JP2715584B2 - Multiplexed rectifier control method - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for controlling a semiconductor rectifier for converting and controlling AC power to DC power.

[Conventional technology]

For example, as shown in FIG. 3, a unit rectifier 1 constituting a multiplexed rectifier is a semiconductor switching element.
A configuration in which a GTO thyristor 2 is used for bridge connection is known. Reference numeral 3 in the figure denotes a load connected to the DC output side of the unit rectifier 1.

FIG. 4 shows a plurality of such unit rectifiers (two in the figure).
A rectifier multiplexed by using the rectifier, in which 4 is a harmonic control filter, and the AC input terminals of the unit rectifiers 1A and 1B are directly connected in parallel.

FIG. 5 shows an AC input current waveform of one phase (R) of the multiplexed rectifier shown in FIG.

That is, as shown in FIGS. 3A and 3B, the AC input currents i _R1 and i _R2 of the unit rectifiers 1A and 1B are reduced by PWM ( (Pulse width modulation), and the unit rectifier 1B is operated with a delay of 30 ° in electrical angle with respect to the unit rectifier 1A.

[Problems to be solved by the invention]

By the way, the AC input currents i _R1 and i of the unit rectifiers 1A and 1B
It has been revealed that _R2 has relatively low low-order harmonic components, but contains higher-order harmonic components at around 20% of the basic group near the current cutting frequency. Also, the total AC input current i _{R obtained} by combining them [FIG. 5 (c)]
It is also clarified that a harmonic current near the current cutting frequency is included in the filter, and this harmonic current causes an increase in the size of the harmonic suppression filter 4 connected to the AC power supply. Has also become.

Further, in order to obtain an AC input current waveform shown in FIG. 5, the current of the GTO thyristor which is a main semiconductor element constituting the unit rectifier shown in Fig. 4, when i _R1 is positive current GTO thyristor in 2a _1, when a negative current is flowing in the GTO thyristor 2a _2. Also, i _R2 is a GTO thyristor 2b ₁ when a positive current, when a negative current is flowing in the GTO thyristor 2b _2.

As a result, the number of switching times of the GTO thyristor becomes
GTO thyristors 2a ₁ and 2a during one cycle of AC input current
b ₁ is five, GTO thyristors 2a _2, 2b ₂ becomes 7 times, this is also true for the other two phases (S and T).

Therefore, the number of switching times of the GTO thyristor constituting the unit rectifier 1A is 5 times / cycle, and the number of switching times of the GTO thyristor constituting the unit rectifier 1B is 7 times / cycle.
This was one cycle, and the equipment used could not be shared or used effectively.

However, the GTO thyristor causes a large switching loss during the transition between ignition and extinction, and the average value of the switching loss during one cycle of the AC input current of the rectifier is almost proportional to the number of switching operations.

SUMMARY OF THE INVENTION An object of the present invention is to eliminate the disadvantages of the prior art, and to reduce the higher-order harmonic currents contained in the combined AC input current in a multiplexed rectifier configured by connecting the AC inputs of each unit rectifier in parallel. The size of the harmonic suppression filter provided on the input side can be reduced, and the unit rectifier can be shared.
It is an object of the present invention to provide a control method for a multiplexed rectifier which can realize a reduction in size and cost of a device by effective use.

[Means for solving the problem]

In order to achieve the above object, the present invention uses N (N ≧ 2) current-type unit rectifiers for determining a cutting phase of an AC input current from an intersection of a carrier signal and a control signal, and connects the AC inputs in parallel. In the multiplexed rectifier configured as above, in each current type unit rectifier, the phase of the carrier signal is shifted by 2π / N from each other to determine the cutting phase of the AC input current, and each current type unit rectifier is configured. The gist is to distribute the ignition and extinction signals to be applied to the respective main semiconductor elements so that the switching frequencies of the main semiconductor elements become equal.

[Action]

According to the first aspect of the present invention, of the triangular carrier signal and the sawtooth control signal used in determining the current cutting phase, the phase of the triangular carrier signal is set to 2π / N (N Is the number of unit rectifiers, and is shifted by N ≧ 2), so that the synthesized AC input current does not include higher harmonic currents near the current cutoff frequency, and the harmonics connected to the AC power supply side The suppression filter can be downsized.

According to the second aspect of the present invention, in addition to the above operation, the PWM current flowing to the GTO thyristor is alternately passed between the same arms of the unit rectifier every cycle of the AC input current. By controlling the GTO thyristor, the switching frequency of the GTO thyristor of each unit rectifier can be equalized on average, and the generated loss of each GTO thyristor can be equalized.

〔Example〕

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

FIG. 1 shows an embodiment of a control method of a multiplexed rectifier according to the present invention, wherein the AC input terminals of three-phase current type unit rectifiers 1A and 1B which do not use a transformer as shown in FIG. FIG. 9 is a waveform diagram for explaining a method of determining a current cutting phase of each unit rectifier 1A, 1B in a multiplexed rectifier configured by directly connecting in parallel.

FIG. 1 shows an electric angle 0 ° of the combined AC input current.
Although shown for the period from el to 60 示 し el, other periods, such as the period from 60 ゜ el to 120 ゜ el, are uncut, 120 ゜ el to 180 ゜ el
Is the same cutting phase as the period of 0 ゜ el to 60 ゜ el, and the description is omitted.

Now, we describe an example units rectifier two duplexed as FIG. 4, the cutting phase of one of the unit rectifier 1A is FIG (a) to the solid line of the triangular wave carrier signal T ₁ and dashed showing From the intersection with the control signal C, it is determined as indicated by i _R1 in FIG.

On the other hand, the cutting phase of the other unit rectifier 1B is determined as follows.

Triangular wave carrier signal T ₂ of the one-dot chain line units rectifier 1B as shown in FIG. (B) is a triangular wave carrier signal T ₁ of the solid line for one of the unit rectifier 1A, 2π / N (N is the number of inverters, N ≧ 2), in this case 180 ° out of phase.

Therefore, from the intersection of the control signal C of the carrier signal T ₂ and the broken line, the cutting phase of the unit rectifier 1B are determined as shown in i _R2 in FIG (c).

As a result, synthetic alternating input current because it is the sum of i _R1 and i _R2, is as i _R in FIG (d).

Harmonic components of these waveforms, like the conventional method for i _R1 and i _R2, although higher harmonic current in the vicinity of the current chopping frequency is contained about 20% with respect to the fundamental wave, synthetic AC input current the i _R, harmonic current in the vicinity of the current chopping frequency can become substantially zero, it revealed from the results of the waveform analysis.

By determining the cutting phase in this manner, harmonic current components near the current cutting frequency can be eliminated.

FIG. 2 shows a second embodiment of the control method of the present invention, and shows an AC input current waveform of one phase of a multiplexed rectifier.

2, i _R1 is the R-phase current waveform of the unit rectifier 1A in FIG. 4, i _R2 is the R-phase current waveform of the unit rectifier 1B, and i _R is the R-phase current of the unit rectifiers 1A and 1B. 8 is an R-phase current waveform of a multiplexed rectifier that combines phase currents.

The pulse number of the R-phase current i _R1 of the unit rectifier 1A is ωt = 0
5 pulses / half cycle in the period from
= 2π to 4π during the period of 7 pulses / half cycle, while the number of pulses of the R-phase current i _R2 of the unit rectifier 1B is 7 pulses / half cycle during the period from ωt = 0 to 2π, ωt = In the period from 2π to 4π,
5 pulses / half cycle.

By the way, the region where the R-phase current of the unit rectifiers 1A and 1B is positive is the GTO thyristors 2a ₁ and 2b ₁ of the U arm of the angular unit rectifiers 1A and 1B.
Share the current, the negative area is the X-arm GTO thyristor 2
Since a ₂ and 2b ₂ are shared, the GTO thyristor constituting each unit rectifier is switched during the period from ωt = 0 to 4π by distributing the ignition and extinction signals given to each main semiconductor element as described above. The number is 12/2 cycles,
The unit rectifiers 1A and 1B are equal.

〔The invention's effect〕

As described above, the control method of the multiplexed rectifier of the present invention is applied to a multiplexed rectifier configured by connecting the AC inputs of the three-phase current source unit rectifiers without using a transformer in parallel.
The synthesized AC input current does not include higher harmonic current components near the current cutting frequency, and as a result, the harmonic suppression filter connected to the AC power supply can be downsized.
This makes the harmonic suppression filter inexpensive.

Also, since the number of times of switching of the main semiconductor elements constituting each unit rectifier was controlled to be equal on average,
The generated losses of all the main semiconductor elements become equal, and as a result, the equipment used for each unit rectifier can be shared and used effectively, and the size and price of the device can be reduced.

[Brief description of the drawings]

FIG. 1 is a waveform diagram showing one embodiment of a control method of a multiplexed rectifier of the present invention, FIG. 2 is a waveform diagram showing a second embodiment of the present invention, and FIG. 3 is a general example of a rectifier comprising a GTO thyristor. FIG. 4 is a circuit diagram showing a general example of a multiplexed rectifier, and FIG. 5 is a waveform diagram showing an AC input current waveform of one phase. 1, 1A, 1B ...... rectifier _{2,2a 1, 2a 2, 2b 1} , 2b 2 ...... GTO thyristor 3 ...... load 4 ...... harmonic suppression filter T _1, T ₂ ...... carrier signal C ...... control signal

Claims (2)

(57) [Claims] A current type unit rectifier for determining a cutting phase of an AC input current from an intersection of a carrier signal and a control signal is an N-type unit rectifier.
In a multiplexed rectifier comprising (N ≧ 2) units and their AC inputs connected in parallel, the current rectifiers cut the AC input current by shifting the phases of the carrier signals by 2π / N from each other. A method for controlling a multiplexed rectifier, comprising determining a phase. 2. A current-type unit rectifier for determining a cutting phase of an AC input current from an intersection of a carrier signal and a control signal.
In a multiplexed rectifier comprising (N ≧ 2) units and their AC inputs connected in parallel, the current rectifiers cut the AC input current by shifting the phases of the carrier signals by 2π / N from each other. A multiplexing rectifier for determining a phase and distributing a firing signal and an extinguishing signal to be applied to each main semiconductor element so that the switching frequency of the main semiconductor element constituting each unit rectifier of each current type becomes equal. Control method.