JP2000217371A - Power regenerative device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a power regenerative device which can secure an approximately constant dead zone and realize a stable and smooth regenerative operation even if the frequency of an AC power supply is varied. SOLUTION: This power regenerative device has a phase detecting circuit 20 which is composed of comparators 20-1-20-3 which compare 3-phase interline voltages detected by an AC power supply line voltage detecting circuit 10-1 with a 1st reference value, and detect timings when value relations of the voltages of the respective phases of a 3-phase AC power supply are changed over and output timing signals, comparators 20-4-20-6 which compare the output values of an absolute value circuit 10-2 with a 2nd reference value, and output dead zone signals which specify the dead zones of respective switching devices of a power supply regenerative converter, and a switching signal generating circuit 20-7 which generates switching signals with dead zones from the timing signals and the dead zone signals and turns on/off the respective switching devices with the switching signals.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] The present invention relates to a power regeneration device.

[0002]

2. Description of the Related Art Referring to FIG. 3, a general power regeneration device applied to a three-phase induction motor will be described. The power regeneration device has a power regeneration converter 40 connected to an inverter 30 for driving a three-phase induction motor IM. In this power regeneration device, the full-wave rectified voltage Vac from the three-phase AC power supply 50 supplied to the inverter 30
And the smoothing capacitor 4 included in the power regeneration converter 40
The powering / regeneration state is determined from the difference from the DC voltage Vdc at both ends of the power supply 1. And if it is determined that it is in the regenerative state,
By turning on and off the six switching elements 42 in the power regeneration converter 40 in synchronization with the phase of the three-phase AC power supply 50, the regenerative power is returned to the three-phase AC power supply 50 side.

[0003] The power regeneration converter 40 includes an inverter 3
0 are connected in parallel with the six full-wave rectifier diodes 31. During the powering operation of the three-phase induction motor IM, the smoothing capacitor 41 is charged with the full-wave rectified voltage Vac of the three-phase AC power supply 50. During the regenerative operation, the DC voltage V across the smoothing capacitor 41 is generated by the regenerative electric power from the three-phase induction motor IM.
dc rises above the voltage Vac during power running. By detecting the rising voltage of the DC voltage Vdc from the voltage Vac, the operating state of powering / regeneration is determined.

When it is determined that the regenerative state is detected, the power regenerative converter 40 turns the six switching elements 42 on and off in synchronization with the voltage phase of the three-phase AC power supply 50, thereby converting the regenerative power to the three-phase AC power. Return to 50.

The following method is employed as a method for synchronizing the on / off of the switching element 42 with the voltage phase of the three-phase AC power supply 50. That is, the three-phase AC power supply 50
And the lower arm of the switching element 42 (one of UP, VP, WP) connected to the phase having the highest voltage and the lower arm of the switching element 42 connected to the phase having the lowest voltage. Arm (UN, VN, WN
On).

In this system, as shown in FIG.
The inter-phase voltages Vrt, Vst, V of each phase of the three-phase AC power supply 50
At the moments ta, tb, tc at which the magnitude relationship of rs switches,
A commutation operation is performed to turn off the switching element that has been turned on and turn on another switching element.

[0007] However, if the on / off switching is performed at the same time, a period during which both switching elements are on may occur due to a difference in switching operation time or the like. In this case, an overcurrent may flow through the power regeneration converter 40, and the operation may be stopped by the protection function or the switching element 42 may be damaged.

In order to avoid this, as shown in FIG.
The timing at which the switching element is turned on is delayed by a shorter time t ₁ than the timing at which the magnitude relationship between the phases of the three-phase AC power source is switched. Further, the time t ₂ from which is counted by the timer, turns off the switching element slightly earlier than the timing of the next switched.
Thus, at the time of switching, a period t ₃ (hereinafter, referred to as a dead zone) in which both switching elements are off is provided.

[0009]

However, if the time t ₂ during which the switching element is turned on is controlled to be constant by a timer, the width of the dead zone changes when the frequency of the AC power supply changes, and the AC power supply changes. There is a disadvantage that the power returned to the fluctuates.

Further, even when the frequency of the AC power supply changes, the width of the dead zone must be widened so that a period in which both switching elements are on does not occur, and a smooth regenerative operation is hindered. Would.

An object of the present invention is to provide a power regeneration device that can secure a substantially constant dead band width even when the frequency of an AC power supply changes, and can realize a stable and smooth regenerative operation. is there.

[0012]

According to the present invention, there is provided a power regeneration converter connected to an inverter for driving a motor, and a full-wave rectified value of a voltage from an AC power supply supplied to the inverter and the converter. A powering / regenerative state is determined from the difference between Vac and the DC voltage Vdc across the smoothing capacitor included in the converter. If the regenerative state is determined, switching is performed in the converter in synchronization with the phase of the AC power supply. In a power regenerating apparatus that returns regenerative power to the AC power supply side by turning on and off an element, a DC voltage V across the smoothing capacitor is provided.
a voltage detection circuit that detects dc, a line voltage detection circuit that detects a line voltage of the AC power supply, an absolute value circuit that detects an absolute value of the line voltage detected by the line voltage detection circuit, A full-wave rectification value detection circuit including a maximum value detection circuit that detects a maximum value from the output of the absolute value circuit and outputs the maximum value as the full-wave rectification value Vac; and the DC voltage Vdc detected by the voltage detection circuit. A regenerative determination circuit that compares the full-wave rectified value Vac to determine a powering / regenerating state of the electric motor and outputs a regenerative determination signal in a regenerative state; Voltage and first reference value RE
Comparing the output of the absolute value circuit with a second reference value by comparing the output of the absolute value circuit with a second reference value. A second comparing means for outputting a dead band signal defining a dead band width of the switching element, and the regeneration determination signal, the timing signal, and the dead band signal as inputs. A switching signal generating circuit for generating a switching signal having a dead zone from the dead zone signal and turning on and off the switching element by the switching signal; and a phase detecting circuit.

When the AC power supply is a three-phase AC power supply, the line voltage detection circuit detects a three-phase line voltage, and the first comparing means outputs the detected three-phase line voltage. And first to third comparators for comparing the line voltage with the first reference value, wherein the second comparing means includes three outputs from the absolute value circuit and the second reference value. The fourth to compare values
A sixth comparator, wherein the switching signal generation circuit includes a regenerative determination signal, three timing signals from the first to third comparators, and a signal from the fourth to sixth comparators. A switching signal for turning on and off the six switching elements is generated based on the three dead zone signals.

[0014]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A power regeneration device according to the present invention will be described with reference to FIGS. FIG. 1 shows a configuration of a full-wave rectified value detection circuit 10 and a phase detection circuit 20 which are characteristic parts of a power regeneration device according to the present invention, and these are built in a power regeneration converter 40 shown in FIG. Is used. In addition to these configurations, a voltage detection circuit 1 for detecting a voltage across the smoothing capacitor 41 is provided.
1 and a regeneration determination circuit 12.

The voltage detection circuit 11 includes a smoothing capacitor 41
Is detected and output. The full-wave rectified value detection circuit 10 includes an AC power supply line voltage detection circuit 10-1, an absolute value circuit 10-2, and a maximum value circuit 10-3.
The AC power line voltage detection circuit 10-1 is a three-phase AC power supply 5.
0 R-phase, S-phase, and T-phase line voltages Vrt, Vst, Vr
s is detected and output.

FIG. 2A shows an example of a detection waveform of the line voltage Vrs based on the R-phase voltage Vr and the S-phase voltage Vs.

The absolute value circuit 10-2 includes the line voltages Vrt and Vs detected by the AC power line voltage detection circuit 10-1.
t, Vrs, and their absolute values | Vrt |, | V
st |, | Vrs | are output.

FIG. 2B shows an example of a detected waveform of the line voltage | Vrs |.

The maximum value circuit 10-3 includes an absolute value circuit 10-
Line voltage absolute value | Vrt |, | Vst detected in step 2.
And | Vrs | are input and the maximum value thereof is taken to detect and output the full-wave rectified voltage Vac of the three-phase AC power supply 50.

The regeneration judging circuit 12 receives the voltage Vdc across the smoothing capacitor 41 detected by the voltage detecting circuit 11 and the full-wave rectified voltage Vac detected by the full-wave rectified value detecting circuit 10 as inputs. The regenerative determination circuit 12 determines the difference between the two (Vdc−
When Vac) exceeds the set reference value, it is determined that the vehicle is in the regenerative state, and a regeneration determination signal is output.

The phase detection circuit 20 includes six comparators 20-
1 to 20-6 and a switching signal generation circuit 20-7.

The comparators 20-1, 20-2, and 20-3 respectively provide line voltages Vrt, Vst, and Vrs of the three-phase AC power supply 50 detected by the AC power supply line voltage detection circuit 10-1.
Is input. Each of the comparators 20-1, 20-2, and 20-3 compares each of the line voltages Vrt, Vst, and Vrs with a first reference value REF1 (generally, a ground level) to thereby control each of the three-phase AC power supplies 50. Phase voltages Vr, Vs, V
The timing at which the magnitude relationship of t switches is detected, and a timing signal is output.

FIG. 2C shows an example of the output waveform of the timing signal from the comparator 20-3. The comparator 20-3 detects a timing 150 ° (see FIG. 2A) at which the voltage Vr and the voltage Vs are switched.

The comparators 20-4, 20-5, and 20-6 receive as input the line voltage absolute values | Vrt |, | Vst |, and | Vrs | detected by the absolute value circuit 10-2, respectively. Is compared with the second reference value REF2,
A dead zone signal that defines a dead zone width is output. This dead zone width can be adjusted by changing the second reference value REF2.

FIG. 2D shows an example of the output waveform of the comparator 20-6. The comparator 20-6 outputs a dead band signal that defines a certain dead band width around a timing 150 ° at which the magnitude relationship between the voltage Vr and the voltage Vs switches.

The switching signal generation circuit 20-7 includes a regeneration determination signal output from the regeneration determination circuit 12,
Three timing signals output from 0-1 to 20-3 and indicating the switching of the voltage magnitude relation, the comparators 20-4 to 20-2
The three dead zone signals output from 0-6 are input.
The switching signal generation circuit 20-7 generates six switching signals having an appropriate dead zone from the timing signal and the dead zone signal when the regeneration state is determined by the regeneration determination signal, and the six switching elements 42 based on these switching signals. On and off.

FIGS. 2 (e) and 2 (f) show timing charts of switching from switching off of the switching element UP shown in FIG. 3 to switching on of the switching element VP. The switching element UP is turned off earlier than the timing signal by (AND) / 2 by ANDing the timing signal of FIG. 2C and the dead zone signal of FIG. 2D. The switching element VP is turned on with a delay (dead band width / 2) behind the timing signal by ANDing the inverted signal of the timing signal of FIG. 2 (c) and the dead band signal of FIG. 2 (d).

As described above, the switching element 42 can be turned on and off in synchronization with the phase of each phase of the three-phase AC power supply 50. Since the dead zone is set by detecting the switching timing of the voltage of each phase, the dead zone width is set substantially constant even when the frequency of the AC power supply fluctuates.

In the above embodiment, a three-phase AC power supply is shown as an AC power supply, but a single-phase AC power supply or a multi-phase AC power supply having four or more phases may be used.

FIG. 6 shows an AC power supply 6 for a single-phase AC power supply.
0 and the power regeneration converter 70. The power regeneration converter 70 includes four switching elements indicated by AP, BP, AN, and BN and a smoothing capacitor 71.

FIG. 7 is a waveform diagram showing switching signals with dead zones set in the four switching elements of FIG. 6 on the same principle as described above. Such switching signals are supplied to the AC power line voltage detection circuit 10-1, the absolute value circuit 10-2, and the maximum value circuit 10 shown in FIG.
-3 for single-phase use, and the comparison circuit compares the line voltage with the reference voltage REF1, and compares the absolute value with the reference voltage REF2.
And two switching circuits are used for the comparison, and the switching signal generation circuit generates four switching signals. However, since the same timing signal may be used for AP and BN and AN and BP, there are practically two types.

[0032]

As is apparent from the above description, in the present invention, the full-wave rectified value detection circuit of the AC power supply is constituted by an AC power supply line voltage detection circuit, an absolute value circuit, and a maximum value circuit. The phase detection circuit can be simplified by using the output signals from the power supply line voltage detection circuit and the absolute value circuit to configure the phase detection circuit.

The dead zone width at the time of the switching operation is
By defining the output from the absolute value circuit (the absolute value of the voltage between the AC power supply lines) and the second reference voltage REF2 by the result of comparison by the three comparators, without being affected by the frequency fluctuation,
An almost constant dead zone width can be secured, and a stable and smooth regenerative operation can be performed.

[Brief description of the drawings]

FIG. 1 is a diagram showing a main part configuration of a power regeneration device according to the present invention.

FIG. 2 is a waveform diagram of voltages and signals for explaining the operation of each unit in FIG. 1;

FIG. 3 is a diagram showing a configuration of an inverter for driving a three-phase induction motor and a power regeneration converter of a general power regeneration device combined with the inverter.

FIG. 4 is a waveform diagram of a voltage and a signal for explaining ON / OFF timing of a switching element in a conventional power regeneration converter.

FIG. 5 is a voltage and signal waveform diagram for explaining a method of setting a dead band width of a switching element in a conventional power regeneration converter.

FIG. 6 is a diagram showing an AC power supply and a power regeneration converter in the case of a single-phase AC power supply.

FIG. 7 is a waveform diagram showing a waveform of a single-phase AC power supply voltage and a switching signal with a dead zone set in the four switching elements of FIG. 6;

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 10 Full-wave rectification value detection circuit 10-1 AC power line voltage detection circuit 10-2 Absolute value circuit 10-3 Maximum value circuit 11 Voltage detection circuit 12 Regeneration judgment circuit 20 Phase detection circuit 20-1 to 20-6 Comparator 20-7 Switching Signal Generation Circuit

Claims (2)

[Claims] 1. A power regeneration converter connected to an inverter for driving an electric motor, a full-wave rectified value Vac of a voltage from an AC power supply supplied to the inverter and the converter, and a smoothing value included in the converter. A powering / regenerative state is determined from a difference between the DC voltage Vdc at both ends of the capacitor, and when the regenerative state is determined, a switching element is turned on and off in the converter in synchronization with the phase of the AC power supply. A power regeneration device that returns regenerative power to the AC power supply side, a voltage detection circuit that detects a DC voltage Vdc across the smoothing capacitor, a line voltage detection circuit that detects a line voltage of the AC power supply, An absolute value circuit for detecting an absolute value of the line voltage detected by the line voltage detection circuit, and detecting a maximum value from an output of the absolute value circuit. A full-wave rectification value detection circuit including a maximum value circuit that outputs the full-wave rectification value Vac; and comparing the DC voltage Vdc detected by the voltage detection circuit with the full-wave rectification value Vac, Powering
A regeneration judging circuit for judging a regenerative state and outputting a regenerative judging signal in a regenerative state; and comparing a line voltage detected by the line voltage detecting circuit with a first reference value REF1 to determine whether the AC power supply has First comparing means for detecting a timing at which the magnitude relation of the voltage is switched and outputting a timing signal; and comparing the output of the absolute value circuit with a second reference value to define a dead zone width of the switching element. Second comparing means for outputting a dead zone signal;
The regeneration determination signal, the timing signal, the dead zone signal is input, when it is determined that the regeneration state, a switching signal having a dead zone is generated from the timing signal and the dead zone signal, the switching signal by the switching element A power regeneration device comprising: a phase detection circuit including a switching signal generation circuit for turning on and off. 2. The power regeneration device according to claim 1, wherein
The AC power supply is a three-phase AC power supply, the line voltage detection circuit detects a three-phase line voltage, and the first comparing means compares the detected three-phase line voltage with the first line voltage. And a second comparator for comparing the three outputs from the absolute value circuit with the second comparator.
And a switching signal generating circuit, wherein the switching signal generation circuit includes: a regeneration determination signal; three timing signals from the first to third comparators;
A power regeneration device, wherein a switching signal for turning on and off the six switching elements is generated based on three dead zone signals from the fourth to sixth comparators.