JP4683386B2 - Insulated direct power converter controller - Google Patents

Description

  The present invention relates to a control device for a direct power converter that directly converts alternating current to alternating current without using a large energy buffer, and more particularly to a high-frequency link-type insulated direct type in which an input side and an output side are insulated by a high-frequency transformer. The present invention relates to a control device that controls a power converter.

FIG. 4 is a configuration diagram of this type of power converter and its control device, which is a prior art substantially the same as that described in Non-Patent Document 1 described later.
In FIG. 4, 1 is a DC power source maintained at a constant DC voltage by a solar cell and a boost chopper, 2 is a high frequency converter (high frequency inverter) composed of semiconductor switches S _ap , _San , S _bp , S _bn , A high-frequency transformer having a primary winding connected to the AC side of the converter 2 and a bidirectional semiconductor switch S _up , S _un , S _vp , S _vn , S _wp connected to a secondary winding of the high-frequency transformer 3 , _Swn , and a load 5 such as a generator (power system) is connected to the three-phase output terminals.
This insulated direct power converter can be applied to, for example, a solar power generation system, a fuel cell power generation system and the like that are linked to a power system.

The operation of the power converter will be described below together with the configuration of the control device.
First, when using a transformer to insulate the power supply side from the system side, the weight and volume of the transformer increase at the commercial frequency, whereas the higher the frequency, the smaller the magnetic flux of the iron core and the smaller the core. Since the weight and volume can be greatly reduced, a method of insulating by a transformer after converting the AC voltage to a high frequency has been adopted. This is called a high frequency link system and is an effective means for reducing the size and weight of the transformer.

In the prior art of FIG. 4, in view of the above points, an AC voltage having a frequency higher than the commercial frequency is generated using the high-frequency converter 2, which is insulated by the high-frequency transformer 3 and transmitted to the high-frequency converter 4. In the high frequency converter 4, the secondary voltage of the high frequency transformer 3 is directly chopped by the semiconductor switches S _up , S _un , S _vp , S _vn , S _wp , S _wn , and a desired magnitude and frequency are obtained from the high frequency AC voltage. Having a three-phase AC voltage.

The high-frequency converter 2 determines the frequency of the high-frequency voltage applied to the high-frequency transformer 3 by using the square wave pulse generator 101 and switches the semiconductor switches S _ap , _San , S _bp , and S _bn to apply a voltage to the high-frequency transformer 3. Apply.
On the other hand, based on the output voltage command output from the output voltage command generation means 105, the angle and magnitude of the output voltage are calculated by the vector analyzer 102, and the voltage vector (space vector) used by the vector selection means 103 based on the angle. And the pulse output time calculation means 104 calculates the output time of each vector so that a desired voltage vector is output. Thereafter, the semiconductor switches S _up , S _un , S _vp , S _vn , S _wp , S _wn of the high-frequency converter 4 are switched by generating pulses in the order determined by the vector selection means 103 using a timer. is doing.

Iku Oba, Tatsuya Kitano, Mikihiko Matsui, “Switching Pattern Generation Method Based on Space Vector of High Frequency Link Soft Switching Converter”, 1999 IEEJ National Conference on Industrial Applications, Paper No. 182, p. 25-26

In the high frequency link type isolated direct power converter shown in FIG. 4, the voltage on the secondary side of the high frequency transformer 3 is directly chopped by the semiconductor switch, so that the energy stored in the leakage inductance of the transformer 3 is used for switching. A surge voltage is generated at both ends of the semiconductor switch. Although this surge voltage can be suppressed by using a snubber circuit or the like, there is a disadvantage that the loss increases.
Therefore, in Non-Patent Document 1 described above, an output voltage vector is selected and a voltage is output while a restriction is provided so that natural commutation can be performed by the high-frequency converter 4 on the secondary side of the transformer 3. For this reason, restrictions arise in the pulse pattern and driving | operation operation area | region with respect to the high frequency converter 4. FIG.

In addition, the circuit configuration of FIG. 4 is applicable when power is supplied from a DC power source such as a solar cell or a fuel cell to a three-phase AC power source on the system side. Power cannot be supplied from the phase generator to the three-phase AC power source. When these three-phase generators are used, it is conceivable that the high-frequency transformer 3 on the primary side of the high-frequency transformer 3 is three-phased similarly to the high-frequency converter 4 on the secondary side. In order to control, it is necessary to select only a pulse pattern capable of natural commutation in some cases, which complicates the control and restricts the operation region.
In addition, when the power source is AC, from the viewpoint of the efficiency and noise of the AC generator constituting the power source, not only the high-frequency converter 4 connected to the system but also the high frequency connected to the AC generator on the power source side. The converter also needs to control the current in a sine wave shape. In addition to the switching restrictions of the high-frequency converter 4 described above, it is very difficult to achieve direct control of the input / output waveform of the power converter, which may further complicate the circuit configuration and control operation of the control device. is there.

  Further, when controlling the high-frequency converter 4 ignoring the energy processing of the leakage inductance of the high-frequency transformer 3, the control device can concentrate only on the control of the input / output waveform, so that the circuit configuration and operation can be simplified to some extent. However, there is a problem that the snubber circuit for processing the energy of the leakage inductance is enlarged and the power conversion efficiency is also lowered.

  Therefore, the problem to be solved by the present invention is that the input / output waveform can be easily controlled in the high frequency link type isolated direct power converter capable of three-phase input / output, and the energy of the leakage inductance of the high frequency transformer can be controlled. It is an object of the present invention to provide a control device that can be reduced in size and reduced in price so as not to be restricted by a switching pattern or the like in processing.

In order to solve the above-mentioned problems, the invention described in claim 1 includes a first converter connected to an AC power source, a high-frequency transformer connected to the primary side of the converter, and a secondary side of the high-frequency transformer. And a second converter whose output side is connected to a load, and by the operation of the semiconductor switch constituting the first and second converters, the AC voltage is directly converted into an AC voltage having an arbitrary magnitude and frequency. High frequency link type isolated direct power converter that supplies
A rectifier connected to an AC power source, a high-frequency link unit connected to the rectifier via a DC link unit and having a high-frequency transformer, connected to the high-frequency link unit via a DC link unit, and on the AC side As a combination with the inverter unit to which the load is connected,
A control device for controlling the isolated direct power converter,
Virtual rectifier control means for generating a pulse for controlling the semiconductor switch of the rectifier using a current command generated from the voltage of the AC power supply and a carrier ;
Virtual high-frequency link unit control means for generating a pulse for controlling the semiconductor switch of the high-frequency link unit according to the rising and falling of the carrier ;
A virtual inverter unit control means for generating a pulse for controlling the semiconductor switch of the inverter unit according to an output voltage command ;
Pulse synthesizing means for synthesizing the pulses respectively output from the control means and converting them to pulses for the semiconductor switches of the first and second converters;
It is equipped with.

The invention described in claim 2 is the invention according to claim 1,
The pulse synthesizing means includes
Means for synthesizing the output pulse of the virtual rectifier control means and the output pulse of the virtual high-frequency link control means, and converting this into a pulse for the semiconductor switch of the first converter;
Means for synthesizing the output pulse of the virtual inverter control means and the output pulse of the virtual high-frequency link control means, and converting this into a pulse for the semiconductor switch of the second converter.

The invention described in claim 3 is, in claim 2,
The pulse synthesizing means includes
Means for generating a switching function for the semiconductor switch of the first converter based on a switching function corresponding to the output pulse of the virtual rectifier control means and a switching function corresponding to the output pulse of the virtual high-frequency link control means;
Means for generating a switching function for the semiconductor switch of the second converter based on a switching function corresponding to the output pulse of the virtual inverter control means and a switching function corresponding to the output pulse of the virtual high-frequency link control means; It is equipped with.

The invention described in claim 4 is any one of claims 1 to 3,
Detecting means for detecting a zero voltage of the output of the virtual inverter unit;
Short circuit means for short-circuiting the primary side of the high-frequency transformer of the virtual high-frequency link section when the zero voltage detected by this means is output.

The invention described in claim 5 is any one of claims 1 to 4,
The insulated direct power converter is a three-phase input-three-phase output type power converter.

According to the first to third aspects of the present invention, the high frequency link type insulated direct power converter including the first and second converters (high frequency converter) and the high frequency transformer is obtained by combining the rectifier, the high frequency link portion, and the inverter portion. As a power converter, the control circuit is configured and controlled by generating control pulses (PWM pulses) equivalent to controlling each of these units individually and controlling the first and second converters. The operation can be simplified.
As a result, the switching pattern and the operation region of the converter are not restricted in order to process the leakage inductance energy of the high-frequency transformer, and the waveform control operation for maintaining the input / output waveform in a sine wave shape can be performed without any trouble. Moreover, since the energy processing of the leakage inductance can be solved by the degree of freedom of the switching pattern of the converter, a large snubber circuit is not required.

In the invention described in claim 4, when the hypothetical inverter unit outputs a zero voltage vector, a large surge voltage is generated. At this time, a pulse pattern is generated to short-circuit the primary side of the high-frequency transformer. By switching the semiconductor switch of 1 converter, the energy accumulated in the leakage inductance of the high-frequency transformer can be reduced and the snubber circuit can be miniaturized.
Further, according to the invention of claim 5, it is possible to connect a three-phase generator such as a wind power generator or an engine generator and a three-phase AC power source.

Hereinafter, embodiments of the present invention will be described with reference to the drawings. First, FIG. 1 is a block diagram showing a first embodiment of the present invention, and corresponds to the first to third aspects of the present invention. Here, the same components as those in FIG. 4 are denoted by the same reference numerals.
In the insulated direct power converter 10 shown in FIG. 1, reference numeral 6 denotes a system-side three-phase AC power supply, and each phase output terminal is connected to the input side of a three-phase high-frequency converter 2A as a first converter. The primary winding of the high frequency transformer 3 is connected to the output side. The secondary winding of the high-frequency transformer 3 is connected to a three-phase high-frequency converter 4 as a second converter similarly to FIG. 4, and a load 5 such as a generator is connected to each phase output terminal. Yes.
Here, the high-frequency converter 2A, 4 are semiconductor switches _S rp, such as IGBT capable of high-speed switching, _{respectively, S rn, S sp, S} sn, S tp, S tn and _{S up, S un, S vp} , S vn, It is comprised by _Swp and _Swn .

The high-frequency converter 2 </ b> A on the system side controls the input current waveform in a sine wave shape by the switching operation and generates a high-frequency single-phase voltage to be applied to the high-frequency transformer 3. At the same time, the high-frequency converter 4 on the load 5 side converts the single-phase voltage output from the high-frequency transformer 3 into a three-phase voltage having an arbitrary magnitude and frequency and supplies it to the load 5.
The control operation will be described in detail below together with the configuration of the control device in the present embodiment. Here, in order to facilitate understanding, the drive operation (motor operation, that is, operation for supplying power from the high-frequency converter 4 to the load 5) will be described assuming that the load 5 is a generator. The power generation operation is substantially the same as the energy flow is reversed.

  First, in general, the relationship between the input voltage and the output voltage of the power converter can be expressed by a switching function. In the high frequency link type isolated direct power converter 10 shown in FIG. 1, the input / output of the input side high frequency converter 2A is input / output. The relationship of the voltage (the input / output voltage on the primary side of the high-frequency transformer 3) is expressed by Equation 1, and the relationship of the input / output voltage of the output-side high-frequency converter 4 (the input / output voltage on the secondary side of the high-frequency transformer 3) is expressed by Equation 2. Each is represented.

In Equation 1, e _pi , e _ni are the primary side voltages of the high-frequency transformer 3, v _r , v _s , v _t are the phase voltages of the three-phase AC power source 6, and in Equation 2, v _u , v _v , v _w are Each phase output voltage, e _po , e _no, of the high-frequency converter 4 is a secondary side voltage of the high-frequency transformer 3.
In addition, in Formulas 1 and 2, the switching function of the semiconductor switch S _mn of each converter 2A, 4 (m, n indicates a suffix attached to the symbol of each semiconductor switch) is represented as s _mn , and the semiconductor switch S _mn is The on state is s _mn = 1, and the off state is s _mn = 0.

Here, in controlling the insulated direct power converter 10 of FIG. 1, a high-frequency link type three-phase to three-phase power converter having a DC link portion as shown in FIG. 2 is considered. This power converter includes a rectifier 7 (the circuit configuration is the same as that of the high-frequency converter 2A in FIG. 1) that converts the AC voltage of the three-phase AC power source 6 into a DC voltage, and generates a high-frequency square wave voltage from the DC voltage. 1 and an inverter unit 9 for converting the output DC voltage into an AC voltage having a desired magnitude and frequency (the circuit configuration is the same as that of the high-frequency converter 4 in FIG. 1). . Incidentally, _S ap in RF link portion _{8, S an, S bp,} S bn, S cp, S cn, S dp, S dn semiconductor switch, 8a is a high-frequency transformer.

  In accordance with the case of FIG. 1, when the relationship between the input and output voltages is determined for the primary side and the secondary side of the high-frequency transformer 8a, respectively, Equations 3 and 4 are obtained.

Here, if the matrix of the switching function on the right side in Equation 1 described above and the matrix product of the switching function on the right side in Equation 3 are the same, even if the shape of the power converter is different in FIGS. The relationship between each phase input voltage from the AC power supply 6 and the primary voltage of the high-frequency transformer 3 or 8a becomes equal.
Therefore, if the switching pattern on the primary side of the high frequency transformer 3 in FIG. 1 (the switching pattern of the high frequency converter 2A) is converted according to Equation 5 and the high frequency converter 2A is switched according to the switching pattern, the insulation type direct power converter of FIG. 10 can be controlled in the same manner as the power converter of FIG.

Similarly, if the matrix of the switching function on the right side in Equation 2 and the matrix product of the switching function on the right side in Equation 4 are equal, the high-frequency transformer 3 or The relationship between the secondary side voltage of 8a and each phase output voltage becomes equal.
Therefore, the switching pattern on the secondary side of the high-frequency transformer 3 in FIG. 1 (switching pattern of the high-frequency converter 4) is converted in the same manner as Expression 5 according to the matrix product of the switching function on the right side of Expression 4, and the high-frequency converter is converted according to the switching pattern. 1 can be controlled in the same manner as the power converter of FIG. 2.

The circuit shown in FIG. 2 is divided by a rectifier 7, a high-frequency link unit 8, and an inverter unit 9, and has a DC link unit at the boundary between these circuits, so that each circuit can be controlled individually. Thus, unlike the power converter 10 of FIG. 1, it is not necessary to control the input / output side simultaneously.
Focusing on the above points, the control device of the present embodiment hypothesizes a power converter configured as shown in FIG. 2 with respect to the insulated direct power converter 10 shown in FIG. The power converter 10 can be easily controlled by converting the pulse pattern for the secondary side to the power converter 10 of FIG.

That is, the control device in FIG. 1 includes virtual rectifier control means 20 for controlling the current on the three-phase AC power supply 6 side, virtual high-frequency link unit control means 30 for controlling the high-frequency link unit 8 in FIG. A virtual inverter section control means 40 for controlling the output voltage on the load side, and a pulse synthesis means 50 for synthesizing, converting and converting the PWM pulses output from these control means 20, 30, 40. It is configured.
The pulse synthesizing unit 50 includes a PWM pulse synthesizing unit 51 that synthesizes the output of the virtual rectifier control unit 20 and the output of the virtual high frequency link unit control unit 30, and the output of the virtual inverter unit control unit 40 and the virtual high frequency link unit control unit 30. PWM pulse synthesizing means 52 for synthesizing the output of the above.

The virtual rectifier control means 20 substantially controls the semiconductor switch of the rectifier 7 of FIG. 2 and controls the current source rectifier in order to prevent a power supply short circuit. The method of controlling the current source rectifier is well known. For example, the power source voltage is detected by the power source voltage detecting means 21 in FIG. 1, and the current command generating means 22 detects a sine wave with a power factor of 1 with respect to the power source voltage. A current command that causes current to flow is generated.
Further, a triangular wave carrier is generated by the carrier generation means 23, and the carrier and the current command are compared by the comparison means 24 to generate a PWM pulse of the voltage-type PWM rectifier. Then, this PWM pulse is inputted to the pulse pattern conversion means 25, and the pattern conversion is performed from the PWM pulse for the voltage source rectifier to the PWM pulse for the current source rectifier.

The virtual inverter unit control means 40 substantially controls the semiconductor switch of the inverter unit 9 of FIG. 2, and a control method for generating a PWM pulse by comparing a carrier and a three-phase output voltage command is well known. is there.
In Figure 1, to obtain a PWM pulse by comparing desired and the size and frequency of the output voltage command generated by the output voltage command generating unit 41, the comparing means 43 and a carrier generated by carrier generator 42.
The virtual inverter can be controlled not only by three-phase modulation in which three phases are always switched, but also in two-phase modulation in which one phase is not switched and the waveform is shaped by switching of the remaining two phases. Further, the carrier generated by the carrier generating means 42 may change the slope according to the output pulse of the virtual rectifier control means 20 in order to prevent distortion of the input current.

  The virtual high-frequency link control unit 30 includes an up / down detection unit 31 that detects the up / down of the carrier on the virtual rectifier side, and a square wave generation unit 32 that generates a square wave according to the up / down of the carrier, A PWM pulse for the semiconductor switch of the high-frequency link unit 8 of FIG. 2 is generated.

The PWM pulse synthesizing means 51 on the high frequency converter 2A side in FIG. 1 synthesizes the output pulse of the pulse pattern converting means 25 and the output pulse of the square wave generating means 32, and the primary side and three phase of the high frequency transformer 8a in FIG. A switching pattern of 10 semiconductor switches with the AC power source 6 is generated, and this switching pattern is converted into a switching pattern of the high-frequency converter 2A on the power source 6 side in FIG.
On the other hand, the PWM pulse synthesizing means 52 on the high frequency converter 4 side in FIG. 1 synthesizes the output pulse of the comparison means 43 and the output pulse of the square wave generating means 32, and the secondary side of the high frequency transformer 8a in FIG. 1 is generated, and the switching pattern is converted into the switching pattern of the high-frequency converter 4 on the load 5 side in FIG.
Note that a commutation pattern corresponding to the dead time of the inverter is added to the output pulses of the PWM pulse synthesizing means 51 and 52 so as not to cause a power supply short circuit and an output end opening.

According to the first embodiment described above, a power converter composed of the rectifier 7, the high frequency link unit 8, and the inverter unit 9 as shown in FIG. Since the PWM pulse for controlling the virtual power converter is generated and synthesized, and the pulse pattern is converted and controlled for the power converter 10, the rectifier 7, the high-frequency link unit 8, and the inverter are substantially controlled. A control method equivalent to controlling the units 9 individually can be used.
This simplifies the configuration and control operation of the control device, and does not restrict the switching pattern or operating operation area of the high-frequency converter 4 in order to process the leakage inductance energy of the high-frequency transformer 3, and the input / output waveforms can be reduced. The waveform control operation for maintaining a sine wave shape can be performed without any trouble. Moreover, since the energy processing of the leakage inductance can be solved by the degree of freedom of the switching pattern of the high-frequency converter 4, a large snubber circuit is not required.
Furthermore, according to the first embodiment, it is possible to link a three-phase generator such as a wind power generator or an engine generator and a three-phase AC power source.

Next, FIG. 3 is a block diagram showing a second embodiment of the present invention, and corresponds to the invention of claim 4.
In this embodiment, when the inverter unit 9 in FIG. 2 (the high-frequency converter 4 in FIG. 3) generates a zero voltage, the high-frequency link unit 8 in FIG. By virtually controlling to short-circuit the primary side of the transformer 8a, the current output from the secondary side of the high-frequency transformer 8a, in other words, the high-frequency transformer 3 in FIG. It is what I did.
Hereinafter, the configuration and operation principle of the present embodiment will be described.

The energy stored in the leakage inductance of the high-frequency transformer appears as a surge voltage when switching the semiconductor switch. In order to prevent the semiconductor switch from being destroyed by this surge voltage, a snubber circuit is usually provided.
When the inverter unit 9 in FIG. 2 (the high-frequency converter 4 in FIG. 3) outputs a zero voltage vector, the direct current of the inverter unit 9 is forced to be zero, so that the surge voltage becomes the largest.

Therefore, in the present embodiment, the timing at which the inverter unit 9 outputs the zero voltage is detected from the output of the comparison unit 43 by the zero vector detection unit 33 of the virtual high frequency link control unit 30A in FIG. 3, and the high frequency transformer 8a in FIG. The transformer primary side short-circuit means 34 generates a pulse pattern that turns on the upper arm or lower arm semiconductor switch in order to short-circuit the primary side of the first and outputs the pulse pattern to the PWM pulse synthesis means 51.
Thereby, in the high frequency converter 2A to which the output pulse of the PWM pulse synthesizing means 51 is given, the semiconductor switch is turned on so as to short-circuit the primary side of the high frequency transformer 3, and the current output from the secondary side is made zero and leaks. Accumulation of energy in the inductance can be avoided.
As a result, while the same zero voltage is output to the output side of the power converter 10, energy can be prevented from being stored in the leakage inductance, and the snubber circuit can be miniaturized.

It is a block diagram which shows 1st Embodiment of this invention. It is a block diagram of the high frequency link system three-phase-three-phase power converter which has a DC link part. It is a block diagram which shows 2nd Embodiment of this invention. It is a block diagram which shows a prior art.

Explanation of symbols

2A, 4: High frequency converter 3: High frequency transformer 5: Load 6: Three-phase AC power supply 7: Rectifier 8: High frequency link unit 8a: High frequency transformer 9: Inverter unit 10: Insulated direct power converter 20: Virtual rectifier control means 21 : Power supply voltage detection means 22: current command generation means 23: carrier generation means 24: comparison means 25: pulse pattern conversion means 30, 30A: virtual high frequency link unit control means 31: up / down detection means 32: square wave generation means 33 : Zero vector detection means 34: Transformer primary side short-circuit means 40: Virtual inverter section control means 41: Output voltage command generation means 42: Carrier generation means 43: Comparison means 50: Pulse synthesis means 51, 52: PWM pulse synthesis means

Claims (5)

A first converter connected to an AC power source, a high-frequency transformer having a primary side connected to the converter, and a second converter connected to a secondary side of the high-frequency transformer and having an output side connected to a load. Insulation type direct power converter of high frequency link system that directly converts an AC voltage into an AC voltage having an arbitrary magnitude and frequency and supplies it to a load by operation of semiconductor switches constituting the first and second converters The
A rectifier connected to an AC power source, a high-frequency link unit connected to the rectifier via a DC link unit and having a high-frequency transformer, connected to the high-frequency link unit via a DC link unit, and on the AC side As a combination with the inverter unit to which the load is connected,
A control device for controlling the isolated direct power converter,
Virtual rectifier control means for generating a pulse for controlling the semiconductor switch of the rectifier using a current command generated from the voltage of the AC power supply and a carrier ;
Virtual high-frequency link unit control means for generating a pulse for controlling the semiconductor switch of the high-frequency link unit according to the rising and falling of the carrier ;
A virtual inverter unit control means for generating a pulse for controlling the semiconductor switch of the inverter unit according to an output voltage command ;
Pulse synthesizing means for synthesizing the pulses respectively output from the control means and converting them to pulses for the semiconductor switches of the first and second converters;
A control device for an insulated direct power converter, comprising: In the control device for an insulated direct power converter according to claim 1,
The pulse synthesizing means includes
Means for synthesizing the output pulse of the virtual rectifier control means and the output pulse of the virtual high-frequency link control means, and converting this into a pulse for the semiconductor switch of the first converter;
Means for synthesizing the output pulse of the virtual inverter section control means and the output pulse of the virtual high frequency link section control means, and converting this into a pulse for the semiconductor switch of the second converter;
A control device for an insulated direct power converter, comprising: In the control apparatus for an insulated direct power converter according to claim 2,
The pulse synthesizing means includes
Means for generating a switching function for the semiconductor switch of the first converter based on a switching function corresponding to the output pulse of the virtual rectifier control means and a switching function corresponding to the output pulse of the virtual high-frequency link control means;
Means for generating a switching function for the semiconductor switch of the second converter based on a switching function corresponding to the output pulse of the virtual inverter control means and a switching function corresponding to the output pulse of the virtual high-frequency link control means;
A control device for an insulated direct power converter, comprising: In the control apparatus of the insulation type direct power converter given in any 1 paragraph of Claims 1-3,
Detecting means for detecting a zero voltage of the output of the virtual inverter unit;
Short-circuit means for short-circuiting the primary side of the high-frequency transformer of the virtual high-frequency link section at the time of outputting zero voltage detected by this means,
A control device for an insulated direct power converter, comprising: In the control apparatus of the insulation type direct power converter given in any 1 paragraph of Claims 1-4,
The controller for an insulated direct power converter, wherein the insulated direct power converter is a three-phase input-three-phase output type power converter.

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