JP3181859B2 - 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 an uninterruptible power supply, thyristor converter, cycloconverter, high power factor converter, active filter, SVG, self-excited B
The present invention relates to a power conversion device such as a TB, a self-excited DC transmission converter, and more specifically, has an inverter connected to an AC power supply, and supplies an appropriate current to the AC power supply from the inverter to connect to the AC power supply. The present invention relates to a power conversion device that exchanges active power, reactive power, and harmonic power between the power conversion devices.

[0002]

2. Description of the Related Art FIG. 10 is a block diagram showing a conventional power converter, which has a configuration employed in, for example, an uninterruptible power supply disclosed in Japanese Patent Publication No. 5-76256. In the figure, a power converter is connected to an AC power source 1 such as a commercial power source or a diesel generator via a power system 2.
It is connected to the.

Further, reference numeral 4 denotes a DC voltage source, and 3 denotes a voltage type inverter connected between the DC voltage source 4 and the AC power supply 1 for switching an output voltage of the DC voltage source 4 and converting the output voltage into an AC voltage. , 6 are capacitors connected in parallel with the voltage type inverter 3 as viewed from the AC power supply 1, 5 is a reactor connected between the voltage type inverter 3 and the capacitor 6, and 7a is a capacitor connected from the reactor 5 to the capacitor 6. A first current detector for detecting the flowing current, 8 is a basic current command generating circuit for outputting a current command value Iref which is a target value of the current, and 9 is based on a difference between the current command value Iref and the detected current Ia. Voltage command Vref
The current control circuit 10 outputs the voltage command Vref
And a drive circuit 11 for turning on / off the voltage-type inverter 3 at a timing based on the pulse.

Next, the operation will be described. The basic current command creation circuit 8 outputs a current command value Iref according to the operation state. The current control circuit 9 receiving the current command value Iref outputs the current command value Iref and a voltage command Vref according to the current Ia flowing through the reactor 5 detected by the current detector 7a. The drive circuit 11 outputs a pulse corresponding to Vref, and switches the voltage type inverter 3 at a timing corresponding to the pulse. As a result, an AC voltage generated by turning on / off the DC voltage from the DC voltage source 4 at a predetermined timing is output from the voltage-type inverter 3, and the output of the voltage-type inverter 3 is output to the reactor 5. A current flows according to the potential difference between the voltage and the charging voltage Vc of the capacitor 6. Further, the current Ia flowing through the reactor 5 is detected by the first current detector 7a, and the current control circuit 9 adjusts the voltage command Vref according to the difference between the detected current Ia and the current command value Iref. The value of the detection current Ia substantially matches the current command value Iref. Therefore, a current substantially coincident with the current command value Iref is output from the inverter 3, whereby the capacitor 6 can be charged and discharged.

Therefore, for example, when the AC voltage is being output from the AC power supply 1 to the power system 2, the current command value Iref is changed in synchronization with the AC voltage of the AC power supply 1, whereby the output of the inverter 3 is changed. A predetermined current can be supplied to the power system 2 while charging and discharging the capacitor 6 with the current Ia. This allows, for example,
Even if the phases of the AC voltage and the AC current of the AC power output from the AC power supply 1 are shifted due to the reactance component of the power system 2, the current difference is appropriately compensated by the power converter, and the phase difference is obtained. Can be adjusted.

The capacitor 6 also has a function of removing a ripple component when the current Ia output from the inverter 3 is supplied to the power system 2 side. Further, assuming that the amplitude of the voltage applied to the capacitor 6 is Vc, the frequency of the voltage Vc is f, the capacitance of the capacitor is C, and the pi is π,
Flows. Ic = 2 * π * f * Vc * C (Equation 1)

[0007]

Since the conventional power conversion device is configured as described above, the conventional power converter includes a case where the AC voltage output from the AC power supply 1 contains harmonic voltage distortion such as a harmonic component. In this case, the harmonic current distortion of the AC current becomes larger than when the power converter is not connected to the AC power supply 1, and the quality of the power supplied to other loads connected to the AC power supply 1 There is a problem that it worsens. More specifically, when the AC voltage output from the AC power supply 1 includes harmonic voltage distortion such as a harmonic component, the harmonic current Is due to the harmonic voltage distortion is calculated according to the following equation (1). And the harmonic distortion of the AC current output from the AC power supply 1 via the power system 2 increases accordingly.

In the above description, an uninterruptible power supply is taken as an example of a specific example of the power converter.
The problem that the harmonic distortion occurs in the AC current due to the harmonic distortion included in the AC voltage from the commercial power supply is the power that the capacitor is arranged in parallel with the current output device from the viewpoint of the AC power supply. This is a problem that occurs in the case of a conversion device.

SUMMARY OF THE INVENTION The present invention has been made to solve the above-described problems, and a power conversion device capable of suppressing an AC current distortion from an AC power supply and obtaining an AC current waveform close to a desired waveform. The purpose is to obtain.

[0010]

According to the first aspect of the present invention, the control unit of the power conversion device is configured to switch from the AC power supply to the capacitor.
Connect the flowing current to the capacitor and the current output section.
At the position closer to the AC power source than the point
And a predetermined transfer function for the harmonic component of the detected current
To obtain the current command value correction value.
The transfer function is expressed as follows: impedance is Z, capacitance of capacitor
Is C and the Laplace differential operator is S, (Z * C *
S-1).

[0011] The power conversion device according to the invention of claim 2, wherein
The control unit calculates the current flowing from the AC power supply into the capacitor,
From the connection point between the load and the power converter,
And between the point of connection to the current output section
In addition, a predetermined transfer function is applied to the harmonic components of the detected current.
Multiply by the number to obtain the correction value of the current command value,
The transfer function can be expressed as follows: impedance is Z, capacitance of capacitor
When the quantity is C and the Laplace differential operator is S, (Z * C
* S-1).

[0012] The power conversion device according to the invention of claim 3, wherein
The control unit calculates the current flowing from the AC power supply into the capacitor,
The AC power source more than the connection point between the power converter and the load
Detect at the near position, and the harmonic of the detected current
Current command by multiplying wave component by predetermined transfer function
Value to obtain a correction value, and the transfer function
Dance is Z, capacitance of capacitor is C, Laplace differential operation
When the child is S, it is (Z * C * S-1).
You.

[0013] The power conversion device according to the invention of claim 4, wherein
The control unit calculates the current flowing from the AC power supply into the capacitor,
The connection point between the capacitor and the current output section is
The current is detected at the position near the sensor and the detected current
Is multiplied by a predetermined transfer function
To obtain a correction value of the flow command value, and the transfer function
Impedance Z, capacitor capacitance C, Laplace fine
When the minute operator is S, (Z * C * S-1) / (Z *
C * S).

According to a fifth aspect of the present invention, there is provided a power conversion apparatus comprising :
The control unit detects the voltage generated in the capacitor and
And a predetermined transfer function for the harmonic component of the detected current
To obtain the current command value correction value.
It is.

[0015] The power conversion device according to the invention of claim 6, wherein
The control unit detects the voltage generated in the capacitor and
And a predetermined transfer function for the harmonic component of the detected current
To obtain the correction value of the current command value.
The transfer function is expressed as follows: impedance is Z, capacitance of capacitor is
C, if the Laplace differential operator is S, then (C * S-1
/ Z).

[0016]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS One embodiment of the present invention will be described below. Embodiment 1 FIG. FIG. 1 is a block diagram showing a power converter according to Embodiment 1 of the present invention. In the figure, a power converter is connected to an AC power supply 1 such as a commercial power supply or a diesel generator via a power system 2. 4 is a DC voltage source, 3
Are connected between the DC voltage source 4 and the AC power supply 1 and switch the output voltage of the DC voltage source 4 to convert it into an AC voltage;
Is a capacitor connected in parallel with the voltage type inverter 3 as viewed from the AC power supply 1, 5 is a reactor connected between the voltage type inverter 3 and the capacitor 6, 7a
Is a first current detector for detecting a current Ia flowing through the reactor 5, 8 is a basic current command generating circuit for outputting a basic current command value Iaref serving as a basic target value of the current Ia, and 7b is an AC power supply 1 A second current detector 12 for detecting a current Is flowing from the capacitor 6 into the capacitor 6 at a position closer to the AC power supply 1 than a connection point between the capacitor 6 and the reactor 5 is detected by the second current detector 7b. Current correction value Ihr according to the harmonic component contained in the detected current Is
The current correction circuit 13a outputs the current correction value I
an adder circuit for outputting a current command value Iref obtained by adding href and the basic current command value Iaref; a current control for outputting a voltage command Vref that changes in accordance with a difference between the current command value Iref and the detected current Ia A circuit 10 is a PWM circuit that generates a predetermined pulse based on the voltage command Vref, and a drive circuit 11 turns on / off the voltage type inverter 3 at a timing based on the pulse.

FIG . 2 is an example of a detailed block diagram of the current control circuit 9 that outputs a voltage command Vref according to the current command value Iref. In the figure, 14a is a current command value I
The subtraction circuit 15a subtracts the current value Ia detected by the first current detector 7a from the ref.
a proportional circuit for proportionally multiplying the subtraction result of a, a integration circuit 16a for integrating the subtraction result of the subtraction circuit 14a, a differentiation circuit 17a for differentiating the subtraction result of the subtraction circuit 14a, 13
b denotes an addition circuit that adds the operation outputs of the operation circuits 15a, 16a, and 17a and outputs the value as a voltage command Vref.

The control circuit that uses the output current Ia of the voltage-type inverter 3 as a feedback value of the current command value Iref and performs calculations by the proportional circuit 15a, the integration circuit 16a, and the differentiation circuit 17a is a linear feedback control. Each of the command value components (the basic current command value Iaref and the correction current value Ihref in this embodiment) included in the command value can be handled as an independent command value.

FIG . 3 is a detailed block diagram of the current correction circuit 12. In the figure, reference numeral 18a denotes a high-pass filter for extracting a harmonic current component having a frequency higher than the commercial frequency from the detection current Is of the second current detector 7b;
Reference numeral 19 denotes an arithmetic circuit that performs an arithmetic operation on the current value output from the high-pass filter 18a using the transfer function of the following (Equation 2).

[0020] (Z * C * S-1 ) ( Equation 2) where, Z is the impedance characteristic, C represents the capacitance of the capacitor, S is the Laplace differential operator. The calculation is performed using the above (Equation 2), and the detection current Is of the second current detector 7b is detected.
A current correction value Ihref is created from the harmonic components of the current and the voltage-type inverter 3 outputs a current Ia that matches the current correction value Ihref.
The current flowing into the connection point between the power supply and the AC power supply 1 is defined as a current in the direction shown in FIG.

Since Is = Ic−Ia (Equation 3), and the voltage Vc generated in the capacitor 6 becomes Vc = Ic / (C * S) (Equation 4), Is = Vc / Z (Equation 5) ) Can be obtained.

[0022] The equation (5), a high-frequency alternating current flowing from the AC power supply 1 to the capacitor 6 is calculated based on the transfer function of the equation (2), the current output of the operation result from the voltage type inverter 3 By using it as the current correction value Ihref of Ia, it means that the high-frequency AC current flowing from the AC power supply 1 to the capacitor 6 can be reduced to 1 / Z. Since the voltage Vc generated in the capacitor 6 is substantially equal to the voltage output from the AC power supply 1, the above (Equation 5) shows the impedance characteristic of the power converter viewed from the AC power supply 1. It can be seen that the impedance characteristic is a characteristic that suppresses the harmonic current flowing into the power converter.

In deriving the above (Equation 5), the transfer function shown in the above (Equation 2) is used. However, in the configuration of the first embodiment, the transfer function is limited to the one shown in the above (Equation 2). However, any transfer function may be used as long as the impedance characteristic of the power converter viewed from the AC power supply 1 is a characteristic that suppresses harmonic current flowing into the power converter.

The impedance characteristic Z shown in the above (Equation 2) may be of any type as long as it has a characteristic of suppressing a harmonic current flowing into the power converter. It may be an impedance characteristic connected in series or an impedance characteristic in which a reactor and a capacitor are connected in series.

[0025] it is preferred that, when such a resistance characteristic and inductance characteristics. In the case of the resistance characteristic, the current Ia flowing into the capacitor 6 from the voltage-type inverter 3 can be controlled by relatively simple voltage control. This is because a high suppression effect is exerted on a high frequency component output from the AC power supply 1, and generation of a harmonic current can be effectively suppressed.

[0026] Next, the operation will be described. The basic current command generation circuit 8 controls the basic current command value Iare according to the operation state.
When f is output, if there is no current correction value Ihref, the adding circuit 13a outputs the basic current command value Iaref as it is as the current command value Iref. The current control circuit 9 having received the current command value Iref outputs a voltage command Vref corresponding to the current command value Iref,
The PWM circuit 10 outputs a pulse corresponding to the voltage command Vref, and the drive circuit 11 switches the voltage type inverter 3 at a timing corresponding to the pulse.

[0027] As a result, this is a voltage type inverter 3 AC voltage generated by ON / OFF at a predetermined timing the DC voltage from the DC voltage source 4 is output, the voltage-type inverter in reactor 5 A current flows according to the potential difference between the output voltage of the capacitor 3 and the charging voltage Vc of the capacitor 6. In addition, current I flowing through reactor 5
a is detected by the first current detector 7a, and the current control circuit 9 adjusts the voltage command Vref according to the difference between the detected current Ia and the current command value Iref. This substantially matches the value Iref. Therefore, the current command value Ire is output from the voltage type inverter 3.
f, a current Ia substantially equal to f is output, whereby the capacitor 6 can be charged and discharged.
Functions as the current output unit of the present invention.

[0028] Thus, for example, in a state where the AC voltage from the AC power supply 1 to the power system 2 is outputted, by changing in synchronization with the current command value Iaref the AC voltage of the AC power supply 1, a voltage type inverter 3 Output current I
The predetermined current can be supplied to the power system 2 while charging and discharging the capacitor 6 by a. This allows
For example, even if the phase of the AC voltage of the AC power output from the AC power supply 1 and the phase of the AC voltage are shifted due to the reactance component of the power system 2 or the like, the current is appropriately compensated by the power conversion device, The phase difference can be adjusted.

When the AC voltage output from the AC power supply 1 contains a harmonic voltage component, a harmonic current Is corresponding to the harmonic voltage is supplied from the AC power supply 1 to the capacitor 6 via the power system 2. Flows against. The second current detector 7b detects the harmonic current Is flowing into the capacitor 6, and the current correction circuit 12 integrates the transfer function of the above (Equation 2) with respect to the harmonic current component to obtain a current correction value. Ihr
Output f. In response to this, the adding circuit 13a converts the current correction value Ihref to the basic current command value Iare.
The current command value Iref added to f is output, and a current Ia corresponding to the current command value Iref flows through the reactor 5. Therefore, the current Ia corresponding to the harmonic AC current Is flows from the reactor 5 into the capacitor 6, and accordingly, the harmonic AC current Is flowing from the AC power supply 1 into the capacitor 6 is reduced, and the AC current of the AC power supply 1 is reduced. The harmonic AC current included in Is is suppressed, and the AC current Is can be made substantially sinusoidal.

The basic current command value Iaref output from the basic current command creation circuit 8 differs depending on the purpose of use and the operating state of the power converter. For example, if the power converter is used as a high power factor converter, a basic current command value Iaref is created from a voltage command value of the DC voltage source 4 and a voltage feedback signal, and an uninterruptible power supply or a secondary battery is used. If used as a load leveling inverter, a basic current command value Iaref is created from a DC current command flowing through the DC voltage source 4 and a DC current feedback signal, and SVG
If it is used as a system stabilizing device, a basic current command value Iaref is created from the AC power supply voltage command value and the voltage feedback value of the AC power supply 1, and power transmission devices such as a self-excited BTB and a thyristor converter for DC power transmission. If it is used as, a basic current command value Iaref is created from the power command value supplied to the AC power supply 1 and the power feedback value, and if it is used as a current compensating device such as an active filter, the current command flowing to the AC power supply 1 is From the current feedback value, the basic current command value Iar
ef may be created.

As described above, according to the first embodiment, the current Is flowing into the capacitor 6 from the AC power supply 1
Is detected by the second current detector 7b at a position closer to the AC power source 1 than the connection point between the capacitor 6 and the reactor 5 and the harmonic current component of the detected current Is ), The current Ia output from the voltage-type inverter 3 is corrected by calculation using the transfer function
The output current Ia of the voltage type inverter 3 has an impedance characteristic that effectively suppresses the inflow of the harmonic current Ia. Even if the output voltage of the AC power supply 1 includes the harmonic voltage, the AC power supply 1 The harmonic current Is flowing into 6 is effectively suppressed. Therefore, distortion of the AC current Is from the AC power supply 1 is effectively suppressed, and the waveform of the AC current Is becomes close to a sine wave.

In the first embodiment, the current output unit 22
However, the AC current Ia flows through the reactor 5 according to the AC voltage output of the voltage type inverter 3, and the AC current Ia
Since the configuration is such that the ON / OFF timing of the voltage-type inverter 3 is detected by detecting a, it is possible to perform the current control necessary for controlling the harmonic current Is with a simple configuration.

The current Is flowing from the AC power supply 1 to the capacitor 6 is directly detected by the second current detector 7b, but the current Ia flowing out of the reactor 5 and the capacitor 6
The current Is may be obtained from the difference from the current Ic flowing into the circuit.

[0034] Embodiment 2. FIG. 4 is a block diagram showing a configuration of a power converter according to Embodiment 2 of the present invention. Reference numeral 20 denotes a load connected to the AC power supply 1, and the load 20 is connected in parallel with the power converter as viewed from the AC power supply 1. The second current detector 7c detects a current Ib flowing from a connection point between the load 20 and the power converter to a connection point between the capacitor 6 and the reactor 5. The other configuration except for the second current detector 7c and the load 20 is the same as that of the first embodiment, and the description is omitted.

[0035] Next, the operation will be described. In the figure,
Since the load 20 and the power converter are connected in parallel as viewed from the AC power supply 1, the AC voltage output from the AC power supply 1 is supplied to the load or the power converter as it is.
Therefore, when a harmonic AC voltage is included in the AC voltage, the harmonic AC voltage is supplied to the power converter as it is, and is directly connected to the load. This power converter operates in the same manner as the power converter of the first embodiment with respect to the harmonic AC voltage, and generates a harmonic AC current Is generated by flowing the harmonic AC voltage into the capacitor 6. Suppress.

In the second embodiment, since the current flowing into the power converter is changed from Is to Ib, the above (Equation 5) is changed to the following (Equation 6). Ib = Vc / Z (Equation 6)

As described above, according to the second embodiment, the harmonic AC current Is flowing from the AC power supply 1 via the power system 2 can be suppressed except for the portion flowing into the load 20. As in the first embodiment, the AC current Is output from the AC power supply 1 can be approximated to a sine wave. Other effects are similar to those of the first embodiment.

[0038] Embodiment 3. FIG. 5 is a block diagram showing a configuration of a power converter according to Embodiment 3 of the present invention. AC power supply 1 to load 20
And a load current detector 24 that detects the current IL flowing into the load 20 at a position closer to the load 20 than the connection point between the power converter and the load 20 is included in the current IL detected by the load current detector 24. The basic current command generation circuit 8 controls the basic current command value Iare so as to suppress the higher harmonic components.
Output f.

FIG . 6 shows an example of a detailed block diagram of the basic current command creation circuit 8. In the drawing, reference numeral 18b denotes a high-pass filter for extracting a harmonic current component having a frequency higher than the commercial frequency from the detection current IL of the load current detector 24, and reference numeral 15b denotes current compensation for the current value output from the high-pass filter 18b. This is a proportional circuit that performs a proportional operation according to the rate.

The other configuration except for the load current detector 24 and the basic current command generating circuit 8 is the same as that of the second embodiment, and the description is omitted.

[0041] Next, the operation will be described. The load current detector 24 detects a current IL flowing from the AC power supply 1 to the load 20, and the basic current command generating circuit 8 generates a basic current command such that a harmonic component included in the current IL is canceled at a predetermined current compensation rate. A value Iaref is output, and the current of the AC power supply 1 is supplied from the voltage-type inverter 3 to a connection point between the power converter and the load 20. Therefore, part or all of the harmonic AC current IL flowing into the load 20 is supplied by the power converter, and the AC current waveform Is of the AC power supply 1 is converted into a sine wave accordingly. Further, the power conversion device according to the third embodiment also suppresses the harmonic AC current Ib flowing into itself as in the second embodiment, whereby the AC current waveform Is of the AC power supply 1 is converted into a sine wave. .

As described above, the power converter according to the third embodiment has the AC current Is output from AC power supply 1.
In this case, it is possible to suppress the inclusion of a harmonic component caused by the load 20 and to operate as an active filter. In particular, the active filter of the third embodiment operates so as to suppress the harmonic component of the current Ib shunted to itself, so that the distortion of the AC current waveform Is due to the connection of the capacitor is suppressed. In addition, since the generation of the harmonic current by the load 20 is suppressed, it is possible to make the current waveform Is close to a sine wave much more accurately than the conventional one. In addition, the current compensation rate is 10
When 0% is set, the current waveform Is is closest to a sine wave.

Embodiment 4 FIG . FIG. 7 is a block diagram showing a configuration of a power converter according to Embodiment 4 of the present invention. In the figure, a second current detector 7d detects a current Ic flowing into the capacitor 6 from the AC power supply 1 at a position closer to the capacitor 6 than a connection point between the capacitor 6 and the reactor 5. Further, the transfer function used by the arithmetic circuit 19 of the current correction circuit 12 is changed to the following (Equation 7). (Z * C * S-1) / (Z * C * S) (Equation 7) where Z is the impedance characteristic, C is the capacitance of the capacitor, and S is the Laplace differential operator. Note that the current Ib flowing into the power converter is Ib = Vc / Z (Equation 8) as in the second embodiment.

[0044] Other configurations except for the second current detector 7d and the arithmetic circuit 19 is omitted because it is similar to that of the second embodiment.

[0045] Next, the operation will be described. In the figure,
Since the load 20 and the power converter are connected in parallel as viewed from the AC power supply 1, the AC voltage output from the AC power supply 1 is supplied to the load 20 or the power converter as it is. Therefore, when a harmonic AC voltage is included in the AC voltage, the harmonic AC voltage is supplied to the power converter as it is and is connected to the load 20 as it is. This power converter operates in the same manner as the power converter of the first embodiment with respect to the harmonic AC voltage, and generates the harmonic AC current Ib generated by applying the harmonic AC voltage to the capacitor 6. Suppress the occurrence.

As described above, according to the fourth embodiment, the harmonic AC current Is flowing from the AC power supply 1 via the power system 2 can be suppressed except for the amount IL flowing into the load 20. AC power supply 1
Can be made to be close to a sine wave. Other effects are the same as those of the second embodiment.

In the power converter shown in FIG.
A load current detector 24 for detecting the current IL of the load 20 is provided in the same manner as in the third embodiment, and the basic current command generation circuit 8 provides a basic current compensation ratio for a harmonic component of the detected current IL that provides a predetermined current compensation rate. When the current command value Iaref is configured to be output, it goes without saying that the same operation and effect as those of the third embodiment are exhibited.

Embodiment 5 FIG . FIG. 8 is a block diagram showing a configuration of a power converter according to Embodiment 5 of the present invention. In the figure, a second current detector 7e detects a current Is flowing from the AC power supply 1 into the capacitor 6 at a position closer to the AC power supply 1 than a connection point between the power converter and the load 20. Further, the transfer function used by the arithmetic circuit 19 of the current correction circuit 12 is changed to the following (Equation 9) similar to the second embodiment. (Z * C * S-1) (Equation 9) where Z is the impedance characteristic, C is the capacitance of the capacitor, and S is the Laplace differential operator. Therefore, when there is no harmonic current component IL flowing from the AC power supply 1 to the load 20, all the harmonic currents Is of the AC power supply 1 become currents Ib flowing into the power converter, and Is = Vc / Z (Equation 10) The relationship is established.

[0049] Other configurations except for the second current detector 7e is omitted because it is the same as the second embodiment.

[0050] Next, the operation will be described. In the figure,
Since the load 20 and the power converter are connected in parallel when viewed from the AC power supply 1, the AC voltage output from the AC power supply 1 is supplied to the load 20 and the power converter as it is. Therefore, when a harmonic AC voltage is included in the AC voltage, the harmonic AC voltage is directly supplied to the power converter. The power converter operates in the same manner as the power converter of the first embodiment with respect to the harmonic AC voltage, and generates a harmonic AC current generated by applying the harmonic AC voltage to the capacitor 6. Suppress. Therefore, at least the harmonic AC current Is of the AC power supply caused by the capacitor 6 is suppressed.

As described above, according to the fifth embodiment, the harmonic AC current Is flowing from the AC power supply 1 via the power system 2 can be suppressed except for the amount IL flowing into the load 20. As in the second embodiment, the AC current Is output from the AC power supply can be made to be close to a sine wave. Other effects are the same as those of the second embodiment.

In the power converter shown in FIG.
A load current detector 24 for detecting the current IL of the load 20 is provided in the same manner as in the third embodiment, and the basic current command generation circuit 8 provides a basic current compensation ratio for a harmonic component of the detected current IL that provides a predetermined current compensation rate. When the current command value Iaref is configured to be output, it goes without saying that the same operation and effect as those of the third embodiment are exhibited.

Embodiment 6 FIG . FIG. 9 is a block diagram showing a configuration of a power converter according to Embodiment 6 of the present invention. In the figure, reference numeral 21 denotes a voltage detector for detecting a voltage Vc generated in the capacitor 6, and the detected voltage Vc is input to the current correction circuit 12. The high-pass filter 18a of the current correction circuit 12
Extracts only an AC voltage having a frequency equal to or higher than the commercial frequency, and the arithmetic circuit 19 performs an arithmetic operation using a transfer function of the following (Equation 11) and outputs a current correction value Ihref. (C * S-1 / Z) (Equation 11) Here, Z is the impedance characteristic, C is the capacitance of the capacitor, and S is the Laplace differential operator. Note that the current Ib flowing into the power converter is Ib = Vc / Z (Equation 12) as in the second embodiment.

The other configuration except for the voltage detector 21 and the current correction circuit 12 is the same as that of the second embodiment, and the description is omitted.

[0055] Next, the operation will be described. In FIG. 9, since the load 20 and the power converter are connected in parallel as viewed from the AC power supply 1, the AC voltage output from the AC power supply 1 is directly supplied to the load 20 and the power converter. Therefore, when a harmonic AC voltage is included in the AC voltage, the harmonic AC voltage is directly supplied to the power converter. When the potential Vc of the capacitor 6 changes at a frequency higher than the commercial frequency due to the harmonic AC voltage, the current correction circuit 12 outputs the current correction value Ihref.
Is output, and the voltage-type inverter 3 outputs the current correction value Ih
The current Ia corrected by ref is output. Therefore,
A part of the current Ic for charging / discharging the capacitor 6 to a potential following the high-frequency AC voltage of the AC power supply 1 is supplied by the output current Ia of the voltage-type inverter 3, and the high-frequency AC current from the AC power supply 1 is correspondingly supplied. Ib is suppressed.

As described above, according to the sixth embodiment, the harmonic AC current Is flowing from the AC power supply 1 via the power system 2 can be suppressed except for the amount of the IL flowing into the load 20. As in the second embodiment, the AC current Is output from the AC power supply 1 can be made to be close to a sine wave. Other effects are the same as those of the second embodiment.

In the power converter shown in FIG.
A load current detector 24 for detecting the current IL of the load 20 is provided in the same manner as in the third embodiment, and the basic current command generation circuit 8 provides a basic current compensation ratio for a harmonic component of the detected current IL that provides a predetermined current compensation rate. When the current command value Iaref is configured to be output, it goes without saying that the same operation and effect as those of the third embodiment are exhibited.

In the above description of the embodiment, the current output section 22 for outputting the current Ia following the current command value Iref is provided with the reactor 5 at the output of the self-excited voltage type inverter 3 and the reactor 5 is provided. 5 is made up of feedback control circuits 9, 10, and 11 for matching the current Ia flowing to the current command value Iref with the current command value Iref. Instead, a current-type inverter such as a thyristor converter that can directly output the current Ia is used. Using the current output unit 22
May be configured.

Although the reactor 5 is provided at the output of the voltage type inverter 3, if it is provided between the capacitor 6 and has an appropriate inductance value, for example, a transformer, etc. Alternatively, the leakage inductance or the like may be used instead.

[0060] Further, the current control circuit 9 is a voltage command Vref
And the PWM circuit 10 and the drive circuit 11 switch the voltage-type inverter 3 in response to this. However, an error-following inverter or the like may be used instead.

[0061] On the other hand, in the above description of the embodiment has a configuration using a DC voltage source 4 as providing a DC voltage to the voltage-type inverter 3, as long as it can provide a DC voltage Since any type can be used, for example, a capacitor, a secondary battery, an AC / DC converter, a rectifier, or the like may be used instead.

[0062]

As described above, according to the first aspect of the present invention, the current flowing from the AC power supply to the capacitor is controlled by
The above-mentioned AC than the connection point of the capacitor and the above-mentioned current output part
At the position near the power supply,
The current is calculated by multiplying the harmonic component by a predetermined transfer function.
Since the correction value of the command value is obtained,
The impedance characteristics of the power converter
Characteristics to suppress the harmonic current flowing into the device.
Wear. Also, the impedance is Z and the capacitance of the capacitor is
C, the transfer function when the Laplace differential operator is S
(Z * C * S-1), so it flows into the capacitor
The current can be reduced most effectively to 1 / Z
You.

[0063] According to the second aspect of the invention, or an AC power source
The current flowing into the capacitor from the
From the connection point with the conversion device
Between the point of connection with
Multiply the harmonic component of the flow by a predetermined transfer function
A correction value for the current command value is obtained.
The impedance characteristics of the power converter
Characteristics to suppress the harmonic current flowing into the conversion device
Can be. The impedance is Z and the capacitance of the capacitor is
Transfer function when the quantity is C and the Laplace differential operator is S
Is (Z * C * S-1), so it flows into the capacitor.
Current can be reduced most effectively to 1 / Z
You.

[0064] According to the third aspect of the present invention, either the AC power source
The current flowing into the capacitor from the power converter
At the position closer to the AC power source than the point of connection between the
As well as the harmonic components of the detected current.
Multiply the constant transfer function to obtain the correction value of the current command value
The power conversion device from the point of view of the AC power supply.
Harmonic power flowing into the power converter
It can have a characteristic of suppressing flow. In addition,
Dance is Z, capacitance of capacitor is C, Laplace differential operation
The transfer function when the child is S is (Z * C * S-1)
Therefore, the current flowing into the capacitor must be
It can be reduced effectively.

[0065] According to the fourth aspect of the present invention, either the AC power source
Current flowing into the capacitor from the
The point closer to the capacitor than the connection point with the current output section
At the position and the harmonic components of the detected current
Is multiplied by a predetermined transfer function to compensate for the current command value.
Since a positive value is obtained, power conversion from the viewpoint of AC power
The impedance characteristic of the device flows into the power converter
Characteristics that suppress higher harmonic currents. Ma
The impedance is Z, the capacitance of the capacitor is C,
When the Lath differential operator is S, the transfer function is (Z * C *
S-1) / (Z * C * S).
The most effective reduction of the inflow current by 1 / Z
it can.

[0066] According to the invention of claim 5, wherein the capacitor
Voltage detected at the
By multiplying the harmonic component by a predetermined transfer function, the current
As I am trying to obtain the correction value of the prescription, I saw it from the AC power supply
The impedance characteristics of the power converter
To suppress the harmonic current flowing into the
You.

[0067] According to the sixth aspect of the present invention, the transfer function
(C * S-1 / Z), so it flows into the capacitor
The current can be reduced most effectively to 1 / Z
You.

[Brief description of the drawings]

FIG. 1 is a block diagram showing a power conversion device according to a first embodiment of the present invention.

FIG. 2 is a block diagram illustrating a current control circuit of FIG. 1;

FIG. 3 is a block diagram illustrating a current correction circuit of FIG. 1;

FIG. 4 is a block diagram showing a power conversion device according to a second embodiment of the present invention.

FIG. 5 is a block diagram showing a power conversion device according to a third embodiment of the present invention.

FIG. 6 is a block diagram showing a current command creation circuit of FIG. 5;

FIG. 7 is a block diagram showing a power conversion device according to a fourth embodiment of the present invention.

FIG. 8 is a block diagram showing a power conversion device according to a fifth embodiment of the present invention.

FIG. 9 is a block diagram showing a power converter according to a sixth embodiment of the present invention.

FIG. 10 is a block diagram showing a conventional power converter.

[Explanation of symbols]

1 AC power supply, 3 voltage type inverter (inverter),
4 DC voltage source, 5 reactors, 6 capacitors, 7a
First current detector, 7b, 7c, 7d, 7e Second current detector, 8 basic current command creation circuit, 12 current correction circuit, 13a, 13b addition circuit, 20 load, 22
Current output unit, 23 control unit.

Continuation of the front page (72) Inventor Kenma Yamamoto 2-3-2 Marunouchi, Chiyoda-ku, Tokyo Inside Mitsubishi Electric Corporation (72) Inventor Masaaki Oshima 4-1 Egasakicho, Tsurumi-ku, Yokohama-shi, Kanagawa Prefecture Tokyo Electric Power Company Stock (72) Inventor Satoshi Miyazaki 4-1 Egasaki-cho, Tsurumi-ku, Yokohama-shi, Kanagawa Prefecture Tokyo Electric Power Company Electric Power Research Laboratory (56) References JP-A-4-200242 (JP, A) JP JP-A-7-107669 (JP, A) JP-A-10-52055 (JP, A) JP-A 7-39253 (JP, U) JP-B 5-76256 (JP, B2) (58) Fields investigated (Int) .Cl. ⁷ , DB name) H02J 3/01 G05F 1/70 H02J 3/18

Claims (6)

(57) [Claims] (1)Has inverter connected to AC power supply
Current output section that outputs a current that follows the current command value
And connected in parallel with the inverter as viewed from the AC power supply
And the current command value to the current output unit
And a control unit for outputting. The control unit includes: Outputs the basic current command value for adjusting the AC current
The current command creating means, The current flowing from the AC power supply is
At the position closer to the AC power source than the connection point with the
A second current detector, Included in the current detected by the second current detector
Current obtained by multiplying the harmonic component by a predetermined transfer function
A current correction circuit that outputs a correction value, The basic current command value and the current correction value are added together.
And an adder circuit that outputs a current command value The transfer function can be expressed as follows: impedance is Z, capacitance of capacitor
When the quantity is C and the Laplace differential operator is S, (Z * C * S-1) Power conversion equipment
Place. (2) Has inverter connected to AC power supply
Current output section that outputs a current that follows the current command value
And connected in parallel with the inverter as viewed from the AC power supply
And the current command value to the current output unit
And a control unit that outputs signals, which are parallel when viewed from the AC power supply.
In a power converter in which a load is connected to The control unit includes: Base for outputting basic current command value for adjusting AC power
The current command creating means, The current flowing from the AC power supply is connected to the load and the power conversion device.
From the connection point to the capacitor and the current output section
A second current detector that detects between the points, The second
Harmonic components included in the current detected by the current detector
The current correction value obtained by multiplying the predetermined transfer function by
An output current correction circuit; The basic current command value and the current correction value are added together.
And an adder circuit that outputs a current command value The transfer function can be expressed as follows: impedance is Z, capacitance of capacitor
When the quantity is C and the Laplace differential operator is S, (Z * C * S-1) Power conversion equipment
Place. (3) Has inverter connected to AC power supply
Current output section that outputs a current that follows the current command value
And connected in parallel with the inverter as viewed from the AC power supply
And the current command value to the current output unit
And a control unit that outputs signals, which are parallel when viewed from the AC power supply.
In a power converter in which a load is connected to The control unit includes: Base for outputting basic current command value for adjusting AC power
The current command creating means, The current flowing from the AC power supply is connected to the power converter and the load.
The second to detect at the position closer to the AC power than the continuation point
A current detector; Included in the current detected by the second current detector
Current obtained by multiplying the harmonic component by a predetermined transfer function
A current correction circuit that outputs a correction value, The basic current command value and the current correction value are added together.
And an adder circuit that outputs a current command value The transfer function can be expressed as follows: impedance is Z, capacitance of capacitor
When the quantity is C and the Laplace differential operator is S, (Z * C * S-1) Power conversion equipment
Place. (4) Has inverter connected to AC power supply
Current output section that outputs a current that follows the current command value
And connected in parallel with the inverter as viewed from the AC power supply
And the current command value to the current output unit
And a control unit that outputs signals, which are parallel when viewed from the AC power supply.
In a power converter in which a load is connected to The control unit is Outputs the basic current command value for adjusting the AC current
The current command creating means, The current flowing from the AC power supply is
At a position closer to the capacitor than the connection point with the output section
A second current detector for detecting, Included in the current detected by the second current detector
Current obtained by multiplying the harmonic component by a predetermined transfer function
A current correction circuit that outputs a correction value, The basic current command value and the current correction value are added together.
And an adder circuit that outputs a current command value The transfer function can be expressed as follows: impedance is Z, capacitance of capacitor
When the quantity is C and the Laplace differential operator is S, (Z * C * S-1) / (Z * C * S)
To be Power converter. (5) Has inverter connected to AC power supply
Current output section that outputs a current that follows the current command value
And connected in parallel with the inverter as viewed from the AC power supply
And the current command value to the current output unit
And a control unit that outputs signals, which are parallel when viewed from the AC power supply.
In a power converter in which a load is connected to The control unit is Outputs the basic current command value for adjusting the AC current
The current command creating means, A voltage detector for detecting a voltage generated in the capacitor; Harmonics included in the voltage detected by the voltage detector
Current correction value obtained by multiplying the component by a predetermined transfer function
A current correction circuit that outputs The basic current command value and the current correction value are added together.
And an adder circuit that outputs a current command value
Sign Power converter. 6. The transfer function is expressed as
When the capacitance of the capacitor is C and the Laplace differential operator is S
If (C * S-1 / Z).
Listed Power converter.