JP6726121B2 - Power conversion system - Google Patents

Description

The present invention relates to a power conversion system.

BACKGROUND ART Conventionally, as seen in Patent Document 1, there is known a power conversion system including a plurality of DCDC converters whose output sides are connected to a common output section. This system includes an overvoltage detection circuit that detects the voltage value of a common output section, and an overvoltage protection section. The overvoltage detection circuit outputs an overvoltage detection signal to the overvoltage protection unit when the detected voltage value exceeds the reference voltage value. The overvoltage protection unit stops the operation of the plurality of DCDC converters when the overvoltage detection signal is input. As a result, it is possible to prevent the output side of the plurality of DCDC converters from having an abnormal overvoltage.

JP, 2010-114996, A

When an abnormality occurs in the overvoltage detection circuit, it becomes impossible to monitor the overvoltage abnormality on the output side. In this case, the reliability of the system will decrease. In addition, in a system having a configuration for detecting other abnormalities, not limited to an overvoltage abnormality on the output side, the reliability of the system is deteriorated even when an abnormality occurs in the configuration.

The main object of the present invention is to provide a power conversion system capable of suppressing a decrease in reliability.

The present invention provides a power conversion system including a plurality of power conversion devices, each of the plurality of power conversion devices having a transformer that transforms and outputs an input voltage, and is provided corresponding to each of the plurality of transformers. , A self-determination unit that determines that an abnormality has occurred in the transformer unit corresponding to itself, and a transformer unit provided corresponding to each of the plurality of transformer units and other than the transformer unit corresponding to itself among the plurality of transformer units. The other determination unit that determines whether an abnormality has occurred in the transformer unit.

The present invention includes a self-determination unit provided corresponding to each of the plurality of transformer units. The self-determination unit can determine that an abnormality has occurred in the transformer unit corresponding to itself. Further, the present invention includes another determination unit provided corresponding to each of the plurality of transformer units. The other determination unit can determine that an abnormality has occurred in a transformer unit other than the transformer unit corresponding to itself among the plurality of transformer units.

According to the present invention, even when an abnormality occurs in the self-determination unit of a certain transformer unit among the plurality of transformer units, the self-determination unit in which the abnormality has occurred is determined by another determination unit corresponding to another transformer unit. It can be determined that an abnormality has occurred in the transformer unit corresponding to. Therefore, it is possible to prevent the reliability of the power conversion system from decreasing.

The whole block diagram of the vehicle-mounted system which concerns on 1st Embodiment. The figure which shows the structure of each DCDC converter. The flowchart which shows the procedure of the overvoltage protection process which a 1st control part performs. The flowchart which shows the procedure of the overvoltage protection process which a 2nd control part performs. The figure which shows the structure of each DCDC converter which concerns on 2nd Embodiment. The flowchart which shows the procedure of the overvoltage protection process which the 1st control part which concerns on 3rd Embodiment performs. The flowchart which shows the procedure of the overvoltage protection process which a 2nd control part performs.

(First embodiment)
Hereinafter, a first embodiment that embodies a power conversion system according to the present invention will be described with reference to the drawings. In this embodiment, the power conversion system is applied to a vehicle including a rotating electric machine that serves as a traveling power source.

As shown in FIG. 1, the in-vehicle system includes a high voltage storage battery 10, an inverter 20, and a motor generator 30 as a rotating electric machine.

The high-voltage storage battery 10 has a terminal voltage of, for example, several hundreds of volts and corresponds to a high-voltage power storage device. The high voltage storage battery 10 is, for example, a lithium ion storage battery.

The positive terminal of the high voltage storage battery 10 is connected to the high potential side terminal of the inverter 20 via the first main high voltage path HM1 which is an electric path. The negative terminal of the high voltage storage battery 10 is connected to the low potential side terminal of the inverter 20 via the second main high voltage path HM2 which is an electric path.

The first main high-voltage path HM1 is provided with a first relay SMR1 and the second main high-voltage path HM2 is provided with a second relay SMR2. When the relays SMR1 and SMR2 are controlled to be in the open state, the high voltage storage battery 10 and the inverter 20 are electrically disconnected. On the other hand, when the relays SMR1 and SMR2 are controlled to be in the closed state, the high voltage storage battery 10 and the inverter 20 are electrically connected.

The inverter 20 converts the DC power output from the high voltage storage battery 10 into AC power and supplies the AC power to the motor generator 30. Thereby, motor generator 30 generates torque, and the vehicle can be driven. A boost converter may be provided on the input side of the inverter 20.

A first sub high voltage path HS1 which is an electric path is connected to the first main high voltage path HM1 on the high voltage storage battery 10 side of the first relay SMR1. A second sub high voltage path HS2, which is an electric path, is connected to the second main high voltage path HM2 closer to the high voltage storage battery 10 than the second relay SMR2. A third sub high voltage path HS3, which is an electric path, is connected to the inverter 20 side of the first main high voltage path HM1 with respect to the first relay SMR1. A fourth sub high voltage path HS4, which is an electric path, is connected to the inverter 20 side of the second main high voltage path HM2 with respect to the second relay SMR2. The relays SMR1 and SMR2 are controlled to be opened/closed by, for example, a host controller (not shown) that controls the vehicle.

The in-vehicle system includes a first DCDC converter 40 as a first power converter and a second DCDC converter 50 as a second power converter. The first sub-high voltage path HS1 is connected to the first A terminal T1A of the first DCDC converter 40, and the second sub high voltage path HS2 is connected to the first B terminal T1B of the first DCDC converter 40. The second sub DC high voltage path HS3 is connected to the second A terminal T2A of the second DCDC converter 50, and the fourth sub high voltage path HS4 is connected to the second B terminal T2B of the second DCDC converter 50.

A low voltage path LL corresponding to a predetermined electric path is connected to the first C terminal T1C of the first DCDC converter 40 and the second C terminal T2C of the second DCDC converter 50. A low voltage storage battery 60 and an electric load 61 are connected to the low voltage path LL. The low-voltage storage battery 60 is a low-voltage power storage device having an output voltage lower than that of the high-voltage storage battery 10, and is, for example, a lead storage battery. In this embodiment, the high-voltage storage battery 10, the low-pressure storage battery 60, the high-voltage paths HM1 and HM2, and the low-voltage path LL form a control system.

The in-vehicle system includes a first input voltage sensor 70A, a first output voltage sensor 71A, a second input voltage sensor 70B, and a second output voltage sensor 71B. The first input voltage sensor 70A detects a potential difference between the first A terminal T1A and the first B terminal T1B as a first input voltage value Vin1. The first output voltage sensor 71A detects the potential difference between the first C terminal T1C and the ground as the first output voltage value Vout1. The second input voltage sensor 70B detects the potential difference between the second A terminal T2A and the second B terminal T2B as the second input voltage value Vin2. The second output voltage sensor 71B detects the potential difference between the second C terminal T2C and the ground as the second output voltage value Vout2.

The first input voltage sensor 70A and the first output voltage sensor 71A may be built in the first DCDC converter 40 or may be provided outside the first DCDC converter 40. Further, the second input voltage sensor 70B and the second output voltage sensor 71B may be incorporated in the second DCDC converter 50 or may be provided outside the second DCDC converter 50.

Subsequently, the first DCDC converter 40 and the second DCDC converter 50 will be described with reference to FIG.

First, the first DCDC converter 40 will be described.

The first DCDC converter 40 includes a first transformer 40A, a first own comparator 40B, a first other comparator 40C, and a first controller 40D. In the present embodiment, the first transformer 40A, the first own comparator 40B, the first other comparator 40C, and the first controller 40D are integrated. For example, the first transformer 40A, the first self-comparator 40B, the first other comparator 40C, and the first controller 40D are housed in a common housing or housed in a plurality of independent housings to be integrated. Just do it.

The first transformer 40A has a semiconductor switch, and has a step-down function of stepping down the voltage input from the first A terminal T1A and the first B terminal T1B to output from the first C terminal T1C by turning the semiconductor switch on and off. There is. The first output voltage value Vout1 detected by the first output voltage sensor 71A is input to the first controller 40D. The first control unit 40D turns on/off the semiconductor switch forming the first transformer 40A so as to control the input first output voltage value Vout1 to the first target voltage value Vtgt1.

The first output voltage value Vout1 is input to the non-inverting input terminal of the first self-comparator 40B. The first overvoltage threshold Vref1 is input to the inverting input terminal of the first self-comparator 40B. The first overvoltage threshold Vref1 is set to a value with which it can be determined that the voltage value of the first C terminal T1C is overvoltage, and is set to a value larger than the first target voltage value Vtgt1. When the first output voltage value Vout1 is smaller than the first overvoltage threshold Vref1, the first self-comparator 40B outputs a signal of logic L as the first self-determination signal S1A. On the other hand, the first self-comparator 40B outputs a signal of logic H as the first self-determination signal S1A when the first output voltage value Vout1 is larger than the first overvoltage threshold Vref1. The first self-determination signal S1A is input to the first controller 40D.

The second output voltage value Vout2 detected by the second output voltage sensor 71B is input to the non-inverting input terminal of the first other comparator 40C. The second overvoltage threshold Vref2 is input to the inverting input terminal of the first other comparator 40C. The second overvoltage threshold Vref2 is set to a value with which it can be determined that the voltage value of the second C terminal T2C is overvoltage, and is set to a value larger than the second target voltage value Vtgt2. The first and second overvoltage thresholds Vref1 and Vref2 may be set to the same value or different values.

When the second output voltage value Vout2 is smaller than the second overvoltage threshold Vref2, the first other comparator 40C outputs a signal of logic L as the first other determination signal S1B. On the other hand, when the second output voltage value Vout2 is larger than the second overvoltage threshold Vref2, the first other comparator 40C outputs a signal of logic H as the first other determination signal S1B. The first other determination signal S1B is input to the first controller 40D.

Subsequently, the second DCDC converter 50 will be described.

The second DCDC converter 50 includes a second transformer 50A, a second own comparator 50B, a second other comparator 50C, and a second controller 50D. In the present embodiment, the second transformer 50A, the second own comparator 50B, the second other comparator 50C, and the second controller 50D are integrated. For example, the second transformer 50A, the second self-comparator 50B, the second other comparator 50C, and the second controller 50D are housed in a common housing or housed in a plurality of independent housings to be integrated. Just do it.

The second transformer section 50A has a semiconductor switch, and has a step-down function of stepping down the voltage input from the second A terminal T2A and the second B terminal T2B and outputting the voltage from the second C terminal T2C by turning the semiconductor switch on and off. There is. The second output voltage value Vout2 is input to the second control unit 50D. The second control unit 50D turns on/off the semiconductor switch that constitutes the second transformer unit 50A in order to control the input second output voltage value Vout2 to the second target voltage value Vtgt2.

The second output voltage value Vout2 is input to the non-inverting input terminal of the second self-comparator 50B. The second overvoltage threshold Vref2 is input to the inverting input terminal of the second self-comparator 50B. When the second output voltage value Vout2 is smaller than the second overvoltage threshold Vref2, the second self-comparator 50B outputs a signal of logic L as the second self-determination signal S2A. On the other hand, when the second output voltage value Vout2 is larger than the second overvoltage threshold Vref2, the second self-comparator 50B outputs a signal of logic H as the second self-determination signal S2A. The second self-determination signal S2A is input to the second controller 50D.

The first output voltage value Vout1 is input to the non-inverting input terminal of the second other comparator 50C. The first overvoltage threshold Vref1 is input to the inverting input terminal of the second other comparator 50C. When the first output voltage value Vout1 is smaller than the first overvoltage threshold Vref1, the second other comparator 50C outputs a signal of logic L as the second other determination signal S2B. On the other hand, the second other comparator 50C outputs a signal of logic H as the second other determination signal S2B when the first output voltage value Vout1 is larger than the first overvoltage threshold Vref1. The second other determination signal S2B is input to the second controller 50D.

Next, the overvoltage protection process of this embodiment will be described.

First, FIG. 3 shows a flowchart of the overvoltage protection process executed by the first controller 40D. This process is repeatedly executed, for example, every predetermined control cycle.

In step S10, it is determined whether the logical sum of the condition that the logic of the first self-determination signal S1A is H and the condition that the operation stop command of the first transformer 40A is input is true. Here, the operation stop command of the first transformer 40A is output from the second controller 50D to the first controller 40D when the logic of the second other determination signal S2B becomes H. In the present embodiment, the processing of the first self-comparator 40B and step S10 corresponds to the first self-determination unit.

When it is determined in step S10 that the logic of the first self-determination signal S1A is H, or when the operation stop command of the first transformer 40A is input, the process proceeds to step S11, and the first transformer The operation of the first transformer 40A is stopped by stopping the switching of the semiconductor switch that constitutes 40A. In the present embodiment, the process of step S11 corresponds to the first stop unit.

When the process of step S11 is completed, or when a negative determination is made in step S10, the process proceeds to step S12. In step S12, it is determined whether the logic of the first other determination signal S1B is H. This process is a process for determining whether or not there is an overvoltage abnormality on the output side of the second transformer 50A. In the present embodiment, the processing of the first other comparator 40C and step S12 corresponds to the first other determination unit.

If an affirmative decision is made in step S12, the operation proceeds to step S13, and an operation stop command for the second transformer 50A is output to the second controller 50D.

Subsequently, FIG. 4 shows a flowchart of the overvoltage protection process executed by the second control unit 50D. This process is repeatedly executed, for example, every predetermined control cycle.

In step S20, it is determined whether the logical sum of the condition that the logic of the second self-determination signal S2A is H and the condition that the operation stop command of the second transformer 50A is input is true. Here, the operation stop command of the second transformer 50A is a command output in the process of step S13 of FIG. In the present embodiment, the processing of the second self-comparator 50B and step S20 corresponds to the second self-determination unit.

In step S20, when it is determined that the logic of the second self-determination signal S2A is H, or when it is determined that the operation stop command of the second transformer 50A is input, the process proceeds to step S21, and the second transformer The operation of the second transformer 50A is stopped by stopping the switching of the semiconductor switch that constitutes 50A. In the present embodiment, the process of step S21 corresponds to the second stop unit.

When the process of step S21 is completed, or when a negative determination is made in step S20, the process proceeds to step S22. In step S22, it is determined whether or not the logic of the second other determination signal S2B is H. This process is a process for determining whether or not there is an overvoltage abnormality on the output side of the first transformer 40A. In the present embodiment, the processing of the second other comparator 50C and step S22 corresponds to the second other determination unit.

If an affirmative decision is made in step S22, the operation proceeds to step S23, and an operation stop command for the first transformer 40A is output to the first controller 40D.

According to the present embodiment described in detail above, the first control unit 40D can determine that the output side of the first transformer 40A has an overvoltage abnormality based on the first output voltage value Vout1. Further, the first control unit 40D can determine that the output side of the second transformer 50A has an overvoltage abnormality based on the second output voltage value Vout2. Therefore, for example, even when an abnormality occurs in the first control unit 40D, the second control unit 50D causes the overvoltage abnormality on the output side of the first transformer 40A corresponding to the abnormal first control unit 40D. The presence or absence of can be determined. As a result, it is possible to suppress a decrease in reliability of the in-vehicle system.

(Second embodiment)
Hereinafter, the second embodiment will be described with reference to the drawings, focusing on the differences from the first embodiment. In the present embodiment, as shown in FIG. 5, the configuration of each DCDC converter 40, 50 is changed. Note that, in FIG. 5, the same or corresponding configurations as those shown in FIG. 2 above are denoted by the same reference numerals for convenience.

As shown in FIG. 5, the first DCDC converter 40 includes a first transformer 40A, a first own comparator 40B, a first other comparator 40C, a first controller 40D, a second own comparator 50B, and a second other comparison. The container 50C and the second controller 50D are provided. In the present embodiment, the first transformer 40A, the first own comparator 40B, the first other comparator 40C, the first controller 40D, the second own comparator 50B, the second other comparator 50C, and the second controller 50D. Are integrated. For example, the first transformer 40A, the first own comparator 40B, the first other comparator 40C, the first controller 40D, the second own comparator 50B, the second other comparator 50C, and the second controller 50D are common. It may be housed in the housing of No. 1 or housed in a plurality of independent housings and integrated.

The second DCDC converter 50 includes a second transformer 50A. In the present embodiment, the second DCDC converter 50 does not include the second own comparator 50B, the second other comparator 50C, and the second controller 50D.

In this embodiment, the first DCDC converter 40 functions as a master and the second DCDC converter 50 functions as a slave. The second controller 50D included in the first DCDC converter 40 controls the output voltage value of the second transformer 50A.

In the present embodiment described above, the voltage control function and the overvoltage determination function are integrated in the first DCDC converter 40 serving as the master. Therefore, the number of components of the second DCDC converter 50 serving as a slave can be reduced, and the cost of the second DCDC converter 50 can be reduced. The reduction effect increases as the number of slave DCDC converters increases.

(Third Embodiment)
Hereinafter, the third embodiment will be described with reference to the drawings, focusing on the differences from the first embodiment. In this embodiment, the overvoltage protection method is changed. In the present embodiment, the second output voltage value Vout2 is input to the first control unit 40D via the second control unit 50D, and the second control unit 50D receives the first output voltage value Vout2 via the first control unit 40D. The output voltage value Vout1 is input.

FIG. 6 shows a flowchart of the overvoltage protection process executed by the first controller 40D. This process is repeatedly executed, for example, every predetermined control cycle. In FIG. 6, the same steps as those shown in FIG. 3 are given the same step numbers for convenience.

If an affirmative decision is made in step S10, the operation proceeds to step S14. In step S14, it is determined whether the absolute value of the difference between the second output voltage value Vout2 and the first target voltage value Vtgt1 is smaller than the first threshold value ΔV1. This process is a process for determining whether to continue the operation of the first transformer 40A.

That is, noise may be mixed in the first output voltage value Vout1. In this case, the logic of the first self-determination signal S1A becomes H or the logic of the second other determination signal S2B becomes H, although the overvoltage abnormality on the output side of the first transformer 40A does not occur. However, the operation of the first transformer 40A is stopped. Here, even if noise is mixed in the first output voltage value Vout1, noise is not necessarily mixed in the second output voltage value Vout2. In addition, since the output side of the first transformer 40A and the output side of the second transformer 50A are short-circuited by the low-voltage path LL, the actual output voltage value of the first transformer 40A and the actual output of the second transformer 50A. It does not differ greatly from the output voltage value of. Therefore, by using the second output voltage value Vout2 instead of the first output voltage value Vout1, the actual output voltage value of the first transformer 40A largely deviates from the first target voltage value Vtgt1 and the first transformer voltage is changed. It is possible to improve the accuracy of determining whether or not the overvoltage abnormality on the output side of the unit 40A actually occurs. As a result, it is possible to prevent an erroneous determination that the overvoltage abnormality has occurred even though the overvoltage abnormality on the output side of the first transformer 40A has not occurred.

When a negative determination is made in step S14, the process proceeds to step S11, and the operation of the first transformer 40A is stopped. On the other hand, if an affirmative decision is made in step S14, the operation proceeds to step S15, and the operation of the first transformer 40A is continued. After the processing of steps S11 and S15 is completed, the process proceeds to step S12.

Subsequently, FIG. 7 shows a flowchart of the overvoltage protection process executed by the second control unit 50D. This process is repeatedly executed, for example, every predetermined control cycle. In FIG. 7, the same steps as those shown in FIG. 4 are given the same step numbers for convenience.

If an affirmative decision is made in step S20, the operation proceeds to step S24. In step S24, it is determined whether the absolute value of the difference between the first output voltage value Vout1 and the second target voltage value Vtgt2 is smaller than the second threshold value ΔV2. This process is a process for determining whether or not to continue the operation of the second transformer 50A. The second threshold value ΔV2 may be set to the same value as the first threshold value ΔV1 or may be set to a different value.

When a negative determination is made in step S24, the process proceeds to step S21, and the operation of the second transformer 50A is stopped. On the other hand, if an affirmative decision is made in step S24, the operation proceeds to step S25, and the operation of the second transformer 50A is continued. After the processing of steps S21 and S25 is completed, the process proceeds to step S22.

According to the present embodiment described above, the accuracy of overvoltage abnormality determination can be increased. As a result, it is possible to prevent the operation of the transformer unit from being stopped even though the overvoltage abnormality has not occurred.

In this embodiment, the DCDC converters 40 and 50 may be configured as described in the second embodiment.

(Other embodiments)
The above embodiments may be modified and implemented as follows.

In step S14 of FIG. 6, it is determined whether the absolute value of the difference between the second target voltage value Vtgt2 and the second output voltage value Vout2 is smaller than the first threshold value ΔV1 instead of the first target voltage value Vtgt1. You may.

Further, in step S24 of FIG. 7, it is determined whether the absolute value of the difference between the first target voltage value Vtgt1 and the first output voltage value Vout1 is smaller than the second threshold value ΔV2 instead of the second target voltage value Vtgt2. You may.

The vehicle-mounted system including the first and second DCDC converters 40 and 50 is not limited to the configuration shown in FIG. For example, the configuration may be such that the output side of the first DCDC converter 40 and the output side of the second DCDC converter 50 are not connected to the common low voltage path LL.

The vehicle-mounted system may have a configuration in which the input sides of the first and second DCDC converters 40 and 50 are not connected to the high voltage paths HM1 and HM2, which are common electric paths. As this configuration, for example, the first storage battery is connected to the input side of the first transformer section 40A of the first DCDC converter 40, and the second storage battery is connected to the input side of the second transformer section 50A of the second DCDC converter 50. Are listed. In this case, the first storage battery and the second storage battery are not limited to having the same output voltage, but may have different output voltages. Further, the output voltage of at least one of the first storage battery and the second storage battery may be lower than the output voltage of the low voltage storage battery 60. In this case, the transformer connected to the storage battery whose output voltage is lower than that of the low-voltage storage battery 60 has a function of boosting the input voltage and outputting it to the low-voltage storage battery 60.

The power conversion system may include three or more DCDC converters. For example, in the case of a power conversion system including three DCDC converters, the configuration described below can be adopted. Each of the first to third DCDC converters includes a transformer, a self-determination unit, and another determination unit. For example, the other determination unit included in the first DCDC converter can determine that the overvoltage abnormality has occurred on the output side of the transformer included in the second and third DCDC converters.

In each of the above-described embodiments, it is determined that the output side overvoltage abnormality of the first and second transformers 40A and 50A has occurred as the abnormality of the first and second transformers 40A and 50A, but the invention is not limited to this. .. For example, an overvoltage abnormality on the input side of the first and second transformers 40A and 50A, an overheat abnormality on the first and second transformers 40A and 50A, or a disconnection abnormality on the output side of the first and second transformers 40A and 50A. It may be determined that is occurring. Note that, for example, the first and second input voltage values Vin1 and Vin2 may be used to determine that the overvoltage abnormality on the input side has occurred.

The high-voltage power storage device and the low-voltage power storage device are not limited to storage batteries, and may be capacitors, for example.

-The power conversion system is not limited to the one installed in a vehicle.

40... 1st DCDC converter, 40A... 1st transformation part, 40D... 1st control part, 50... 2nd DCDC converter, 50A... 2nd transformation part, 50D... 2nd control part.

Claims (5)

In a power conversion system including a plurality of power conversion devices (40, 50), each of the plurality of power conversion devices having a transformer unit (40A, 50A) that transforms and outputs an input voltage,
A self-determination unit that is provided corresponding to each of the plurality of transformer units and that determines that an abnormality has occurred in the transformer unit corresponding to itself.
A power conversion system that is provided corresponding to each of the plurality of transformer units, and another determination unit that determines that a transformer unit other than the transformer unit corresponding to itself of the plurality of transformer units is abnormal. .. The power conversion system according to claim 1, wherein each of the plurality of power conversion devices includes the self determination unit and the other determination unit. The power conversion system according to claim 1, wherein only one power conversion device among the plurality of power conversion devices has the self determination unit and the other determination unit. The self-determination unit, based on the output voltage value of the transformer unit corresponding to itself, determines that an overvoltage abnormality on the output side of the transformer unit corresponding to itself has occurred,
The other determination unit, based on the output voltage value of the transformer unit other than the transformer unit corresponding to itself among the plurality of transformer units, the output of the transformer unit other than the transformer unit corresponding to itself among the plurality of transformer units. The power conversion system according to claim 1, wherein it is determined that an overvoltage abnormality has occurred on the side. In a power conversion system applied to a control system including a predetermined electric path (LL),
The plurality of power conversion devices include a first power conversion device (40) and a second power conversion device (50),
The transformer included in the first power conversion device is a first transformer (40A) that transforms an input voltage and outputs the transformed voltage to the predetermined electric path.
The transformer included in the second power conversion device is a second transformer (50A) that transforms an input voltage and outputs the transformed voltage to the predetermined electric path.
The self-determination unit corresponding to the first transformer unit determines, based on the output voltage value (Vout1) of the first transformer unit, that an overvoltage abnormality has occurred on the output side of the first transformer unit. 1 self-determination unit,
The other determination unit corresponding to the first transformer unit determines whether an overvoltage abnormality on the output side of the second transformer unit has occurred, based on the output voltage value (Vout2) of the second transformer unit. 1 other determination unit,
The self-determination unit corresponding to the second transformer unit determines, based on the output voltage value of the second transformer unit, that the overvoltage abnormality on the output side of the second transformer unit has occurred. Is a department
The other determination unit corresponding to the second transformer determines the second other determination based on the output voltage value of the first transformer to determine that an overvoltage abnormality has occurred on the output side of the first transformer. Is a department
A first control unit that controls the output voltage value of the first transformer unit to a first target voltage value (Vtgt1);
A second control unit that controls the output voltage value of the second transformer unit to a second target voltage value (Vtgt2);
The first self-determination unit has determined that an overvoltage abnormality on the output side of the first transformer has occurred, or the second other determination unit has caused an overvoltage abnormality on the output side of the first transformer. A first stop unit that stops the operation of the first transformer unit on condition that it is determined that
The second self-determination unit has determined that an overvoltage abnormality on the output side of the second transformer has occurred, or the first other determination unit has caused an overvoltage abnormality on the output side of the second transformer. A second stop unit that stops the operation of the second transformer unit on the condition that it is determined that
Even when the first stop unit determines that the overvoltage abnormality has occurred by the first self determination unit or the second other determination unit, the first target voltage value or the second target voltage value And, when it is determined that the absolute value of the difference from the output voltage value of the second transformer is smaller than the first threshold value (ΔV1), the operation of the first transformer is continued,
Even when the second stop unit determines that the overvoltage abnormality has occurred by the second self determination unit or the first other determination unit, the second target voltage value or the first target voltage value When the absolute value of the difference between the output voltage value of the first transformer and the second threshold (ΔV2) is smaller than the second threshold (ΔV2), the operation of the second transformer is continued. Conversion system.

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