Power conversion device, control method of power conversion device, and elevator

Abstract

To reduce loss imbalance by a simple control method even when there is on-resistance difference in a plurality of semiconductor switching elements connected in parallel with one another.SOLUTION: In a power conversion device comprising a power conversion circuit and a control unit, the power conversion circuit comprises a plurality of semiconductor switching elements connected in parallel with each other, the control unit comprises: a partial drive mode for turning only a part of the plurality of semiconductor switching elements connected in parallel with each other on; and an all drive mode for turning all of the plurality of semiconductor switching elements connected in parallel with each other on as a control state, and performs control by inserting the all drive mode at predetermined ratio according to on-resistance difference of the plurality of semiconductor switching elements connected in parallel with each other while performing control in the partial drive mode as changing objects of the semiconductor switching element to be turned on among the plurality of semiconductor switching elements connected in parallel with each other.SELECTED DRAWING: Figure 4

Description

Technical Field

[0001] The present invention relates to a power conversion device, a control method of 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 vice versa, or converts DC power into DC power with different voltages, by the switching operation of a power semiconductor element, which is a semiconductor switching element, and is applied to various fields such as elevators.

[0003] For example, an IGBT (Insulated Gate Bipolar Transistor) is used as a power semiconductor element in a power conversion device used in an elevator. The IGBT includes an IGBT module in which a plurality of IGBT chips are formed into one module, and a discrete IGBT in which one IGBT chip is formed into one package.

[0004] A power conversion device used in an elevator or the like repeats operation / stop. Such an operation method increases the temperature change of the power semiconductor element caused by the on / off operation of the power semiconductor element, so there is concern about a decrease in the life of the power semiconductor element.

[0005] In order to suppress the decrease in life, there is a method of connecting discrete IGBTs in parallel. By the parallel connection, the inflowing current is dispersed, and the current flowing through one discrete IGBT decreases. As a result, the temperature change of the discrete IGBT can be suppressed, and the life can be extended.

[0006] Also, as a technology related to a DC / DC converter which is a type of power conversion device, for example, there is Patent Document 1. In the summary of Patent Document 1 and FIG. 3, there is a description that "an object is to provide a DC / DC converter capable of using a small reactor without causing shunt variation in parallel-connected switching elements and without increasing the switching frequency." and a description that "Three semiconductor elements 411, 421, and 431 which are semiconductor elements connected in parallel to each other are used to control the on / off of the three switching elements 411s, 421s, and 431 so that the frequency of the voltage applied to the reactor 5 becomes three times the switching frequency of the switching element, and the phases are shifted from each other by 1 / 3 = 120° of the switching period of the switching element."

Prior Art Documents

Patent Documents

[0007]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0008] However, when semiconductor switching elements such as IGBTs are connected in parallel, since the on-resistances of the semiconductor switching elements are different from each other due to individual differences, a loss imbalance occurs between a plurality of semiconductor switching elements connected in parallel to each other. When such a loss imbalance occurs, a difference occurs in the temperature change of each semiconductor switching element, and as a result, the lifetimes between a plurality of semiconductor switching elements connected in parallel to each other become different, which hinders the extension of the lifetime.

[0009] In Patent Document 1, a technique of switching three semiconductor elements connected in parallel with each other while shifting their phases by 120° is disclosed. However, even when this technique is used, if there is a difference in the on-resistance of a plurality of semiconductor switching elements connected in parallel with each other, the losses generated in each semiconductor switching element will be different. Therefore, loss imbalance will occur as in the previous explanation.

[0010] In addition, in order to suppress loss imbalance, methods such as sorting and using only those with similar on-resistances based on the on-resistance of semiconductor switching elements measured in advance, and methods of detecting imbalance using a sensor and controlling to suppress the imbalance can be considered. However, those methods have problems such as a significant increase in cost due to the selection of semiconductor switching elements, and a significant increase in cost for the configuration for detecting and controlling imbalance in real time using a sensor.

[0011] The problem to be solved by the present invention is to provide a power conversion device, a control method for the power conversion device, and an elevator that can reduce loss imbalance by a simple control method even when there is an on-resistance difference in a plurality of semiconductor switching elements connected in parallel with each other.

Means for Solving the Problem

[0012] In order to solve the above problems, the power conversion device / control method of the power conversion device according to the present invention has a power conversion circuit using semiconductor switching elements and a control unit for controlling the on / off of the semiconductor switching elements. In the power conversion device / control method of the power conversion device, the power conversion circuit has, as the semiconductor switching elements, a plurality of semiconductor switching elements connected in parallel to each other, and the control unit has, as control states, a partial drive mode in which only a part of the plurality of semiconductor switching elements connected in parallel to each other are turned on and a full drive mode in which all of the plurality of semiconductor switching elements connected in parallel to each other are turned on. While controlling in the partial drive mode while changing the target of the semiconductor switching elements to be turned on among the plurality of semiconductor switching elements connected in parallel to each other, the full drive mode is inserted and controlled at a predetermined ratio according to the on-resistance difference of the plurality of semiconductor switching elements connected in parallel to each other.

[0013] Further, the elevator according to the present invention is characterized by having the above-described power conversion device.

Effect of the Invention

[0014] According to the present invention, it is possible to realize a power conversion device, a control method of the power conversion device, and an elevator that can reduce loss imbalance by a simple control method even when there is an on-resistance difference among a plurality of semiconductor switching elements connected in parallel to each other.

Brief Description of the Drawings

[0015]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6

Embodiments for Carrying Out the Invention

[0016] Hereinafter, embodiments of the present invention will be described with reference to the drawings. In each figure and each embodiment, the same or similar components are denoted by the same reference numerals, and redundant descriptions are omitted.

Examples

[0017] FIG. 1 is a functional block diagram showing an example of the power conversion device of Example 1 and an elevator using the same.

[0018] The elevator 101 of Example 1 includes, for example, a converter 110, an inverter 111, filter circuits 103 and 104, a motor 108, a rope 105, a car 106, and a weight 107.

[0019] In the elevator 101 of this embodiment, AC power from the power grid 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 to drive the motor 108.

[0020] A car 106 is connected to one side of the rope 105, and a weight 107 for balancing with the car 106 is connected to the other side of the rope 105. By moving the rope 105 by the motor 108, the car 106 of the elevator 101 can be moved up and down. In this way, the power of the motor 108 is consumed to move the car 106 up and down.

[0021] The power conversion device of this embodiment includes a power conversion circuit using semiconductor switching elements and a control unit that controls the on / off of the semiconductor switching elements. And the power conversion circuit of this embodiment has, as semiconductor switching elements, a plurality of semiconductor switching elements connected in parallel to each other.

[0022] An example of the power conversion device of this embodiment is the converter 110. The converter 110 includes a power conversion circuit 112 which is a circuit that converts AC power into DC power, and a converter control unit 114 that controls the power conversion circuit 112.

[0023] FIG. 2 is a circuit diagram showing an example of the power conversion circuit of the converter of Embodiment 1.

[0024] The power conversion circuit 112 of the converter 110 includes a leg composed of an upper arm and a lower arm, and a capacitor 12. Here, as an example, an example having legs for three phases is shown, but it is not limited thereto. Each of the upper arm and the lower arm has, for example, a semiconductor switching element 10 such as an IGBT, and a diode 11 connected in anti-parallel to the semiconductor switching element 10.

[0025] In this embodiment, the semiconductor switching element 10 in each arm is composed of a plurality of semiconductor switching elements connected in parallel to each other. Specifically, as a plurality of semiconductor switching elements 10 connected in parallel to each other, a configuration is adopted that includes a first semiconductor switching element 10A and a second semiconductor switching element 10B connected in parallel to the first semiconductor switching element 10A. The first semiconductor switching element 10A and the second semiconductor switching element 10B are independently controlled to be turned on and off by the converter control unit 114. The plurality of semiconductor switching elements connected in parallel to each other may be realized by connecting a plurality of discrete IGBTs in parallel, or may be realized by an IGBT module having a plurality of IGBT chips connected in parallel to each other.

[0026] Another example of the power conversion device of this embodiment is the inverter 111. As shown in FIG. 1, the inverter 111 includes a power conversion circuit 113 that is a circuit for converting DC power into AC power, and an inverter control unit 115 that controls the power conversion circuit 113.

[0027] FIG. 3 is a circuit diagram showing an example of the power conversion circuit of the inverter of Embodiment 1.

[0028] The power conversion circuit 113 of the inverter 111 also has the same configuration as the power conversion circuit 112 of the converter 110, so a detailed description thereof will be omitted. Note that the first semiconductor switching element 10A and the second semiconductor switching element 10B are independently turned on and off by the inverter control unit 115.

[0029] FIG. 4 is a diagram for explaining the control mode of Embodiment 1.

[0030] The converter control unit 114 and the inverter control unit 115, which are the control units of this embodiment, have, as control states, a partial drive mode in which only a part of a plurality of semiconductor switching elements connected in parallel with each other are turned on, and a full drive mode in which all of the plurality of semiconductor switching elements connected in parallel with each other are turned on.

[0031] The partial drive mode is a mode in which control is performed while changing the target of the semiconductor switching element to be turned on among a plurality of semiconductor switching elements connected in parallel with each other. Therefore, the partial drive mode has a first mode in which the first semiconductor switching element 10A is turned on and the second semiconductor switching element 10B is turned off, and a second mode in which the first semiconductor switching element 10A is turned off and the second semiconductor switching element 10B is turned on. Then, control is performed by alternately repeating the first mode and the second mode.

[0032] The full drive mode has a third mode in which both the first semiconductor switching element 10A and the second semiconductor switching element 10B are turned on.

[0033] Here, consider the case where the on-resistance Ron1 of the first semiconductor switching element 10A and the on-resistance Ron2 of the second semiconductor switching element 10B are different due to individual differences, and Ron1 > Ron2.

[0034] In the first mode, since only the first semiconductor switching element 10A is on, the current I flows through the first semiconductor switching element 10A. The loss P1 at this time is P1 = I 2 ·Ron1.

[0035] In the second mode, since only the second semiconductor switching element 10B is on, assuming that a current I of the same magnitude as in the first mode flows, the current I flows through the second semiconductor switching element 10B. The loss P2 at this time is P2 = I 2 ·Ron2. Here, since Ron1 > Ron2, P2 < P1. Therefore, a loss imbalance occurs only in the partial drive mode.

[0036] In the third mode, since both the first semiconductor switching element 10A and the second semiconductor switching element 10B are on, assuming that a 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 switching element 10A and a current I2 flowing through the second semiconductor switching element 10B and flows. Note that I = I1 + I2. Also, since Ron1 > Ron2, I1 < I2.

[0037] Here, the voltages V of the first semiconductor switching element 10A and the second semiconductor switching element 10B are V = Ron1·I1 = Ron2·I2. Therefore, the loss P31 generated in the first semiconductor switching element 10A is P31 = I1 2 ·Ron1 = V·I1. The loss P32 generated in the second semiconductor switching element 10B is P32 = I2 2·Ron2 = V·I2. Since the relationship between P31 and P32 is such that I1 < I2, P31 < P32. Therefore, in the all - drive mode, a loss imbalance in the opposite direction to the partial - drive mode occurs.

[0038] Therefore, the control unit of this embodiment controls in the partial - drive mode while changing the target of the semiconductor switching element to be turned on among a plurality of semiconductor switching elements connected in parallel to each other, and inserts and controls the all - drive mode at a predetermined ratio according to the on - resistance difference of the plurality of semiconductor switching elements connected in parallel to each other. As described above, in the all - drive mode, a loss imbalance in the opposite direction to the partial - drive mode occurs. Therefore, according to the control method of this embodiment, the loss imbalance can be reduced. Details will be described with reference to FIG. 5.

[0039] FIG. 5 is a flowchart for explaining an example of the control method of Embodiment 1.

[0040] In FIG. 5, from step S1 to step S6, control is performed in the partial - drive mode while changing the target of the semiconductor switching element to be turned on among a plurality of semiconductor switching elements connected in parallel to each other. And, as described above, the all - drive mode of step S7 is inserted at a predetermined ratio according 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 repeating the first mode and the second mode alternately, the third mode of step S7 is inserted and controlled at a predetermined ratio according to the on - resistance difference between the first semiconductor switching element 10A and the second semiconductor switching element 10B. 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. Also, the position where the third mode is inserted can be anywhere from step S1 to step S7. Note that the flow in FIG. 5 is repeatedly executed.

[0041] The aforementioned predetermined ratio can be set in advance based on the on-resistance difference measured in advance. Note that the on-resistance can be measured using information provided by the manufacturer or measured by oneself. In either case, since it is not necessary to measure in real time using a sensor during control, a significant increase in cost can be suppressed.

[0042] Also, the control of inserting the full drive mode at a predetermined ratio during the control of the partial drive mode by the control unit may be executed when the on-resistance difference is equal to or greater than a predetermined magnitude, that is, when the loss imbalance becomes large in normal control. When the on-resistance difference is smaller than the predetermined magnitude, since the loss imbalance is also small, if the magnitude of the loss imbalance is within an acceptable range, it is not necessarily required to perform the control of this embodiment as shown in FIG. 5, and normal control, for example, only the full drive mode or only the partial drive mode may be used for control.

[0043] In this embodiment, the case of two parallel connections has been described as an example, but it is not limited thereto, and three or more parallel connections may be used. For example, in the case of three parallel connections, it may be appropriately extended by increasing the partial drive mode to three modes.

[0044] As described above, according to this embodiment, even when there is an on-resistance difference in a plurality of semiconductor switching elements connected in parallel to each other, the loss imbalance can be reduced by a simple control method.

Embodiment

[0045] 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.

[0046] FIG. 6 is a circuit diagram showing an example of the DC / DC converter of Embodiment 2.

[0047] The DC / DC converter 120 includes a power conversion circuit 121 that is a circuit for converting DC power into DC power with different voltages, and a DC / DC converter control unit 122 that controls the power conversion circuit 121.

[0048] Since the basic configuration of the power conversion circuit 121 is the same as that of a general DC / DC converter power conversion circuit, a detailed description will be omitted. However, it has a semiconductor switching element 10, a diode 11, a capacitor 12, and an inductor 13. Note that the configuration shown in FIG. 6 is merely an example and is not limited thereto.

[0049] Similar to the first embodiment, the power conversion circuit 121 of this embodiment uses a first semiconductor switching element 10A and a second semiconductor switching element 10B connected in parallel to each other as the semiconductor switching element 10. Note that the first semiconductor switching element 10A and the second semiconductor switching element 10B are independently controlled to be turned on and off by the DC / DC converter control unit 122.

[0050] Also in this embodiment, by controlling in the same manner as in the first embodiment, the same effects can be obtained.

[0051] As described above, the embodiments of the present invention have been described. However, the present invention is not limited to the configurations described in the embodiments, and various modifications are possible within the scope of the technical idea of the present invention. Also, a part or all of the configurations described in each embodiment may be combined and applied.

[0052] For example, the DC / DC converter 120 of the second embodiment may be used as a part of the elevator 101 of the first embodiment.

Explanation of Reference Numerals

[0053] 10 Semiconductor switching element 10A First semiconductor switching element 10B Second semiconductor switching element 11 Diode 12 Capacitor 13 Inductor 101 Elevator 102 System 103, 104 Filter circuit 105 Rope 106 Car 107 Weight 108 Motor 110 Converter 111 Inverter 112, 113 Power conversion circuit 114 Converter control unit 115 Inverter control unit 120 DC / DC converter 121 Power conversion circuit 122 DC / DC converter control unit I, I1, I2 Current Ron1, Ron2 On-resistance P1, P2, P31, P32 Loss

Claims

1. In a power conversion device having a power conversion circuit using a semiconductor switching element and a control unit that controls on / off of the semiconductor switching element, the power conversion circuit has, as the semiconductor switching element, a plurality of semiconductor switching elements connected in parallel to each other, the control unit has, as control states, a partial drive mode in which only a part of the plurality of semiconductor switching elements connected in parallel to each other are turned on, and an all drive mode in which all of the plurality of semiconductor switching elements connected in parallel to each other are turned on, and controls while inserting the all drive mode at a predetermined ratio according to an on-resistance difference of the plurality of semiconductor switching elements connected in parallel to each other while changing a target of the semiconductor switching element to be turned on in the partial drive mode. A power conversion device characterized by that.

2. In Claim 1, the power conversion circuit has, as the plurality of semiconductor switching elements connected in parallel to each other, a first semiconductor switching element and a second semiconductor switching element connected in parallel to the first semiconductor switching element, the control unit has, as the control states, a first mode in which the first semiconductor switching element is turned on and the second semiconductor switching element is turned off, a second mode in which the first semiconductor switching element is turned off and the second semiconductor switching element is turned on, and a third mode in which both the first semiconductor switching element and the second semiconductor switching element are turned on, and controls while inserting the third mode at a predetermined ratio according to an on-resistance difference between the first semiconductor switching element and the second semiconductor switching element while alternately repeating the first mode and the second mode. A power conversion device characterized by that.

3. In Claim 2, the on-resistance of the first semiconductor switching element is larger than the on-resistance of the second semiconductor switching element, In the third mode, a power conversion device, wherein a loss generated in the first semiconductor switching element is smaller than a loss generated in the second semiconductor switching element.

4. In claim 1, control for inserting the full drive mode at the predetermined ratio during control of the partial drive mode by the control unit is executed when the on-resistance difference is equal to or greater than a predetermined magnitude, a power conversion device characterized by this.

5. In claim 1, the predetermined ratio is preset based on the on-resistance difference measured in advance, a power conversion device characterized by this.

6. In claim 1, the power conversion circuit is a circuit that converts DC power into AC power, a power conversion device characterized by this.

7. In claim 1, the power conversion circuit is a circuit that converts AC power into DC power, a power conversion device characterized by this.

8. In claim 1, the power conversion circuit is a circuit that converts DC power into DC power with a different voltage, a power conversion device characterized by this.

9. An elevator, characterized by having the power conversion device according to any one of claims 1 to 8.

10. In a control method of a power conversion device having a power conversion circuit using semiconductor switching elements and a control unit for controlling on / off of the semiconductor switching elements, the power conversion circuit has, as the semiconductor switching elements, a plurality of semiconductor switching elements connected in parallel to each other, The control unit has, as control states, a partial drive mode in which only a part of the plurality of semiconductor switching elements connected in parallel with each other is turned on, and an all drive mode in which all of the plurality of semiconductor switching elements connected in parallel with each other are turned on, and while controlling in the partial drive mode while changing the target of the semiconductor switching elements to be turned on among the plurality of semiconductor switching elements connected in parallel with each other, the all drive mode is inserted and controlled at a predetermined ratio according to the on-resistance difference of the plurality of semiconductor switching elements connected in parallel with each other. A control method for a power conversion device characterized by this.

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