4. The system 100 shown in Fig. 4 differs from the system 100 shown in Fig. 1 in that the system 100 has an input-side switching unit 60 on the input side of each power conversion unit 10, which switches the parallel connection between the inputs of the power conversion units 10.

[0032] 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 the switching elements 61a and 61b are in the ON state, all of the power conversion units 10a, 10b, and 10c are connected in parallel.

[0033] 4, only switching element 61b is in the ON state, so power conversion units 10b and 10c are connected in parallel. Switching element 3 in the AC circuit is in the OFF state, so AC power supply 1 is not connected to the power conversion units. Furthermore, in output-side switching unit 40, switching elements 41b and 41c are in the ON state, so the outputs of power conversion units 10b and 10c are connected to load 53.

[0034] In this embodiment, the load 53 is a storage battery.

[0035] With the above configuration, a current as shown by arrow 14 in FIG. 4 flows between power conversion units 10b and 10c connected in parallel, with storage battery 53 as the power source.

[0036] In this case, too, by executing a flow similar to that shown in FIG. 2, it is possible to determine the deterioration state of each power conversion unit 10 and further control the operation so as to suppress deterioration of the elements.

[0037] 5 is executed in the system 100 according to this embodiment. First, in step S501, the power supply is adjusted so that the output of the load (storage battery) connected to the power conversion unit 10 falls within a range suitable for diagnosing the power conversion unit 10.

[0038] After the adjustment is completed, the process proceeds to step S502, where the power conversion units 10 to be diagnosed are connected in parallel and diagnosis is started. Then, the power conversion unit controller 20 acquires the state value of each power conversion unit 10 (step S503). Thereafter, the same process as in FIG. 2 is executed to diagnose the deterioration state of the power conversion units 10.

[0039] As described above, in this embodiment, the operation of the AC power supply 1 is not required, and therefore it is possible to diagnose the state of the unit in a self-contained manner when there is no need to supply power to another load 51 (for example, at night when the factory in which the load 51 is installed is not operating), which is advantageous in terms of efficiency and cost.

[0040] 1, in this embodiment, the power conversion units to be diagnosed can be freely combined in any desired manner, which makes it possible to ensure the completeness of the diagnosis, for example, by diagnosing a unit that could not be diagnosed during the operation (daytime) of the factory at night.

[0041] According to the embodiment of the present invention described above, the following advantageous effects are achieved. (1) A power conversion unit diagnostic system according to the present invention includes a plurality of power conversion units each having an input section that receives AC power from an AC power source and an output section that converts the AC power into DC power and outputs it, the plurality of power conversion units supplying DC power to at least one load and each connected in series to the AC power source; a control section that controls the plurality of power conversion units; and an output-side switching unit that is capable of connecting the output sections of at least some of the plurality of power conversion units in parallel to a single load. When the output sections of at least some of the plurality of power conversion units are connected in parallel to a single load, the control section determines the state of each of the plurality of power conversion units and compares the determined states of the plurality of power conversion units to diagnose whether the characteristics of each of the plurality of power conversion units have deteriorated.

[0042] With the above configuration, when multiple power conversion units are operated simultaneously, it is possible to individually determine changes in the characteristics of each unit, thereby making it possible to appropriately adjust the control of a deteriorated unit based on the changes in its characteristics and thereby extend the life of the unit.

[0043] (2) The power conversion unit has a power semiconductor element and a capacitor, and the state of the power conversion unit is the change in thermal resistance of the power semiconductor element and the change in temperature of the capacitor. These states are directly related to the deterioration of the power conversion unit, but since they can be easily measured using existing temperature sensors, the degree of deterioration of the power conversion unit can also be easily determined.

[0044] (3) The control unit controls a power conversion unit determined to have deteriorated characteristics so as to suppress changes in the thermal resistance of the power semiconductor elements and / or changes in the temperature of the capacitor. More specifically, the control unit reduces the fluctuation range of the power output from the power conversion unit to suppress changes in the thermal resistance of the power semiconductor elements, and provides a period during which no power is output from the power conversion unit to suppress changes in the temperature of the capacitor. This allows the effects of the present invention to be easily achieved, for example, by simply adjusting the control signal supplied to the power conversion unit.

[0045] (4) The power conversion device further includes an input-side switching unit that switches the parallel connection between the input sections of the plurality of power conversion units, and when the plurality of power conversion units are connected in parallel by the input-side switching unit, the output sections of the plurality of power conversion units are connected to a single DC power source. In this way, since the operation of the AC power source is not required, it is possible to self-containedly diagnose the status of the unit when there is no need to supply power to another load (for example, at night when the factory where the load is installed is not operating), which is advantageous in terms of efficiency and cost.

[0046] The present invention is not limited to the above-described embodiments, and various modifications are possible. For example, the above-described embodiments have been described in detail to clearly explain the present invention, and the present invention is not necessarily limited to embodiments including all of the described configurations. Furthermore, it is possible to replace part of the configuration of one embodiment with the configuration of another embodiment. It is also possible to add the configuration of another embodiment to the configuration of one embodiment. It is also possible to delete part of the configuration of each embodiment, or to add or replace other configurations. [Explanation of symbols]

[0047] 1 AC power supply, 10a to 10c power conversion units, 11a to 11c power semiconductor elements, 12a to 12c smoothing capacitors, 20 power conversion unit controller (control unit), 40 output side switching unit, 51, 53 load, 60 input side switching unit, 100 power conversion unit diagnostic system

Claims

1. a plurality of power conversion units each having an input section that receives AC power from an AC power supply and an output section that converts the AC power into DC power and outputs the DC power, the power conversion units supplying the DC power to at least one load and each being connected in series to the AC power supply; a control unit that controls the plurality of power conversion units; an output-side switching unit capable of connecting the output sections of at least some of the plurality of power conversion units to one of the loads in parallel, Each power conversion unit has a power semiconductor element and a smoothing capacitor. When output sections of at least some of the plurality of power conversion units are connected in parallel to the single load, the control section diagnoses whether or not characteristics of each of the plurality of power conversion units have deteriorated by determining whether an increment in thermal resistance of the power semiconductor element and / or an increment in temperature of the smoothing capacitor of any of the plurality of power conversion units has reached a specified value or more. A power conversion unit diagnostic system comprising:

2. 2. The power conversion unit diagnostic system according to claim 1, the control unit controls the power conversion unit determined to have deteriorated characteristics so as to suppress a change in thermal resistance of the power semiconductor element and / or a change in temperature of the smoothing capacitor. A power conversion unit diagnostic system comprising:

3. 3. The power conversion unit diagnostic system according to claim 2, the control unit reduces a fluctuation range of the power output from the power conversion unit in order to suppress a change in thermal resistance of the power semiconductor element, and provides a time during which no power is output from the power conversion unit in order to suppress a temperature change of the smoothing capacitor. A power conversion unit diagnostic system comprising:

4. 2. The power conversion unit diagnostic system according to claim 1, an input-side switching unit for switching the parallel connection between the input sections of the plurality of power conversion units; When the plurality of power conversion units are connected in parallel by the input-side switching unit, output ports of the plurality of power conversion units are connected to a single DC power source. A power conversion unit diagnostic system comprising:

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