Power conversion device, method for controlling power conversion device, and elevator

Abstract

The invention relates to a power conversion device, a control method of the power conversion device, and an elevator. The purpose of the present invention is to reduce loss imbalance by a simple control method even when there is an on-resistance difference between a plurality of semiconductor switching elements connected in parallel to each other. In a power conversion device having a power conversion circuit and a control unit, the power conversion circuit has a plurality of semiconductor switching elements connected in parallel with each other. The control unit has, as a control state, a partial drive mode in which only some of the plurality of semiconductor switching elements connected in parallel are turned on, and an all drive mode in which all of the plurality of semiconductor switching elements connected in parallel are turned on. The present invention controls in a partial drive mode while changing the object of an on semiconductor switching element among a plurality of semiconductor switching elements connected in parallel, and controls by inserting in an all drive mode at a predetermined ratio corresponding to the difference in on resistance of the plurality of semiconductor switching elements connected in parallel.

Description

Technical Field

[0001] The present invention relates to a power conversion device, a control method for a power conversion device, and an elevator. Background Art

[0002] A power conversion device is a device that converts DC power into AC power, or converts it in the opposite direction, or converts DC power into DC power of a different voltage through the switching action of a power semiconductor element as a semiconductor switching element. It is used in many fields such as elevators.

[0003] In the power conversion device used in the elevator, for example, an IGBT (Insulated Gate Bipolar Transistor) is used as a power semiconductor element. IGBTs include an IGBT module in which a plurality of IGBT chips are used as one module and a discrete IGBT in which one IGBT chip is used as one package.

[0004] The power conversion device used in elevators and the like is repeatedly operated and stopped. Such an operation method increases the temperature change of the power semiconductor element caused by the on / off operation of the power semiconductor element, and there is a concern that the life of the power semiconductor element is reduced.

[0005] In order to suppress the reduction of life, there is a method of connecting discrete IGBTs in parallel. By connecting in parallel, the current flowing in is dispersed, and the current flowing through one discrete IGBT is reduced. This can suppress the temperature change of the discrete IGBT and achieve a longer life.

[0006] In addition, as a technology related to a DC / DC converter, which is one type of power conversion device, there is, for example, Patent Document 1. In the abstract and Figure 3 There is a description that "its object is to provide a DC / DC converter that does not generate shunt deviation in switching elements connected in parallel and can use a small inductor without increasing the switching frequency" and a description that "the semiconductor elements are composed of three semiconductor elements 411, 421, and 431 connected in parallel with each other, so that the frequency of the voltage applied to the inductor 5 becomes three times the switching frequency of the switching element, and the on-off control of the three switching elements 411s, 421s, and 431s is performed with the phases shifted by 1 / 3=120° of the switching period of the switching element."

[0007] Prior art literature

[0008] Patent Literature

[0009] Patent Document 1: Japanese Patent Application Publication No. 2015-213402 Summary of the invention

[0010] Problems to be solved by the invention

[0011] However, when semiconductor switch elements such as IGBTs are connected in parallel, the on-resistance of the semiconductor switch elements varies due to individual differences, thereby causing loss imbalance between the plurality of semiconductor switch elements connected in parallel. If such loss imbalance occurs, the temperature changes of the respective semiconductor switch elements differ, thereby causing differences in the lifespan of the plurality of semiconductor switch elements connected in parallel, thereby hindering the extension of the lifespan.

[0012] In addition, Patent Document 1 discloses a technology for switching three semiconductor elements connected in parallel with each other at a phase shift of 120°. However, even when this technology is used, if there is a difference in the on-resistance of the multiple semiconductor switching elements connected in parallel, the losses generated in each semiconductor switching element are also different, so loss imbalance occurs in the same way as described previously.

[0013] In addition, in order to suppress loss imbalance, a method of distinguishing and using only semiconductor switch elements with similar on-resistances based on the on-resistances of semiconductor switch elements measured in advance, a method of controlling in a manner of detecting imbalance using a sensor and suppressing the imbalance, etc. However, these methods have the problem of a significant increase in cost due to the selection of semiconductor switch elements and a significant increase in cost of a structure for detecting and controlling imbalance in real time using a sensor.

[0014] The problem to be solved by the present invention is to provide a power conversion device, a control method for a power conversion device, and an elevator that can reduce loss imbalance by a simple control method even when a plurality of semiconductor switch elements connected in parallel have a difference in on-resistance.

[0015] Means for solving problems

[0016] In order to solve the above-mentioned problems, in a power conversion device and a control method for a power conversion device of the present invention, the power conversion device has a power conversion circuit using a semiconductor switching element and a control unit that controls the conduction and disconnection of the semiconductor switching element, characterized in that the power conversion circuit has a plurality of semiconductor switching elements connected in parallel with each other as the semiconductor switching elements, and the control unit has a partial drive mode that turns on only a part of the plurality of semiconductor switching elements connected in parallel with each other, and a full drive mode that turns on all of the plurality of semiconductor switching elements connected in parallel with each other as control states, and controls with the partial drive mode while changing the object of the semiconductor switching element to be turned on among the plurality of semiconductor switching elements connected in parallel with each other, and controls by inserting the full drive mode at a prescribed ratio corresponding to the on-resistance difference of the plurality of semiconductor switching elements connected in parallel with each other.

[0017] Furthermore, the elevator of the present invention is characterized by comprising the above-mentioned power conversion device.

[0018] Effects of the Invention

[0019] According to the present invention, it is possible to realize a power conversion device, a power conversion device control method, and an elevator that can reduce loss imbalance by a simple control method even when a plurality of semiconductor switching elements connected in parallel have a difference in on-resistance. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 This is a functional block diagram showing an example of the power conversion device of the first embodiment and an elevator using the power conversion device.

[0021] Figure 2 This is a circuit diagram showing an example of a power conversion circuit of the converter according to the first embodiment.

[0022] Figure 3 This is a circuit diagram showing an example of a power conversion circuit of the inverter according to the first embodiment.

[0023] Figure 4 This is a diagram for explaining the control mode of the first embodiment.

[0024] Figure 5 This is a flowchart for explaining an example of the control method of the first embodiment.

[0025] Figure 6 This is a circuit diagram showing an example of a DC / DC converter according to the second embodiment. DETAILED DESCRIPTION

[0026] Hereinafter, embodiments of the present invention will be described using the drawings. In each drawing and each embodiment, the same or similar components are denoted by the same reference numerals, and repeated descriptions are omitted.

[0027] [Example 1]

[0028] Figure 1 This is a functional block diagram showing an example of the power conversion device of the first embodiment and an elevator using the power conversion device.

[0029] The elevator 101 of the first embodiment includes, for example, a converter 110 , an inverter 111 , filter circuits 103 , 104 , a motor 108 , a rope 105 , a car 106 , and a counterweight 107 .

[0030] In the elevator 101 of this embodiment, AC power from the system 102 is input to the converter 110 via the filter circuit 103, and is converted into DC power by the converter 110. Then, the converted DC power is converted into AC power by the inverter 111. Then, the converted AC power is input to the motor 108 via the filter circuit 104, and the motor 108 is driven.

[0031] A car 106 is connected to one side of the rope 105, and a counterweight 107 for balancing the car 106 is connected to the other side of the rope 105. The motor 108 moves the rope 105, thereby moving the car 106 of the elevator 101 up and down. In this way, the power of the motor 108 is consumed to move the car 106 up and down.

[0032] The power conversion device of this embodiment has a power conversion circuit using a semiconductor switching element and a control unit that controls the on / off of the semiconductor switching element. In addition, the power conversion circuit of this embodiment has a plurality of semiconductor switching elements connected in parallel as semiconductor switching elements.

[0033] An example of a power conversion device according to the present embodiment is a converter 110 . The converter 110 includes a power conversion circuit 112 which is a circuit for converting AC power into DC power, and a converter control unit 114 which controls the power conversion circuit 112 .

[0034] Figure 2 This is a circuit diagram showing an example of a power conversion circuit of the converter according to the first embodiment.

[0035] The power conversion circuit 112 of the converter 110 has a leg composed of an upper arm and a lower arm and a capacitor 12. Here, as an example, an example of a leg having three phases is shown, but it is not limited to this. The upper arm and the lower arm each have a semiconductor switching element 10 such as an IGBT and a diode 11 connected in reverse parallel to the semiconductor switching element 10.

[0036] In this embodiment, the semiconductor switch element 10 in each arm is composed of a plurality of semiconductor switch elements connected in parallel. Specifically, as the plurality of semiconductor switch elements 10 connected in parallel, there are a first semiconductor switch element 10A and a second semiconductor switch element 10B connected in parallel with the first semiconductor switch element 10A. The first semiconductor switch element 10A and the second semiconductor switch element 10B are independently controlled to be turned on and off by the converter control unit 114. The plurality of semiconductor switch elements connected in parallel can be realized by connecting a plurality of discrete IGBTs in parallel, or by an IGBT module having a plurality of IGBT chips connected in parallel.

[0037] Another example of the power conversion device of this embodiment is the inverter 111. Figure 1 As shown, the inverter 111 includes a power conversion circuit 113 which is a circuit for converting DC power into AC power, and an inverter control unit 115 which controls the power conversion circuit 113 .

[0038] Figure 3 This is a circuit diagram showing an example of a power conversion circuit of the inverter according to the first embodiment.

[0039] The power conversion circuit 113 of the inverter 111 has the same configuration as the power conversion circuit 112 of the converter 110 , and thus detailed description thereof is omitted. The first semiconductor switch element 10A and the second semiconductor switch element 10B are independently turned on and off by the inverter control unit 115 .

[0040] Figure 4 This is a diagram for explaining the control mode of the first embodiment.

[0041] The converter control unit 114 and the inverter control unit 115 as the control units of this embodiment have, as control states, a partial drive mode in which only a part of the plurality of semiconductor switch elements connected in parallel to each other is turned on, and a full drive mode in which all of the plurality of semiconductor switch elements connected in parallel to each other are turned on.

[0042] The partial drive mode is a mode in which control is performed while changing the semiconductor switch element to be turned on among a plurality of semiconductor switch elements connected in parallel. Therefore, the partial drive mode includes a first mode in which the first semiconductor switch element 10A is turned on and the second semiconductor switch element 10B is turned off, and a second mode in which the first semiconductor switch element 10A is turned off and the second semiconductor switch element 10B is turned on. Furthermore, control is performed while repeating the first mode and the second mode alternately.

[0043] In addition, all driving modes include a third mode in which both the first semiconductor switch element 10A and the second semiconductor switch element 10B are turned on.

[0044] Here, it is considered that the on-resistance Ron1 of the first semiconductor switch element 10A and the on-resistance Ron2 of the second semiconductor switch element 10B are different from each other due to individual differences, and Ron1>Ron2.

[0045] In the first mode, only the first semiconductor switch element 10A is turned on, so the current I flows through the first semiconductor switch element 10A. The loss P1 at this time is P1=I 2 ·Ron1.

[0046] In the second mode, only the second semiconductor switch element 10B is turned on. Therefore, if the same current I as in the first mode flows, the current I flows through the second semiconductor switch element 10B. The loss P2 at this time is P2=I 2 · Ron2. Here, since Ron1>Ron2, P2<P1. Therefore, loss imbalance occurs only in some driving modes.

[0047] In the third mode, since both the first semiconductor switch element 10A and the second semiconductor switch element 10B are turned on, if the current I of the same magnitude as in the first mode flows, the current I is divided into a current I1 flowing through the first semiconductor switch element 10A side and a current I2 flowing through the second semiconductor switch element 10B side. In addition, I=I1+I2. In addition, since Ron1>Ron2, I1<I2.

[0048] Here, the voltage V between the first semiconductor switch element 10A and the second semiconductor switch element 10B is V=Ron1·I1=Ron2·I2. Therefore, the loss P31 generated in the first semiconductor switch element 10A is P31=I1 2 ·Ron1=V·I1. The loss P32 generated in the second semiconductor switch element 10B is P32=I2 2 Ron2 = V·I2. The magnitude relationship between P31 and P32 is I1 < I2, so P31 < P32. Therefore, in the full drive mode, a loss imbalance occurs in the opposite direction to that in the partial drive mode.

[0049] Therefore, the control unit of the present embodiment is configured to control in a partial drive mode while changing the object of the semiconductor switch element that is turned on among the plurality of semiconductor switch elements connected in parallel to each other, and insert the full drive mode to control at a predetermined ratio corresponding to the difference in the on-resistance of the plurality of semiconductor switch elements connected in parallel to each other. As described above, in the full drive mode, a loss imbalance in the opposite direction to that in the partial drive mode occurs, so according to the control method of the present embodiment, the loss imbalance can be reduced. Figure 5 The details are explained.

[0050] Figure 5 This is a flowchart for explaining an example of the control method of the first embodiment.

[0051] exist Figure 5 In steps S1 to S6, the objects of the semiconductor switching elements that are turned on among the plurality of semiconductor switching elements connected in parallel to each other are changed while controlling in a partial drive mode. Then, as described above, all the drive modes of step S7 are inserted at a prescribed ratio corresponding to the on-resistance difference. Specifically, in steps S1, S3, and S5, control is performed in the first mode, and in steps S2, S4, and S6, control is performed in the second mode. In this way, while the first mode and the second mode are repeated alternately, the third mode of step S7 is inserted at a prescribed ratio corresponding to the on-resistance difference between the first semiconductor switching element 10A and the second semiconductor switching element 10B for control. Here, as an example, the third mode is inserted at a ratio of 1 / 7, but it is not limited to this as long as it is a ratio that can reduce the loss imbalance. In addition, the position of inserting the third mode can be any position in steps S1 to S7. In addition, repeatedly executing Figure 5 process.

[0052] The above-mentioned prescribed ratio can be set in advance based on the on-resistance difference measured in advance. In addition, the on-resistance can be measured using information provided by the manufacturer or measured by oneself. In any case, it is not necessary to use a sensor to measure in real time during control, so a significant increase in cost can be suppressed.

[0053] In addition, the control of inserting the full drive mode at a predetermined ratio into the control of the partial drive mode by the control unit can also be executed when the on-resistance difference is greater than a predetermined value, that is, when the loss imbalance becomes large in the normal control. When the on-resistance difference is less than the predetermined value, the loss imbalance is also small, so as long as the loss imbalance is within the allowable range, it is not necessary to perform the control. Figure 5 The control of this embodiment as shown may be performed in a normal manner, for example, control may be performed only in the full drive mode or only in the partial drive mode.

[0054] In this embodiment, the case of 2 parallel connections is used as an example for explanation, but it is not limited thereto, and it can also be 3 or more parallel connections. For example, in the case of 3 parallel connections, some driving modes can be increased to 3 modes, and the expansion can be done appropriately.

[0055] As described above, according to the present embodiment, even when there is a difference in on-resistance among a plurality of semiconductor switch elements connected in parallel to each other, loss imbalance can be reduced by a simple control method.

[0056] [Example 2]

[0057] Embodiment 2 is a modification of Embodiment 1, and is an embodiment applied to a DC / DC converter 120 as an example of a power conversion device.

[0058] Figure 6 This is a circuit diagram showing an example of a DC / DC converter according to the second embodiment.

[0059] The DC / DC converter 120 includes a power conversion circuit 121 which is a circuit for converting DC power into DC power of a different voltage, and a DC / DC converter control unit 122 which controls the power conversion circuit 121 .

[0060] The basic structure of the power conversion circuit 121 is the same as that of a general DC / DC converter power conversion circuit, so detailed description is omitted, but it includes a semiconductor switch element 10, a diode 11, a capacitor 12, and an inductor 13. Figure 6 The structure shown is just an example and is not limited to this.

[0061] The power conversion circuit 121 of this embodiment uses the first semiconductor switch element 10A and the second semiconductor switch element 10B connected in parallel as the semiconductor switch element 10 as in the first embodiment. The first semiconductor switch element 10A and the second semiconductor switch element 10B are independently controlled to be turned on and off by the DC / DC converter control unit 122.

[0062] In the case of this embodiment, the same effect can be obtained by performing control in the same manner as in the first embodiment.

[0063] Although the embodiments of the present invention have been described above, the present invention is not limited to the structures described in the embodiments, and various changes can be made within the scope of the technical concept of the present invention. In addition, part or all of the structures described in the embodiments can also be combined and applied.

[0064] For example, the DC / DC converter 120 of the second embodiment may be used for a part of the elevator 101 of the first embodiment.

[0065] Description of Reference Numerals

[0066] 10Semiconductor switching elements

[0067] 10A first semiconductor switch element

[0068] 10B second semiconductor switch element

[0069] 11 diode

[0070] 12 Capacitors

[0071] 13 Inductor

[0072] 101 Elevator

[0073] 102 System

[0074] 103, 104 filter circuit

[0075] 105 Rope

[0076] 106 Car

[0077] 107 Counterweight

[0078] 108 Electric Motor

[0079] 110 Converter

[0080] 111 Inverter

[0081] 112, 113 Power conversion circuit

[0082] 114 Converter control unit

[0083] 115 Inverter control unit

[0084] 120DC / DC Converter

[0085] 121 Power conversion circuit

[0086] 122DC / DC converter control unit

[0087] I, I1, I2 current

[0088] Ron1, Ron2 on-resistance

[0089] P1, P2, P31, P32 loss.

Claims

1. A power conversion device comprising a power conversion circuit using a semiconductor switch element and a control unit for controlling the on / off of the semiconductor switch element, wherein the conversion feature is: The power conversion circuit includes a plurality of semiconductor switching elements connected in parallel with each other as the semiconductor switching elements. The control unit has a partial drive mode for turning on only a part of the plurality of semiconductor switch elements connected in parallel with each other, and a full drive mode for turning on all of the plurality of semiconductor switch elements connected in parallel with each other as control states, and controls with the partial drive mode while changing the object of the semiconductor switch element turned on among the plurality of semiconductor switch elements connected in parallel with each other, and controls by inserting the full drive mode at a prescribed ratio corresponding to the on-resistance difference of the plurality of semiconductor switch elements connected in parallel with each other.

2. The power conversion device according to claim 1, characterized in that: The power conversion circuit includes a first semiconductor switching element and a second semiconductor switching element connected in parallel with the first semiconductor switching element as the plurality of semiconductor switching elements connected in parallel with each other. The control unit has a first mode, a second mode and a third mode as the control states, and controls by inserting the third mode at a specified ratio corresponding to the on-resistance difference between the first semiconductor switch element and the second semiconductor switch element while repeating the first mode and the second mode alternately. The first mode turns on the first semiconductor switch element and turns off the second semiconductor switch element, the second mode turns off the first semiconductor switch element and turns on the second semiconductor switch element, and the third mode turns on both the first semiconductor switch element and the second semiconductor switch element.

3. The power conversion device according to claim 2, characterized in that: The on-resistance of the first semiconductor switch element is greater than the on-resistance of the second semiconductor switch element, In the third mode, a loss generated in the first semiconductor switching element is smaller than a loss generated in the second semiconductor switching element.

4. The power conversion device according to claim 1, characterized in that: When the on-resistance difference is equal to or larger than a predetermined value, control is performed in which the entire drive mode is inserted at the predetermined ratio into the control of the partial drive mode by the control unit.

5. The power conversion device according to claim 1, characterized in that: The predetermined ratio is set in advance based on the on-resistance difference measured in advance.

6. The power conversion device according to claim 1, characterized in that: The power conversion circuit is a circuit that converts DC power into AC power.

7. The power conversion device according to claim 1, characterized in that: The power conversion circuit is a circuit that converts AC power into DC power.

8. The power conversion device according to claim 1, characterized in that: The power conversion circuit is a circuit that converts DC power into DC power of a different voltage.

9. An elevator, characterized in that: A power conversion device according to any one of claims 1 to 8.

10. A control method for a power conversion device, the power conversion device comprising a power conversion circuit using a semiconductor switch element and a control unit for controlling on / off of the semiconductor switch element, characterized in that: The power conversion circuit includes a plurality of semiconductor switching elements connected in parallel with each other as the semiconductor switching elements. The control unit has a partial drive mode for turning on only a part of the plurality of semiconductor switch elements connected in parallel with each other, and a full drive mode for turning on all of the plurality of semiconductor switch elements connected in parallel with each other as control states, and controls with the partial drive mode while changing the object of the semiconductor switch element turned on among the plurality of semiconductor switch elements connected in parallel with each other, and controls by inserting the full drive mode at a prescribed ratio corresponding to the on-resistance difference of the plurality of semiconductor switch elements connected in parallel with each other.

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