JP6576846B2 - Power converter - Google Patents

Description

  The present invention relates to a power conversion device.

  Inverters, converters, and choppers, which are power converters, include industrial power converters such as UPS (Uninterruptable Power-supplied System), PCS (Power Conditioning System), AC drives, and hybrid vehicles (HEV: It is widely used in in-vehicle power converters such as Hybrid Electric Vehicles (EVs) and electric vehicles (EVs), power converters for home appliances, and the like. For these power converters, in addition to downsizing, long-life products are desired in which running costs resulting from power converter efficiency and maintenance costs such as component replacement are kept low.

  In addition to the semiconductor module and the cooler, the power conversion device includes a power conversion unit formed of components such as a bus bar for electrically connecting the components and a capacitor for smoothing DC power. In a power converter configured by multi-parallelization of power conversion units, in order to multiply the output by N times, the power conversion units can be handled in N parallel.

  On the other hand, when the operation and stop of the power conversion unit are repeated, the power load applied to the power semiconductor module fluctuates (power cycle) and changes to a high temperature state and a low temperature state. At this time, since the power semiconductor module is composed of materials with different thermal expansion coefficients (insulating members such as copper wiring, solder, silicon chip, resin, and metal cases such as aluminum), thermal stress due to repeated thermal expansion and contraction Occurrence of solder causes cracking of the solder, peeling of the insulating member, and the like, and deteriorates the insulating characteristics and heat dissipation characteristics (thermal resistance characteristics) of the power semiconductor module. As described above, when the operation and stop of the power conversion unit are repeated, thermal fatigue due to the power cycle progresses, causing a failure of the power semiconductor module. Therefore, in order to extend the life of the power conversion unit and the power semiconductor module, operation control without causing thermal fatigue becomes a problem.

  For example, Patent Document 1 proposes a method of estimating the thermal resistance between the chip and the outer case of the power semiconductor module from the temperature rise of the cooling fin.

JP 2012-191849 A

  However, although Patent Document 1 can detect deterioration information of the power semiconductor module with respect to the power cycle, a specific control method for extending the life is a problem.

  Then, an object of this invention is to provide the power converter device which enables the lifetime improvement of a power converter device.

  In order to solve the above problems, for example, a power conversion device having a plurality of power conversion units each including a power semiconductor module, and optimizing the number of operating power conversion units in the power converter according to load power, The power conversion device according to the present invention includes a plurality of power conversion units each including a power semiconductor module and a cooler, and the power conversion unit includes output power load information and the power semiconductor module. Based on the thermal resistance value, the operation and stop of each power conversion unit is controlled, the power conversion unit having the thermal resistance value larger than the predetermined value is set to the operating state, and the thermal conversion value is smaller than the predetermined value. The unit is stopped.

  ADVANTAGE OF THE INVENTION According to this invention, the lifetime of a power converter device can be extended, optimizing the efficiency of a power converter device.

The structure of a three-phase inverter part is shown. It is a figure which shows the power cycle life characteristic example of a power semiconductor module. The block diagram of the inverter 103 in a present Example is shown. The operation | movement and stop switching flow of power semiconductor module PM1 in this example and PM2 are shown. The operation | movement and stop switching flow of power semiconductor module PM1 in the 2nd Embodiment of this invention is shown. The block diagram of the single phase power converter of the inverter in the 2nd Embodiment of this invention is shown. The block diagram of the inverter in the 3rd Embodiment of this invention is shown. It is a structure figure of the single phase power converter 301 in the 4th Embodiment of this invention. The parallel operation switching flow in the 4th Embodiment of this invention is shown.

  Hereinafter, embodiments for carrying out the present invention will be described with reference to the drawings. In the following, a three-phase inverter power converter is taken as an example, but the present invention can also be applied to a single-phase inverter unit, a converter unit, and a DCDC converter.

  FIG. 1 shows a configuration of a three-phase inverter unit.

  The inverter 103 converts DC power between PNs into three-phase AC power. Each phase converter 301, 302, 303 includes a power semiconductor module 20 composed of power semiconductors 21, 22, 23, 24. The inverter control unit 304 controls the switching timing of the DC voltage supplied from the PN terminal in the switching element 21 and the rectifying element 23 of the upper arm and the switching element 22 and the rectifying element 24 of the lower arm provided for each phase. By doing so, it is converted into AC power and output to the AC terminals U, V, W of the phase converters 301, 302, 303.

  In this embodiment, an IGBT (Insulated Gate Bipolar Transistor) is used as the switching element and a diode is used as the rectifying element. However, the present invention is not limited to this, and other types of elements can be applied.

  The inverter 103 according to the present embodiment has a two-level half bridge unit 20 in which an upper arm switching element 21 and a rectifying element 23 and a lower arm switching element 22 and a rectifying element 24 are connected in series. However, it is also possible to apply an inverter, a converter, and a booster having a basic configuration of three levels.

  FIG. 2 is a diagram illustrating an example of power cycle life characteristics of the power semiconductor module. The vertical axis represents the number of power cycle lifetimes, and the horizontal axis represents the power semiconductor module temperature change, showing the relationship between the parameters.

  The power semiconductor module is made up of copper wiring, solder, silicon chip, resin, etc., which is a material with a different coefficient of thermal expansion, and a metal case such as aluminum. Occurrence causes cracking of the solder, peeling of the insulating member, and the like. This degrades the insulation characteristics and heat dissipation characteristics (thermal resistance characteristics) of the power semiconductor module. As shown in FIG. 2, when the temperature change ΔT of the power semiconductor module is large, the internal thermal stress increases, and the number of power cycle lifespans until the characteristics of the power semiconductor module deteriorates decreases.

  FIG. 3 shows an overall configuration diagram of an inverter in the case where a power module in which two phases are connected in parallel is provided.

  Each of the U phase 301, the V phase 302, and the W phase 303 constituting the three-phase inverter is composed of two power semiconductor modules 20. A DC voltage is input to each phase from a DC power supply via a PN terminal, and the power semiconductor module PM1 and the power semiconductor module PM2 have the chip junction temperatures of the power semiconductor devices 21, 22, 23, and 24 inside the power semiconductor module. A temperature sensor 31 (not shown) to be monitored is provided, and temperature information is input to the control unit 304.

  Each of the phase converters 301, 302, and 303 includes a current sensor 32 (shown) that monitors the load current, and the load current information is input to the control unit 304.

  FIG. 4 shows an operation / stop switching flow of the power semiconductor modules PM1 and PM2 in the present embodiment.

  2 When the power semiconductor modules PM1 and PM2 connected in parallel are both operating (step 401), when the output load current becomes equal to or lower than the load current reference value (yes in step 402), one of the power modules is It is determined to stop (step 403). That is, the switching determination to the one-side operation mode is performed in which the power semiconductor IGBTs of both the upper and lower arms are turned off and the other power semiconductor module is brought into the operating state by PWM control. On the other hand, when the output current is not less than the specified value (no in step 402), the two parallel operation (step 401) is continued.

  Next, the control unit 304 calculates the thermal resistance of the two power semiconductor modules PM1 and PM2 based on the temperature sensor 31 attached to the power semiconductor module 20 and the temperature and load current information from the current sensor 32. At this time, when at least one of the thermal resistances of the two power semiconductor modules PM1 and PM2 is equal to or less than the specified value (Yes in Step 404), the process shifts to the one-side operation mode. On the other hand, when the thermal resistance is larger than the predetermined value, two parallel operations (step 401) are performed.

  Next, the calculated thermal resistances of the two power semiconductor modules PM1 and PM2 are compared, and the power semiconductor module having a low thermal resistance is brought into a stopped state (step 405). For example, when the thermal resistance of the power semiconductor module PM1 is larger than the thermal resistance of the power semiconductor module PM2, the power semiconductor module PM1 is continuously operated and the power semiconductor module PM2 is stopped (step 406). On the other hand, when the thermal resistance of the power semiconductor module PM2 is large, the power semiconductor module PM1 is brought into a stopped state (step 407).

  In the one-side operation mode, when the load current becomes equal to or higher than the specified value (Yes in Step 408), the stopped power semiconductor module is set in the operating state and returned to the parallel operation mode.

  On the other hand, the one-side operation is performed while the load current is less than the specified value (No in Step 408) and the thermal resistance of the power semiconductor module operating during the one-side operation satisfies the specified value or less (Yes in Step 410). Continue. At this time, when the thermal resistance of the power semiconductor module operating during the one-side operation becomes equal to or higher than the specified value (no in step 410), the stopped power semiconductor module is operated during the one-side operation, and the two parallel operations are performed. Return to.

  According to the present embodiment, the efficiency of the power converter can be optimized for each load by optimizing the number of operating power conversion units of the power converter based on the power load information. When switching from the operating state to the stopped state and then back to the operating state, the power semiconductor module changes from high temperature to low temperature, and then again changes to high temperature and temperature, increasing the number of power cycle accumulation, and thermal fatigue characteristics due to thermal fatigue inside the power semiconductor module In addition, the insulation characteristics deteriorate. In response to this problem, the present embodiment monitors the thermal resistance and avoids temperature changes (operation to stop control) of the power semiconductor module where the thermal resistance is large, that is, thermal fatigue is progressing. Life can be extended. In addition, since it is possible to determine the thermal resistance value under a condition where the initial thermal resistance characteristic variation of the power module is small, in this embodiment, the determination is performed based on the thermal resistance value.

  FIG. 5 shows an operation / stop switching flow of the power semiconductor modules PM1 and PM2 in the second embodiment of the present invention.

  2 When the power semiconductor modules PM1 and PM2 connected in parallel are both operating (step 501), when the output load current becomes equal to or lower than the load current reference value (yes in step 502), one of the power modules is It is determined to be in a stop state (step 503). That is, the switching determination to the one-side operation mode is performed in which the power semiconductor IGBTs of both the upper and lower arms are turned off and the other power semiconductor module is brought into the operating state by PWM control. On the other hand, when the output current is not less than the specified value (no in step 502), the two parallel operation (step 501) is continued.

  Next, the control unit 304 calculates the thermal resistance of the two power semiconductor modules PM1 and PM2 based on the temperature sensor 31 attached to the power semiconductor module 20 and the temperature and load current information from the current sensor 32. Further, the calculated current thermal resistance value and the initial thermal resistance value are compared, and the thermal resistance increment values of the two power semiconductor modules PM1 and PM2 are calculated. At this time, when at least one of the thermal resistance increment values of the two power semiconductor modules PM1 and PM2 is equal to or less than a specified value (yes in step 504), the mode shifts to the one-side operation mode. . On the other hand, when the thermal resistance increment value is larger than the predetermined value, the two parallel operation (step 501) is performed.

  Next, the calculated thermal resistance increment values of the two power semiconductor modules PM1 and PM2 are compared, and the power semiconductor module having a small thermal resistance increment value is set in a stopped state (step 505). For example, when the thermal resistance increment value of the power semiconductor module PM1 is larger than the thermal resistance increment value of the power semiconductor module PM2, the power semiconductor module PM1 is continuously operated and the power semiconductor module PM2 is stopped (step 506). . On the other hand, when the thermal resistance increment value of the power semiconductor module PM2 is large, the power semiconductor module PM1 is brought into a stopped state (step 507).

  In the one-side operation mode, when the load current becomes equal to or greater than the specified value (Yes in Step 508), the stopped power semiconductor module is set in the operating state and returned to the parallel operation mode.

  On the other hand, while the load current is less than the specified value (No in step 508) and the thermal resistance increment value of the power semiconductor module operating during one-side operation satisfies the specified value or less (yes in step 510), Continue one-sided operation. At this time, when the increment value of the thermal resistance of the power semiconductor module operating during the one-side operation becomes equal to or greater than a specified value (no in step 510), the stopped power semiconductor module is operated during the one-side operation. Return to parallel operation.

  By optimizing the number of operating power conversion units of the power converter based on the power load information, the efficiency of the power converter can be optimized for each load. When switching from the operating state to the stopped state and then back to the operating state, the power semiconductor module changes from high temperature to low temperature, and then again changes to high temperature and temperature, increasing the number of power cycle accumulation, and thermal fatigue characteristics due to thermal fatigue inside the power semiconductor module In addition, the insulation characteristics deteriorate. In response to this problem, the present embodiment monitors the thermal resistance increment value, and avoids a temperature change (operation to stop control) of the power semiconductor module in which the thermal resistance increment value is large, that is, thermal fatigue is progressing. This makes it possible to extend the service life. Further, by using the thermal resistance increment value as a determination criterion, a more suitable determination can be made in consideration of variations in the initial thermal resistance characteristics.

  FIG. 6 shows a configuration diagram of the single-phase power converter 301 of the inverter 103.

  The control unit 304 includes a load current voltage loss data table 305, a thermal resistance storage memory 306, a thermal resistance calculation unit 307, a parallel operation determination unit 308, and a control signal generation unit 309.

  Output load current information and output voltage information from a load current sensor 32 (not shown) are input to the load current voltage loss data table 305.

  The load current voltage loss data table 305 calculates loss information that is the loss amount of the power semiconductor module 20 from the output load current information and the output voltage information, and inputs the loss calculation result to the thermal resistance calculation unit 307.

  The thermal resistance calculation unit 307 receives the loss calculation result, the power semiconductor temperature information of the power semiconductor modules PM1 and PM2, and the temperature information of the power semiconductor module cooling fins included in the power conversion unit 301. Is done. The thermal resistance calculation unit 307 calculates the internal thermal resistance of the power semiconductor module 20 from the loss calculation result, the power semiconductor temperature information, and the power conversion unit cooling fin temperature information. Then, the calculated thermal resistance information of each of the power semiconductor module PM1 and the power semiconductor module PM2 is input to the parallel operation determination unit 308.

  The parallel operation determination unit 308 includes output load current information from a load current sensor 32 (not shown), thermal resistance information of each of the power semiconductor modules PM1 and PM2 from the thermal resistance calculation unit 307, and thermal resistance storage. The initial thermal resistance information of each of the power semiconductor module PM1 and the power semiconductor module PM2 from the memory 306 is input.

  The parallel operation determination unit 308 determines the parallel operation and the one-side operation, and the stop power semiconductor module during the one-side operation, according to the parallel operation and one-side operation switching flow shown in FIGS.

  2 When both the power semiconductor module PM1 and the power semiconductor module PM2 connected in parallel are in operation, when the load current becomes less than the specified value, one of the power modules is stopped, that is, the power semiconductors of both the upper and lower arms The switching determination to the one-side operation mode is performed in which the IGBT is turned off and the other power semiconductor module is put into an operation state by PWM control.

  At this time, the thermal resistance information of the power semiconductor module PM1 and the power semiconductor module PM2 input to the parallel operation determination unit 308 and the initial heat of each of the power semiconductor module PM1 and the power semiconductor module PM2 from the thermal resistance storage memory 306. From the resistance information, the respective thermal resistance increment values of the power semiconductor modules PM1, PM2 are calculated, and at least one of the thermal resistance increment values of the two power semiconductor modules PM1, PM2 is equal to or less than the specified value. When it is, it shifts to the one-side operation mode.

Further, the calculated thermal resistance increment values of the two power semiconductor modules PM1 and PM2 are compared, and the power semiconductor module having a small thermal resistance increment value is set in a stopped state. For example, when the thermal resistance increment value of the power semiconductor module PM1 is larger than the thermal resistance increment value of the power semiconductor module PM2, the power semiconductor module PM1 is continuously operated and the power semiconductor module PM2 is stopped. As described above, the power semiconductor module having a large thermal resistance increment value is continuously operated to cause destruction of the power semiconductor module. By selecting based on the thermal resistance increment information calculated from the resistance and the current thermal resistance, early failure of some power conversion units can be avoided and the life of the power conversion device can be extended. Further, by using the thermal resistance increment value as a determination criterion, it becomes possible to determine a deteriorated device without depending on variations in the initial thermal resistance value.

  FIG. 7 shows a configuration diagram of an inverter in the third embodiment of the present invention.

  Here, the common configuration with FIG. 3 is omitted. The AC outputs of the two power semiconductor modules PM1 and PM2 constituting the single-phase power conversion unit 301 are input to individual reactors 408, respectively.

  Each phase converter 301, 302, 303 includes a current sensor 32 that monitors the load current, and the load current information is input to the control unit 304. Then, the control unit 304 switches between the parallel operation mode and the one-side operation mode according to the load current information.

  According to the present embodiment, the AC outputs of the two power semiconductor modules PM1 and PM2 are connected to the individual reactors 408, so that current imbalance between the two power semiconductor modules can be avoided. If two power semiconductor modules PM1 and PM2 are connected to a common reactor 408, impedance variation from each AC terminal of the two power semiconductor modules PM1 and PM2 to the reactor 408, or two power semiconductor modules Due to variations in characteristics of PM1 and PM2, output current imbalance between power semiconductor modules becomes a problem. On the other hand, by providing each reactor 408 individually, the impedance from the output load terminal to the AC terminal of each power semiconductor module is dominated by the impedance of each reactor 408, so that the two power semiconductor modules PM1, PM2 Current imbalance due to characteristic variation can be reduced.

  For example, in a power converter in which load power fluctuates, such as a power converter such as an elevator, PCS, or general-purpose inverter, the number of operating power conversion units of the power converter is optimized based on the power load information. The efficiency of the power converter can be optimized for each load. Further, by selecting the power conversion unit that operates and stops based on the thermal resistance information, it is possible to avoid early failure of some of the power conversion units and extend the life of the power conversion device.

  Furthermore, according to the load current information, switching between the parallel operation mode and the one-side operation mode, and by setting the number of reactors energized at light load among the reactors connected to each power semiconductor module to one side, the fixed loss of the reactor ( (Iron loss) can be reduced, and the power conversion efficiency at light load can be improved.

  FIG. 8 is a structural diagram of the single-phase power conversion unit 301 in the fourth embodiment of the present invention.

  The single-phase power converter 301 includes three power conversion units 30a, 30b, and 30c, an interphase bus bar 34 that connects DC terminals (P and N terminals) of each power conversion unit, three reactors 408, and three AC bus bars. 33, each power conversion unit includes a capacitor 25, a control unit board 304, a power semiconductor module 20, a power semiconductor module cooling fin 29, and a main bus bar 35 that electrically connects the capacitor and the power semiconductor module. Contains.

  The AC output terminal of each power conversion unit is connected to an individual AC bus bar and a reactor, respectively.

  The single-phase power conversion unit 301 including three power conversion units switches between three parallel operation, two parallel operation, and one parallel operation based on the two load current specified values P1 and P2. The load current regulation value is P1> P2, and when the load current> P1, three parallel operations are performed, when P1> load current> P2, two parallel operations are performed, and when P2> load current, one parallel operation is determined. .

  FIG. 9 shows a parallel operation switching flow in the present embodiment. Here, it is assumed that the specified load current value P1 is larger than the specified load current value P2.

  The control unit 304 uses the load current information and temperature information from the power conversion unit to select the number of parallel operations and the operation / stop power conversion unit.

  For example, in the 3-parallel power conversion unit operation (step 901), when the load current is P1 or less and P2 or less (yes in step 902, yes in step 903), one-parallel operation determination is performed (step 904). Here, when the output load current is larger than the specified value P1 (no in step 902), the three parallel operation is continued (step 901).

  Returning to step 904, when the thermal resistance increment value of at least two units of the power semiconductor modules PM among the three parallel power conversion units is equal to or less than the specified value (yes in step 905), the thermal resistance increments of each power semiconductor module PM. The values are compared (step 906), and the two power conversion units having a small thermal resistance increment value are stopped (step 907).

  Returning to step 803, if the load current is P2 or less (no in step 903), two parallel operations are performed (step 908). In addition, among the three parallel power conversion units, when the increment of the thermal resistance of the power semiconductor module PM is equal to or less than the specified value (no in step 905, yes in step 909), two parallel operations A determination is made (yes in step 909). Among the three parallel power conversion units, when the thermal resistance increment value of at least one unit of the power semiconductor module PM is equal to or less than the specified value, the thermal resistance increment value of each power semiconductor module PM is compared (step 910), and the thermal resistance is compared. One power conversion unit with a small increment value is stopped (step 911).

  According to the present embodiment, by connecting power conversion units 30 connected in parallel to individual reactors 408, current imbalance between power semiconductor modules in each unit can be avoided.

  Further, in the single-phase power conversion unit in which the power conversion units 30 are arranged in parallel, the allowable output capacity of the power conversion device can be easily adjusted by changing the number of parallel connections of the same unit. That is, the efficiency of the power conversion device can be optimized for each load by optimizing the number of operating power conversion units of the power converter based on the power load information.

  Furthermore, according to the load current information, switching between the parallel operation mode and the one-side operation mode, that is, among the reactors connected to each power semiconductor module, the number of reactors energized at the time of light load is set to one side. Fixed loss (iron loss) can be reduced, and power conversion efficiency at light loads can be improved.

  Although the embodiments described above refer to single-phase / three-phase inverters, application to different power converters is also possible, and the present invention is not limited to the configuration of the above-described embodiments.

20 ... 2 level half bridge part, power semiconductor module 21, 22 ... switching element (IGBT)
23, 24 ... Rectifier element (diode)
25 ... Capacitor element 29 ... Power semiconductor module cooling fin 30 ... Power conversion unit 31 ... Temperature sensor 32 ... Current sensor 33 ... AC bus bar 34 ... DC connection bus bar 35 ... Bus bar 103 ... Inverter 301 ... Inverter U-phase power conversion unit 302 ... Inverter V-phase power conversion unit 303 ... inverter W-phase power conversion unit 304 ... inverter control unit 305 ... load current voltage loss data table 306 ... thermal resistance storage memory 307 ... thermal resistance calculation unit 308 ... parallel operation determination unit 309 ... power semiconductor module control Signal generation unit 408 ... reactor 502 ... inverter AC output terminal

Claims (4)

A plurality of power semiconductor modules;
A power semiconductor module control unit that controls the plurality of power semiconductor modules;
The power semiconductor module control unit sets a power semiconductor module in which a thermal resistance value of the power semiconductor module is larger than a predetermined value in an operating state, and puts a power semiconductor module in which the thermal resistance value is smaller than a predetermined value in a stopped state. The power conversion device according to claim 1,
The power semiconductor module has a temperature sensor that detects the temperature of a built-in power semiconductor element,
The power semiconductor module control unit is a power conversion device that obtains a thermal resistance value of each power semiconductor module based on a temperature detection signal output from the temperature sensor. The power conversion device according to claim 1 is:
A current sensor for monitoring an output load current value output from the power converter;
The power semiconductor module control unit, when the output current value obtained by the current sensor is smaller than the load current reference value, the power conversion apparatus for controlling at least one stopped of the power semiconductor module.   The power converter device described in Claim 1 is provided with a some reactor, These power semiconductor modules are each connected with the said each reactor individually, The power converter device characterized by the above-mentioned.

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