KR930000225Y1 - Ripple reducing circuit - Google Patents

Abstract

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Description

Resonant Damping Device for LC Filter of Power Converter

1 is a view showing an inverter device for a railcar including an LCR type resonance damping device according to an embodiment of the present invention.

FIG. 2 is a board diagram for explaining the resonance damping effect of the resonance damping apparatus shown in FIG.

3 is a board diagram showing a resonance peak of a conventional LC filter for an inverter to which no resonance attenuation means is applied.

4 is a rail car inverter device having an electronic circuit-type resonance damping device according to a second embodiment of the present invention.

FIG. 4a is a modification of part of the circuit shown in FIG.

5A is a waveform diagram of an example of oscillation of the filter output voltage due to resonance of the DC filter shown in FIG.

FIG. 5B is a waveform diagram for explaining the operation of the electronic circuit shown in FIG. 4 for detecting the voltage oscillation shown in FIG. 5A.

6 is a view showing an inverter device for a rail car including an electronic circuit type resonance attenuating device according to a third embodiment of the present invention.

FIG. 7A is a waveform diagram of an example of filter output voltage oscillation due to resonance of the DC filter shown in FIG.

FIG. 7B is a waveform diagram for explaining the operation of the electronic circuit shown in FIG. 6 for detecting the voltage oscillation shown in FIG.

8 is a view showing an inverter device for a rail car including an electronic circuit type resonance attenuating device according to a fourth embodiment of the present invention.

The present invention relates to a technique for damping the peak level of the transfer function of a lowpass filter configured on the DC input side of a power converter, and particularly DC / AC for an electric railcar. A resonance attenuation apparatus for effectively attenuating the resonance Q of an LC filter inserted between a DC input side of an inverter (or a DC / DC converter) and a power line.

An electric rail car is a power converting apparatus, for example, an inverter apparatus, as a power source for supplying power to a load such as a rail motor driving electric motor, various controllers, air conditioners and lighting devices. use. The power converter converts the high line voltage supplied through the pantagraph into a low voltage suitable for each load.

The inverter device of this type includes an LC type DC filter having low pass characteristics to remove high frequency noise contained in the line voltage supplied through the fantagraph. The filter has a positive gain characteristic with a high peak of about +20 dB in the range of about 50-220 rad / sec (8-35 kHz).

The above-mentioned power converter having an inverter device is known, for example, as disclosed in Japanese Patent Laid-Open No. 63-174501.

L (reactor) and C (capacitor) that make up the filter when the load and / or DC input of the inverter device change suddenly, for example, when the load of inverter or line voltage changes due to the start of the air conditioner in the railcar. The voltage ratio assigned by This change causes the DC input of the inverter device to change, and eventually fluctuations occur in the envelope of the inverter output voltage.

If the envelope of the inverter output voltage fluctuates, the load current of the inverter device also changes accordingly, and the DC input voltage of the inverter device also changes. Such a chain of loops of voltage / current variation causes resonance at the output voltage of the LC filter (the DC input voltage of the inverter device).

As described above, in a conventional power converter used for a rail car, a truck, and the like, power is supplied to an inverter device through an LC filter to remove high frequency components of line voltage. Therefore, if periodic fluctuations in the input voltage due to sudden load fluctuations or sudden line voltage fluctuations cannot be completely corrected by the phase control circuit in the inverter device, the output voltage is periodically oscillated. As a result, a stable AC voltage cannot be supplied to a lighting device such as a fluorescent lamp, and flicker occurs in the lighting device.

The above-mentioned resonance phenomenon can be prevented by the following method.

1) Increasing the power capacity of the inverter device reduces the effects of load variations.

2) Increase the capacity of the capacitors constituting the LC filter.

3) Connect a limiting resistor with relatively high resistance in series with the LC filter.

In order to carry out the method (1) or (2) above, the size of the device must be turned on. Bulky devices are not suitable for use in electric rail cars.

In the case of the method (3), since the amount of heat emitted from the limiting resistor is large, the efficiency of the inverter device is lowered and is not suitable.

An object of the present invention is to provide an apparatus capable of effectively attenuating resonance due to load fluctuations or sudden line voltage fluctuations without unnecessarily increasing the capacity of the power converter or degrading the driving efficiency of the device.

In order to achieve the object of the present invention, a resonance circuit formed of a series circuit composed of a reactor and a capacitor and a resistor having a resonance frequency substantially equal to a frequency at which a resonance phenomenon occurs due to a load or line voltage variation is used as a high frequency component. Connect in parallel to the reactor that constitutes the LC-type DC filter circuit for removal.

According to the power converter used for a vehicle, a railcar, etc. having a DC filter circuit having the above-described configuration, when a load or line voltage is rapidly changed, a current component of a frequency close to the resonance frequency is parallel to the reactor of the DC filter circuit. Some flow into the connected resonant damping circuit. Therefore, considering the DC filter circuit as a whole, the gain at and near the resonant frequency of the DC filter circuit is reduced, so that the resonance Q is finally attenuated.

In addition, in the present invention, a limited time period immediately after a severe oscillation due to resonance occurs at the DC output of the DC filter in order to achieve the above object, that is, to attenuate the resonance Q of the DC filter without degrading the driving efficiency of the power converter. Only an electric circuit for temporarily increasing the equivalent DC resistance component value connected in series with the DC filter is provided. The resonance Q of the DC filter is attenuated by the increased equivalent DC resistance component.

Although the power loss increases with the increased equivalent DC resistance component, the resistance component increases only in a very short period of time immediately after the occurrence of resonance, and there is no power loss in a steady state where resonance does not occur. Since the period in which the resonance occurs is very short compared to the normal driving period, the resonance Q of the DC filter can be attenuated without substantially deteriorating the driving efficiency of the power converter.

When explaining the embodiment of the present invention in detail with reference to the accompanying drawings as follows.

1 is a configuration diagram of a resonance damping device of the present invention, in which an inverter is used as a power converter. As shown in FIG. 1, one DC input terminal of the DC / AC inverter (or DC / DC converter) 5 is connected to the fantagraph 1 through a limiting resistor 2 and a reactor 3 connected in series. do. The other DC input terminal of the DC / AC inverter 5 is connected to the ground circuit. The capacitor 4 is connected in parallel between the 2DC input terminals of the inverter 5.

Capacitor 4 and reactor 3 constitute a DC low pass filter (LPE) that removes high frequency components from the voltage supplied from line 10. The three-phase AC output terminal of the inverter 5 is connected to a load 6 such as an electric motor or a lighting device. The load 6 is supplied with three phase AC power. In this case there are, in fact, the internal impedance of the transformer itself, the impedance of the line and the internal resistance component in the reactor 3 present in series with the reactor 3.

However, it is considered that these impedance and resistance components are contained in the limiting resistor 2 and the reactor 3.

As shown in FIG. 1, a series circuit (resonance attenuation circuit: LCR circuit) of the reactor 7, the capacitor 8, and the resistor 9 generates a resonance phenomenon due to a change in the load 6 and the line voltage. Has substantially the same resonance point as. Such an LCR circuit is connected in parallel with the reactor 3 constituting the DC filter LPF. The LCR circuit acts as a band-pass filter (BPF), that is, a resonance attenuation circuit, for selectively passing the resonance frequency.

In the inverter having the above-described configuration, if the resonance frequency is set to about 20 Hz, the circuit constant of the LCR of the resonance attenuation circuit BPF is selected next.

1 / (2π LC) = 20 ‥‥ (1)

The resistance component R is set to a value higher than the impedance of the reactor 3 at a frequency of 20 Hz so that the peak of resonance is suppressed to +10 dB to +15 dB or less.

As described above, the resonance damping circuit BPF in which the circuit constant is selected is connected in parallel to the reactor 3. 2 shows the frequency-gain characteristics of the output voltage V1 of the DC filter LPF in this case. The impedance between the terminals of the resonance damping circuit BPF is given by the following equation (2).

(j2π fL) + (1 / j2π fc) + R ‥‥ (2)

When f = fo, the impedance has a maximum value R. The resonance frequency fo is given by the following equation (3).

fo = 1 / 2π LC ‥‥ (3)

A current component having a frequency near the resonance frequency fo branches and flows into the resonance attenuation circuit, and then flows to the input side of the inverter 5.

In this case, as compared to the gain indicated by the dotted line in FIG. 2, the gain of the DC filter LPF is lowered in the vicinity of the resonance frequency fo so that the fluctuations in the envelope of the inverter output caused by the resonance phenomenon may occur. There is no possibility.

As described above, in this embodiment, the resonance attenuation circuit BPF is configured in parallel with the reactor 3 of the DC filter LPF configured on the input side of the inverter circuit 5, and this circuit BPF is a load ( Due to the fluctuation of 6) or the sudden fluctuation of the line voltage, the resonance point is substantially the same as the frequency at which the resonance occurs. If the load 6 and the line voltage are maintained in a steady state (i.e., no resonance), the resonance attenuation circuit BPF has a high impedance with respect to the frequency component of the input voltage supplied in this state and is electrically The circuit is set in the open state. On the other hand, when the load fluctuates or the line voltage fluctuates rapidly, the resonant damping circuit exhibits low impedance with respect to the resonant frequency component contained in the input voltage and absorbs a current including the resonant frequency component. Thus, the resonance Q can be attenuated without adversely affecting other circuits. Resonance Q can also be attenuated regardless of the sequence of L, C and R series connections.

In conclusion, the fluorescent lamp serving as the load 6, unlike in the conventional apparatus, is flickered by the fluctuation which is the main memory of the output voltage of the inductor 5.

In addition, since the LCR circuit (resonance damping circuit BPF) in which the large current does not flow constantly is simply connected to the reactor 3 of the DC filter LFF, the volume of the device is not substantially increased and the driving efficiency of the inverter 5 is lowered. It doesn't work. Therefore, practical advantages can be obtained.

In the above embodiment, the inverter is used as a power converter. However, the same advantages can be obtained by replacing the inverter with a DC / DC converter.

4 shows an inverter device for an electric rail car provided with an electric circuit type resonance attenuation device according to a second embodiment of the present invention. The same reference numerals are used for the components shown in FIG.

The output response of the DC filter (DC input to the inverter 5) V1 is lowered to a signal voltage V2 of about several volts by a voltage driver including resistors R3 and R4. The voltage V2 has the same waveform as that of the output voltage V1 of the filter (FIG. 5A).

When the voltage V1 is not adversely affected by oscillation due to the resonance of the filter, the voltage V2 is smaller than the reference voltage Vref.

When voltage V1 is adversely affected by oscillation due to filter resonance, voltage V2 exceeds the value of reference voltage Vref at time 11 immediately after the occurrence of oscillation. At that time, the comparator 11 generates a reference voltage V3. The one-shot 12 is triggered by the reference voltage V3 to supply the switch driver 13 with a signal V4 (FIG. 5B) having a predetermined pulse width T. As shown in FIG. Upon receiving signal V4, switch driver 13 directs signal V5 to switch SW for period T.

The switch SW is always connected in parallel to a resistor R2 which is one of the resistors R1 and R2 connected in series. Resistor R1 serves to limit overcurrent. The resistor R2 serves to sufficiently attenuate the resonance Q of the DC filter, which cannot be completely attenuated by the resistor R1 alone.

When the voltage V5 is supplied to the switch SW, the switch SW is turned off in the time period T. During the period T, the series resistance component of the reactor 3 of the DC filter increases from R1 to R1 + R2, so that the resonance of the DC filter is sufficiently attenuated.

The capacity of the overcurrent limiting resistor R1 is determined by the specification (maximum current allowable value) of the DC filter or inverter 5. After the capacity of the resistor R1 is determined, the capacity of the resistor R2 is determined based on the experiments performed on each actual device.

The peak value shown in FIG. 2 is less than +10 dB to +15 dB. The period T is also determined based on preliminary or practical experiments on actual feasts. Thus, the period T is sufficient to damp the resonance.

As shown in FIG. 4A, the switch SW can be replaced with a semiconductor switching element such as a power MOS transistor. In this case, the internal resistance component ("ON" resistance component) of the transistor in the "ON" state can be used as the Q attenuation resistor R2.

The internal resistance component of the MOS transistor can be controlled by the gate voltage V5. Therefore, the overcurrent limiting resistor R1 can be omitted, and instead the " ON " resistance component of the transistor can be adjusted to change between " R1 " and " R1 + R2 " by using the voltage V5. In addition, the BPF shown in FIG. 1 may be connected in parallel with the reactor 3 shown in FIGS. 4, 6 or 8. Resistors 2 and R1 and R2 may be inserted between reactor 3 and capacitor 4.

When the DC voltage V1 changes greatly in an accident, the reference voltage Vref may change in proportion to the change of the voltage V1.

6 shows an inverter device used in an electric rail car having an electric circuit type resonance damping device according to a third embodiment of the present invention.

In FIG. 6, the one-shot 12 shown in FIG. 4 is removed, and the switch driver 13 is driven directly by the output V3 from the comparator 11.

In the configuration shown in FIG. 6, the comparison output V3 is generated whenever the voltage V2 (FIG. 7A) exceeds the reference voltage Vref. Only while the comparison output V3 is generated (T1, T2), the " always on " switch SW is turned off so that resonance is attenuated.

8 shows an inverter device used in an electric rail car having an electric circuit type resonance damping device according to a fourth embodiment of the present invention. In the embodiments shown in FIGS. 4 and 6, the ON / OFF timing of the switch SW is detected in accordance with the voltage V2 including the DC component of the voltage V1. In contrast, in the embodiment of FIG. 8, the ON / OFP timing of the switch SW is detected according to the voltage V2a which does not include the DC component of the voltage V1.

In other words, the DC component of the voltage V1 is cut off by the capacitor C1, and only the variable component AC component is converted into the voltage V2a through a voltage driver including the resistors R3 and R4. The voltage V2a is amplified by the AC amplifier 14, and the amplified signal V2b is converted into the DC signal V2c through the rectifier 15.

Then, as in the case of FIG. 6, the signal V2c is compared with the reference voltage Vref, and then the comparison result V3 is sent to the switch driver 13. The switch driver 13 receives the comparison result V3, and then turns off the switch SW only for a period corresponding to the pulse width of the comparison result V3.

As a result, the resonance of the DC filter is attenuated.

As described above, the device according to the present invention can efficiently reduce the cavitation phenomenon caused by the load fluctuation or the sudden fluctuation of the line voltage without increasing the volume of the power converter and lowering the driving efficiency of the device. .

Claims (16)

A device for attenuating the resonance of LC type low pass filters 3, 4 provided on the DC input side of a power converter 5 having a DC input terminal, comprising: a rig actor 3 constituting the LC type low pass filter. And an electric circuit (7, 8, 9) connected in parallel with the LC circuit of the power converter, characterized in that it has an impedance that takes a substantially minimum value at the same frequency as the resonant frequency of the LC type lowpass filter. Resonance damping device 2. The electric circuit of claim 1, wherein the electrical circuit comprises a series circuit formed of an inductor 7 of inductive component L, a capacitor 8 of capacitive component C, and a resistor 9 of resistive component R, wherein the inductive component of the inductor The value of (L) and the value of the capacitance component (C) of the capacitor are such that the resonant frequency of the inductor and capacitor is made to substantially match the resonant frequency of the combination of the LC type lowpass filter and the load coupled to the local pass filter. And the value of the resistance component (R) of the resistor is selected so that the peak level of the output voltage of the LC type low pass filter at the resonance frequency is about +15 dB or less. Device. The LC filter of a power converter according to claim 2, wherein the resistance component (R) of the resistor is selected such that the peak level of the output voltage of the LC type low pass filter is about +10 dB or less at the resonance frequency. Resonance damping device. The resonant damping device for an LC filter of claim 1, wherein the power converter includes an inverter for converting DC power supplied from the LC type low pass filter into AC power. The resonant damping device for an LC filter of claim 1, wherein the power converter includes a converter for converting DC power supplied from the LC type low pass filter into DC power. A device for attenuating the resonance of an LC type low pass filter provided on the DC input side of a power converter having a DC input terminal, the apparatus comprising: a first signal which varies with a change in the output voltage V1 of the LC type low pass filter; Q attenuation control signal generating means for generating a Q attenuation control signal V5 when the level of the first signal exceeds the level of the reference signal by comparing V2 with a predetermined reference signal Vref; A power converter comprising a resistance circuit means (2) connected in series with the reactor of the LC type low pass filter to increase the DC resistance of the reactor (3) only for a period of time after the attenuation control signal is generated Resonance damping device for LC filter. 7. The value of the increased resistance component of the resistance circuit means (2) is selected so that the peak level of the output voltage of the LC type low pass filter is +15 dB or less at the resonant frequency of the LC type low pass filter. Resonance damping device for LC filter of the power converter characterized in that the. 7. The value of the increased resistance component of the resistance circuit means (2) is selected so that the peak level of the output voltage of the LC type low pass filter is +10 dB or less at the resonant frequency of the LC type low pass filter. Resonance damping device for LC filter of the power converter characterized in that the. 7. The control circuit according to claim 6, wherein said Q attenuation control signal generating means comprises: voltage distribution means (3, 4) for dividing an output voltage of an LC type low pass filter to provide said first signal, and A comparison means (11) for generating a second signal (V3) when the level of the first signal exceeds the level of the reference signal compared to a reference voltage, and the LC type low pass after the second signal is generated; And pulse generating means (12) for generating a Q attenuation control signal having a predetermined pulse width substantially covering the voltage change period while the level of the first signal changes due to the resonance of the filter. Resonant damping device for LC filter of converter. The resistance circuit means (2) is connected in series with the reactor, and the first resistance component (R1) for limiting the maximum current flowing to the power converter and the resonance in the LC type low pass filter. A variable resistance circuit formed of a second resistance component R2 for attenuation, and a value of the resistance component of the variable resistance circuit only within a period of a predetermined pulse width after the Q attenuation control signal is generated; Means for setting the value of the component and setting the value of the resistance component of the variable resistance circuit to the value of the first resistance component within a period other than a period of a predetermined pulse width. Resonance damping device. 7. The control circuit according to claim 6, wherein said Q attenuation control signal generating means comprises: voltage means (3, 4) for dividing an output voltage of an LC type low pass filter to provide said first signal, and said first signal being a predetermined reference; Means (11) for generating a second signal (V3) when the level of the first signal exceeds the reference level in comparison with a voltage, and the level of the first signal immediately after the second signal is generated; And a means (13) for generating a Q attenuation control signal while exceeding the level of the reference signal. 7. The resistor circuit according to claim 6, wherein said resistance circuit means (2) is connected in series with said reactor and further comprises: a first resistance component for limiting the maximum current flowing to said power converter and an attenuator for attenuating resonance in the LC type low pass filter. The variable resistance circuit formed of the two resistance components and the resistance component of the variable resistance circuit are set to the value of the second resistance component only within the period in which the Q attenuation control signal is generated, and other than the period of the predetermined pulse width. And means for setting the value of the resistance component of the variable resistance circuit to the value of the first resistance component within a period. 7. The apparatus of claim 6, wherein the Q attenuation control signal generating means comprises: means for detecting a change in an output voltage of an LC type low pass filter as the first signal, and a comparison input signal corresponding to the amplitude of the first signal. And means for generating the Q attenuation control signal when the level of the comparison input signal exceeds the level of the reference signal in comparison with a predetermined reference signal. 7. The resistor circuit according to claim 6, wherein the resistance circuit means is connected in series with the reactor, and further includes a first resistance component for limiting the maximum current flowing to the power converter and a second resistance component for attenuating resonance in the LC type low pass filter. And a value of the resistance component of the variable resistance circuit to the value of the second resistance component only within a period during which the Q attenuation control signal is generated and within the period other than a period of a predetermined pulse width. And a means for setting the value of the resistance component of the variable resistance circuit to the value of the first resistance component. The resonance converter of claim 6, wherein the power converter includes an inverter for converting DC power extracted from the LC type low pass filter into AC power. The resonance converter of claim 6, wherein the power converter includes a converter for converting DC power drawn from the LC type low pass filter into DC power.