JP2016220442A - Switching speed setting method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To optimally drive-control a switching element by taking account also of an induced electromotive force generated at a bus bar.SOLUTION: A method for setting switching speeds of a plurality of switching elements (Swp, Swn) that are parallely connected to a smoothing capacitor (C1) through a bus bar (BB) includes setting a switching speed of each switching element in accordance with inductance of a bus bar between the smoothing capacitor and each switching element.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a setting method for setting a switching speed of a switching element.

  There is a technique for changing the switching speed of the switching state of the switching elements constituting the inverter connected to the in-vehicle main machine according to the input voltage of the inverter. This is because the surge voltage is suppressed by reducing the switching speed of the switching state, while the power loss associated with the switching of the switching state is increased. That is, in order to maintain the reliability of the switching element, it is necessary to avoid a situation in which a voltage exceeding the withstand voltage is applied to the switching element, thereby determining the upper limit value of the surge voltage. For this reason, suppression of the power loss accompanying switching of a switching state will be aimed at by making switching speed as large as possible in the range in which a surge voltage does not exceed an upper limit.

  Patent Document 1 discloses an appropriate gate voltage map based on characteristic information (gate threshold voltage, gate capacitance, etc.) of a semiconductor switching element, temperature of the semiconductor switching element, etc. in order to maximize the switching speed of the semiconductor switching element. And a switching speed is determined based on the map.

JP 2014-150701 A

  Assume a configuration in which an inverter is connected to a battery via a converter. In this case, a smoothing capacitor is provided on the output side (inverter side) of the converter, and a bus bar is provided between the smoothing capacitor and a switching element constituting the inverter. In such a configuration, an induced electromotive force is generated in the bus bar when the switching element is turned off. In the technique described in Patent Document 1, the induced electromotive force generated in the bus bar is not taken into consideration, and there is still room for improvement in terms of power loss.

  The present invention has been made to solve the above-described problems, and a main object of the present invention is to optimally control the switching element in consideration of the induced electromotive force generated in the bus bar.

  The present invention is a setting method for setting a switching speed of a plurality of switching elements connected in parallel to a smoothing capacitor via a bus bar, according to an inductance of the bus bar between the smoothing capacitor and each switching element. The switching speed of each of the switching elements is set.

  According to the above configuration, the present invention relates to a setting method for setting the switching speed of a plurality of switching elements connected in parallel to a smoothing capacitor via a bus bar. The switching speed of each switching element is set according to the inductance of the bus bar between the smoothing capacitor and each switching element. Accordingly, it is possible to maximize the switching speed within a range that does not exceed the withstand voltage of the switching element in consideration of the difference in the inductance of the bus bar between the smoothing capacitor and each switching element.

  Further, the present invention is a setting method for setting the switching speed of a plurality of switching elements connected in parallel with a converter, the fluctuation of the voltage applied to the switching element is measured, and the measured fluctuation of the voltage The switching speed of the switching element is set according to the above.

  According to the said structure, it is related with the setting method which sets the switching speed of the several switching element connected in parallel with the converter. The variation in voltage applied to the switching element created by the converter is measured, and the switching speed of the switching element is set according to the measured variation in voltage. This makes it possible to maximize the switching speed within a range that does not exceed the withstand voltage of the switching element in consideration of fluctuations in the voltage applied to the switching element.

  The present invention is also a setting method for setting a switching speed of a plurality of switching elements, wherein a voltage applied to the switching element when the switching element is switched is measured, and the measured voltage is the switching element. The switching speed of the switching element is set to be a predetermined voltage lower than the withstand voltage.

  According to the above configuration, the voltage applied when the plurality of switching elements are switched is measured, and the switching speed is set so that the measured voltage is lower than the withstand voltage of the switching element by a predetermined voltage. If the measured voltage is not a predetermined voltage lower than the withstand voltage when switching the switching element, the surge voltage may be higher than the withstand voltage when performing the next switching. Reduce the switching speed. Accordingly, it is possible to set an appropriate switching speed in consideration of a surge voltage generated when the switching element is actually switched.

It is a figure which shows schematic structure of the drive device of the switching element which concerns on this embodiment. It is a figure which shows an example of a gate voltage map. It is a time change figure of the voltage applied to a switching element.

  Hereinafter, a switching device driving apparatus according to the present invention will be described with reference to the drawings.

  FIG. 1 shows the system configuration of this embodiment. As shown in the figure, a three-phase motor 10 as an in-vehicle main machine is connected to a high voltage battery 12 via an inverter IV and a converter CV. The inverter IV is configured by connecting three series connection bodies of a high potential side switching element Swip and a low potential side switching element Swin in parallel. The connection points of these high potential side switching elements Swip and low potential side switching elements Swin are connected to the respective phases of the three-phase motor 10.

The converter CV includes a capacitor C1 (corresponding to a smoothing capacitor), a series connection body of a high potential side switching element Swcp and a low potential side switching element Swcn, and a high potential side switching element Swcp and a low potential side switching element Swcn. A reactor (corresponding to an inductor) L for connecting the connection point and the high voltage battery 12 is provided. The capacitor C1 provided in the converter CV and the high-potential side switching element Swip and the low-potential side switching element Swin provided in the inverter IV are connected by a conductor (bus bar) BB having a large cross-sectional area that is connected with low resistance. Yes. In FIG. 1, it is described that there are six bus bars BB. However, this is schematically shown, and actually one bus bar BB is provided on each of the high potential side and the low potential side. Is provided.
Further, a smoothing capacitor C <b> 2 is connected in parallel between the converter CV and the high voltage battery 12. The converter CV boosts the voltage of the high voltage battery 12 (for example, several hundred volts) and uses it as the input voltage of the inverter IV.

  Between the input / output terminals (between the collector and the emitter) of the high potential side switching element Swip and the low potential side switching element Swin provided in the inverter IV, the high potential side freewheel diode FDip and the low potential side freewheel diode FDin The cathode and anode are connected. The switching elements Swcp and Swcn included in the converter CV have the same configuration, and the cathodes of the high-potential side freewheel diode FDcp and the low-potential side freewheel diode FDcn are connected between the input / output terminals of the switching elements Swcp and Swcn. The anode is connected.

  The drive unit DU is connected to the conduction control terminals (gates) of the switching elements Swip and Swin constituting the inverter IV. Thus, the switching elements Swip and Swin are driven by the control device 16 using the low voltage battery 14 as a power source via the drive unit DU. Based on detection values of various sensors (not shown), the control device 16 operates operation signals gup, gvp, gwp for operating the high potential side switching elements Swip for the U phase, the V phase, and the W phase of the inverter IV, Operation signals gun, gvn, and gwn for operating the low potential side switching element Swin are generated and output. Further, operation signals gcp and gcn for operating the switching elements Swcp and Swcn of the converter CV are generated and output. As a result, the switching elements Swcp and Swcn are operated by the control device 16 via the drive unit DU.

  The switching elements Swip, Swin, Swcp, and Swcn are all formed of insulated gate bipolar transistors (IGBT).

  In such a configuration, the capacitor C1 and the switching elements Swip and Swin are connected by the bus bar BB. Therefore, when it is attempted to set the switching speed of the switching elements Swip and Swin by a conventional method (for example, the switching speed is set based on the temperature and characteristics of the switching elements Swip and Swin), power loss is caused by the inductance of the bus bar BB. There may be room for room.

  As a countermeasure, in this embodiment, the switching speed of the switching elements Swip and Swin is set in consideration of the inductor of the bus bar BB. A method for setting the switching speed of the switching elements Swip and Swin will be described below.

  Boosted voltage VH is affected by the inductance of bus bar BB existing between capacitor C1 and switching elements Swip, Swin. Therefore, it is necessary to change the switching speed of the switching elements Swip and Swin according to the inductance of the bus bar BB. The inductance of the bus bar BB is set according to the length of the bus bar BB between the capacitor C1 and the switching elements Swip and Swin. Therefore, the inductance of the bus bar BB is set by acquiring the length of the bus bar BB from the design value. Information about a change in the boosted voltage VH that is influenced by the set inductance of the bus bar BB is acquired.

  The degree of voltage change of boosted voltage VH varies according to the charge capacity of capacitor C1 provided in converter CV. Therefore, the charge capacity of the capacitor C1 is acquired from the design value, and information about the degree of voltage change of the boost voltage VH that is affected by the acquired charge capacity of the capacitor C1 is acquired.

  The boosted voltage VH is affected by the temperature of the capacitor C1. This is because the charge capacity of the capacitor C1 changes depending on the temperature of the capacitor C1. Therefore, the temperature of the capacitor C1 is measured, and information about changes in the boost voltage VH under various temperature environments is acquired.

  The degree of voltage change of boosted voltage VH changes according to the inductance of reactor L. Therefore, the inductance of the reactor L is acquired from the design value, and information about the degree of voltage change of the boosted voltage VH that is affected by the acquired inductance of the reactor L is acquired.

  By comprehensively examining the above information, a gate voltage map corresponding to various situations is created by experiment or computer simulation so that the surge voltage is less than the withstand voltage and the power loss is minimized. An example of the gate voltage map is shown in FIG. As shown in FIG. 2, the gate voltage map is obtained by changing the target value of the gate voltage Vg of the switching elements Swip, Swin into a voltage change mode (change locus or time chart of the gate voltage Vg) with time. It is what was recorded in.

  Hereinafter, the target value of the gate voltage Vg determined by the gate voltage map at an arbitrary time t is referred to as “gate voltage target value Vge (t)”. In FIG. 2, “tVth” is the time from when the gate voltage target value Vge (t) starts to rise from 0 until it reaches the gate threshold voltage Vth. “Vm” is a mirror voltage. “TVm” is the time from when the gate voltage target value Vge (t) starts to rise from 0 until it reaches the mirror voltage Vm.

  When actually controlling the switching speed, based on other information such as the temperature of the capacitor C1 and operating parameters (temperatures of the switching elements Swip, Swin, collector-emitter voltage, collector-emitter current, etc.) Select an appropriate gate voltage map. Thereby, the subsequent switching speeds of the switching elements Swip and Swin are appropriately controlled so that the gate voltage Vge approaches the gate voltage target value Vge (t) indicated in the gate voltage map.

  As described above, even if the switching speeds of the switching elements Swip and Swin are set, when a surge voltage is actually generated, the switching elements Swip and Swin may have a withstand voltage higher than that. Therefore, when the switching elements Swip and Swin are switched based on the selected gate voltage map, the surge voltage generated in the switching elements Swip and Swin is measured. At this time, when the measured surge voltage is not a predetermined voltage lower than the withstand voltage of the switching elements Swip and Swin, the surge voltage measured when the switching elements Swip and Swin are switched next time is changed to the switching element. The gate voltage map is reselected so that the voltage is lower than the withstand voltage of Swip and Swin. At this time, the predetermined voltage is set as a value that does not increase beyond the withstand voltage of the switching elements Swip and Swin even if the surge voltage increases due to a measurement error or a change in operating parameters.

  When setting the switching speeds of the switching elements Swip and Swin, for example, a case is assumed in which only the switching speed of the high potential side switching element Swip is changed and the switching speed of the low potential side switching element Swin is not changed. In this case, there is a possibility that the series connection body of the high potential side switching element Swip and the low potential side switching element Swin is short-circuited. Therefore, when setting the switching speeds of the switching elements Swip and Swin, the switching speeds of the two switching elements Swip and Swin constituting the series connection body existing in each phase of the inverter IV are set simultaneously.

  According to the embodiment described in detail above, the following effects can be obtained.

  The switching speed of each switching element Swip, Swin is set according to the inductance of the bus bar BB existing between the capacitor C1 and each switching element Swip, Swin. As a result, it is possible to increase the maximum switching speed in consideration of the inductance of the bus bar BB between the capacitor C1 and each switching element Swip, Swin, and in a range not exceeding the withstand voltage of the switching elements Swip, Swin. .

  The inductance of the bus bar BB is set according to the length of the bus bar BB between the capacitor C1 and each switching element Swip, Swin. In this case, since the length of the bus bar BB can be known from the design value, a gate voltage map according to the inductance of the bus bar BB can be easily created. As a result, it becomes possible to control to an appropriate switching speed based on the created gate voltage map.

  The switching speed of each switching element Swip, Swin is set according to the charge capacity of the capacitor C1. At this time, since the charge capacity of the capacitor C1 can be known from the design value, a gate voltage map corresponding to the charge capacity of the capacitor C1 can be easily created.

  The temperature of the capacitor C1 is measured, and the switching speed of each switching element Swip, Swin is set according to the measured temperature of the capacitor C1. Since the temperature of the capacitor C1 is actually measured, the gate voltage map can be appropriately selected according to the temperature change of the capacitor C1.

  -The switching speed of each switching element Swip, Swin is set according to the inductance of the reactor L. At this time, since the inductance of the reactor L can be known from the design value, a gate voltage map corresponding to the inductance of the reactor L can be easily created.

  -The voltage applied when each switching element Swip, Swin is switched is measured, and the gate voltage map is selected so that the measured voltage is lower than the withstand voltage of each switching element Swip, Swin. The If the measured voltage is not lower than the withstand voltage when the switching speed is controlled based on the selected gate voltage map, the surge voltage will be less than the withstand voltage the next time switching is performed. Therefore, the switching speed is lowered. Thus, even when an inappropriate gate voltage map is selected and the surge voltage may exceed the withstand voltage, an appropriate gate voltage map can be selected again by the above control.

  -Each phase of the inverter IV is provided with a series connection body of two switching elements Swip and Swin. In such a configuration, when setting the switching speed, the switching speeds of the two switching elements Swip and Swin constituting the series connection body are simultaneously set. For example, when only the switching speed of the high potential side switching element Swip is changed and the switching speed of the low potential side switching element Swin is not changed, the series connection body of the high potential side switching element Swip and the low potential side switching element Swin is There is a possibility of short circuit. For this reason, it becomes possible to suppress a short circuit of each phase by simultaneously switching the switching speeds of the two switching elements Swip and Swin existing in each phase.

  In addition, the said embodiment can also be changed and implemented as follows.

  The switching elements Swip, Swin, Swcp, Swcn were composed of IGBTs. About this, you may comprise by MOSFET, for example.

  When changing the switching speeds of the switching elements Swip and Swin, two switching speeds of the high potential side switching element Swip and the low potential side switching element Swin existing in each phase of the inverter IV are changed simultaneously. With regard to this, if switching is performed in consideration of preventing all paths in the inverter IV from conducting, there is no need to stick to this control.

  In the above embodiment, the length of the bus bar BB between the capacitor C1 and each switching element Swip, Swin is obtained from the design value. In this regard, the length of the bus bar BB between the capacitor C1 and each switching element Swip, Swin may be actually measured. In this case, since the length of the bus bar BB between the capacitor C1 and each switching element Swip, Swin is measured by actual measurement, the inductance of the bus bar BB can be set more accurately without causing an error. .

  In the above embodiment, the charge capacity of the capacitor C1 is obtained from the design value. In this regard, the charge capacity of the capacitor C1 may actually be measured. In this case, since the charge capacity of the capacitor C1 is actually measured, it is possible to cope with a change in the charge capacity that changes with the deterioration of the capacitor C1, and more appropriately set the switching speed of each switching element Swip, Swin. It becomes possible to do.

  In the above embodiment, the inductance of the reactor L is obtained from the design value. In this regard, the inductance of the reactor L may actually be measured. In this case, since the inductance of the reactor L is actually measured, it is possible to appropriately set the switching speed of the switching elements Swip and Swin in accordance with the change in inductance.

  In the above embodiment, when setting the switching speeds of the switching elements Swip and Swin, an appropriate gate voltage map is selected based on other information such as the temperature and operating parameters of the capacitor C1. With respect to this, the switching of the switching elements Swip and Swin may be actually performed, and the gate voltage map may be set so that the surge voltage generated thereby becomes lower than the withstand voltage of the switching elements Swip and Swin by a predetermined voltage. Accordingly, it is possible to set an appropriate switching speed in consideration of a surge voltage generated when the switching elements Swip and Swin are actually switched.

  FIG. 3 shows a variation example of the boosted voltage VH as a voltage boosted by the converter CV applied to the switching elements Swip and Swin provided in the inverter IV. At this time, the boosted voltage VH is controlled so as to rise and fall between a preset upper limit value and lower limit value by connecting and disconnecting the switching elements Swcp and Swcn included in the converter CV. When this control is performed and the boosted voltage VH is higher than a predetermined value, switching of the switching elements Swip and Swin provided in the inverter is performed, and a case where a surge voltage is generated is assumed (time) t1). In this case, since a surge voltage is generated when the boosted voltage VH is higher than a predetermined value, the surge voltage may increase correspondingly and exceed the withstand voltage (see time t2). Therefore, the switching speeds of the switching elements Swip and Swin are set according to the fluctuation of the boost voltage VH. For example, when the boosted voltage VH becomes higher than a predetermined value, the gate voltage map is selected so that the switching speed becomes lower.

  By actually measuring fluctuations in the voltages applied to the switching elements Swip and Swin created by the converter CV, the switching speeds of the switching elements Swip and Swin can be set appropriately in accordance with the fluctuations in the boost voltage VH. It becomes possible.

BB ... bus bar, C1 ... capacitor, Swip ... high potential side switching element, Swin ... low potential side switching element.

Claims (14)

A setting method for setting switching speeds of a plurality of switching elements (Swip, Swin) connected in parallel to a smoothing capacitor (C1) via a bus bar (BB),
A switching speed setting method, wherein the switching speed of each switching element is set according to the inductance of the bus bar between the smoothing capacitor and each switching element.   2. The switching speed setting method according to claim 1, wherein an inductance of the bus bar is set according to a length of the bus bar between the smoothing capacitor and each of the switching elements.   The length of the said bus bar between the said smoothing capacitor and each said switching element is measured, The inductance of the said bus bar is set according to the measured length of the said bus bar. Switching speed setting method described in 1.   4. The switching speed setting method according to claim 1, wherein the switching speed of the switching element is set according to a charge capacity of the smoothing capacitor. 5.   5. The switching speed setting method according to claim 1, wherein a charge capacity of the smoothing capacitor is measured, and a switching speed of the switching element is set according to the measured charge capacity. 6. .   6. The switching speed setting according to claim 1, wherein a temperature of the smoothing capacitor is measured and a switching speed of the switching element is set according to the measured temperature of the smoothing capacitor. Method. The smoothing capacitor is included in a converter including an inductor,
The switching speed setting method according to any one of claims 1 to 6, wherein the switching speed of the switching element is set according to the inductance of the inductor.   The switching speed setting method according to claim 7, wherein an inductance of the inductor is measured, and a switching speed of the switching element is set according to the measured inductance.   The switching speed setting method according to claim 7 or 8, wherein a fluctuation of a voltage applied to the switching element is measured, and a switching speed of the switching element is set according to the measured fluctuation of the voltage. . A setting method for setting a switching speed of a plurality of switching elements (Swip, Swin) connected in parallel with a converter (CV),
A switching speed setting method, comprising: measuring a change in voltage applied to the switching element; and setting a switching speed of the switching element according to the measured change in voltage.   Measuring a voltage applied to the switching element when the switching element is switched, and setting a switching speed of the switching element so that the measured voltage is lower than a withstand voltage of the switching element by a predetermined voltage. The switching speed setting method according to claim 1, wherein the switching speed is set. A setting method for setting a switching speed of a plurality of switching elements (Swip, Swin),
Measuring a voltage applied to the switching element when the switching element is switched, and setting a switching speed of the switching element so that the measured voltage is lower than a withstand voltage of the switching element by a predetermined voltage. A characteristic switching speed setting method.   The voltage applied to the switching element is measured when the switching element is switched, and on the condition that the measured voltage is not lower than the withstand voltage of the switching element by a predetermined voltage, The switching speed of the switching element is reset so that a voltage applied to the switching element when switching is lower than a withstand voltage of the switching element by a predetermined voltage. The switching speed setting method according to the item. The switching element is included as a series connection of two switching elements in each phase of an inverter having a plurality of phases.
The switching speed setting method according to any one of claims 1 to 13, wherein the switching speeds of two switching elements constituting the series connection body are simultaneously changed.

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