JPH05328735A - Gate driving method of modular igbt - Google Patents

Abstract

PURPOSE:To equalize turn-on characteristics between each upper and lower arm IGBT of an IGBT module constituting the main circuit bridge of a voltage type inverter, and to prevent the overlapping of a DC component in the output ACs of the inverter. CONSTITUTION:The resistance values of each gate resistor such as RGV to each lower side arm IGBT such as IGBT in each U, V, W phase module 1, 2, 3 constituting the main circuit bridge of a voltage type inverter are properly made smaller than those of each gate resistor such as RGU to each upper side arm IGBT such as IGBTU. A time constant in a gate-on signal voltage applying path to each lower side arm IGBT is reduced in response to the magnitude of the emitter-side back electromotive force of each lower side arm IGBT such as ECV and the lapse of time, thus equalizing turn-on characteristics between each IGBT of both arms.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a modularized IGBT in which a main circuit of a voltage source inverter is formed in a bridge.
To the gate driving method.

[0002]

2. Description of the Related Art Generally, a modularized IGBT
The main circuit of a voltage source inverter having an (insulated gate bipolar transistor) as its switching element is constructed as shown in the circuit diagram of FIG. 1, and the gate signal for each IGBT shown in the figure is applied as a voltage signal from the gate drive circuit. However, as a conventional gate driving method for this kind of IGBT, a gate signal voltage application path from each gate driving circuit to the corresponding IGBT gate is provided for each modularized IGBT having uniform characteristics. It is known that the resistance values are the same.

The circuit diagram of FIG. 1 will be described below. Figure 1
Shows a circuit configuration of a three-phase bridge which forms a main circuit of a three-phase voltage source inverter which receives a direct current voltage E _DC and converts it into a required three-phase alternating current and drives a three-phase induction motor 4.
It should be noted that, regardless of the presence or absence of the subscript, the elements having the same shape in the figure indicate elements having the same specifications and the same characteristics.

In FIG. 1, reference numerals 1, 2 and 3 denote U-phase, V-phase, and W-phase modules of the three-phase bridge, respectively. The U-phase FD _U and IGBT _U or the V-phase FD _{V are shown.}
And an IGBT _V having an anti-commutation diode (FD) connected in anti-parallel as a combination of them are used as constituent elements of the upper and lower arms of the IGBT, and the elements in the range surrounded by the dotted line in the figure are formed with the same circuit configuration. It is a summary. Also, for example, R _GU is a gate drive circuit (not shown)
It is a gate resistance provided in the gate signal voltage application path to the gate of T _U , and is an example when it is provided outside the U-phase module 1. Similarly, R _GV is a gate resistance for the IGBT _V. The circuit configuration in each module is assumed such that the wiring resistance itself of the gate signal voltage application path is the same in any path.

The L _EV in the V-phase module 2, which is also present in the other U-phase and W-phase modules, extends from the emitter of the IGBT _{V to} the external terminal on the negative bus side of the V-phase module. This shows the inductance in the wiring in the module, and its reduction is limited due to the module structure. That is, in the conventional gate driving method, the resistance value of the gate resistance such as R _GU and R _GV is the same for any IGBT.

[0006]

In the main circuit of the voltage source inverter having the bridge structure as shown in FIG. 1 by the above-mentioned IGBT module, the collector current of the lower arm IGBT of each module is increased by the turn-on operation. At this time, the counter electromotive force resulting from the wiring inductance on the emitter side acts so as to substantially reduce the magnitude of the gate-on signal voltage to each lower arm IGBT, and the output voltage of each IGBT has its average value. Lowers at. Therefore, a voltage difference is generated between the average value of the output voltage of the upper arm IGBT of each module, which has a relatively small effect of reducing the signal voltage, and a DC component is superimposed on the output AC of the inverter.

The DC component superposition in the inverter output AC as described above will be described below with reference to the circuit diagram of FIG. 1 and the operation waveform diagram of FIG. Taking the V-phase module 2 shown in FIG. 1 as an example, when the collector current I _L is applied to the emitter side wiring inductance L _EV of the IGBT _V in the direction of the arrow shown in the figure, L _EV · dI _L / dt Back electromotive force E given
_CV is the inductance L _EV , that is, the IG
Between the emitter of BT _V and its negative bus, the current I
It occurs as the direction of the arrow to inhibit any changes of the current I _L in accordance with the polarity of the _L of the change rate dI _L / dt. When the current change rate is positive, that is, when the IGBT _V receives the gate-on signal voltage V _GV through its gate resistance R _GV and shifts to the conductive state, and the collector current I _L thereof increases. In addition, the back electromotive force E _CV acts as a transient voltage reduction component with respect to the signal voltage V _GV to substantially reduce the gate-on signal voltage with respect to the IGBT _V.
This will increase the turn-on time of _V.

Therefore, if the signal voltage V _GV is a pulsed signal, the time width of the pulsed output voltage of the IGBT _V is reduced as the turn-on time is increased, and the average value of the output voltage is also reduced. Become. The gate-on signal voltage for each of the IGBTs including the signal voltage V _GV forms a pulse train under PWM control, for example.
If the duration of the counter electromotive force E _CV becomes relatively large compared to the pulse width of the signal voltage V _GV due to the increase of the carrier frequency in the PWM control or the like, the decrease of the output voltage average value also becomes relatively large. It will be great.

Next, the operation waveform diagram of FIG. 2 shows the operation pattern as described above in comparison with the circuit diagram shown in FIG. 1. V _GU and V _GV are the U-phase module 1 shown in FIG. 1, respectively. Of the gate train for the upper arm IGBT _U and the lower arm IGBT _{V of the} V-phase module 2
ON signal voltage, and V _UN is the above-mentioned IGBT _U and I
Three-phase induction motor 4 of the U by the turn-on of the GBT _V
DC power supply voltage E, which is the voltage applied to the phase and V phase windings
_{The peak} value E has positive and negative polarities with reference to the zero potential point P of _DC.
It changes at _DC / 2.

With respect to the voltage V _UN , the signal voltage V _GU
The output voltage component of the IGBT _U corresponding to the above has a phase delay of Δθ _{1 in} the phase angle θ from the signal voltage V _GU at the time of its rise, and similarly the IGBT corresponding to the signal voltage V _GV.
Although the output voltage of V has a phase delay of Δθ ₂ with respect to the signal voltage V _GV, Δθ ₁ <Δθ ₂ due to the influence of the emitter side wiring inductance of the IGBT _V , and the positive voltage of the voltage V _UN . The average value of the side voltage component is larger than that of the negative side component. As a result, a positive DC component is superimposed on the fundamental AC voltage of the voltage V _UN , which is a composite value of the positive and negative voltage components forming the pulse train.

In the main circuit of the voltage source inverter whose configuration is shown in FIG. 1, the IGBTs of the upper and lower arms are turned on and controlled with a predetermined phase difference from each other, and are in the turn on state. The combination between the upper and lower arm IGBTs changes according to a predetermined phase order. In the case of FIG. 1, the IGBT _U and the IGBT _{V form a} pair and are turned on, and a current I _L is applied to the U-phase and V-phase windings of the electric motor 4 in the direction of the arrow. It shows a state.

However, in the conventional IGBT gate driving method, the above turn-on characteristic difference between the upper and lower arm IGBTs of each module due to the wiring inductance on the emitter side is not corrected. A direct current component is superimposed on the output AC of the voltage source inverter whose main circuit is composed of the IGBT module and whose output voltage is composed of a voltage pulse train subjected to PWM control or the like, and an induction motor driven by the inverter. Is biased to be DC-biased and adversely affected by uneven rotation.

In view of the above, the present invention has a modularized IGBT in which the main circuit of the voltage source inverter is formed in a bridge.
Regarding T, upper and lower arm IGBTs in the bridge
It is an object of the present invention to provide a gate driving method for a modular IGBT capable of removing the DC component in the inverter output AC as described above by making the turn-on characteristics uniform during the period.

[0014]

In order to achieve the above object, a method of driving a gate of a modularized IGBT according to the present invention is a gate driving method of a modularized switching IGBT in which a main circuit of a voltage source inverter is formed in a bridge. In the method, the resistance value of the gate-on signal voltage application path for each upper and lower arm IGBT when the IGBT of the upper and lower arms forming a pair for each phase of the bridge is formed in a module, Each arm IGB
The gate-emitter voltage is made different from each other so that the time-dependent rising characteristics of the gate-emitter voltage are the same.

[0015]

When the gate-emitter voltage of each of the two IGBTs having the same element characteristics is raised at the same time with the predetermined polarity, the two IGBTs are turned after the same time.
Turn on. Therefore, if the time lapses in the turn-on operations of both the IGBTs are different, the I
It is possible to make the turn-on operations of both of the IGBTs identical by attempting to make them identical because the rise time of the gate-emitter voltage for each of the IGBTs is different.

In general, the gate-on signal voltage application circuit of the IGBT charges the gate-emitter of the IGBT exhibiting the capacitive characteristic with the gate-on signal voltage via the gate resistance, and the gate-emitter voltage between the gate and the emitter of the IGBT is charged. The circuit is configured so that the required gate-emitter voltage for IGBT turn-on is obtained by using a charging voltage that elapses in time according to a time constant given by the product of the electrostatic capacitance and the resistance value of the gate resistor. ..

Therefore, if the gate-on signal voltage is reduced by some external voltage, the turn-on of the IGBT is turned on by reducing the resistance value of the gate resistor to reduce the time constant. The decrease in the charging voltage in the required period is equivalently compensated, and the increase time of the charging voltage in the period is made substantially the same so that the I
The turn-on operation of the GBT can be made the same.

In accordance with the above, according to the present invention, with respect to the resistance value of the gate resistance for each IGBT of the IGBT module which constitutes the main circuit of the voltage source inverter in a bridge shape, the resistance value for the lower arm IGBT is appropriately smaller than that for the upper arm. In other words, the effect of the counter electromotive force as described above due to the emitter side wiring inductance of the lower arm IGBT is substantially compensated.

[0019]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT An embodiment of the present invention will be described below with reference to the circuit diagram of FIG. That is, according to the present invention, in FIG. 1, the device characteristics of each IGBT such as IGBT _U and IGBT _V in the U, V and W phase modules 1, 2 and 3 which constitute the main circuit of the voltage source inverter in a bridge shape are the same. In addition, the magnitudes of the gate-on signal voltages for the respective IGBTs such as V _GU and V _GV are made the same, and the wiring resistance itself of the application path of the respective signal voltages is made the same in any path. Regarding the gate resistance inserted in each of the signal voltage application paths, assuming that the circuit configuration in each module is made,
The resistance value of the gate resistance to the lower arm IGBT of each phase module such as R _{GV is} set to the upper arm IGBT of each R _GU or the like.
It is smaller than the resistance value of the gate resistance with respect to T.

The degree of reduction in the resistance value of the gate resistance depends on the expected magnitude and duration of the counter electromotive force such as E _CV due to the emitter side wiring inductance L _EV of each of the lower arm IGBTs. Is appropriately determined in accordance with. As described above, by making the resistance values of the upper and lower arm IGBT gate resistors of the U, V, W phase modules different, for example, IGBT _U and IGBT _V shown in the figure.
When paired with and turn on and the collector current I _L is _conducted , the transient reduction of the gate-on signal voltage V _GV is caused by the counter electromotive force E _CV in the emitter side wiring inductance L _EV of the IGBT _V. By equivalently compensating by reducing the time constant of the signal voltage application path, the turn-on operation characteristic of the IGBT _V can be made substantially the same as that of the IGBT _U , and the same is supplied to the induction motor 4 serving as its load. It is possible to avoid superimposing a DC component on the AC output voltage of the inverter.

[0021]

According to the present invention, there is provided a method of driving a gate of a modularized switching IGBT in which a main circuit of a voltage-source inverter is formed in a bridge, and a gate for each upper and lower arm IGBT forming a pair of each phase of the bridge. The resistance values of the resistors are made different from each other so that the time-dependent rising characteristics of the gate-emitter voltage in each of the upper and lower arm IGBTs are the same, and the gate-on signal voltage for each of the lower arm IGBTs is set. By making the time constant of the application path appropriately smaller than that for each upper arm IGBT, the lower arm I
It becomes possible to correct the turn-on characteristic difference between the upper and lower arm IGBTs caused by the wiring inductance on the emitter side in each of the GBTs, and avoid the superimposition of the DC component on the output AC of the inverter. It is possible to prevent DC bias excitation in the load induction motor and prevent adverse effects such as uneven rotation.

[Brief description of drawings]

FIG. 1 is a main circuit diagram of a voltage source inverter using an IGBT as its switching element.

FIG. 2 is an operation waveform diagram corresponding to FIG.

[Explanation of symbols]

1 U-phase module of three-phase bridge 2 V-phase module of three-phase bridge 3 W-phase module of three-phase bridge 4 Three-phase induction motor FD _U U phase upper arm commutation diode FD _V V V phase lower arm commutation diode IGBT _U U Phase upper arm IGBT IGBT _V V Phase lower arm IGBT L _EV IGBT _V emitter side wiring inductance R _GU IGBT _U gate resistance R _GV IGBT _V gate resistance E _CV L _EV back electromotive force E _DC Inverter power supply DC voltage V _GU IGBT _U gate-on signal voltage V _GV IGBT _V gate-on signal voltage

Claims (1)

[Claims] 1. A method of driving a gate of a modularized switching IGBT in which a main circuit of a voltage source inverter is configured in a bridge, wherein IGBTs of upper and lower arms forming a pair for each phase of the bridge are provided in a module. When formed, the resistance values of the gate-on signal voltage application paths for the upper and lower arm IGBTs are different from each other so that the temporal rise characteristics of the gate-emitter voltage in the upper and lower arm IGBTs are the same. A method of driving a gate of a modularized IGBT, characterized in that: