JP2006158128A - Power conversion device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To enable suitable cooling down of each semiconductor element regardless of individual mode operations. <P>SOLUTION: The power conversion device has three levels of which DC voltage is bisected. A plurality of switching elements Q1 to Q4 and cooling fins 31 to 33, 37 to 39 arranged on both sides of the respective switching elements Q1 to Q4, and respective flywheel diodes D1 to D4 constituting a pair with the respective switching elements and cooling fins 26 to 30 arranged on both sides of the respective flywheel diodes are constructed by each stack 2, 1. Cooling fans 26-31, 27-32, 28-35, 29-38, 30-39 are connected so as to be a series water system, which are arranged on the same sides of the switching elements Q1 to Q4 and the flywheel diodes D1 to D4 constituting a pair of with the switching elements Q1 to Q4. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a power converter having a stack for flat semiconductor elements in which a plurality of flat semiconductor elements and heat sinks are alternately stacked.

  Conventionally, there are three levels of power converters among power converters. In this three-level power converter, clamp capacitors C1 and C2 are connected between P and N of a DC voltage converted by a converter (not shown) connected to a three-phase AC power source as shown in FIG. The DC voltage is divided by creating an intermediate potential point 0. For example, the U phase among the three phases constituting the inverter is described. Among the switching elements Q1 to Q4 that are serially connected between P and N and are capable of self-extinguishing, the switching elements Q1 and Q2 are turned on to increase the level Potential point voltage (P point voltage), switching elements Q2 and Q3 are turned on, intermediate point voltage (0 point voltage), switching elements Q3 and Q4 are turned on and low potential point voltage (N point voltage) is selectively extracted. This constitutes a so-called three-level inverter. Further, flywheel diodes D1 to D4 are connected in parallel so as to form a pair with each of the switching elements Q1 to Q4. In addition, the V phase and W phase which are other phases which comprise an inverter have the structure similar to the U phase mentioned above.

  Such a three-level power conversion device has a stack for a flat semiconductor element. Specifically, as shown in FIG. 3, for example, a flywheel diode stack 1 composed of flywheel diodes D1 to D4 and The switching element stack 2 composed of switching elements Q1 to Q4 such as IGBT (Insulated Gate Bipolar Transistor) is configured as an independent stack, and power loss due to energization to the switching elements Q1 to Q4 is given priority as indicated by the arrows in the figure. The structure of the cooling water system for compensating automatically. That is, in the cooling water system of the flywheel diodes D1 to D4 and the switching elements Q1 to Q4, the cooling water flowing from the cooling inlet side is sent to the cooling fins 3 to 6 corresponding to the switching elements Q1 to Q4, where the switching element Q1 After heat exchange by heat generation of ~ Q4, the heat is sent to the cooling fins 7 to 10 corresponding to the flywheel diodes D1 to D4. Therefore, in the cooling water system having such a configuration, the cooling water having the initial water temperature is not supplied to the flywheel diodes D1 to D4, and is heated by the heat generated by the switching elements Q1 to Q4 when the switching elements Q1 to Q4 are cooled. Cooling water is supplied.

  In the original cooling of the semiconductor element, the allowable junction temperature (internal temperature) of the semiconductor element is defined to be 125 ° C. or lower, and it is fundamental to sequentially cool the semiconductor elements with more severe heat loss. For the purpose of simply cooling the semiconductor elements, a cooling water system may be provided for each semiconductor element. However, as many cooling water systems as the number of semiconductor elements are required, and the amount of water (flow rate) used for the power converter is also large. A large amount. As a result, the capacity of the cooling device that circulates the cooling water increases, the product cost and occupied space increase, and the degree of freedom in device design is lost.

  Therefore, when considering the situation as described above, the amount of cooling water can be reduced by adopting a series water system configuration as much as possible, rather than a parallel water system in which a cooling water system is provided for each semiconductor element. This also leads to a compact cooling device. Furthermore, with the downsizing of the power conversion device and the cooling device, the limited space can be effectively used, and the degree of freedom in designing the system including each device can be increased. However, in the case of a series water system, depending on the distribution of heat loss to each semiconductor element, it is influenced by the water temperature warmed toward the downstream, and it is considered that the optimum cooling effect cannot be obtained.

  In recent years, the loss generated in each semiconductor element tends to increase as the capacity of the power converter increases. Furthermore, as power conversion devices and cooling devices become more compact and lower in cost, the semiconductor elements become closer to each other and the generated loss increases, so it is essential to cool the semiconductor devices optimally. Become. In particular, in an apparatus using water cooling, since the cooling capacity and cooling efficiency are determined by the configuration of the cooling water system, it is desired to grasp the operation status of the apparatus and realize the configuration of the cooling water system for the semiconductor element. .

  By the way, the cooling water system of the power converter as described above is configured to cool the flywheel diodes D1 to D4 after cooling the switching elements Q1 to Q4 using the cooling water flowing from the cooling inlet side. It is doubtful whether such a configuration of the cooling water system increases the cooling capacity and the cooling efficiency from the operating state of the apparatus.

  Thus, when considering an operation pattern (mode) in this type of power conversion device, there are converter mode and inverter mode operations. Normally, during the converter mode operation, the flywheel diodes D1 to D4 are main heat sources, and among them, the heat generation amount of the flywheel diodes D1 and D4 is large. On the other hand, during the inverter mode operation, the switching elements Q1 to Q4 are main heat generation sources, and among them, the heat generation amounts of the switching elements Q1 and Q4 are large.

  However, in the three-level power conversion device that divides the DC voltage into two, it is in the switching elements Q1 to Q4 that are unloaded at the time of converter mode operation, and the switching elements Q2 and Q3 maintain the water temperature even in the unloaded state. There is heat generation to the extent that it increases. Conversely, during the inverter mode operation, the flywheel diodes D1 to D4 do not generate heat.

  As a result, in the case of the configuration of the cooling water system shown in FIG. 3, the cooling water rising by the switching elements Q2 and Q3 is sent to the flywheel diodes D1 to D4 on the downstream side, and the cooling capacity of the flywheel diodes D1 to D4 and The cooling efficiency is lowered and the optimum cooling effect cannot be obtained.

  In addition, the generation loss of the semiconductor element increases as the capacity of the power conversion device increases. In this case, the following problem occurs. That is, during the converter mode operation, when the flywheel diodes D1 to D4 that are originally cooled are supplied with the cooling water heated by the heat generated by the switching elements Q2 and Q3, the cooling capacity of the flywheel diodes D1 to D4 is increased. There is a problem that it becomes difficult to suppress the temperature to an allowable junction temperature of 125 ° C. or lower.

  The present invention has been made in view of the above circumstances, and constitutes a cooling water system that enables optimum cooling of each semiconductor element in spite of each mode operation, and a power conversion device that improves cooling capacity and cooling efficiency. The purpose is to provide.

(1) In order to solve the above problems, a three-level power converter according to the present invention that divides a DC voltage into two parts includes a plurality of switching elements, cooling fins disposed on both sides of each of the switching elements, Each flywheel diode paired with the switching element and cooling fins arranged on both sides of each flywheel diode are configured in separate stacks, and the same flywheel diode paired with the switching element and the switching element It is the structure which connected the water cooling fans arrange | positioned at the side so that it might become a serial water system.

  Since the present invention is configured as described above, the water cooling fans disposed on the same side of the switching element and the flywheel diode paired with the switching element are configured in a series water system. It can be configured with a cooling water system that is significantly smaller than the number of semiconductor elements consisting of switching elements and multiple flywheel diodes, etc., which can greatly reduce the amount of cooling water and realize a compact power conversion device including a cooling device. it can.

(2) Further, according to the present invention, in the configuration of the power conversion device described in the above (1), the cooling fin disposed on the flywheel diode side is more cooled than the cooling fin disposed on the switching element side. If installed on the upstream side of the water, the switching element with a heat generation loss that raises the water temperature at the time of no load in converter mode operation is cooled by water flow downstream of the flywheel diode. The accompanying switching element does not adversely affect other semiconductor elements, and an optimal cooling water system can be realized. Therefore, it is possible to increase the cooling capacity and the cooling efficiency by the configuration in which the semiconductor elements do not affect the cooling of the other semiconductor elements. Also, by combining with the configuration of (1) etc., the semiconductor element that is the main heat generation target during each mode operation can be cooled by the initial cooling water that is not thermally affected by the semiconductor elements other than itself. Thus, the cooling capacity and the cooling efficiency can be increased, and the junction temperature of the semiconductor element can be surely suppressed to a predetermined temperature or lower.

  Further, according to the present invention, in the configuration of the power conversion device described in the above item (1), a plurality of flywheel diodes constituting the flywheel diode stack are cooled by independent water systems, and the flywheel diodes having these flywheel diodes are cooled. By configuring the wheel diode stack and the switching element stack having the switching elements as a total of five water systems, it is possible to realize an optimum cooling water system using relatively simple five systems.

  ADVANTAGE OF THE INVENTION According to this invention, regardless of each mode driving | operation, the cooling water system which enables the optimal cooling of each semiconductor element can be comprised, and the power converter device which can improve cooling capacity and cooling efficiency can be provided.

  Hereinafter, an embodiment of a power converter according to the present invention will be described with reference to FIG. In the figure, the same parts as those in FIG.

  FIG. 1 is a diagram showing a configuration of a cooling water system of a power converter, and is branched from an initial cooling water supply pipe 20 into, for example, five flow pipes 21 to 25 and introduced into a flywheel diode stack 1. The flywheel diode stack 1 has a configuration in which water-cooled fins 26 to 30 and flywheel diodes D1 to D4 are alternately stacked. That is, the respective flow path pipes 21 to 25 branched from the initial cooling water supply pipe 20 are individually connected to the corresponding water cooling fins 26 to 30 of the flywheel diode stack 1, and the initial cooling water is supplied to the respective flow path pipes 21 to 21. 25 and supplied to each water cooling fin 26-30. Therefore, each flywheel diode D1-D4 is cooled by the water cooling fins 26-30 arrange | positioned at both sides.

  On the other hand, a switching element stack 2 is provided independently of the flywheel diode stack 1. In the switching element stack 2, switching elements Q1 to Q4 such as IGBTs (Insulated Gate Bipolar Transistors) including auxiliary fins DP and DN are alternately stacked. And the water cooling fins 26 and 31, 27 and 32, 28 and 35, 29 and 38, 30 and 39 are connected by connection piping 34,42,43,44,45, and cooling water is from each water cooling fin 26-30. The switching elements Q1 to Q4 including the auxiliary rectifying elements DP and DN are cooled by being sent to the cooling fins 31, 32, 35, 38, and 39 configured as the switching element stack 2 through the corresponding connection pipes 41 to 45. That is, in this power converter, the water-cooled fins 26 to 30 and the cooling fins 31, 32, 35, 38, and 39 are connected via the connection pipes 41 to 45 to constitute a so-called series water system.

  And the output side of each cooling fin 31, 32, 35, 38, 39 is connected to the cooling outlet side piping 40 through the cooling fins 33, 34, 36, 37 on the intermediate side of the switching element stack 2, and by heat exchange. Warmed cooling water is output from the cooling outlet pipe 40.

  In such a power conversion device, the flywheel diode stack 1 and the switching element stack 2 have an independent stack configuration. Further, the water cooling fins 26 and 31, 27 and 32 on the same side of the flywheel diode D1 paired with the switching element Q1 form a series water system by the connection pipes 41 and 42, respectively, and also pair with the switching element Q4. The water cooling fins 29 and 38, 30 and 39 on the same side of the flywheel diode D4 form a series water system by connecting pipes 44 and 45, respectively.

  Therefore, according to the embodiment as described above, the following effects are achieved by the configuration of the series water system unique to the present invention.

(1) Regarding the semiconductor power conversion device according to the present invention having the configuration of the cooling water system shown in FIG. 1, the relationship between the converter mode operation and the inverter mode operation and the cooling of the semiconductor element while changing the power factor of the power conversion device. I'll think about it.

  In the converter mode operation, the flywheel diode stack 1 is subject to heat generation, among which the flywheel diodes D1 and D4 generate heat mainly. Meanwhile, the switching element stack 2 is unloaded. On the contrary, in the inverter mode operation, the switching element stack 2 becomes a heat generation target, and among them, the switching elements Q1 and Q4 generate heat mainly. Meanwhile, the flywheel diode stack 1 is unloaded. Therefore, in each mode operation, the heat generation of the flywheel diodes D1 and D4 or the heat generation of the switching elements Q1 and Q4 causes the water cooling fins 26 and the water cooling fins 31 to be connected by the connection pipe 41, and the water cooling fins 27 and the water cooling fins are connected. 32 is connected by the connecting pipe 42, the water-cooled fins 29 and the water-cooled fins 38 are connected by the connecting pipe 44, and the water cooling fins 30 and the water-cooled fins 39 are connected by the connecting pipe 45. The number of cooling water systems can be significantly smaller than the number of semiconductor elements comprising the switching elements Q1 to Q4 and the plurality of flywheel diodes D1 to D4, etc., the amount of cooling water can be greatly reduced, and power conversion including a cooling device The apparatus can be made compact.

  In addition, the semiconductor elements such as the diodes D1 and D4 and the switching elements Q1 and Q4 that are main heat generation targets in each mode operation can be cooled by the initial cooling water that is not thermally affected by the semiconductor elements other than itself. An optimal cooling water system can be realized.

(2) According to the semiconductor power conversion device according to the present invention, the initial water flow of the initial cooling water pipe 20 is performed from the flywheel diode stack 1 side. As a result, the cooling water at the initial water temperature is always supplied to the flywheel diode stack 1, and the flywheel diodes D1 and D4 that generate heat at the time of the converter mode operation can be efficiently cooled. During the inverter mode operation, the diodes D1 to D4 in the flywheel diode stack 1 do not generate heat due to the no-load state, and therefore, the initial water temperature of the switching elements Q1 and Q4 that generate heat in the switching element stack 2 is higher. Cooling water can be supplied.

  Further, in the three-level power conversion device that divides the DC voltage into two, the switching elements Q2 and Q3 among the switching elements Q1 to Q4 that are unloaded during converter mode operation generate heat that raises the water temperature. If it is the structure of the power converter device which concerns on invention, since it was set as the structure which water-cools the switching elements Q2 and Q3 accompanied by the heat_generation | fever loss of the grade which raises water temperature at the time of no load with respect to converter mode driving | operation, other than itself The semiconductor device is not adversely affected, and an optimum cooling water system can be realized. Therefore, with the configuration in which each semiconductor element does not affect the cooling of other semiconductor elements, the cooling capacity and cooling efficiency can be increased in the same manner as described above, and the junction temperature of the semiconductor element is reliably suppressed to a specified temperature or less. Can do. This can sufficiently cope with downsizing of the power conversion device and the cooling device and expansion of the capacity of the power conversion device.

(3) Further, according to the semiconductor power conversion device of the present invention, the flywheel diode that generates main heat among the flywheel diodes D1 to D4 in the flywheel diode stack 1 and the switching elements Q1 to Q4 in the switching element stack 2. D1 and D4 / switching elements Q1 and Q4 are cooled so as not to be affected by thermal effects from the series water system and other semiconductor elements, and can be efficiently cooled by the cooling water at the initial water temperature. By outputting the remaining water system from the cooling outlet side pipe 40 through the cooling fins 33 to 37 in the center of the stack 2, it is possible to realize five optimal cooling water systems.

  In addition, this invention is not limited to the said embodiment, In the range which does not deviate from the summary, various deformation | transformation can be implemented. Moreover, each embodiment can be implemented in combination, and in that case, the effect of the combination can be obtained.

The block diagram which shows the cooling water system as one Embodiment of the power converter device which concerns on this invention. The figure which shows the structure of the one part phase of the conventional 3 level power converter device. The block diagram which shows the cooling water system of the conventional power converter device.

Explanation of symbols

  D1 to D4 ... flywheel diode, Q1 to Q4 ... switching element, 1 ... flywheel diode stack, 2 ... switching element stack, 20 ... initial cooling water supply pipe, 21-25 ... flow path pipe, 26-30 ... cooling fin 31-39 ... Cooling fins, 40 ... Cooling outlet piping, 41-45 ... Connection piping.

Claims (3)

In the three-level power converter that divides the DC voltage into two parts,
A plurality of switching elements and cooling fins disposed on both sides of each switching element, and each flywheel diode paired with each switching element and cooling fins disposed on both sides of each flywheel diode are separately stacked. A power conversion device comprising: a water cooling fan connected between the switching element and a flywheel diode paired with the switching element so as to form a series water system. In the power converter device according to claim 1,
The power conversion device characterized in that the cooling fins arranged on the flywheel diode side are installed on the upstream side of the cooling water flow than the cooling fins arranged on the switching element side. In the power converter device according to claim 1 or 2,
A plurality of flywheel diodes constituting the flywheel diode stack are each cooled by an independent water system, and the flywheel diode stack having the flywheel diode and the switching element stack having the switching element are configured by a total of five water systems. The power converter characterized by the above-mentioned.

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