JP3237719B2 - Power regeneration controller - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electric power regeneration device in which a self-extinguishing semiconductor switching device and an arm composed of a diode connected in anti-parallel to the switching device are bridge-connected to enable the regeneration of electric power to an AC power supply. It relates to a control device.

[0002]

2. Description of the Related Art FIG. 6 is a block diagram showing a conventional example of a voltage-type three-phase inverter device having a power regeneration function. In the figure, 1 is a three-phase AC power supply, 2 is an internal inductance of the AC power supply 1, 3 is an AC reactor, 4 is a current transformer (C
T), 5 is an inverter device (simply referred to as an inverter or a power conversion device) including a converter unit 51, an inverter unit 52, a smoothing capacitor 53, etc., 6 is an induction motor (IM), and 7 is an induction motor. Power supply voltage detector, 8 is an ignition signal generator, 9 is a setting device, 10
Is a comparator, 11 is a latch circuit, 12 is an AND gate, 1
3 is a base drive circuit. Converter unit 51 has diodes D1 to rectifiers D1 to T6 as self-extinguishing semiconductor switching elements T1 to T6.
D6 is connected in a reverse-parallel connection to form a bridge connection. Note that the inverter unit 52 is similarly configured.

In such a configuration, first, an AC power supply 1
When power is supplied from the power supply 1 to the load side (inverter unit 52), the AC from the power supply 1 is full-wave rectified by the diode bridge of the converter unit 51 and stored in the smoothing capacitor 53 as DC power. This power is supplied to the inverter unit 5
In 2, it is converted into an arbitrary three-phase alternating current and supplied to the motor 6. On the other hand, electric power from the motor 6 as a load is
In the case of regenerating to the power supply side, the electric power from the motor 6 charged in the smoothing capacitor 53 via the inverter unit 52 is regenerated to the power supply 1 side via the transistors T1 to T6 of the converter unit 51. The firing order of transistors T1 to T6 of converter unit 51 at this time will be described with reference to FIG.

FIG. 7A shows phase voltages V _R , V _S , and V _T of the three-phase AC power supplies R, S, T, and (B) to (G) show the ignition timing (T) of the transistors T1 to T6. (Firing signal) and (h) indicate sections, respectively. That is, regeneration is performed in the section RS phase (transistor T
1, T5 is fired). Regeneration in the section RT phase (transistor T
1, T6 is fired). Regeneration in the section ST phase (transistor T
2, T6 is fired). Regeneration in section SR phase (transistor T
2, T4 is fired). Regeneration in section TR phase (transistor T
3, T4 is fired). Regeneration in section TS phase (transistor T
3, T5 is fired). And the inverter unit 52 between the phases having the highest power supply phase voltage.
The operation for regenerating the electric power from the power supply is performed.

The power supply voltage detector 7 detects the phase of the power supply phase voltage, and the ignition signal generator 8 generates an ignition signal to be distributed to each of the transistors T1 to T6 based on this output. Then, the ignition signal is amplified to drive the transistors T1 to T6. At this time, the transistors T1 to T6 may be driven only when power is regenerated to the power supply side, or may be driven constantly. In the case of driving only during regeneration, it is necessary to detect the voltage of the smoothing capacitor 53 and determine whether regeneration is necessary or not. The AC reactor 3 is provided for coordination between the AC power supply 1 and the inverter 5, reduces harmonic components flowing through the AC power supply 1, and reduces the current duty of the diode and transistor of the converter unit 51.

In the above-described apparatus, if the regenerative power increases rapidly for some reason or if the AC power supply 1 momentarily loses power for some reason (also referred to simply as a momentary power failure), the collectors of the transistors T1 to T6 are removed. The current may increase rapidly (overcurrent state), and these may be destroyed. Therefore, conventionally, a current transformer (CT) 4 is provided on the AC power supply side to monitor the power supply current (regeneration current), and when the regenerative current flows beyond the current level set in the setting unit 9, a constant hysteresis is provided. The output of the comparator 10 having a width is inverted from the high level to the low level, and the firing signal from the firing signal generator 8 is blocked by closing the AND gate 12;
The transistors T1 to T6 are turned off (cut off) to stop the regenerative operation, thereby preventing the transistors from being destroyed. At this time, the output of the comparator 10 is temporarily held in the latch circuit 11.

The commutation operation of the regenerative current will be described with reference to FIGS. Here, it is assumed that the R-phase voltage is the highest and the S-phase voltage is the lowest (see the section in FIG. 7).
That is, the transistors T1 and T5 are on, and the other transistors are off. In this case, the path through which the normal regenerative current flows is, as shown by the solid line R1 in FIG. 8, a capacitor 53 as a DC power supply → transistor T1 → AC reactor 3 → AC power supply 1 → AC reactor 3 → transistor T5 → capacitor 53. . Here, if an overcurrent state occurs for some reason, the output signal of CT4 increases in proportion to the current, and the comparator 10 is inverted from the high level to the low level, so that the overcurrent state is detected. In order to suppress this overcurrent, all the transistors T1 to T1
When a cutoff signal is given to T6, the current of AC reactor 3 is commutated to diode D4 → AC reactor 3 → AC power supply 1 → AC reactor 3 → Diode D2 as shown by dotted line R2 in FIG. This is an operation of charging the capacitor 53 as.

[0008]

That is, the voltage V _AB between the input points A and B of the converter section 51 must be V _AB ≒ Ed, but since the diodes D 4 and D 2 are conducting, the DC power supply , The terminal voltage of the capacitor 53 appears at points A and B as it is, and reverses to V _AB ≒ −Ed. For this reason, there is a problem that the voltage V _CD between the connection points C and D between the AC power supply and the inverter is greatly reduced. Since these points C and D are also connection points with other devices, such power fluctuations must be reduced. That is, since the potential V _{CD at the} points C and D is determined by the voltage dividing ratio between the AC reactor 3 and the power supply internal inductance 2, V _CD <0 may occur depending on the capacitance ratio. For this reason,
The capacity of the AC reactor 3 must be selected to be large in order to reduce power supply fluctuations, which results in an increase in size and cost. To reduce the potential fluctuation at the connection point between the power supply and the AC power supply so that the operation can be continued .

[0009]

Means for Solving the Problems In order to solve such a problem, according to the present invention, a converter section in which a self-extinguishing type semiconductor element in which a rectifier diode is connected in anti-parallel is bridge-connected, and a DC power supply section is provided. A power conversion device comprising: a current detection unit for detecting a regenerative current from the converter unit to the AC power supply; a comparison unit for comparing an output signal from the current detection unit with a reference value; and an output of the comparison unit. When the regenerative current exceeds a reference value, either of the upper and lower arm elements of the converter section is turned on during the normal ON period of these elements.
After the signal is cut off and a certain time elapses within the normal ON period
If the regenerative current is below the reference value, the cutoff is performed.
Signal generating means for outputting a signal for releasing and turning on the element again . In the present invention, the comparing means may be provided with hysteresis, and the predetermined time may be determined by the hysteresis. Similarly, a timer can be provided on the output side of the comparing means, and the predetermined time can be determined by the timer.

[0010]

The regenerative current from the load is monitored, and when the regenerative current exceeds a predetermined level, the positive-side or negative-side self-extinguishing semiconductor element is turned off for a certain period of time within the normal ON period of these elements. It is increased and instantaneous stop of the regenerative power is generated from, as the potential variation at the connection point between the inverter and the AC power supply is not increased, Ru FIG continuous operation.

[0011]

FIG. 1 is a block diagram showing an embodiment of the present invention. In the figure, 9A and 9B are setting devices, 10A and 1
0B is a comparator, 11 is a latch circuit, 12A and 12B are AND gates, and 13A and 13B are base drive circuits.
This is because, in the conventional example shown in FIG. 6, the base drive circuit is divided into a positive-side transistor drive 13A and a negative-side transistor drive 13B, and the base drive circuit 13B performs the cutoff control in the same manner as in the related art. The base drive circuit 13A performs stop control by comparing the power supply current with the set value set in the setter 9A, and the other points are the same as in FIG. explain.

Now, if the regenerative electric power suddenly increases for some reason or the instantaneous stoppage of the AC power occurs at the time of electric power regeneration, the regenerative current rapidly increases. Therefore, this current is monitored by CT4, and the output from CT4 is compared with the set value set by setter 9A in comparator 10A. If the former (regenerative current) becomes larger, the output of comparator 10A becomes high. Invert from level to low. This inverted signal is used as an overcurrent generation signal in the AND gate 12A from the power supply voltage detector 7 through the ignition signal generator 8 to the transistor T.
After ANDing with the firing signal distributed to 1 to T6,
The signal is supplied to the base drive circuit 13A and becomes a cutoff signal for the positive side transistors T1 to T3.

For the above operation, the same conditions as in FIG.
In other words, with the R-phase voltage being the highest and the S-phase voltage being the lowest,
Considering the case where the regenerative power suddenly increases or the instantaneous interruption of the AC power occurs, the regenerative current in this case is as shown by a dotted line R3 in FIG. 2, AC reactor 3 → AC power supply 1 → AC reactor 3 → transistor T5 → diode It is commutated along a route such as D4. That is, conventionally, all transistors are cut off (turned off), so that the potential V _AB between points A and B is V _AB ≒ −Ed. In this embodiment, V _AB ≒ 0. And V determined by the voltage division between the AC reactor 3 and the internal inductance 2 of the power supply.
_CD can satisfy V _CD > 0, and as a result, power supply fluctuation can be reduced.

FIG. 3 is a waveform diagram showing the above operation. 14A shows the relationship between the power supply phase (R phase) current and the comparison level, FIG. 14B shows the output waveform of the comparator 10A, FIG. 14C shows the firing signal waveform for the transistor, and FIG. The output of the unit 8 is shown. That is, the power supply phase current (output of CT4) detected at CT4 is
When the output level of the comparator A becomes equal to or higher than the inversion level L1, the output of the comparator 10A is inverted from a high level to a low level as shown in FIG. This low-level signal is ANDed with the ignition signal from the ignition signal generator 8 as shown in FIG. 3D in the AND gate 12A, and as a result, the signal as shown in FIG. The signal is supplied to the positive-side transistors T1 to T3 via the drive circuit 13A. In this case, the positive-side transistor T1 is cut off.

Thereafter, when the regenerative current attenuates to the return level L2 of the comparator 10A as shown in FIG.
0A goes high again as shown in FIG. 2B, and the transistor T1 starts switching operation again as shown in FIG. As described above, the regenerative operation is continued while the regenerative current is suppressed within a certain range as shown in FIG. 2A, and therefore the DC power supply voltage does not increase. At this time, a comparator having a hysteresis of the inversion level and the return level is used as the comparator 10A. In this way, the overcurrent is suppressed and the potential fluctuations at the power supply connection points C and D are also minimized. However, when the overcurrent state has further progressed, this is determined by the setting unit 9B and the comparator 10B as in the related art. Detect and invert its output from high to low. This signal is latched by the latch circuit 11 and cuts off the AND gates 12A and 12B.
〜T6 are all extinguished, and their destruction is prevented. Therefore, the comparison reference voltage of the comparator 10B is
It will be set higher than that of.

FIG. 4 is a block diagram showing another embodiment of the present invention, and FIG. 5 is a waveform diagram of each part for explaining the operation. As is clear from FIG. 4, this embodiment is different from the embodiment shown in FIG. 1 in that a timer 14 for holding the output of the comparator 10A for a certain time is provided. The difference will be described with reference to FIG. Now, when the power supply phase current is in an overcurrent state and the output of CT4 reaches the inversion level of the comparator 10A, the output of the comparator 10A is inverted from a high level to a low level as shown in FIG. The output (low-level signal) is given to the timer 14 and held for a certain time T as shown in FIG. The output of the timer 14 is supplied to an AND gate 12A, where it is ANDed with the output signal from the ignition signal generator 8 as shown in FIG.
A signal as shown in FIG.
To T3.

That is, the transistor T1 is also cut off here, but the transistor T5 is conducting, so that the regenerative current is the same as in FIG. 2, ie, the AC reactor 3, the AC power source 1, the AC reactor 3, the transistor T5, and the diode D4. It will be diverted along such a route. After that, the timer 14
After the elapse of the predetermined time T defined by the above, the output returns to the high level again, and the operation of the positive electrode side transistor is started. Therefore, as shown in FIG. 5A, the regenerative operation is continued while the regenerative current is suppressed to a certain range, so that the DC power supply voltage does not increase and the potential fluctuations at the power supply connection points C and D do not occur. Will also be minimized.
When the overcurrent state further advances, as in the case of FIG. 1, this is detected by the setter 9B and the comparator 10B, and the output is inverted from a high level to a low level. This signal is latched by the latch circuit 11 and cuts off the AND gates 12A and 12B.
〜T6 are all extinguished, and their destruction is prevented.

In the above, a transistor is used as the self-extinguishing type semiconductor element. However, the present invention is not limited to this.
Semiconductor devices such as (field effect transistors) and IGBTs (insulated gate bipolar transistors) can be used. Further, although the AC power supply has three phases, it may be a single phase or three or more phases. Furthermore, although the positive-side transistor is turned off by the output of the comparator 10A, the negative-side transistor may be turned off.
Similar effects can be obtained.

[0019]

According to the present invention, when the regenerative current from the load exceeds a certain fixed value, the operation of the positive-side or negative-side self-extinguishing semiconductor elements of the converter section is controlled by these elements.
Is stopped for a fixed time within the normal ON period, the operation can be continued while reducing the potential fluctuation at the connection point of the power converter to the AC power supply. As a result, the AC reactor capacity of the converter unit can be reduced, and as a result, there is obtained an advantage that the power converter can be small and inexpensive. In addition, a circuit for shutting off all self-extinguishing semiconductor elements is provided in addition to a circuit for stopping the operation of the positive-side or negative-side self-extinguishing type semiconductor elements for a certain period of time. Can be protected from an overcurrent state.

[Brief description of the drawings]

FIG. 1 is a configuration diagram showing an embodiment of the present invention.

FIG. 2 is a circuit diagram for explaining a regenerative current path in the case of FIG.

FIG. 3 is a waveform chart of each part for explaining the operation of FIG. 1;

FIG. 4 is a configuration diagram showing another embodiment of the present invention.

FIG. 5 is a waveform chart of each part for explaining the operation of FIG. 4;

FIG. 6 is a configuration diagram showing a conventional example of a regenerative current control device.

FIG. 7 is an explanatory diagram for describing a power supply voltage and a firing timing of a transistor in FIG. 6;

FIG. 8 is a circuit diagram for explaining a regenerative current path in a normal state in FIG. 6;

FIG. 9 is a circuit diagram for explaining a regenerative current path when a transistor is turned off in FIG. 6;

[Explanation of symbols]

1 ... three-phase AC power supply, 2 ... power supply internal inductance, 3 ...
AC reactor, 4 current transformer (CT), 5 inverter device (power conversion device), 6 induction motor (IM: motor), 7 power supply voltage detector, 8 firing signal generator, 9,
9A, 9B: setting device, 10, 10A, 10B: comparator,
11: Latch circuit, 12, 12A, 12B: AND gate, 13, 13A, 13B: Base drive circuit, 14: Timer, 51: Converter unit, 52: Inverter unit, 53
... Smoothing capacitors.

──────────────────────────────────────────────────続 き Continued on front page (58) Field surveyed (Int.Cl. ⁷ , DB name) H02M 7/219 H02M 7/155

Claims (3)

(57) [Claims] 1. A power conversion apparatus comprising: a converter section in which a self-extinguishing type semiconductor element in which rectifier diodes are connected in anti-parallel and bridge-connected; and a DC power supply section. Current detecting means for detecting a regenerative current; comparing means for comparing an output signal from the current detecting means with a reference value; and the regenerative current exceeding a reference value according to an output of the comparing means.
When there was example, compared either upper or lower arm element of the converter part, within the normal on-period of the element
To shut off the ON signal to the element, the normal ON period
Within a certain period of time, the regenerative current falls below the reference value.
And a signal generating means for outputting a signal to turn off the element and turn on the element again if it is provided. 2. The method according to claim 1, wherein the comparing means has hysteresis.
2. The power regeneration control device according to claim 1, wherein the predetermined time is determined based on the hysteresis. 3. A timer is provided on the output side of said comparing means,
The power regeneration control device according to claim 1, wherein the fixed time is determined by the timer.