JP3067389B2 - Gate drive method for modular IGBT - Google Patents

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 the main circuit of a voltage source inverter is constructed as a bridge.
To a gate driving method.

[0002]

2. Description of the Related Art In general, a modularized IGBT
The main circuit of a voltage-source inverter having an insulated gate bipolar transistor as its switching element is configured as shown in the circuit diagram of FIG. 1, and gate signals for each IGBT shown are applied as voltage signals from a gate drive circuit. However, as a conventional gate driving method for this type of IGBT, a gate signal voltage application path from each gate driving circuit to a corresponding IGBT gate is provided for each IGBT having a modularized and uniform characteristic. A device having the same resistance value is known.

Hereinafter, the circuit diagram of FIG. 1 will be described. FIG.
1 shows a circuit configuration of a three-phase bridge which receives a DC voltage E _DC and converts it into a required three-phase AC to drive a three-phase induction motor 4 to form a main circuit of a three-phase voltage type inverter.
Regardless of the presence or absence of the suffix, elements having the same shape in the drawings are elements having the same specifications and the same characteristics.

[0004] 1,2,3 1 are each U-phase and V-phase and W-phase each phase module of the three-phase bridge, the illustrated U-phase FD _U and IGBT _U or V-phase of FD _V
An IGBT having a commutation diode (FD) connected in anti-parallel, such as a combination of a IGBT and an IGBT _V, is used as a component of each of the upper and lower arms of the IGBT, and has the same circuit configuration. It is an aggregation. The example wherein the gate driving circuit R _GU is not shown IGB
A gate resistance provided to the gate signal voltage application path to the gate of T _U, illustrates the case in which provided on the outside of the U-phase module 1. Similarly, R _GV is a gate resistance for the IGBT _V. It is assumed that the circuit configuration in each module is configured such that the wiring resistance itself of the gate signal voltage application path is the same in any path.

[0005] L _EV in V-phase module 2 is being present also in other U-phase and W-phase module, leading to negative bus side external terminal of the V-phase module from the emitter of the IGBT _V It shows the inductance in the wiring inside the module, and its reduction is limited due to the module structure. That is, in the conventional gate driving method, the resistance values of the gate resistances such as R _GU and R _GV are the same for any IGBT.

[0006]

In the main circuit of a voltage source inverter having a bridge configuration as shown in FIG. 1 by the IGBT module, the collector current is increased by the turn-on operation of the lower arm IGBT of each module. At this time, the back electromotive force caused by the emitter-side wiring inductance acts to substantially reduce the magnitude of the gate-on signal voltage for each of the lower arm IGBTs, and the output voltage of each IGBT is the average value thereof. Decrease. Therefore, a voltage difference is generated between the output voltage average value of the upper arm IGBT of each module and the influence of reducing the signal voltage is relatively small, and a DC component is superimposed on the output AC of the inverter.

The superposition of the DC component in the AC output from the inverter as described above will be described below with reference to the circuit diagram of FIG. 1 and the operation waveform diagram of FIG. Now, taking a V-phase module 2 shown in FIG. 1 as an example, if the collector current I _L is energized in the direction of the arrow on the emitter side wiring inductance L _EV of IGBT _V is the _{L EV} · dI L / dt Back electromotive force E given
_CV is at the inductance _LEV , that is, at the IG
The emitter of BT _V and between the negative bus, the current I
_In accordance with the polarity of the rate of change dI _L / dt of _L , the current I _L is generated in the direction that obstructs the change of the current I _L as shown by the arrow in the figure. Now, if the current change rate is positive, that is, if the IGBT _V receives a gate-on signal voltage V _GV via its gate resistance R _GV and shifts to a conductive state, and the collector current _IL increases. In the meantime, the back electromotive force E _CV acts as a transient voltage reduction component for the signal voltage V _GV to substantially reduce the gate-on signal voltage for the IGBT _V to reduce the IGBT voltage.
_This results in an increase in the _V turn-on time.

Accordingly, if the signal voltage V _GV is a pulse-like signal, the time width of the pulse-like output voltage of the IGBT _V decreases as the turn-on time increases, and the average value of the output voltage also decreases. Become. The gate-on signal voltage for each of the IGBTs including the signal voltage V _GV forms a pulse train subjected to, for example, PWM control.
If the duration of the back electromotive force E _CV becomes relatively longer than the pulse width of the signal voltage V _GV due to an increase in the carrier frequency or the like in the PWM control, the output voltage average value also decreases relatively. 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 of FIG. 1, and V _GU and V _GV correspond to the U-phase module 1 shown in FIG. Gates forming a pulse train for the upper arm IGBT _U of the V-phase module 2 and the lower arm IGBT _{V of the} V-phase module 2
The ON signal voltage, and V _UN is the IGBT _U and I
By turning on the GBT _V , the three-phase induction motor 4
And the DC power supply voltage E
_{The peak} value E has positive and negative polarities with respect to the _DC zero potential point P.
_It changes at _DC / 2.

With respect to the voltage V _UN , the signal voltage V _GU
The output voltage of the IGBT _U corresponding to the signal voltage V _GU has a phase delay of Δθ _{1 at} the phase angle θ with respect to the signal voltage V _GU at the time of the rise, and the IGBT _U corresponding to the signal voltage V _GV
Output voltage of _V is comes to have a phase lag of [Delta] [theta] ₂ than the signal voltage V _GV, positive the voltage V _UN becomes [Delta] [theta] ₁ <[Delta] [theta] ₂ due to the influence of the emitter side wiring inductance of the IGBT _V 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 a pulse train.

In the main circuit of the voltage source inverter shown in FIG. 1, the IGBTs of the upper and lower arms are controlled to be turned on with a predetermined phase difference from each other, and the IGBTs are in a turned 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 are turned on in pairs and the current _IL is supplied to the U-phase and V-phase windings of the electric motor 4 in the directions indicated by arrows. It shows the status.

However, in the conventional gate driving method of the IGBT, the above-described turn-on characteristic difference between the module upper and lower arms IGBT caused by the emitter side wiring inductance is not corrected. A DC component is superimposed on the output AC of a voltage-type inverter whose main circuit is constituted by an IGBT module and whose output voltage is formed by a voltage pulse train subjected to PWM control or the like, and the induction motor driven by the inverter Is subjected to DC bias excitation and suffers from adverse effects such as generation of rotation unevenness.

In view of the above, the present invention relates to a modularized IGB in which the main circuit of a voltage source inverter is configured as a bridge.
Regarding T, upper and lower arm IGBTs in the bridge
It is an object of the present invention to provide a method of driving a gate of a modularized IGBT which can make the turn-on characteristics uniform and remove the DC component in the AC output from the inverter as described above.

[0014]

In order to achieve the above object, a method of driving a gate of a modularized IGBT according to the present invention comprises a gate drive of a modularized switching IGBT in which a main circuit of a voltage source inverter is configured as a bridge. In the method, when the IGBTs of the upper and lower arms forming a pair for each phase of the bridge are formed in a module, the resistance value of the gate-on signal voltage application path for each of the upper and lower arms IGBT is determined by the above-mentioned upper and lower arms. Each arm IGB
It is assumed that the gate-emitter voltages are different from each other so that the time rise characteristics of the gate-emitter voltages at each T are the same.

[0015]

When the gate-emitter voltage of each of two sets of IGBTs having the same element characteristics is raised at the same time with a predetermined polarity, the two IGBTs are turned on at the same time.
Make an ON operation. Therefore, if the lapse of time in the turn-on operation of each of the two IGBTs is different,
By assuming that the rise time of the gate-emitter voltage for each of the GBTs is different, the turn-on operation of both IGBTs can be made the same by achieving the same.

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

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

According to the present invention, as described above, the resistance value of the gate resistance for each IGBT of the IGBT module in which the main circuit of the voltage source inverter is formed in a bridge shape is appropriately smaller for the lower arm IGBT than for the upper arm. Thus, the effect of the back electromotive force caused by the wiring inductance on the emitter side of the lower arm IGBT is substantially compensated.

[0019]

FIG. 1 is a circuit diagram showing an embodiment of the present invention. That is, in the present invention, in FIG. 1, the device characteristics of each IGBT such as IGBT _U and IGBT _V in the U, V, W phase modules 1, 2, and 3 constituting the main circuit of the voltage type inverter in a bridge shape are the same. And the magnitude of the gate-on signal voltage for each of the IGBTs such as V _GU and V _GV is the same, and the wiring resistance of the application path of each signal voltage is the same in any of the paths. Assuming that the circuit configuration in each module is made, regarding the gate resistance inserted in each of the signal voltage application paths,
Each of the upper arm IGB of R _GU such a resistance value of the gate resistance to the lower arm IGBT of the phase modules, such as R _GV
This is smaller than the resistance value of the gate resistance with respect to T.

The degree of reduction of the resistance value of the gate resistance depends on the expected magnitude and duration of the back electromotive force such as E _CV due to the emitter side wiring inductance L _EV of each lower arm IGBT. Is appropriately determined according to the following. By making the resistance values of the upper and lower arm IGBT gate resistors of the U, V, and W phase modules different from each other as described above, for example, the illustrated IGBT _U and the IGBT _V
Doo is when the collector current I _L to turn on in pairs are energized, a transient reduction of the gate-on signal voltage V _GV by the back electromotive force E _CV at the emitter side wiring inductance L _EV of the IGBT _V Compensation is equivalently performed by reducing the time constant of the signal voltage application path, the turn-on operation characteristics of the IGBT _V can be made substantially the same as those of the IGBT _U , and the IGBT _V is supplied to the induction motor 4 serving as a load. It is possible to avoid the superposition of the DC component on the AC output voltage of the inverter.

[0021]

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

[Brief description of the drawings]

FIG. 1 is a main circuit diagram of a voltage source inverter using an IGBT as a 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-phase lower arm commutation diode IGBT _U U Phase upper arm IGBT IGBT _V V phase lower arm IGBT _LEV IGBT _V emitter side wiring inductance R _GU IGBT _U gate resistance R _GV IGBT _V gate resistance E _{CV LEV} Back electromotive force E _DC inverter power supply DC voltage V _GU IGBT Gate-on signal voltage for _U V _GV Gate-on signal voltage for IGBT _V

Claims (1)

(57) [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 as a bridge, wherein the IGBTs of upper and lower arms forming a pair for each phase of the bridge are integrated into a module. The resistance value of the gate-on signal voltage application path for each of the upper and lower arms IGBT when formed is different from each other so as to make the time rise characteristics of the gate-emitter voltage in each of the upper and lower arms IGBT the same. A method of driving a gate of a modularized IGBT, characterized in that: