JP5473399B2 - Overheat protection device - Google Patents

Description

  The present invention relates to a power converter, and more particularly to an overheat protection device that performs overheat protection of a main circuit element used in the power converter.

  In a conventional power converter, the temperature of a protection target such as a main circuit element of the inverter, a regenerative resistor or a load is detected by a temperature detector such as a thermistor, and the inverter is turned on when the detected temperature is equal to or higher than a preset temperature. It is common to perform overload protection by stopping. However, depending on the installation state of the protection target such as the main circuit element and the temperature detector, there is a problem that overload protection against a rapid temperature rise may not be possible because heat conduction takes time.

  On the other hand, as a means for solving such a problem, the conventional technique shown in Patent Document 1 below is used when the integrated value of the current command and the output current exceeds a preset threshold without using a temperature detector. It is configured to perform overload protection by stopping the inverter. Specifically, when the load current is detected, the power loss of the main circuit element is obtained from the load current, and the integrated value of the power loss for each predetermined time is obtained, this integrated value indicates the amount of power loss within the predetermined time. It will be. Since the temperature rises in proportion to the amount of power loss, it is compared with a preset value. When the measured integrated value exceeds the set value, the load current is limited or cut off to prevent an abnormal temperature rise of the apparatus.

Japanese Patent Laid-Open No. 05-056557

  However, the prior art disclosed in Patent Document 1 has a problem that when the use environment (ambient temperature) is low, the overload protection setting becomes conservative, and the performance of the main circuit element cannot be fully exhibited. . That is, the power converter changes overload characteristics depending on the ambient temperature. For example, the power that can be supplied to the main circuit element when the ambient temperature is low is the power that can be supplied to the main circuit element when the ambient temperature is high. Can be larger than Therefore, if overload protection is set assuming that the ambient temperature is high as in the past, the performance of the main circuit elements can be fully utilized when the power converter is operated in an environment where the ambient temperature is low. There was a problem that there might not be.

  The present invention has been made in view of the above, and provides an overheat protection device capable of maximizing the performance of a power converter while enabling overload protection according to use conditions. Objective.

  In order to solve the above-described problems and achieve the object, the present invention provides a power converter including a power converter composed of a plurality of semiconductor switching elements and a control unit that controls the operation of the power converter. In an overheat protection device that outputs an overload protection signal that stops the power converter to the control unit, current detection that detects a current supplied from the power converter to the load and outputs it as a load current detection value A temperature detection unit that detects an ambient temperature of the inverter main circuit element and outputs the detected temperature as an ambient temperature detection value, and estimates a junction temperature of the inverter main circuit element based on the load current detection value and the ambient temperature detection value An overload protection unit that calculates a value and outputs the overload protection signal according to the level of the estimated junction temperature value.

  According to this invention, the load current detection circuit that detects the load current and the temperature detection unit that measures the temperature of the radiating fin of the inverter, etc. are provided, and the junction temperature of the main circuit element is estimated according to the operating environment of the power converter. Since the operation of the power converter is interrupted when the junction temperature exceeds the threshold value, the maximum performance of the power converter can be used while enabling overload protection according to the usage conditions. There is an effect that can be.

FIG. 1 is a diagram illustrating the configuration of the overheat protection device according to the first embodiment of the present invention. FIG. 2 is a diagram for explaining a state in which heat generated in the main circuit element moves around the radiating fin. FIG. 3 is a diagram for explaining a state observer inside the temperature estimation unit. FIG. 4 is a diagram illustrating a configuration of an overload protection unit that receives a current command value. FIG. 5 is a diagram illustrating the configuration of the overheat protection device according to the second embodiment of the present invention.

  Embodiments of an overheat protection device according to the present invention will be described below in detail with reference to the drawings. Note that the present invention is not limited to the embodiments.

Embodiment 1 FIG.
FIG. 1 is a diagram illustrating the configuration of the overheat protection device according to the first embodiment of the present invention. The power converter shown in FIG. 1 includes a converter 3 and an inverter 2 as main components. The control unit 1 generates a current command value 9, and the inverter 2 supplies a load current corresponding to the current command value 9 to a load 4 such as a motor.

  The load current detection unit 14 detects the current supplied to the load 4 and outputs it as a load current detection value 10. The temperature detector 5 is installed in the vicinity of the radiation fin of the inverter main circuit element, detects the ambient temperature of the radiation fin, and outputs it as an ambient temperature detection value Ta. The overload protection unit 20 includes a temperature estimation unit 6 that estimates the junction temperature of the inverter main circuit element, and a comparator 8 that is a comparison unit. The load current detection unit 14, the temperature detection unit 5, and the overload protection unit 20 described above are referred to as an overheat protection device.

  Note that the ambient temperature detection value Ta is not limited to the ambient temperature of the radiating fin, and for example, the ambient temperature of the inverter main circuit element may be used. Further, even if the current detection means is not arranged in all the three connections connecting the inverter 2 and the load 4, for example, CT is arranged in two connections of the u phase and the v phase, and CT is arranged in the connection of the W phase. The arrangement may be such that the W-phase current iW is obtained by calculation without being arranged.

(Overload protection unit)
Hereinafter, the outline of the operation of the overload protection unit 20 will be described. First, the temperature estimation unit 6 calculates the load current detection value 10 detected by the load current detection unit 14 and the ambient temperature detection value Ta from the temperature detection unit 5. Based on the above, a junction temperature estimated value (hereinafter simply referred to as “estimated value”) 11 of the inverter main circuit element is calculated. Next, the comparator 8 compares the estimated value 11 with a preset overload protection set value (hereinafter simply referred to as “set value”) 7, and the chip temperature Tc of the inverter main circuit element is larger than the set value 7. In the case, the overload protection signal 12 is output. The control unit 1 stops the inverter 2 according to the overload protection signal 12 output from the overload protection unit 20 and performs overload protection of the power converter.

  FIG. 2 is a diagram for explaining a state in which heat generated in the main circuit element moves around the radiating fin, and FIG. 3 is a diagram for explaining a state observer inside the temperature estimation unit. .

  In FIG. 2, when the semiconductor chip 31 as the main circuit element generates heat, the chip temperature Tc rises, but the semiconductor chip 31 is cooled by the amount of heat Qcf moving from the semiconductor chip 31 to the radiation fin 32. Similarly, the heat radiation fin 32 is cooled by the amount of heat Qfa moving from the heat radiation fin 32 to the outside. Thus, the temperature estimation unit 6 shown in FIG. 1 estimates the temperature of the semiconductor chip 31 from the relationship between the heat generation and the movement of the heat amount.

Hereinafter, the calculation by the temperature estimation unit 6 will be described in detail. First, symbols used for the calculation are defined as follows.
Tc: Chip temperature of the inverter main circuit element Tf: Radiation fin temperature Ta: Ambient temperature detection value W: Chip heat generation per unit time Qcf: Heat transferred from the semiconductor chip to the heat dissipation fin Qfa: Heat dissipation from the heat dissipation fin to the surroundings Amount of heat Cc: heat capacity of semiconductor chip Cf: heat capacity of radiating fin Kcf: constant proportional to reciprocal of thermal resistance between semiconductor chip and radiating fin Kfa: constant proportional to reciprocal of thermal resistance between radiating fin and air

  The amount of heat Qcf transferred from the semiconductor chip 31 to the radiation fins 32 is proportional to the temperature difference between the two as shown in the equation (1).

  It is assumed that the temperature Tc of the semiconductor chip 31 is equal to the junction temperature. The amount of heat Qfa moving to the outside from the radiating fin 32 is proportional to the temperature difference between the two as shown in the equation (2).

  The temperature Tc of the semiconductor chip 31 is proportional to the amount of heat accumulated in the semiconductor chip 31 as shown in the equation (3).

  The chip heat generation amount W per unit time is given by equation (4). However, Rj is the resistance value of the junction. As described above, the loss calculation unit 40 shown in FIG. 3 calculates the chip heat generation amount W, which is a heat loss, based on the load current detection value 10.

  The temperature Tf of the radiating fin 32 is proportional to the amount of heat accumulated in the radiating fin 32 as shown in the equation (5).

  When the expressions (3) and (5) are differentiated by time and the expressions (1) and (2) are substituted, the expressions (6) and (7) are obtained.

  The expressions (6) and (7) are written in the state equation with the state variable as [Tc Tf Ta], and the expressions (8) and (9) are obtained.

  Expressions (8) and (9) are expressed as Expression (10).

  However, A, B, C, D, x, and y are as follows. The content of equation (10) is shown on the upper side of FIG.

  Further, when the state observer is constructed using the observer gain h, the system equation of the state observer shown at the lower side of FIG. Here, x2 is a state estimation vector, and y1 is an output estimation signal.

  The chip temperature estimated value Tc1 is obtained by the equation (12) from the state estimation vector x2. The detected ambient temperature value Ta shown in FIG. 1 is added to the estimated chip temperature value Tc1 obtained by the equation (12), and is output to the comparator 8 as the estimated junction temperature value 11.

  As described above, the first control system 41 shown in FIG. 3 estimates the fin temperature of the inverter main circuit element based on the chip heat generation amount W. The second control system 42 has a control system equivalent to the first control system 41, estimates the fin temperature of the inverter main circuit element, and the fin temperature estimated by the first control system 41 and the self estimate. It functions as an observer incorporating a feedback system that feeds back the difference value from the fin temperature by the observer gain h.

  The comparator 8 shown in FIG. 1 compares the estimated value 11 output from the temperature estimating unit 6 with the set value 7, and controls the overload protection signal 12 when the estimated value 11 is larger than the set value 7. The control unit 1 stops the inverter 2. In this way, the overheat protection device according to the present embodiment performs overload protection of the power converter.

  The overheat protection device according to the present embodiment may be configured to calculate the estimated value 11 using the current command value 9 instead of the load current detection value 10. FIG. 4 is a diagram illustrating a configuration of the overload protection unit 20 that receives the current command value 9.

  The estimation unit 6 shown in FIG. 5 outputs an estimated value 11 based on the detected ambient temperature value Ta and the current command value 9. In this case, the loss calculation unit 40 shown in FIG. 3 calculates the chip heat generation amount W based on the detected bus current value 13.

  As described above, the overheat protection device according to the present embodiment estimates the junction temperature of the inverter main circuit element using the ambient temperature detection value Ta and the load current detection value 10 of the radiation fin 32. Therefore, when the power converter is operated in an environment where the ambient temperature of the main circuit element is low, it is solved that the performance of the main circuit element cannot be fully utilized, and the performance of the power converter is maximized. It is possible to perform overload protection while pulling it out.

Embodiment 2. FIG.
FIG. 5 is a diagram illustrating the configuration of the overheat protection device according to the second embodiment of the present invention. Hereinafter, the same parts as those of the first embodiment are denoted by the same reference numerals, description thereof is omitted, and only different parts are described. In order to protect the converter main circuit element, the overheat protection device according to the second embodiment detects the ambient temperature of the converter main circuit element and uses the bus current value detection value 13 to generate the overload protection signal 12. It is configured to output.

  The overheat protection device according to the second embodiment, the overload protection 20 having the comparator 8 and the temperature estimation unit 6, and the temperature detection unit 5 installed in the vicinity of the radiation fin 32 of the main circuit element of the converter 3 are configured. .

  Based on the bus current value detection value 13 detected by the bus current detection unit 15 and the ambient temperature detection value Ta, the temperature estimation unit 6 calculates the junction temperature estimation value of the converter main circuit element by the calculation described in the first embodiment. 11 is calculated. The ambient temperature detection value Ta is not limited to the ambient temperature of the radiating fins, and the ambient temperature of the converter main circuit element may be used.

  The estimation unit 6 shown in FIG. 5 outputs an estimated value 11 based on the detected ambient temperature value Ta and the detected bus current value 13. In this case, the loss calculation unit 40 shown in FIG. 3 calculates the chip heat generation amount W based on the detected bus current value 13.

  Similarly to the first embodiment, the comparator 8 compares the estimated value 11 with the set value 7, and outputs an overload protection signal 12 to the control unit 1 when the estimated value 11 is larger than the set value 7. The control unit 1 stops the inverter 2. In this way, the overheat protection device according to the present embodiment performs overload protection of the power converter.

  As described above, the overheat protection device according to the present embodiment estimates the junction temperature of the converter main circuit element using the detected ambient temperature value Ta and the bus current value detected value 13 of the converter main circuit element. Thus, overload protection can be performed while maximizing the performance of the power converter.

  As described above, the overheat protection device according to the present invention is applicable to an overheat protection device that performs overheat protection of a main circuit element, and in particular, maximizes the performance of a power converter used under various temperature environments. It is useful as an invention that can be utilized to the limit.

DESCRIPTION OF SYMBOLS 1 Control part 2 Inverter 3 Converter 4 Load 5 Temperature detection part 6 Temperature estimation part 7 Overload protection setting value 8 Comparator (comparison part)
9 Current command value 10 Load current detection value 11 Junction temperature estimation value 12 Overload protection signal 13 Bus current detection value 14 Load current detection unit 15 Bus current detection unit 20 Overload protection unit 31 Semiconductor chip 32 Radiation fin 40 Loss calculation unit 41 1st control system 42 2nd control system Tc Chip temperature of inverter main circuit element Tf Heat dissipation fin temperature Ta Ambient temperature detection value W Chip heat generation per unit time Qcf Heat transfer from semiconductor chip to heat dissipation fin Qfa Heat dissipation fin Of heat radiated from

Claims (3)

Applied to a power converter comprising a power converter composed of a plurality of semiconductor switching elements and a control unit for controlling the operation of the power converter, and controls the overload protection signal for stopping the power converter In the overheat protection device having the overload protection unit that outputs to the unit,
The overload protection unit is
Based on the detected value of the load current supplied to the load from the power converter and the detected value of the ambient temperature of the inverter main circuit element, a loss calculation unit that calculates heat loss
A first control system for estimating a fin temperature of the inverter main circuit element based on the heat loss calculated by the loss calculation unit;
A fin having a control system equivalent to the first control system, estimating the fin temperature based on the heat loss calculated by the loss calculation unit, and the fin temperature and the fin estimated by the first control system; A second control system as an observer incorporating a feedback system that multiplies the difference value with temperature by an observer gain and feedback;
Using the value drawn from the inside of the second control system as the junction temperature estimated value of the inverter main circuit element, the junction temperature estimated value is compared with a predetermined threshold value, and the junction temperature estimated value is determined as the predetermined threshold value. A comparator that outputs the overload protection signal,
An overheat protection device comprising: Applied to a power converter comprising a power converter composed of a plurality of semiconductor switching elements and a control unit for controlling the operation of the power converter, and controls the overload protection signal for stopping the power converter In the overheat protection device having the overload protection unit that outputs to the unit,
The overload protection unit is
A loss calculation unit that calculates heat loss based on a detected value of the ambient temperature of the inverter main circuit element and a current command value that is output from the control unit and controls the operation of the power converter ;
A first control system for estimating a fin temperature of the inverter main circuit element based on the heat loss calculated by the loss calculation unit;
A fin having a control system equivalent to the first control system, estimating the fin temperature based on the heat loss calculated by the loss calculation unit, and the fin temperature and the fin estimated by the first control system; A second control system as an observer incorporating a feedback system that multiplies the difference value with temperature by an observer gain and feedback;
Using the value drawn from the inside of the second control system as the junction temperature estimated value of the inverter main circuit element, the junction temperature estimated value is compared with a predetermined threshold value, and the junction temperature estimated value is determined as the predetermined threshold value. A comparator that outputs the overload protection signal,
An overheat protection device comprising: Applied to a power converter comprising a power converter composed of a plurality of semiconductor switching elements and a control unit for controlling the operation of the power converter, and controls the overload protection signal for stopping the power converter In the overheat protection device having the overload protection unit that outputs to the
The overload protection unit is
Based on the detected value of the bus current and the detected value of the ambient temperature of the inverter main circuit element, a loss calculation unit that calculates heat loss,
A first control system for estimating a fin temperature of the inverter main circuit element based on the heat loss calculated by the loss calculation unit;
A fin having a control system equivalent to the first control system, estimating the fin temperature based on the heat loss calculated by the loss calculation unit, and the fin temperature and the fin estimated by the first control system; A second control system as an observer incorporating a feedback system that multiplies the difference value with temperature by an observer gain and feedback;
Using the value drawn from the inside of the second control system as the junction temperature estimated value of the inverter main circuit element, the junction temperature estimated value is compared with a predetermined threshold value, and the junction temperature estimated value is determined as the predetermined threshold value. A comparator that outputs the overload protection signal,
An overheat protection device comprising:

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