JP3331456B2 - Power converter - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a power converter such as a converter for converting AC to DC, and more particularly to control for stopping the operation of a power converter such as a converter when an AC power supply fails.

[0002]

2. Description of the Related Art FIG. 1 shows a power converter for a railway vehicle and a control device therefor as an example of a power converter for converting AC to DC. The railway vehicle power converter collects power from the overhead line 111 connected to the AC power supply 1 by the power collection means 11. The AC voltage collected by the current collecting means 11 is input to the primary side of the transformer 3, and the secondary voltage es obtained by stepping down the voltage by the transformer 3 is supplied to the reactor 4 via the reactor 4 for self-consumption of GTO, IGBT, transistor, etc. It is input to an AC terminal of a converter 2 composed of a semiconductor element having an arcing capability and a diode connected in anti-parallel to this semiconductor element. A capacitor 5 is connected to the DC terminal of the converter 2.
DC voltage obtained by the above is smoothed. Further, an inverter 6 that operates using the voltage of the capacitor 5 as a DC voltage source
Are connected, and the AC motor 7 is driven by the inverter 6. Note that the reactor 4 may use the leakage impedance element of the transformer 3.

Next, a control device of the converter 2 will be described. The voltage ed of the capacitor 5 is detected by the voltage detecting means 33, and is subtracted from the DC voltage command value Ed * by the subtractor 95, and is input to the DC voltage control means 93 to obtain the AC current effective value command Is *. The multiplication unit 96 multiplies this AC current effective value command Is * by a sine wave output from the sine wave generating means 8 described later to obtain an AC current instantaneous command is *.
The instantaneous AC output voltage command ec of the converter 2 is obtained by subtracting the instantaneous value is of the AC current detected by the current detecting means 32 from the instantaneous command is * of the AC current by the subtracter 97 and inputting it to the AC current control means 94, A PWM pulse is input to the PWM pulse generation means 21 and is applied to a semiconductor element constituting the converter 2 to generate a PWM pulse.

Here, the operation of the sine wave generating means 8 will be described. In the control system described above, the output Is * of the DC voltage control means 93 is an effective value command of the AC current, has an effective value of this value, and has an effective value command of the AC current having the same frequency as the AC voltage ep. * Need to be converted. In order to convert the effective value into an instantaneous value, a unit reference sine wave having the same frequency as the AC voltage ep and having an effective value of 1, that is, an amplitude of √2 is required. In the prior art, a unit reference sine wave is generated by the method shown in FIG. In FIG. 6, the current collecting means 1
The AC voltage ep collected by 1 is the train AC power supply es
s, the power of the converter 2, the power from the same overhead wire 111, or the power of the regenerating electric train, and greatly varies depending on the rated voltage.
0%. Further, the AC voltage ep contains a lot of distortion generated by switching of the converter 2. Even in such a situation, in order to obtain a stable unit reference sine wave, the effective value is 1, that is, the amplitude is √2, and is synchronized with the AC power supply voltage regardless of the magnitude and distortion of the voltage collected by the current collecting means 11. It is necessary to obtain a unit reference sine wave.
Therefore, the sine wave generating means shown in FIG. 6 generates a reference sine wave as follows. The AC voltage ep is detected by the voltage detecting means 31 and input to the frequency detecting means 91 to detect the frequency Fss of the AC voltage. The unit reference sine wave generating means 92 generates a sine wave having an effective value of 1 at the frequency Fss of the AC voltage detected by the frequency detecting means 91.
As a result, a unit reference sine wave synchronized with the AC voltage ep can be obtained regardless of the fluctuation of the AC voltage ep and the presence or absence of distortion.
It is possible to provide a control device for the converter 2 that can make the voltage ed of the smoothing capacitor 5 equal to the command value Ed * while keeping the power factor of the AC current is 1 during power running and -1 during regeneration.

[0005]

As described above, when the sine wave generation method shown in FIG. 6 is used, the period of the AC voltage (1/1) is required until the frequency detecting means 91 detects the frequency of the AC voltage. Obviously, it takes more time than Fss). Therefore, even if the AC power supply 1 fails, the converter 2 does not stop instantaneously. Continue to operate at frequency Fss. Thereafter, the converter 2 itself operates to generate an AC voltage ep having a frequency of Fss.
Although the power failure occurs, the frequency detecting means 91 detects the frequency Fss generated by the converter 2, so that the converter 2 continues to operate at the frequency Fss (that is, the control system enters an oscillation state). If a power failure occurs during power running, the power required by the inverter 6 cannot be obtained from the AC power supply 1, so that the DC voltage sharply decreases. On the other hand, if a power failure occurs during regeneration, the power regenerated by the load cannot be regenerated to the AC power supply 1, and the DC voltage rises sharply. Therefore, the apparatus can be stopped by detecting the abnormality of the DC voltage. However, the train on which the converter 2 is mounted is in a regenerative state, and another train exists on the overhead wire 11, and the train is connected to the converter. In the case where the power running operation is performed while consuming an amount of power substantially equal to the regenerated power of the DC power source 2, the DC voltage does not rapidly increase or decrease even if the AC power supply 1 is cut off. Since it moves in the normal fluctuation range,
Converter 2 continues the regenerative operation. This operation continuation time is determined by the relationship between the regenerative electric power and the electric power of the powering vehicle, but in the worst case, the operation may be continued for several minutes. In a railroad, an AC power supply may be intentionally cut off due to a security problem. Therefore, it is not desirable for safety to continue operation for several minutes even if a power cut occurs. Even in such a case, as an example of a method for detecting a power failure, as disclosed in Japanese Patent Application Laid-Open No. 6-46501, an increase in harmonics included in an AC voltage is detected, and this value becomes larger than a specified value. In the case of a power failure, the frequency of oscillation of the control device is slightly shifted from the frequency Fss of the AC power supply voltage as described in JP-A-6-169501, and the frequency is gradually shifted from the frequency Fss at the time of AC power failure. There is a method of detecting a power failure when the frequency of the AC voltage deviates from Fss by a specified value or more, etc. It is necessary to set a large value in advance, and there is a problem in its accuracy, and it is practically difficult to detect. In the method of shifting the frequency of the unit reference sine wave,
Depending on the power factor of the load, the frequency may not be shifted, and another problem such as the occurrence of low-order harmonics and subharmonics in the alternating current during normal operation occurs. In any case, in the prior art, the reason that the converter continues to operate at the same frequency as the AC power supply after the power failure is that the frequency Fs of the AC voltage ep detected before the power failure even after the AC power failure.
s and a sine wave having an effective value of 1 is continuously generated.

[0006] Therefore, an object of the present invention is to provide a power converter that operates in the event of an AC power failure during regenerative operation, regardless of the presence or absence of a load that consumes regenerative power of the power converter.
An object of the present invention is to provide a power conversion device in which a regenerative operation stops reliably.

[0007]

In order to solve the above-mentioned problems, a detecting means for detecting an AC voltage supplied from an AC power supply and a normal gain by multiplying the detected AC voltage by a predetermined constant gain. Means for generating a normalized reference sine wave signal, DC voltage control means for controlling the voltage of the smoothing capacitor to a predetermined value, and a multiplier for multiplying the output of the DC voltage control means by the reference sine wave signal to output an AC current command AC current control means for generating a signal for controlling the converter so that the output of the multiplier and the AC output current of the converter match,
It comprises a pulse generator for driving the converter based on the output of the current control means. Here, when the magnitude of the signal output from the DC voltage control means deviates from a preset range,
Means for detecting this and stopping the operation of the converter is provided.

[0008]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 2 shows an embodiment of the present invention.
FIG. 2 shows the configuration of the sine wave generating means 8 in the control device for controlling the converter 2 shown in FIG. 1, and the other configuration is the same as that of FIG. 1 and operates. In FIG. 2, the amplifier 81 has a function of multiplying a gain for normalizing the AC voltage ep detected by the voltage detecting means 31 with the rated voltage of the AC voltage ep. The fundamental wave detecting means 82 allows, of the output of the amplifier 81, a frequency component only in a frequency range where the AC voltage ep normally fluctuates,
From the AC voltage ep to the sine wave k · proportional to the fundamental frequency component of ep
It has a function to obtain sinωt. With this configuration,
Since the sine wave output from the sine wave generating means 8 fluctuates in proportion to the fluctuation of the fundamental frequency component included in the AC voltage ep, the fluctuation range of the AC voltage ep (-20% to +2 in the case of railway)
0%), the effective value of the sine wave also fluctuates. However, even if the effective value, that is, the amplitude of the sine wave fluctuates due to the operation of the DC voltage control means 93, the operation of the converter 2 can be maintained.

The operation will be described. Current collecting means 11
If the collecting AC voltage ep drops below the rated voltage,
The amplitude of the sine wave generated by the sine wave generating means 8 is also the AC voltage ep
Becomes smaller according to the decrease of Therefore, the instantaneous current command is
The amplitude of * is also smaller, and the input power is less than the required amount of power. As a result, the DC voltage ed shows a tendency to decrease, but the deviation of the ed from the DC voltage command value Ed *, that is, the input of the DC voltage control means 93 increases, so that the output Is * of the DC voltage control means 93 increases. growing. As a result, is * becomes the same value as before the AC voltage drop, the required power is obtained, and the DC voltage ed is kept constant. Similarly, when the AC voltage ep rises above the rated voltage, the amplitude of the sine wave generated by the sine wave generating means 8 also increases according to the rise of the AC voltage ep. For this reason, the amplitude of the instantaneous current command is * also increases, and the input power increases more than the required power amount, so that the DC voltage ed tends to increase. Since the deviation value, that is, the input of the DC voltage control means 93 is small, the output Is * of the DC voltage control means 93 becomes small. As a result, is * becomes the same value as before the AC voltage rise, the required power can be obtained, and the DC voltage ed is kept constant.

Next, the operation at the time of a power failure will be described. In the converter 2 operated by the control system having the sine wave generating means 8 shown in FIG. 2, consider a case where the AC power supply ess fails while the converter 2 is performing a regenerative operation. Even if the AC power supply ess fails, the fundamental wave component of the AC voltage does not immediately attenuate, so that the converter 2 does not stop instantaneously with the power failure as in the related art. But,
When the sine wave generating means 8 shown in FIG. 2 is used, unlike the prior art shown in FIG. 6, after the AC power supply ess is interrupted, the control system of the converter 2 uses the component of the frequency Fss of the AC power supply by itself. The oscillating element no longer exists. Here, the fundamental wave detecting means 82 is a means for detecting a fundamental wave included in the AC voltage ep, and is not an element that itself generates a frequency having the same component as the AC power supply voltage. For this reason, AC power supply es
Due to the power failure of s, the component of the frequency Fss attenuates with the passage of time, and finally, the component of the frequency Fss does not exist at all. As a result, the regenerative operation of converter 2 is stopped, and the situation that converter 2 continues to operate even after a power failure unlike the related art does not occur.

FIG. 3 shows another embodiment of the sine wave generating means according to the present invention. In FIG. 3, in addition to the function of FIG. 2, a phase adjusting unit 85 for adjusting the phase of the sine wave of the fundamental frequency component detected from the AC voltage ep is provided. As the output of the phase adjusting means 85, a sine wave k · sin (ωt + φ) proportional to the fundamental frequency component of ep is obtained from the AC voltage ep. Even when the sine wave generating means 8 is configured in this manner, the control system of the converter 2 has no element for transmitting the component of the frequency Fss itself, and the component of the frequency Fss attenuates with the power failure of the AC power supply ess. Converter 2 no longer continues the regenerative operation. In this embodiment, the provision of the phase adjusting means 85 has an advantage that the power factor of the alternating current is can be set freely.

FIG. 4 shows another embodiment of the sine wave generating means according to the present invention. In the configuration of FIGS. 2 and 3,
Although the fundamental wave detecting means 82 for detecting only the fundamental wave component of the AC voltage ep is provided, in the present embodiment, an amplifier 89 is provided instead of the fundamental wave detecting means 82, and the waveform distortion appearing in the AC voltage ep is small. In the case and when the distortion is neglected, as shown in FIG. 4, a waveform obtained by multiplying the gain of the waveform of the AC voltage ep, that is, a waveform similar to the AC voltage ep is set as the output k2 · ep of the sine wave generating means 8 and the AC current command Is used to generate the instantaneous value is *. In this embodiment, the same effects as those in the embodiment shown in FIGS. 2 and 3 can be obtained. Also, since no filter is required,
It can be easily realized.

FIG. 5 shows another embodiment of the sine wave generating means according to the present invention. In this embodiment, in addition to the frequency detecting means 91 and the unit reference sine wave generating means 92 of FIG. 6, an effective value detecting means 83 for detecting an effective value of the AC voltage ep detected by the voltage detecting means 31 and a multiplier 84 are provided. Provide. Frequency Fss of AC voltage ep detected by frequency detecting means 91
Is input to the unit reference sine wave generation unit 92 to generate a unit reference sine wave having an effective value of 1 at the frequency Fss, and multiply the output of the unit reference sine wave generation unit 92 by the output of the effective value detection unit 83. Here, the gain is set in the effective value detecting means 83 so that a sine wave having an effective value of 1 is output when the AC voltage ep is the rated voltage. As a result, a sine wave proportional to the AC voltage ep is obtained at the same frequency as the AC voltage ep. here,
As described with reference to FIG. 2, when there is a load in which converter 2 is performing regenerative operation and power is obtained from the same AC power supply, and the power of this load is equal to the power regenerated by converter 2, Consider the case where the power supply ess fails. When the AC power supply ess fails, even if the load power and the regenerative power of the converter 2 match, the effective value of the AC voltage ep always changes, albeit slightly, due to the power failure of the AC power supply ess. The direction of this fluctuation is a downward direction. In the prior art shown in FIG. 6, even if the AC voltage ep decreases, the unit reference sine wave generating means 92 continues to generate a sine wave having an effective value of 1 regardless of the amplitude of the AC voltage ep. There is no change in the instantaneous command is * and the AC current is controlled by the converter 2, and the converter 2 stably regenerates power and generates a stable AC voltage ep. That is, the AC voltage ep decreases stepwise due to the power failure, but does not change thereafter. For this reason, even if the AC power supply ess fails, the regenerative operation is continuously performed. on the other hand,
In the case of the present embodiment, when the AC voltage ep decreases due to a power outage of the AC power supply ess, the effective value, that is, the amplitude output by the effective value detection unit 83 also decreases in proportion to the AC voltage ep. The output of the multiplier 84 obtained by the multiplication with the means 92 decreases. That is, since the effective value output by the sine wave generating means 8 decreases in proportion to the AC voltage ep, the instantaneous command is * of the AC current decreases, and the power regenerated by the converter 2 naturally decreases, and The voltage ep further decreases. That is, the AC voltage ep attenuates with time. Since the DC voltage ed increases due to the decrease in the regenerative power of the converter 2, the effective value command Is * of the AC current is increased by the operation of the DC voltage control means 93, and acts to keep the AC current is constant.
The speed at which the effective value of the sine wave, which is the output of the sine wave generating means 8 having an amplitude proportional to the AC voltage ep and the AC voltage ep, decreases faster than the response of the DC voltage control means 93. The AC voltage ep attenuates and eventually becomes zero, and the operation of the converter 2 stops. This allows
In the present embodiment, a situation in which converter 2 continues to operate even after a power failure unlike the related art does not occur.

In the above embodiment, a case has been described in which an AC voltage, that is, a primary voltage of a transformer is detected and a sine wave is generated. However, the AC voltage is not limited to the primary voltage of the transformer. It is clear that the same effect can be obtained by detecting the voltage of the tertiary winding and using it for generating a sine wave when the secondary voltage or the tertiary winding is provided.

Next, FIG. 7 shows another embodiment of the present invention. In this embodiment, the variation range detecting means 100 of the AC voltage is provided in each of the embodiments of FIGS. The AC voltage fluctuation range detecting means 100 has a function of detecting, when the AC voltage ep deviates from a voltage range that can normally fluctuate, and stopping the operation of the converter 2. In this embodiment,
In each of the above embodiments, the converter 2 is stopped when the AC voltage ep deviates from the range of the voltage that can normally fluctuate in the process of the attenuation of the frequency Fss component. Thereby, the time from the power failure of the AC power supply to the stop of converter 2 can be drastically shortened.

FIG. 8 shows another embodiment of the present invention. This embodiment is provided with the fluctuation range detecting means 200 of the AC current effective value command in each of the embodiments of FIGS. The AC current effective value command fluctuation range detection means 200 has a function of detecting when the absolute value of the AC current effective value command Is * deviates from a range in which the AC value can normally fluctuate, and stopping the operation of the converter 2. When the response of the DC voltage control means 93 is fast, the regenerative power decreases with a decrease in the frequency component of Fss in the process of attenuating the frequency component of Fss included in the AC voltage ep after the power failure, so that the DC voltage control Means 93
Is the AC effective value command Is * to ensure regenerative power.
Works in the direction of increasing the absolute value of. Therefore, when the AC power supply fails, if the frequency component of Fss included in the AC voltage ep becomes smaller than the range that can normally fluctuate, the absolute value of the AC current effective value command Is *, which is the output of the DC voltage control unit 93, is obtained. Is usually larger than the range that can be varied. In the present embodiment, the converter 2 is stopped when the absolute value of the alternating current effective value command Is * deviates from a range where the absolute value of the alternating current effective value command Is * generally fluctuates in the process of attenuating the component of the frequency Fss in each of the above embodiments. Thereby, the time from the power failure of the AC power supply to the stop of converter 2 can be drastically shortened.

[0017]

As described above, according to the present invention,
Since the converter control system does not have an element that generates an AC component by itself, the frequency component of the AC power supply attenuates with a power outage of the AC power supply, regardless of the presence or absence of a power running vehicle serving as a load and the magnitude of the power, Since the control system for controlling the converter does not exist, as described in the related art, the operation is not continued by the oscillation source contained therein after the power failure, and the operation of the power converter is stopped immediately after the power failure. be able to. In addition, when the magnitude of the signal output from the DC voltage control means deviates from a preset range, a means for stopping the converter is additionally provided, so that the time from the power failure to the stop of the power converter is dramatically reduced. Can be shortened.

[Brief description of the drawings]

FIG. 1 is a power converter for a railway vehicle to which the present invention is applied and a control device therefor.

FIG. 2 is a configuration diagram of a sine wave generating unit in a control device according to an embodiment of the present invention.

FIG. 3 is a configuration diagram of a sine wave generating unit in a control device according to another embodiment of the present invention.

FIG. 4 is a configuration diagram of a sine wave generating means in a control device according to another embodiment of the present invention.

FIG. 5 is a configuration diagram of a sine wave generating means in a control device according to another embodiment of the present invention.

FIG. 6 is a configuration diagram of a sine wave generating means in a conventional control device.

FIG. 7 is a control device showing another embodiment of the present invention.

FIG. 8 is a control device showing another embodiment of the present invention.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... AC power supply, 111 ... Overhead wire, current collection means ... 11, 2 ... Converter, 21 ... PWM pulse generation means, 3 ... Transformer,
4 reactor, 5 smoothing capacitor, 6 inverter, 7 AC motor, 31 voltage detecting means, 32 current detecting means, 33 voltage detecting means, 8 sine wave generating means,
81: amplifier, 82: fundamental wave detecting means, 83: effective value detecting means, 84: multiplier, 85: phase adjusting means, 89: amplifier, 91: frequency detecting means, 92: unit reference sine wave generating means, 93 ... DC voltage control means, 94 AC current control means, 95 subtractor, 96 multiplier, 97 subtractor, 1
00: AC voltage fluctuation range detecting means, 200: AC current effective value command fluctuation range detecting means

Continuation of the front page (56) References JP-A-6-46501 (JP, A) JP-A-6-169501 (JP, A) JP-A-8-331860 (JP, A) JP-A-8-251707 (JP) JP-A-5-122943 (JP, A) JP-A-8-331765 (JP, A) (58) Fields studied (Int. Cl. ⁷ , DB name) H02M 7/72 B60L 3/04 H02H 3/24 H02M 7/21

Claims (2)

(57) [Claims] 1. A power converter comprising: a converter for converting an AC voltage supplied from an AC power supply to a DC; an inverter for converting a DC to an AC through a smoothing capacitor; and an AC motor driven by the inverter. A detecting means for detecting the AC voltage; a means for multiplying the detected AC voltage by a predetermined constant gain to generate a normalized reference sine wave signal; and setting the voltage of the smoothing capacitor to a predetermined value. DC voltage control means, a multiplier for multiplying the output of the DC voltage control means by the reference sine wave signal to output an AC current command, and the output of the multiplier and the AC output current of the converter match. AC current control means for generating a signal for controlling the converter, and driving the converter based on the output of the current control means. Power conversion apparatus characterized by a pulse generator. 2. The apparatus according to claim 1, further comprising means for detecting when the magnitude of a signal output from said DC voltage control means deviates from a preset range, and stopping the operation of said converter. Power converter.