JPH06245532A - Pwm waveform control system of multiple inverter - Google Patents

Abstract

PURPOSE:To provide the PWM waveform control system of multiple inverters, in which inverters and output transformers can have the same capacity and the same specifications. CONSTITUTION:(n) multiplexed (such as quintupled) rectangular waves are expanded in Fourier series, a phase angle theta, where each order of higher harmonic quantity reaches a desired value or less, is arithmetically operated, and the output voltage waveforms of (n) multiple inverters are computed on the basis of said theta respectively. The half period of a sine wave is divided into ten at every 18 deg., pulses P1-P10 having width equal to the area ratios of each segment are arranged at a center in the theta direction, and said pulses are superposed (subtracted) to the output voltage waveforms of each inverter computed every five waveforms (at the time of the multiple number of five of the inverter).

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a multiplex structure of a single-phase large-capacity power converter and a PWM waveform control system for reducing harmonics.

[0002]

2. Description of the Related Art Thyristors and gate turn-off thyristors (GTOs) are used as semiconductor elements for high withstand voltage and large currents used in large capacity converters. Here, FIG. 6 shows an example of a multiple structure of a single-phase large-capacity conversion device using a self-turn-off device (GTO). FIG. 6 shows a device having a 5-multiplex structure, in which 1 to 5 are inverters, 6 to 10 are output transformers, and 11 is an electrolytic capacitor.

The voltage vector after the output voltage multiplexing of each inverter is as shown in FIG. Further, FIG. 8 shows a PWM waveform for varying the output voltage (in the case of 3-pulse control).

According to the conventional control method, each inverter is driven by the PWM waveform shown in FIG. In order to reduce harmonics, the phase angle of the inverter is 0 °, ± 20 as shown in FIG.
, ± 40 °, and the winding ratio of the secondary windings of the output transformers 6 to 10 is 1: 0.742: 0.742: 0.
By setting 395: 0.395, harmonics up to the 15th order are removed. The order of harmonics generated in this system is 18n ± 1 (n = 1, 2, 3 ...) That is, 17,
19, 35, 37 ... Only the next harmonics are generated, and no other harmonics are generated.

[0005]

In the conventional multiplexing method, basically, as described above, the phase angle of each inverter is shifted by a required angle, and the winding ratio of the multiplexing output transformer is changed to generate the generated harmonics. It uses a method that limits the order to a specific harmonic. In this case, the output voltage of each inverter is the same, and therefore the output transformer primary voltage is the same. The secondary output current is the same because the secondary side of the output transformer is directly connected. Since the secondary voltage value is different,
There were the following problems.

(1) The capacity of the output transformer for multiplexing is equal to the secondary winding voltage ratio, and three types of transformers are required in the case of 5 multiplexing. (2) Three types of inverter capacity are also required. (3) If the inverter capacities are the same, the utilization rate becomes worse. Therefore, there is a drawback that the device becomes large. (4) Since several types of transformers and inverters are required, there are drawbacks such as high cost, difficulty in configuration, and increase in size.

The present invention has been made in view of the above points, and an object thereof is to make an inverter and an output transformer have the same capacity,
An object of the present invention is to provide a PWM waveform control method for multiple inverters that can have the same specifications.

[0008]

Means and Actions for Solving the Problems The present invention is
(1) A rectangular wave having the same crest value when the number of times of switching in one cycle is set to 1 is n-multiplexed, the waveform is configured as an even function and an odd function, and Fourier series expansion is performed to obtain each harmonic. The phase angle θ is calculated so that the wave amount becomes equal to or smaller than a desired value, and the output voltage waveforms of the n multiple inverters are calculated based on the θ, and the half cycle of the sine wave is set to the same phase angle. N × (m−1) (where m is the number of pulses of the PWM waveform) so that a plurality of pulses having a width equal to the area ratio of each of the divided sections are divided by θ of each of the divided sections.
Each of them is arranged at the center in the direction, and the pulse is superposed (subtracted) on the output voltage waveform of each inverter every n times. (2) Half cycle of the sine wave has the same phase angle. Divide n × (m−1) (where m is the number of pulses of the PWM waveform), and divide a plurality of pulses having a width equal to the area ratio of each divided section into two equal areas. Each of the pulses is arranged at a position in the θ direction, and the pulse is superimposed (subtracted) on the output voltage waveform of each inverter every n times, and (3) the half cycle of the sine wave is equal to the area of each section. N × (m−1) division in the θ direction so that
Is the number of pulses of the PWM waveform), a plurality of pulses having the same height and the same width are respectively arranged at the center of the divided sections in the θ direction, and the output voltage waveform of each of the inverters is every n pulses. Is characterized by superimposing (subtracting) on
(4) The half cycle of the sine wave is divided into n × (m−1) in the θ direction so that the areas of the sections are the same (where m is the PWM
The number of pulses of a waveform), a plurality of pulses having the same height and the same width are arranged at θ-direction positions that divide the area of each section into two equal parts, and the output voltage of each inverter is every n pulses. It is characterized by superimposing (subtracting) on the waveform.

[0009]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments of the invention described in claims 1 and 2 will be described below with reference to the drawings. Although the control method of the present invention can be applied to any number of multiplexes, the five multiplex method will be described as an example. The device configuration is the same as in FIG. This method uses a method of obtaining a PWM control method that minimizes harmonics in a computer under the precondition that the primary and secondary turns ratio of the output transformer is the same.

(1) First, five multiplexed waveforms are formed when the number of times of switching in one cycle is once (on / off once in 360 °). Then, the waveform as shown in FIG. 1 can be considered. The height of each step is the same (value of DC voltage)
Becomes FIG. 1 shows a waveform that is an even function and an odd function.

Next, the 90 ° to 180 ° portion in FIG. 1 is taken out and subjected to Fourier series expansion. That is, the horizontal axis is 0-9
The angle is reset to 0 °, the x and θ coordinates of each vertex are set as shown in FIG. 2, and the nth harmonic component is calculated. The nth harmonic component is given by the following equation.

En = (4 / nπ) {sin (nθ ₁ ) + sin (nθ ₂ ) + sin (nθ ₃ ) + sin (nθ ₄ ) + sin (nθ ₅ )} ... (1) θ _{1 to} θ ₅ = 0 By changing between 90 °, θ _{1 to} θ _{5 at} which the respective harmonics have values not more than the desired value are calculated by a computer. As a result, the output voltage waveform of each inverter is as shown in FIG.
That is, in the first inverter INV1, −θ _{5 to} θ ₁ has a + side output waveform, and 180−θ _{5 to} 180 + θ ₁ has a − side output waveform. Similarly, INV2 to INV5 also output the voltage waveform having the flow width shown in FIG.

(2) PWM for adjusting the output voltage
Must be wavy. For example, the waveform of 1 inverter is 3
The case of using pulse PWM will be described below. First, the waveform of FIG. 8 described above represents the output voltage waveform of the 3-pulse PWM waveform of one inverter. It can be considered that two dents of a rectangular wave are superimposed on the + side and the-side of the output voltage.
In the case of 5 multiplexes, a total of 10 dents will occur on the + side and the-side, respectively.

(3) The phase of this pulse is obtained as follows. First, as shown in FIG. 4A, the output voltage waveform after five-multiplexing is a sine wave, and 180 ° is divided by 10 and divided into 18 °. Then, each area ratio is calculated, and a pulse having the same ratio as the area ratio is placed at the midpoint of each section (at 9 °) as shown in FIG. 4B. Each pulse is set to P1 to P10, and FIG.
As shown in, P1 and P6 for INV1 and P for INV2
2 and P7, P3 and P8 for INV3, P4 for INV4
Make a dent on P9 and P9, and P5 and P10 on INV5. 3
Pulse PWM is used. By doing so, it is possible to construct a device with less harmonics.

In another embodiment, the output voltage waveform is a sine wave, the sine wave is divided by 18 °, and a pulse proportional to the area ratio of each section is arranged at the midpoint of the area of each section. May be.

Next, embodiments of the invention described in claims 3 and 4 will be described. First, the method until the output voltage waveform of each inverter is obtained as shown in FIG. 3 (that is, FIGS. 1, 2, and 3) is exactly the same as the method described above. Next, FIG. 5 (a)
As shown in, the output voltage waveform after 5 multiplexing is a sine wave,
The area of the sine wave is divided into 10 equal parts, and the middle point in the θ direction is shown in FIG.
A pulse having a constant width is arranged as shown in (b). This pulse has the same height and the same width. This pulse is P1
To P10, and as shown in FIG. 5 (c), INV1 has P
1 and P6, P2 and P7 for INV2, P3 for INV3
And P8, P4 and P9 are made in INV4, and P5 and P10 are made in INV5, and the pulse waveform of each inverter is determined. By doing so, harmonics can be reduced.

In another embodiment, as shown in FIG. 5 (a), a sine wave area is divided into 10 equal parts, and a pulse having the same height and width is placed at a position in the θ direction where the area of each section is divided into two parts. It may be arranged.

[0018]

As described above, according to the present invention, since the inverter and the output transformer can have the same capacity and the same specification, the following excellent effects can be obtained. (1) The number of designing, testing, and manufacturing steps can be reduced, and the cost can be reduced. (2) The utilization factor of the inverter is 100%, which makes it possible to downsize the device as compared with the conventional system. (3) Since the inverter utilization rate is 100%, the number of elements can be reduced, snubber loss and other losses are reduced, and efficiency can be improved. (4) The responsibility of the inverter is the same and the evaluation is easy. (5) In case of trouble, it is easy to deal with it because all the specifications are the same.
One is good).

[Brief description of drawings]

FIG. 1 is a voltage waveform diagram showing an embodiment of the present invention as claimed in claims 1 to 4 in the case of 5 multiplexing.

FIG. 2 is an explanatory view showing an embodiment of the inventions of claims 1 to 4, and showing a Fourier series expansion of a part of the waveform of FIG.

FIG. 3 is a diagram showing an output voltage waveform of each inverter, showing an embodiment of the invention of claims 1 to 4.

FIG. 4 shows an embodiment of the invention of claims 1 and 2, (a) is an explanatory diagram of a dividing method, (b) is a pulse waveform diagram, and (c) is 3
Waveform diagram of pulse PWM.

5A and 5B show an embodiment of the invention of claims 3 and 4, (a) is an explanatory diagram of a dividing method, (b) is a pulse waveform diagram, and (c) is 3
Waveform diagram of pulse PWM.

FIG. 6 is a configuration diagram of a general five-multiplex power conversion device.

FIG. 7 is a voltage vector diagram of the inverter.

FIG. 8 is a voltage waveform diagram showing a PWM waveform of the inverter.

[Explanation of symbols]

 1-5 ... Inverter 6-10 ... Output transformer 11 ... Electrolytic capacitor

─────────────────────────────────────────────────── ───

[Procedure amendment]

[Submission date] December 27, 1993

[Procedure Amendment 1]

[Document name to be corrected] Drawing

[Correction target item name] Figure 8

[Correction method] Change

[Correction content]

[Figure 8]

Claims (4)

[Claims] 1. A rectangular wave having the same crest value when the number of times of switching in one cycle is once is n-multiplexed, and the waveform is configured as an even function and an odd function to perform Fourier series expansion, and The phase angle θ is calculated so that the amount of the next harmonic becomes equal to or less than the desired value, and the output voltage waveforms of the n multiple inverters are calculated based on the θ, and the half cycle of the sine wave is the same phase. N × to be a corner
(M-1) divided (where m is the number of pulses of the PWM waveform), and a plurality of pulses having a width equal to the area ratio of each divided section are respectively provided at the center in the θ direction of each divided section. A PWM waveform control system for a multi-inverter, characterized in that the pulse is arranged and the pulse is superposed on the output voltage waveform of each inverter every n times. 2. A rectangular wave having the same crest value when the number of times of switching in one cycle is once is n-multiplexed, the waveform is configured as an even function and an odd function, and Fourier series expansion is performed, The phase angle θ is calculated so that the amount of the next harmonic becomes equal to or less than the desired value, and the output voltage waveforms of the n multiple inverters are calculated based on the θ, and the half cycle of the sine wave is the same phase. N × to be a corner
(M-1) division (where m is the number of pulses of the PWM waveform), and a plurality of pulses having a width equal to the area ratio of each divided section divides the area of each section into halves. A PWM waveform control method for a multiple inverter, wherein the PWM waveform control method is characterized by arranging the pulses at respective positions and superposing the pulses every n times on the output voltage waveform of each inverter. 3. A rectangular wave having the same crest value when the number of times of switching in one cycle is set to 1 is n-multiplexed, and the waveform is configured as an even function and an odd function, and Fourier series expansion is performed. The phase angle θ is calculated so that the amount of the next harmonic becomes equal to or less than the desired value, and the output voltage waveforms of the n multiple inverters are calculated based on the θ, and the half cycle of the sine wave is calculated as the area of each section. So that
Direction is divided into n × (m−1) (where m is the number of pulses of the PWM waveform), and a plurality of pulses having the same height and the same width are arranged at the center of each divided section in the θ direction,
A PWM waveform control system for a multi-inverter, characterized in that the pulse is superimposed on the output voltage waveform of each inverter every n times. 4. A rectangular wave having the same crest value when the number of times of switching in one cycle is set to 1 is n-multiplexed, and the waveform is configured as an even function and an odd function, and Fourier series expansion is performed. The phase angle θ is calculated so that the amount of the next harmonic becomes equal to or smaller than the desired value, and the output voltage waveforms of the n multiple inverters are calculated based on the θ, and the half cycle of the sine wave is calculated as the area of each section. So that
Direction is divided into n × (m−1) (where m is the number of pulses of the PWM waveform), and a plurality of pulses having the same height and the same width are respectively divided into the θ direction positions which divide the area of each section into two equal parts. P of a multiple inverter, which is arranged and superimposes every nth pulse on the output voltage waveform of each inverter.
WM waveform control method.