JPH06327291A - Control method for regenerative current feedback - Google Patents

Abstract

PURPOSE:To reduce strain on supply voltage by minimizing variation in current when changing the phase of power supply in which a regenerative current is fed back. CONSTITUTION:When changing the phases R2, S2 and T2 of power supply in which a regenerative current is fed back, one of switching elements SW1-SW6 is turned on before the previous one is turned off. These two switching elements' being on during switching operation, represents a short circuit between the phase terminals of the power supply. However, the voltage of a phase in which one switching element is to be turned off is almost equal to that of a phase in which another switching element is to be turned on; therefore, variation in voltageis slight. For the reason variation in current is slight as well, which minimizes strain on supply voltage. This prevents the malfunctions of electrical apparatus and machines connected to the power supply due to strain thereon.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a regenerative current feedback control method during a power regeneration operation in a motor drive inverter device.

[0002]

2. Description of the Related Art In a motor drive inverter device or the like, as a method of feeding back a regenerative current to a power source, a switching element is provided so that a regenerative current flows in two phases having a high absolute value of a power source voltage with respect to a three-phase power source. Is controlled on and off. FIG. 1 is a diagram showing a main part of means relating to the power regeneration operation. In the figure, R, S, and T are the R phase and S of the three-phase power supply.
Phase and T phase terminals, and reference numeral 1 indicates the AC reactor and the A
It is an inductance including stray inductance from the C reactor to the power supply. SW1 to SW6 are switching elements, D1 to D6 are diodes, and C is a DC link capacitor.

FIG. 4 is an explanatory diagram of the regenerative current control operation at the time of power source regenerative operation by the conventional method in the above-mentioned configuration. In FIG. 1, assuming that the phase terminals on the power supply side of the inductance 1 are R1, S1, T1 and the terminals on the switching element side are R2, S2, T2, the curves shown in the uppermost stage in FIG. 4 are the terminals R2, S2, T2. Voltage (each phase voltage of the power supply) of each of SW1 to SW6 described below the curve.
Indicates the on / off state of the switching element. Further, ir indicates the output current of the R phase. In FIG. 4, power supply noise is shown only for the R phase.

When the R-phase voltage of the power source is the highest, the switching element SW1 is turned on and the switching element S is turned on.
Turn on W5 (when the voltage of the S phase is the lowest) or switching element SW6 (when the voltage of the T phase is the lowest),
The regenerative current ir is made to flow in the R phase-S phase or the R phase-T phase. When the S-phase voltage is the highest, the switching element SW2 is turned on, and the switching element SW4 (when the R-phase voltage is the lowest) or switching element SW6 (when the T-phase voltage is the lowest) is turned on. The regenerative current is made to flow in the S phase-R phase or the S phase-T phase. Furthermore, when the T-phase voltage is the highest, the switching element SW3 is turned on and the switching element S3 is turned on.
W4 (when the voltage of the R phase is the lowest) or switching element SW5 (when the voltage of the S phase is the lowest) is turned on so that the regenerative current flows in the T phase-R phase or the T phase-S phase.

When one of the switching elements SW1 to SW6 is switched from on to off and the other switching element is switched from off to on, there is a slight delay, at which time noise is generated in the power supply. For example, point a in FIG.
That is, when the switching elements SW1 and SW6 are on,
The regenerative current is switched from the DC link voltage side to the switching element S.
W1, terminal R2, R-phase inductance L, terminal R1,
When a regenerative current is flowing through the power supply, the terminal T1, the T-phase inductance L, the switching element SW6, and the circuit to the DC link voltage side, the voltage of the S-phase of the power supply increases next and switching is performed to feed back to this S-phase. When the element SW1 is turned off and the switching element SW2 is turned on, the switching elements SW1 and SW2 are delayed during the on / off delay therebetween.
Are both off, and energy accumulated in the R-phase and T-phase inductances causes the terminals R2, R-phase inductance L, terminal R1, power supply, terminal T1, T-phase inductance L, terminal T2, switching element SW6, A current flows through the diode D4 and the terminal R2, the terminals R2 and T2 are short-circuited, and the voltages of the terminals R2 and T2 are the same. As a result, as shown in FIG. 4, the voltage at the terminal R2 changes to the midpoint between the voltage at the terminal R2 and the voltage at the terminal T2 up to then (note that only the R-phase power supply noise is shown in FIG. 4). However, at the point a, the voltage of the terminal T2 also changes (in the case of FIG. 4, it rises), and becomes the same as the terminals R2 and T2.

Since the voltage at the terminal R2 changes greatly in this way, the feedback current ir to the R phase changes abruptly, as shown in the bottom row of FIG. Even when the other switching elements are switched, the power supply voltage is similarly distorted, and the feedback current changes abruptly.

[0007]

As described above, when the power supply voltage is distorted when the switching element is switched, that is, when the phase of the power supply to which the regenerative current is fed back is switched, the other power supply connected to the power supply is distorted. The influence of the distortion of the power supply voltage occurs on the electric equipment, which causes the malfunction of these other electric equipment.

Therefore, an object of the present invention is to provide a regenerative current feedback control method for reducing the distortion with respect to the power source voltage that occurs when switching the feedback of the regenerative current to each phase of the power source.

[0009]

According to the present invention, when a phase of a power source for supplying a regenerative current is switched by controlling a switching element, a preset predetermined section overlaps a phase to which a regenerative current has flowed and a phase to flow next. By controlling the switching elements so that they are caused to flow simultaneously, the distortion of the power supply voltage generated when switching the regenerative current is reduced.

[0010]

When the regenerative current is fed back, the switching element is switched so that the regenerative current flows in two phases having a large absolute value of the power supply voltage. Therefore, the voltage of the phase in which the regenerative current is currently flowing and the voltage of the phase in which the regenerative current is switched so that the regenerative current flows next are the same at the time of switching.
As a result, even when the switching element to be turned off and the switching element to be turned on next are simultaneously turned on and both ends are short-circuited, the voltage change is small and the distortion of the power supply voltage can be suppressed to a small level. Further, since the change in voltage is small, the change in current is small.

[0011]

FIG. 3 is an explanatory diagram of a regenerative current feedback control method according to an embodiment of the present invention. In this embodiment, as can be seen by comparing with FIG. 4, the switching element to be turned on next is turned on before turning off the switching element which has been turned on until now.

That is, in the section where T-R is shown in FIG. 3 in which the voltage of the terminal T2 is the highest and the voltage of the terminal R2 is the lowest, the switching elements SW3 and SW4 are arranged so that the regenerative current flows in the T-phase and the R-phase. It is controlled to be turned on, and the regenerative current is passed through the path of the switching element SW3, the T-phase inductance L, the power supply, the R-phase inductance L, and the switching element SW4. Then, in the section shown as T-S in the next FIG. 3, the phases in which the absolute value of the power supply voltage is large are the T phase and the S phase, and therefore the switching element SW4 is used to switch the regenerative current from the R phase to the S phase. Is turned off and the switching element SW5 is turned on. In this case, the switching element SW5 is turned on before turning off the switching element SW4. When both the switching elements SW4 and SW5 are both turned on, the terminal R2 and the terminal S2 are short-circuited, and both terminals have the same voltage. However, the voltages at both terminals have almost the same value at the time of switching, so that the voltage change is small. Although FIG. 3 shows only the change in the voltage at the terminal R2, the voltage at the terminal S2 also changes, and when both the switching elements SW4 and SW5 are both on, the terminal R2
The voltage of S2 is the same. Since the voltage change is small as described above, the change in the R-phase current ir and the S-phase current is (the slope of the current) is small as shown in FIG.

Before switching to the next RS section, the switching element SW1 is turned on before the switching element SW3 is turned off. The terminal R2 and the terminal T2 are short-circuited and both terminals have the same voltage. Also in this case, since the voltage difference between the two terminal voltages before the short circuit is small, the change in voltage is small and the change degree of the R-phase current is also small. When switching to the next RT section,
The switching elements SW5 and SW6 are both turned on to short-circuit the terminals S2 and T2. Even in this case, the terminals S2 and T2 are also short-circuited.
Since the voltage difference of T2 is small, the voltage change is small. In addition,
In FIG. 3, only the voltage change of the terminal R2 is shown, and the terminal S2,
Although the change of T2 is not described, both terminal voltages are at the same level.

Furthermore, even when switching from the RT section to the next ST section, the switching elements SW1 and SW2 are switched.
Although the terminals R2 and S2 are short-circuited to have the same voltage level by providing a section in which both are turned on, the amount of change is small, so the amount of change in the R-phase current ir is small as shown in FIG.

As described above, each phase current ir of the regenerative current
, Is and it can be reduced in absolute value, and the principle thereof will be described below. As a representative of the explanation, FIG.
The state at point b in FIG. FIG. 2 is a circuit diagram in which the moment when both the switching elements SW2 and SW3 are turned on at point b in FIG. 3 is expressed as a direct current. In this state of point b, V1 is the power supply voltage.
1 is a voltage between terminals R1 and T1, V2 is a voltage phase lower than the power supply voltage, a voltage between S1 and T1 in FIG. 1, and V3 is a DC link voltage which is a DC link voltage in FIG.
When the R, S, and T phase currents are ir, is, and it, the following expressions 1 to 3 are established.

V3−L (dir / dt) −V1−L (dit / dt) = 0 (1) V3−L (dis / dt) −V2−L (dit / dt) = 0 (2) ( dir / dt) + (dis / dt) = (dit / dt) (3) From the above formulas 1 to 3, (dit / dt) = (2V3-V1-V2) / 3L (4) (dir / dt) ) = (V3-2V1 + V2) / 3L ... (5) (dis / dt) = (V3-2V2 + V1) / 3L ... (6) Then, V3-V1 = .alpha. (Difference between DC link voltage and power supply voltage) V1 Assuming that -V2 = β (voltage difference after advancing the phase), (dir / dt) = (α-β) / 3L (7) (dis / dt) = (α + 2β) / 3L (8) (Dit / dt) = (2α + β) / 3L (9) From the above equation 7, the switching element SW2 is turned on so that β> α at the point b. By doing so, the current ir can be reduced. The current reduced from the R-phase current ir is 8 above.
According to the formula, it is included in the increment of the S-phase current is. By this operation, the current can be switched from the R-phase current ir to the S-phase current is. The distortion applied to the power supply terminal voltages R2 and S2 at this time is (R2 + S2) / 2.

At the point a in FIG. 4 in the conventional method corresponding to the point b in FIG. 3, the change in the current flowing in the R phase is such that the terminals R2 and T2 are short-circuited. -L (dir / dt) -V1 -L (dir / dt) = 0 (10) Since ir = it, (dir / dt) =-V1 / 2L (11) Values of equations (5) and (11) Is a negative value, the magnitudes of the absolute values are compared. | 5 ||-| 11 || = | (V3 -2V1 + V2) / 3L |-| -V1 / 2L | = {(-V3 + 2V1 -V2) / 3L}-(V1 / 2L) = (V1-2V3-2V2) / 6L (12) From equation 12, it is understood that (| 5 equation |-| 11 equation |) <0. This means that Equation 5 has a smaller absolute value, that is, the current change is smaller in the present invention, and thus the distortion of the voltage applied to the power supply at the time of current switching is smaller.

As described above, according to the present invention, when the feedback of the regenerative current to each phase of the power source is switched, the change in current (gradient of current) can be suppressed to be small and the distortion with respect to the power source voltage can be reduced. . In the above embodiment, the on timing of the switching element to be turned on next is advanced, and the interval to be turned on together with the switching element to be turned off is provided, but on the contrary, the off timing of the switching element to be turned off is delayed, You may make it provide the area which turns on with the switching element which turns on next.
For example, to explain at the position of point b in FIG. 3, in this embodiment,
When the R-phase voltage is the highest and the S-phase voltage is the highest, the switching element SW1 is turned off.
Before that, turn on the switching element SW2,
Although a section is provided in which both the two switching elements SW1 and SW2 are turned on, the timing when the switching element SW1 is turned off is S-T when the voltage of the S phase is the highest.
The switching element SW2 is slightly extended to the region of the section and turned off, and the switching element SW2 is turned on when the phase in which the first voltage becomes high changes from the R phase to the S phase.
You may make it form the area where 2 is turned on together.

[0019]

According to the present invention, when the phase of the power source to which the regenerative current is fed back is switched, the change in current (gradient of current) is suppressed to be small and distortion with respect to the power source voltage is reduced. It is possible to reduce the influence of the distortion of the power supply voltage on the electric device and reduce malfunctions of these other electric devices.

[Brief description of drawings]

FIG. 1 is a diagram showing a main part of means relating to a power regeneration operation in a motor drive inverter device or the like to which an embodiment of the present invention is applied.

FIG. 2 is an explanatory diagram of a regenerative current feedback control method at the time of power source regenerative operation in one embodiment of the present invention.

FIG. 3 is a diagram showing an example of switching on / off of a switching element in the same embodiment.
It is explanatory drawing which analyzes the flow of the electric current at the time of OFF switching.

FIG. 4 is an explanatory diagram of a conventional regenerative current feedback control method at the time of power regeneration operation.

[Explanation of symbols]

1 Inductance including AC reactor and stray inductance SW1 to SW6 Switching element C DC link capacitor R Power supply R phase S Power supply S phase T Power supply T phase

Claims (2)

[Claims] 1. In a regenerative current feedback control method at the time of regenerative operation of a power supply, when switching a phase of a power supply for supplying a regenerative current,
A regenerative current feedback control method, characterized in that a phase in which a regenerative current has flown so far and a phase in which a regenerative current has flowed so far are overlapped and flowed at the same time in a set predetermined section. 2. A regenerative current feedback control method for selecting a phase of a power source for flowing a regenerative current by turning on / off a switching element during a power regeneration operation, and turning off the switching element to flow the regenerative current to the selected phase. To turn on the switching element for flowing the regenerative current to the next phase. When switching the switching element, the regenerative current feedback that controls both on and off of the switching element so that both switching elements are turned on for a preset period. Control method.