JPH03112365A - Multiplex pulse width modulation inverter - Google Patents

Abstract

PURPOSE:To limit torque ripple to a low level over the entire control range by lagging the reference sine wave and reference triangular wave from a second inverter, by 1/12 of the wavelength of the reference sine wave, behind the reference sine wave and reference triangular wave having the frequency 3M times that of the reference sine wave from a first inverter. CONSTITUTION:In the case of N=15(M=5, N=3XM=15), reference sine wave and reference triangular wave from a second inverter are lagged, respectively, by 1/12 of the wavelength of the reference sine wave with respect to a first inverter 11, and a zigzag winding is applied onto the second output transformer 22 thus cancelling 17, 29, 31, 43th higher harmonics out of 13, 17, 29, 31, 43, 47, 59, 61th higher harmonics produced from the first and second inverters 11, 12. Consequently, even if the waveform is degenerated due to overmodulation at the time of high output voltage and 5th and 7th higher harmonics are produced, they are cancelled and torque ripple can be limited to a low level.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Field of Application] This invention relates to a pulse width modulation inverter (pulse width modulation inverter), for example, to reduce output voltage harmonics generated from an inverter and torque ripple caused by the output voltage harmonics. The present invention relates to a multiple pulse width modulation inverter that reduces the number of pulse widths.

[Prior art] Figure 5 is from the paper by Mr. Takahashi and Mr. Miyairi, ``Relationship between the output waveform of a PWM inverter and the gate control signal'' (Transactions of the Institute of Electrical Engineers of Japan 95)
FIG. 2 is a circuit diagram showing the configuration of a multiplexed pulse width modulation inverter that reduces output voltage harmonics according to the principle of Vol. 2, No. 1975, pp. 73-83).

In the figure, (1) is a DC power supply, (2) is an electric motor, and (1) is a DC power supply.
11), (112) are the first and second transistor inverters connected in parallel to the DC power supply (1), (
121) and (122) are first and second transistor inverters (111).

(112) first and second output transformers that are respectively connected to the AC output side and combine the inverter outputs on the secondary side;
(130) is a control device that controls firing signals supplied to transistors that are constituent elements of the first and second transistor inverters (111) and (112).

FIG. 6 is a block diagram showing the configuration of the control device (130), in which (131) is a reference sine wave generation circuit, (132) is a reference sine wave generation circuit;
), (133) are reference triangular wave generation circuits for the first and second transistor inverters (111) and (112), (134) and (135) are comparators that compare the reference sine wave and the reference triangular wave, (136) ),
(137) is a comparator (134).

This is a base amplifier which inputs the output signal of (135) and supplies an ignition signal to the first and second transistor inverters (111) and (112).

Next, the operation will be explained. The DC voltage supplied from the DC power supply (1) is converted into AC by the first and second transistor inverters (111) and (112), and
, an output transformer (121) connected to (112)
, (122) and is supplied to the electric motor (2) to start the electric motor (2) and drive a load machine (not shown).

At this time, the frequency of the reference sine wave (101) output from the reference sine wave generation circuit (131) is changed to the reference triangular wave whose phase is shifted by π/N from the f1 reference triangular wave generation circuits (132) and (133). (102), (10
When the frequency of 3) is NXf, the comparator (134) outputs the reference sine wave (1
01) and a reference triangular wave (102) to generate and output an ignition signal to be supplied to the first transistor inverter (111), and the comparator (135)
), the reference sine wave (101) and the reference triangular wave (1
02) with a reference triangular wave (103) whose phase is shifted by π/N, and generates and outputs an ignition signal to be supplied to the second transistor inverter (112).

From the first transistor inverter (111) and the second transistor inverter (112) whose ignition is controlled by the above-mentioned ignition signal, (2 to -1) ± 2nd order, 2kN ± 1st order (here -1 , 2, 3°...) output voltage harmonics are generated, but the (2 to -1) N±2nd order harmonics are coupled by the secondary sides of the output transformers (121) and (122), respectively. 2kN±1st order harmonics remain, which is effective in reducing output voltage harmonics.

Note that the output voltage harmonics generated by the pulse width modulation inverter are not only (2 to 1)N ± 2nd order and 2kN ± 1st order, but also many side wave components centered on (2 to 1)N and 2kN. However, since the majority are (21cm1)N±2nd order and 2kN±1st order, their explanation will be omitted.

[Problems to be Solved by the Invention] Conventional multiplex pulse width modulation inverters are configured as described above and are effective in reducing harmonics, but sine wave pulse width modulation inverters have The ratio of possible output voltage is small.

Therefore, in order to increase the voltage utilization rate, overmodulation is performed to obtain a high output voltage, but due to waveform degeneration, (2 to -1)
In addition to N±2nd and 2kN±1st, lower harmonics 5th, 7th, and
... occurs and torque ripple increases.

In particular, when the load machine is an existing blower, low torque ripple is often required over the entire control range, and the multiplex pulse width modulation inverter is difficult to apply due to the increase in torque ripple as described above. There was a problem.

The present invention has been made to solve the above-mentioned problems, and an object of the present invention is to obtain a multiplex pulse width modulation inverter device that does not increase the torque ripple generated in the driving electric motor over the entire control range. shall be.

[Means for Solving the Problems] The multiplex pulse width modulation inverter according to the present invention compares a reference sine wave and a reference triangular wave and supplies the results to first and second inverters connected in parallel to a power source. When generating an arc signal, a triangular wave having a frequency 3XM times the frequency of the reference sine wave of the first inverter is used as the reference triangular wave of the first inverter, and the reference sine wave of the first inverter and the reference a control device that delays a reference sine wave and a reference triangular wave of the second inverter by 1/12 wavelength of the reference sine wave wavelength with respect to the triangular wave; and a control device that is connected to the second inverter and has a staggered winding connection on the secondary side. It is equipped with an output transformer.

[Operation] When the control device of the present invention compares the reference sine wave and the reference triangular wave and generates the firing signal to be supplied to the first and second inverters, the control device compares the frequency of the reference sine wave of the first inverter. A triangular wave with a frequency 3XM (M-3, 5, 7...) times higher than that of the first inverter is used as a reference triangular wave, and a second The ignition signal is controlled to delay the reference sine wave and reference triangular wave of the inverter by 1/12 wavelength of the reference sine wave wavelength, and the secondary output transformer of the second output transformer connected to the second inverter is controlled to The staggered winding on the sides makes it possible to limit the torque ripple to a small value over the entire control range.

[Example 1] An example of the present invention will be described below with reference to the drawings. 1st
In the figure, (1) is a DC power supply, (2) is an electric motor, and (1) is a DC power supply.
1), (12) are the first and second inverters connected in parallel to the DC power supply (1), (21), (
22) are the first and second inverters (11),
The second output transformer (22) has a staggered winding on the secondary side, and the second output transformer (22) is connected to the AC output side of the first output transformer (12). Vessel (21)
is connected to the secondary side of the motor (2).

(30) are first and second inverters (11);
(12) This is a control device that controls the ignition signal supplied to the transistor which is the component element. This control device (30)
As shown in Figure 2, the reference sine wave (61), (6
2) rReference sine wave generation circuit that outputs Fig. 4a, cl (
31), (33), Reference triangular wave (63), (64)r Figure 3, Reference triangular wave generation circuit (32) that outputs dJ
, (34), reference sine wave (61) and reference triangular wave (6
3) a comparator (41) that generates a control signal by comparing the
A comparator (42) generates a control signal by comparing a reference sine wave (62) and a reference triangular wave (64), and a first inverter receives control signals from the respective comparators (41) and (42). (11) and base ups (51) and (52) that supply ignition signals to the second inverter (12).

FIG. 3 is a diagram for explaining the operation of the first inverter (11), and the reference sine wave generating circuit (31) of the first inverter (11) is connected to each of the U-phase, ■-phase, and W-phase standards. Sine wave generation circuit (31u), (31v), (31w)
It consists of

The comparator (41) is composed of a U-phase comparator (41u), a v-phase comparator (41V), and a W-phase comparator (41W).
U of the first inverter (11) in the phase comparator (41u)
Generates a phase firing signal.

The base amplifier (51) has a comparator for each phase (41u).

Base amplifiers (51u-a) and (51v-a) that directly amplify the outputs of (41v) and (41w).

(51W-a) and NOT gate (71u), (71v
), (71w) to amplify the bass amplifier (5
1u-b), (51v-b), and (51w-b), and supplies an ignition signal to the transistor of the first inverter (11).

The reference sine wave generation circuit (33), comparator (42), and base amplifier (52) for the second inverter (12) also have a similar configuration.

Next, the operation in the case of N-1N-15 (, N-3N-3x 5) will be explained. 13.17, 29, 31°43.47.59.61 generated from the first inverter (11) and second inverter (12) in FIG.
Among the harmonics, for the first inverter (11),
By delaying the reference sine wave and reference triangular wave of the second transformer (12) by 1/12 wavelength of the reference sine wave wavelength, and providing a staggered winding to the second output transformer (22), , 13.47, 59.61 harmonics are canceled out.Here, the secondary winding of the second output transformer (22) has the relationship of At: 1Bl=1:1/, fT. It has been established.

At high output voltage, overmodulation occurs and the waveform degenerates, resulting in 5th and 7th orders.
Even if harmonics occur, the second output transformer (21)
The second output transformer (22
), the 5th and 7th harmonics are canceled out and the torque ripple can be limited to a small value.

In addition, although the case where AC output is obtained from a DC power supply was demonstrated in the said Example, the DC power supply may be a combination of an AC power supply and a rectifier. Furthermore, the constituent elements of the inverter are not limited to transistor elements.

[Effects of the Invention] As described above, according to the present invention, the reference triangular wave frequency is 3M times the reference sine wave frequency (M-3, 5°7,...)
and the phases of the reference sine wave and reference triangular wave of the second inverter are delayed by 1/12 wavelength of the reference sine wave wavelength with respect to the reference sine wave and reference triangular wave of the first inverter, and the second output transformer is Since a staggered winding is provided on the secondary side of the transformer and the output is coupled to the first output transformer, the torque ripple can be effectively limited to a small value over the entire control range.

[Brief explanation of drawings]

FIG. 1 is a block diagram showing a multiplexed pulse width modulation inverter according to an embodiment of the present invention, FIG. 2 is a block diagram of a control device used in the multiplexed pulse width modulation inverter of FIG. 1, and FIG. 3 4 is a block diagram showing a part of the control device in detail, FIG. FIG. 5 is a block diagram of a conventional multiple pulse width modulation inverter, FIG. 6 is a block diagram of a control device used in the multiple pulse width modulation inverter of FIG.
FIG. 7 is a waveform diagram showing the U-phase reference sine wave and reference triangular wave in the reference sine wave generation circuit and reference triangular wave generation circuit of FIG. 6. In the figure, (11) is the first inverter, (12) is the second inverter, (21) is the first output transformer, (2
2) is a second output transformer, 1 (30) is a control device, (61) and (62) are reference sine waves, and (63) and (64) are reference triangular waves. In addition, in the figures, the same reference numerals indicate the same or corresponding parts.

Claims (1)

[Scope of Claims] First and second inverters connected in parallel to a power source, and first and second inverters whose primary sides are individually connected to the AC output sides of each of the inverters and whose outputs are combined on the secondary side. When generating the ignition signal to be supplied to the first and second inverters by comparing the reference sine wave and the reference triangular wave with the second output transformer, the frequency of the reference sine wave of the first inverter is A triangular wave having a frequency three times an odd integer of 3 or more is used as a reference triangular wave for the first inverter, and a reference sine wave for the second inverter is used for the reference sine wave for the first inverter and a reference triangular wave for the first inverter. and a control device that delays the reference triangular wave by 1/12 wavelength of the reference sine wave wavelength, and a staggered winding connection is provided on the secondary side of the output transformer connected to the second inverter. A multiplexed pulse width modulation inverter.