JP2760745B2 - Constant power control method for AC / DC interconnection system - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a constant power control method for maintaining a constant transmission power of an AC / DC interconnection system.

[0002]

2. Description of the Related Art FIG. 5 is a block diagram showing an AC / DC interconnection system. In FIG. 5, the AC / DC interconnection system roughly converts an electric power transmitted to an AC bus 1 a as one AC system into a direct current by a forward converter 3 a and converts the electric power into an inverse converter 3 b via a DC transmission line 5. And the power converted into AC by the inverter 3b is sent to the AC bus 1b as the other AC system. In this AC / DC interconnection system, constant current control for keeping the DC current constant and constant power control for keeping the DC power constant are performed. On the side of the forward converter 3a, the constant power control is generally positioned higher than the constant current control. FIG.
Reference numerals 2a and 2b denote transformers for converters, which are ordinary three-phase transformers except that they have a winding structure that reduces eddy current loss because current contains many high-frequency components. Is the same as Reference numerals 4a and 4b denote DC reactors for smoothing a DC current flowing by being distorted due to firing of a thyristor valve or the like.

FIG. 6 is a block diagram showing a conventional constant power control shown on page 83 of “DC Power Transmission Technology Description” published by the Institute of Electrical Engineers of Japan on March 30, 1978, for example. In FIG. 6, a power setting device 6 sets a power setting value Pref, and a divider 7 divides the power setting value Pref set by the power setting device 6 by a forward converter side DC voltage Edc to set a DC current setting value Ir.
Find ef. This DC current set value Iref is used for constant current control. That is, the DC current is controlled to the current set value Iref by the constant current control. Normally, in the AC / DC system, the DC voltage is maintained at the rated value, and the DC power is controlled by changing the current set value Iref, so that the DC power corresponding to the power set value Pref is transmitted. Can be.

[0004]

Since the conventional constant power control method is configured as described above, it is possible to control DC power, but it is necessary to accurately consider the power loss of transformers, converters and transmission lines. There was a problem that it was not possible to control the power of a simple AC system.

SUMMARY OF THE INVENTION The present invention has been made to solve the above problems, and a first object of the present invention is to accurately convert the power of an AC system in consideration of the power loss of transformers, converters, transmission lines, and the like. To obtain a controllable method.

A second object is to reduce the number of operations.

A third object is to eliminate the rounding error caused by the divider.

A fourth object is to eliminate a rounding error caused by a divider with a small number of operations.

[0009]

A first aspect of the present invention is the first aspect.
The constant power control method for an AC / DC interconnection system according to the present invention obtains a difference between a forward converter-side DC voltage and an inverter-side DC voltage, obtains a correction value obtained by multiplying the difference by a DC current, and obtains the correction value. And a power set value, and the sum is divided by the forward converter-side DC voltage to obtain a DC current set value.

According to a second aspect of the present invention, there is provided a constant power control method for an AC / DC interconnection system, wherein a difference between the forward converter-side AC power and the inverter-side AC power is obtained as a correction value. The power set value is added to the value, and the added value is divided by the forward converter side DC voltage to obtain a DC current set value.

According to a third aspect of the present invention, there is provided a constant power control method for an AC / DC interconnection system according to a third aspect of the present invention, wherein a DC current is converted into a difference between a forward converter side DC voltage and an inverter side DC voltage. A correction value is obtained by multiplying the divided value by the DC voltage, the power set value is divided by the forward converter side DC voltage, and this divided value is added to the correction value to obtain a DC current set value.

According to a fourth aspect of the present invention, a constant power control method for an AC / DC interconnection system according to a fourth aspect of the present invention obtains a difference between the forward converter-side AC power and the inverter-side AC power, and forward-converts the difference. A correction value is obtained by dividing by the DC voltage on the converter side, and a value obtained by dividing the power set value by the DC voltage on the forward converter side is added to the correction value to obtain a DC current set value.

[0013]

According to the first aspect of the present invention, a constant power control method for an AC / DC interconnection system performs a correction operation including a power loss of a converter or the like in a set DC current output value.

According to a second aspect of the present invention, there is provided a constant power control method for an AC / DC interconnection system, wherein only a subtraction of a forward converter-side AC power and an inverter-side AC power is used to reduce power loss of a converter or the like to a DC current set value. Since the calculation including the correction for the correction is performed, the number of calculations is reduced.

According to a third aspect of the present invention, there is provided a constant power control method for an AC / DC system, wherein a value obtained by dividing a DC current by a DC voltage on the forward converter side is added to a difference between the DC voltage on the forward converter side and the DC voltage on the inverter side. Since the divided value obtained by dividing the power set value by the DC voltage on the forward transformer side is added to the corrected value obtained by multiplication, even if the correction value is sufficiently small, the power on the AC side is not deleted as a rounding error by the divider. Perform the correction calculation including the loss.

According to a fourth aspect of the present invention, there is provided a constant power control method for an AC / DC interconnection system, wherein the correction value obtained by dividing the difference between the forward converter side AC power and the inverter side AC power by the forward converter side DC voltage. In addition, since the divided value obtained by dividing the power set value by the DC voltage on the forward transformer side is added, even if the correction value is sufficiently small, it is not deleted as a rounding error by the divider, and the power on the AC flow side can be reduced with a small number of operations. Perform the correction calculation including the loss.

[0017]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments of the present invention will be described below with reference to FIGS. Embodiment 1 (corresponding to claim 1). FIG. 1 is a configuration diagram of an apparatus used in a constant power control method for an AC / DC interconnection system according to a first embodiment of the present invention. In FIG. 1, a power setter 6, a divider 7, a calculator 8a and an adder 9 are provided, and the calculator 8a corrects the forward converter side DC voltage Edc, the inverter side DC voltage Vinv and the DC current Idc by a correction value = (Edc−Vinv) · Idc (1) By substituting into the equation, the forward converter side DC voltage Edc is obtained.
Edc-Vinv between the inverter and the DC voltage Vinv on the inverter side
And a correction value obtained by multiplying the difference Edc-Vinv by the DC current Idc is obtained. The DC voltage Edc on the forward converter side
Is a voltage value measured by the voltage transformer PT2 provided on the DC transmission line 5 is transmitted to the computing unit 8a via a communication line, and the inverter-side DC voltage Vinv is a current transformer C provided on the DC transmission line 5
The current value measured at T4 is transmitted to the computing unit 8a via a communication line. Then, the adder 9 calculates the correction value = (Edc−Vi)
nv) · Idc and the power set value Pref set by the power setter 6 are added, and the divider 7 calculates a correction value = (Edc)
−Vinv) · Calculates the DC current set value Iref by dividing the sum of the Idc and the power set value Pref by the forward converter side DC voltage Edc.

Therefore, in the first embodiment, the calculation is performed using the DC voltage at both ends. However, in other control such as constant voltage control of the converter, the DC voltage at both ends is already introduced into one end. According to the method of the first embodiment, the DC power can be controlled to a desired value without increasing the cost.

Embodiment 2 (corresponding to claim 2). Second Embodiment FIG. 2 is a configuration diagram of an apparatus used in a constant power control method for an AC / DC interconnection system as a second embodiment of the present invention. In FIG. 2, a power setter 6, a divider 7, a calculator 8b, and an adder 9 are provided.
By substituting the forward converter-side AC power Pacrec and the inverter-side AC power Pacinv into the correction value = Pacrec-Pacinv (2), the forward converter-side AC power Pacr is obtained.
The difference Pacr between ec and the inverter-side AC power Pacinv
ec-Pacinv is obtained as a correction value. That is, in the AC buses 1a and 1b, the forward converter-side AC power Pacrec and the inverter-side AC power Pa
cinv is measured and transmitted to the arithmetic unit 8b via the communication line.
For example, on the AC bus 1a side, the currents I1 and I2 flowing into the AC bus 1a are measured by CT1 and CT2, and the total current I of these currents I1 and I2 is measured by CT3 and transmitted to the power measuring device 10, while The voltage V of the bus 1a is measured by the voltmeter PT1 and transmitted to the power measuring device 10. The voltage V is multiplied by the current I = I1 + I2 by the power measuring device 10 to measure the forward converter side AC power Pacrec. . Inverter-side AC power Pacinv is similarly measured on the inverter 3b side. Then, the adder 9 calculates the correction value = Pacre
c-Pacinv is added to the power set value Pref set by the voltage setter 6, and the divider 7 calculates a correction value = Pac
The DC current set value Iref is obtained by dividing the sum of rec-Pacinv and the power set value Pref by the forward converter side DC voltage Edc.

Therefore, in the second embodiment, the correction including the power loss on the AC side can be performed with a smaller number of operations than in the first embodiment. That is, in the first embodiment, the forward converter-side DC voltage Edc and the inverse converter-side DC voltage Vinv are subtracted from each other, and the subtraction result is multiplied by the DC current Idc. In the second embodiment, the forward converter-side AC voltage is reduced. Since it is only necessary to subtract the power Pacrec and the AC power Pacinv on the inverter side,
In the second embodiment, the number of operations is smaller than in the first embodiment.

Embodiment 3 (corresponding to claim 3). Third Embodiment FIG. 3 is a configuration diagram of an apparatus used in a constant power control method for an AC / DC interconnection system according to a third embodiment of the present invention. 3 includes a power setter 6, a divider 7, a calculator 8c, and an adder 9, and the divider 7 has a power set value Pref set by the power setter 6.
Is divided by the forward converter side DC voltage Edc, and the calculator 8c calculates the forward converter side DC voltage Edc and the inverse converter side DC voltage Vinv
And the DC current Idc into the correction value = (Edc−Vinv) · Idc / Edc (3) to obtain the forward converter side DC voltage Edc.
Edc-Vinv between the inverter and the DC voltage Vinv on the inverter side
Is multiplied by a value Idc / Edc obtained by dividing the DC current Idc by the forward converter-side DC voltage Edc to obtain a correction value. Then, the adder 9 divides the power set value Pref by the forward converter-side DC voltage Edc to a value Pref / Edc, and calculates a difference E between the forward converter-side DC voltage Edc and the inverter-side DC voltage Vinv.
A power set value Pref is added to a correction value obtained by multiplying dc-Vinv by a value Idc / Edc obtained by dividing a DC current Idc by a forward converter-side DC voltage Edc, and this added value is obtained as a DC current set value Iref. .

Therefore, in the third embodiment, even when the correction value is sufficiently small, the correction including the power loss on the AC side can be performed without being deleted as a rounding error by the divider 7. Further, since the configuration can be achieved by simply adding the output of the arithmetic unit 8c to the conventional output, the conventional device can be effectively used.

Embodiment 4 (corresponding to claim 4). FIG. 4 is a configuration diagram of an apparatus used in a constant power control method for an AC / DC interconnection system as a fourth embodiment of the present invention. 4 includes a power setter 6, a divider 7, a calculator 8d, and an adder 9, and the divider 7 has a power set value Pref set by the power setter 6.
Is divided by the forward converter side DC voltage Edc, and the calculator 8d calculates the forward converter side AC power Pacrec and the inverter side AC power P
By substituting acinv and the DC voltage Edc of the forward converter into the correction value = (Pacrec−Pacinv) / Edc (4), the AC power Pac of the forward converter is obtained.
difference Pac between rec and inverter-side AC power Pacinv
rec-Pacinv, and the difference Pacrec-P
ainv is divided by the forward converter side DC voltage Edc to obtain a correction value. Then, the adder 9 divides the power set value Pref by the forward converter side DC voltage Edc to obtain a value Pref / Ed.
c is a difference Pacrec-Pacinv between the forward converter side AC power Pacrec and the inverter side AC power Pacinv.
Is divided by the forward converter-side DC voltage Edc, and a correction value obtained by the division is added, and the added value is obtained as a DC current set value Iref.

Therefore, in the fourth embodiment, even when the correction value is sufficiently small, the correction including the power loss on the AC side can be performed with a smaller number of operations than in the third embodiment without being eliminated as a rounding error by the divider 7. It becomes possible. That is, in the third embodiment, the subtraction between the forward converter-side DC voltage Edc and the inverse converter-side DC voltage Vinv, the result of the subtraction, and the DC current Id
c, the result of the multiplication and the DC voltage Ed
In this fourth embodiment, the forward converter-side AC power Pacrec and the inverter-side AC power Pacinv are divided.
, And the result of the subtraction and the DC voltage Edc on the forward converter side.
Therefore, in the fourth embodiment, the number of operations is smaller than that in the third embodiment.

[0025]

As described above, according to the first aspect,
Since the correction calculation including the power loss of the converter and the like is performed on the output DC current set value, the power of the AC system can be accurately controlled.

According to the second aspect of the present invention, the DC current set value includes a correction amount for correcting a power loss of the converter or the like only by subtracting the forward converter side AC power and the inverter side AC power. Since the calculation is performed, the power of the AC system can be accurately controlled with a small number of calculations.

According to the third aspect, the correction value obtained by multiplying the difference between the forward converter side DC voltage and the inverse converter side DC voltage by the value obtained by dividing the DC current by the forward converter side DC voltage is used as the correction value. Since the divided value obtained by dividing the power set value by the DC voltage on the forward transformer side is added, even if the correction value is sufficiently small, the correction operation including the power loss on the AC side is performed without being removed as a rounding error by the divider. The power of the AC system can be accurately controlled.

According to the fourth aspect, the power set value is converted to a correction value obtained by dividing the difference between the forward converter-side AC power and the inverse converter-side AC power by the forward converter-side DC voltage. Since the division value obtained by dividing by the unit side DC voltage is added, even if the correction value is sufficiently small, the correction operation including the power loss on the AC flow side is performed with a small number of operations without being removed as a rounding error by the divider. The power of the AC system can be accurately controlled.

[Brief description of the drawings]

FIG. 1 is a configuration diagram illustrating an apparatus used for a constant power control method for an AC / DC interconnection system according to a first embodiment.

FIG. 2 is a configuration diagram illustrating an apparatus used for a constant power control method for an AC / DC interconnection system according to a second embodiment.

FIG. 3 is a configuration diagram illustrating an apparatus used for a constant power control method for an AC / DC interconnection system according to a third embodiment.

FIG. 4 is a configuration diagram illustrating an apparatus used for a constant power control method for an AC / DC interconnection system according to a fourth embodiment.

FIG. 5 is a schematic configuration diagram showing an AC / DC interconnection system.

FIG. 6 is a configuration diagram showing an apparatus used in a conventional constant power control method for an AC / DC interconnection system.

[Explanation of symbols]

 1a, 1b AC bus 3a Forward converter 3b Inverter 5 DC transmission line 6 Power setter 7 Divider 8a, 8b, 8c, 8d Arithmetic unit 9 Adder

Claims (4)

(57) [Claims] 1. An electric power transmitted to one AC system is converted into direct current by a forward converter and sent to an inverter via a direct current transmission line. In the AC / DC system to be sent to the system, the difference between the DC voltage on the forward converter side and the DC voltage on the inverter side is obtained, a correction value obtained by multiplying the difference by the DC current is obtained, and the power set value is added to this correction value. A constant power control method for an AC / DC interconnection system in which the added value is divided by the DC voltage on the forward converter side to obtain a DC current set value. 2. The power sent to one AC system is converted to DC by a forward converter, sent to an inverter via a DC transmission line, and the power converted to AC by the inverter is converted to AC by the other AC system. In the AC / DC interconnection system to be sent to the system, the difference between the forward converter-side AC power and the inverter-side AC power is obtained as a correction value, a power set value is added to this correction value, and this added value is used as the forward converter side. A constant power control method for an AC / DC interconnection system that obtains a DC current set value by dividing by a DC voltage. 3. The power sent to one AC system is converted to DC by a forward converter, sent to an inverter via a DC transmission line, and the power converted to AC by the inverter is converted to AC by the other. In an AC / DC system to be sent to the system, the difference between the DC voltage on the forward converter side and the DC voltage on the inverter side is multiplied by the value obtained by dividing the DC current by the DC voltage on the forward converter side to obtain a correction value, and the power setting is made. A constant power control method in which a value is divided by a forward converter side DC voltage, and the divided value is added to the correction value to obtain a DC current set value. 4. The power sent to one AC system is converted to DC by a forward converter, sent to an inverter via a DC transmission line, and the power converted to AC by the inverter is converted to AC by the other converter. In the AC / DC interconnection system to be sent to the system, the difference between the forward converter side AC power and the inverter side AC power is obtained, this difference is divided by the forward converter side DC voltage to obtain a correction value, and the power set value is obtained. A constant power control method for an AC / DC interconnection system in which a value obtained by dividing a DC voltage on a forward converter side is added to the correction value to obtain a DC current set value.