JP2762003B2 - 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 conversion device for converting a power forward and backward by connecting a switching element to a single-phase or three-phase AC power supply and performing PWM control on the switching element. In the event of a power outage, power conversion prevents the reverse flow of power from the DC side to the AC side, and prevents the capacitor that constitutes the filter circuit etc. connected to the AC side from being charged by the reverse flow of power and becoming an overvoltage. Related to the device.

[0002]

2. Description of the Related Art Japanese Patent Application Laid-Open No. 61-227 discloses an invention for preventing regeneration or reverse flow of power on the DC side during a power failure.
There is an invention of a thyristor power supply device described in Japanese Patent Publication No. 688. According to the present invention, a regenerative current is cut off by turning off a parallel circuit of a diode connecting the DC side and the AC input side and a self-extinguishing switching element at the time of a power failure.

[0003]

A switching element is connected to a single-phase or three-phase AC power supply, and the switching element is subjected to PWM control, so that the DC output side of a power conversion device that performs forward and reverse conversion of power. If there is a load that generates a voltage, and a power failure occurs, a capacitor included in a filter circuit or the like connected to the AC input side of the power converter is charged by the power generated by the load connected to the DC output side . As a result, an overvoltage occurs on the AC input side of the power converter, and the equipment connected to the AC power supply connected to the power converter is damaged, and when the equipment is a magnetic circuit device such as a transformer, the magnetic field is demagnetized. Therefore, when the power supply is restored, an overcurrent may flow and the power supply may be damaged.

On the other hand, as described above, a self-extinguishing switching circuit (a diode and a self-extinguishing switching element) provided between a thyristor converter and a smoothing capacitor at the time of a power failure as a conventional power converter of this type. Is configured to cut off regenerative power.

However, in this conventional device, it is necessary to provide a self-extinguishing switching circuit in order to prevent power from flowing backward from the DC output side to the AC input side during a power failure.

When an induction motor is connected to the AC power supply having a power failure, it operates as a generator temporarily after the power failure, and a low-amplitude power supply voltage is temporarily supplied to the power conversion device from the time of the power failure. A so-called incomplete power failure condition may occur.

On the other hand, in the above-mentioned conventional power converter, there is no other way than to cut off the DC output side and the AC input side by a switching circuit at the time of a power failure. It was impossible to temporarily generate an overvoltage on the AC input side.

The present invention has been made in view of such circumstances, and does not require a switching circuit for preventing power from flowing back from a DC output side to an AC input side during a power failure as in the conventional apparatus. It is another object of the present invention to provide a power converter that can cope with an incomplete power failure.

[0009]

The power converter of the present invention has a filter circuit connected to an AC power supply and including a capacitor, and includes a switching element for exchanging power input through the filter circuit. In the power conversion device configured to perform forward conversion and reverse conversion of power, the switching element is configured to perform PWM based on a given modulation rate command value.
PWM control means for controlling, voltage detection means for detecting an output voltage of the power converter, output voltage command means for outputting a command value of the output voltage of the power converter, and a command value of the output voltage command means. and voltage control means for outputting a current command value corresponding to the deviation between the detected output of said voltage detecting means, said
Modulation rate according to current command value output from voltage control means
A modulation rate command value generating means for generating a command value;
A power failure detection means for detecting a power failure state of the AC power supply based on a phase difference between a source voltage and a modulated wave; and a magnitude of a current flowing from the input side of the switching element to the AC power supply side based on a detection output of the power failure detection means. And a voltage adjusting means for adjusting the level of the input voltage of the voltage control means so that a modulation rate command value such that the value becomes zero is given to the PWM control means.

Further, the power converter of the present invention is characterized in that the level of the input voltage of the voltage control means is adjusted to zero at the time of a power failure based on the detection output of the power failure detection means.

Further, the power converter of the present invention has a filter circuit connected to an AC power supply, including a filter circuit including a capacitor, and including a switching element for exchanging power input through the filter circuit. In a power conversion device that performs forward and inverse conversion of a PWM signal by performing PWM control on the switching element based on a given modulation rate command value.
M control means, current detection means for detecting an input current of the power conversion device, voltage control means for outputting a command value of an output current of the power conversion device, a current command value of the voltage control means, and the current detection Current control means for outputting a current command value according to a deviation from the detection output of the means, and a modulation rate command value generation means for generating a modulation rate command value according to the current command value output from the current control means, Voltage and modulation wave of the AC power supply
A power failure detection means for detecting a power failure state of the AC power supply based on a phase difference of the AC power supply; The modulation rate command value is PW
A modulation rate command value adjusting means for adjusting an output of the modulation rate command value generating means so as to be provided to the M control means.

The power converter according to the present invention is characterized in that the output of the modulation rate command value generating means is adjusted to zero at the time of a power failure based on the detection output of the power failure detecting means.

[0013]

In the power converter having the above configuration, an AC power supply
When a power outage or incomplete power outage is detected by the power outage detecting means due to the phase difference between the voltage and the modulated wave, the input side of the switching element in the power converter is detected based on the detection output of the power outage detecting means. The level of the input voltage of the voltage control means for outputting the current command value of the power converter so that the modulation rate command value such that the magnitude of the current flowing into the AC power supply from the inverter becomes zero is given to the voltage control means. It is adjusted by adjusting means.

Further, in the power converter having the above configuration,
When a state in which the AC power supply is in a power outage or an incomplete power outage is detected by the power outage detection means due to a phase difference between the voltage of the AC power supply and a modulated wave , based on a detection output of the power outage detection means, the switching element of the power conversion device is Modulation for generating a modulation rate command value according to a current command value of a power converter so that a modulation rate command value such that the magnitude of a current flowing from the input side to the AC power supply side becomes zero is given to the PWM control means. The output of the rate command value generating means is adjusted by the modulation rate command value adjusting means.

Therefore, a capacitor such as a filter circuit connected to the AC input side of the power conversion device is charged by a reverse flow of electric power and becomes an overvoltage in a power failure or incomplete power failure state without using a switching circuit unlike the conventional device. Can be prevented.

[0016]

Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 shows the configuration of a power converter for a single-phase power supply to which the present invention is applied. In the figure,
U and V terminals as input terminals of the power converter 1 are connected to a single-phase AC power supply 2, and output terminals P and N of the power converter 1 are connected to a load 3.

The power converter 1 includes a filter circuit 22 and
A current detector 4 for detecting a current on the input side of the switching element 5, a voltage detection circuit 6 for detecting an output voltage of the power converter 1, a storage switch 8, a storage circuit 9, and an output of the power converter 1. A command circuit 10 for outputting a voltage command value;
A setting unit 11 for outputting a setting signal for setting the output voltage of the power conversion device 1 to the command circuit 10;
2, a voltage control circuit 7, an adder 20 for calculating a deviation between a current command value output from the voltage control circuit 7 and a detection output output from the current detection circuit 12, and a current control circuit 13
A sine wave conversion circuit 14 for generating a modulation ratio command value based on an output signal of the current control circuit 13, and a drive circuit 16 based on the modulation ratio command value output from the sine wave conversion circuit 14.
, A PWM control circuit 15 that outputs a PWM control signal to the switching element 5, a drive circuit 16, a power failure detection circuit 23 that detects a power failure state of the single-phase power supply 2, and switching control by a detection output of the power failure detection circuit 23. Power failure switch 2 that selectively takes in an input signal to voltage control circuit 7
And 4.

The power failure switch 24 is normally switched to the contact A side, and is switched to the contact B side during a power failure, at which time the input of the voltage control circuit 7 becomes zero.

As the switching element 5, a transistor, IGBT, GTO or the like is used.

Further, the power failure detection circuit 23
Are connected to the U and V terminals of the
The power failure is detected based on the phase difference between the single-phase power supply 2 and the modulated wave of the sine wave circuit 14.

Next, an example of the operation of the power converter to which the present invention is applied will be described with reference to FIG. In the figure,
When the power supply voltage is lost at time T1, that is, when a power failure occurs, a phase difference occurs between the modulated wave of the sine wave conversion circuit 14 and the power supply voltage, and the phase difference is detected by the power failure detection circuit 23.
The detection output of the power failure detection circuit 23 falls from 0 volt to a voltage level at which the power failure switch 24 is turned off.

When the power failure switch 24 is turned off by the detection output of the power failure detection circuit 23, the contacts B and C of the power failure switch 24 are short-circuited, and the input voltage of the voltage control circuit 7, that is, the output of the command circuit 10 and the voltage detection circuit The deviation input from 6 becomes zero. As a result, the output voltage of the voltage control circuit 7,
That is, the current command value to the current control circuit 13 becomes zero.
Therefore, the output of the sine wave conversion circuit 14, that is, PW
Since the modulation rate command value of the M control circuit 15 becomes zero and the PWM modulation rate becomes 0%, the current flowing from the single-phase power supply 2 to the power converter 1 is controlled to be zero. As a result, the electric power generated by the load 3 does not flow to the single-phase power supply 2 side and does not charge the capacitors such as the filter circuit 22.

FIG. 3 shows the configuration of an embodiment of the power converter according to the present invention when the power supply 2 is a three-phase AC power supply. In the figure, the operation at the time of the power failure of the power supply 2 is the same as that in the case where the power supply 2 is a single-phase power supply, and the description thereof is omitted.

FIG. 4 shows the configuration of another embodiment of the power converter according to the present invention. This embodiment uses a PWM
By making the input of the control circuit 15, that is, the modulation ratio command value zero, the backflow of power from the DC output side to the AC input side of the power converter is prevented. In this embodiment as well, the same effects as those in the embodiment in which the input of the voltage control circuit 7 is forcibly set to zero at the time of a power failure can be naturally obtained.

In the above embodiment, the input of the voltage control circuit is set to zero or the modulation factor command value of the PWM control circuit is set to zero at the time of a power failure. When a complete power failure state is detected, the PWM control circuit 15 outputs a modulation rate command value such that the magnitude of the current flowing from the DC output side to the AC power supply 2 side of the power converter becomes zero corresponding to this state. To the level of the input voltage of the voltage control circuit 7 or directly to PW
The modulation ratio command value to the M control circuit 15 may be adjusted.

FIG. 5 shows a specific configuration of the power failure detection circuit 23. The power failure detection circuit 23 includes a comparator 30 that converts a power supply synchronization signal A synchronized with a power supply voltage of the power supply 2 into a rectangular wave B, a comparator 31 that converts a modulated wave C into a rectangular wave D, inverters 32 and 33, Gate 34,
35 and an OR gate 36.

The operation of the power failure detection circuit 23 having the above configuration will be described with reference to FIG.

The power supply synchronizing signal A synchronized with the power supply 2 is converted by the comparator 30 into a rectangular wave B.

On the other hand, the output of the sine wave conversion circuit 14, that is, the modulated wave C is input to the comparator 31 and converted into a rectangular wave D. Here, when a power failure of the power supply 2 occurs at time T1, the modulated wave C performs an operation of inverting the sign by the operation of the current control circuit 13, and is inverted at time T2.

When the sign of the modulated wave C is inverted, the output of the comparator 31 falls, and a drive signal E for operating the power failure switch 24 is generated by a logic circuit including inverters 32 and 33, AND gates 34 and 35, and an OR gate 36. , The power failure switch 24 is operated.

In the present embodiment, the power failure switch 24 is configured using a relay contact. However, the present invention is not limited to this, and an analog switch, a non-contact switch, or the like can be used.

Next, an embodiment in which the power converter according to the present invention is applied to an uninterruptible power supply is shown in FIG. In FIG. 1, an uninterruptible power supply 4 is configured by combining a power converter 1 according to the present invention, a load 3 as a battery, and an inverter 41.

By configuring the uninterruptible power supply as described above, even when the power supply 2 is interrupted, there is no reverse flow of power from the battery constituting the load 3 to the power supply 2, and normal operation is possible.

[0035]

According to the present invention, the voltage of the AC power supply and the modulation
Power outage or incomplete power outage detected due to wave phase difference
At this time, the power conversion apparatus is configured such that the modulation rate command value such that the magnitude of the current flowing from the input side of the switching element to the AC power supply side becomes zero is given to the PWM control means. In the event of a power outage, the voltage and modulation of the AC power supply are eliminated without providing a switching circuit to prevent the power from flowing back from the DC output side to the AC input side.
Power outage or incomplete power outage detected due to wave phase difference
Sometimes, it is possible to prevent the power from flowing back from the DC output side of the power converter to the AC power supply side.

[Brief description of the drawings]

FIG. 1 is a block diagram illustrating a configuration of an embodiment of a power conversion device according to the present invention.

FIG. 2 is a waveform diagram showing an operation state of the power converter shown in FIG.

FIG. 3 is a block diagram showing a configuration of another embodiment of the power converter according to the present invention.

FIG. 4 is a block diagram showing a configuration of still another embodiment of the power converter according to the present invention.

FIG. 5 is a circuit diagram showing a specific configuration of a power failure detection circuit.

6 is a waveform chart showing an operation state of the power failure detection circuit shown in FIG.

FIG. 7 is a block diagram illustrating a configuration of an uninterruptible power supply configured using the power converter according to the present invention.

[Explanation of symbols]

 REFERENCE SIGNS LIST 1 power conversion device 2 power supply 3 load 4 current detector 5 switching element 6 voltage detection circuit 7 voltage control circuit 8 storage switch 9 storage circuit 10 command circuit 11 setting device 12 current detection circuit 13 current control circuit 14 sinusoidal circuit 15 PWM Control circuit 16 Drive circuit 22 Filter circuit 23 Power failure detection circuit 24 Power failure switch 30 Comparator 31 Comparator 32 Inverter 33 Inverter 34 AND gate 35 AND gate 36 OR gate

──────────────────────────────────────────────────続 き Continuing from the front page (72) Inventor Naruhisa Mizutani 3-2-1, Sachimachi, Hitachi, Ibaraki Prefecture Within Hitachi Engineering Co., Ltd. (72) Hidefumi Shirahama 3-1-1, Sachimachi, Hitachi, Ibaraki No. Hitachi, Ltd. Hitachi Plant (72) Inventor Keizo Shimada 3-1-1, Komachi, Hitachi, Ibaraki Pref. Hitachi, Ltd. Inside Hitachi Plant (56) References JP-A-63-23567 (JP, A) (58) Field surveyed (Int.Cl. ⁶ , DB name) H02M 7/00-7/98

Claims (4)

(57) [Claims] 1. A power supply, comprising: a switching circuit connected to an AC power supply, including a filter circuit including a capacitor, for exchanging electric power input through the filter circuit, and performing forward and reverse conversion of electric power. In the power conversion device, a PWM control unit that performs PWM control on the switching element based on a given modulation rate command value; a voltage detection unit that detects an output voltage of the power conversion device; an output voltage command means for outputting a command value, and voltage control means for outputting a current command value corresponding to the deviation between the detected output of the command value and said voltage detecting means of the output voltage command means, the output from the voltage control means Modulation according to the current command value
A modulation rate command value generating means for generating a rate command value, a power failure detecting means for detecting a power failure state of the AC power supply by a phase difference between a voltage of the AC power supply and a modulation wave, and a detection output of the power failure detecting means. The magnitude of the current flowing from the input side of the switching element to the AC power supply side
There voltage conversion apparatus characterized by having a voltage adjustment means for the modulation factor command value that becomes zero to adjust the level of the input voltage of said voltage control means as given in the PWM control means. 2. The power supply system according to claim 1, wherein said voltage adjustment means adjusts the level of the input voltage of said voltage control means to zero at the time of a power failure based on a detection output of said power failure detection means.
3. The power converter according to claim 1. 3. A forward conversion and a reverse conversion of electric power, comprising a filter element connected to an AC power supply and including a capacitor, and including a switching element for converting electric power inputted through the filter circuit. In the power conversion device, a PWM control unit that performs PWM control based on a given modulation factor command value for the switching element; a current detection unit that detects an input current of the power conversion device; and an output current of the power conversion device. Voltage control means for outputting a command value; current control means for outputting a current command value corresponding to a deviation between a current command value of the voltage control means and a detection output of the current detection means; a modulation rate instruction value generating means for generating a modulation rate instruction value corresponding to a current command value that, detects the power failure condition of the AC power source through a phase difference between the voltage and the modulation wave of the AC power source Power failure detection means, and a modulation rate command value such that the magnitude of the current flowing from the input side of the switching element to the AC power supply side becomes zero based on the detection output of the power failure detection means is given to the PWM control means. And a modulation rate command value adjusting means for adjusting an output of the modulation rate command value generating means. 4. The modulation rate command value adjusting means adjusts an output of the modulation rate command value generating means to zero at the time of a power failure based on a detection output of the power failure detecting means. Power converter.