JP3364588B2 - Control device for hybrid DC power transmission equipment - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a control device for a DC power transmission facility that converts AC into DC for power transmission, and then converts the AC into AC again at a load place, and more particularly, the DC power transmission facility includes a separately excited converter and a self-excited converter. The present invention relates to a control device for a hybrid type DC power transmission facility configured by combining power converters, and relates to a control technology for a self-excited converter that enables continuous operation when an AC system accident occurs on the separately excited converter side.

[0002]

2. Description of the Related Art A self-excited converter that can perform power conversion without being affected by an AC system and can control reactive power from advance to delay arbitrarily and at high speed is being developed for DC transmission. There is. Considering the application form of the self-excited converter, the self-excited converter is used for the inverse converter and the conventional separately-excited converter is used for the forward converter in order to take advantage of the application advantages. Hybrid type DC power transmission system, which is configured by combining devices, is considered promising in the future. In this case, the self-excited converter is operated by constant voltage control from the main circuit configuration to keep the voltage of the DC circuit constant, and the separately excited converter is operated by constant current control (constant power control) to keep the transmitted power at a specified value. . However, if this driving method is adopted,
If an accident occurs in the AC system on the forward converter side and the AC voltage drops and the DC voltage of the forward converter cannot exceed the rated value,
Since the DC voltage on the reverse converter side becomes higher than the voltage on the forward converter side, current cannot flow from the forward converter to the reverse converter, and DC power transmission stops. On the other hand, in the inverse converter performing the constant DC voltage control, the inflow of electric power from the forward converter is eliminated, so that the tidal current voltage tends to decrease. Therefore, the power converted to the AC side is reduced to prevent the DC voltage from dropping,
Operates to keep the DC voltage constant. As described above, the DC transmission may be stopped due to the AC system accident on the forward converter side, which is an obstacle to the practical application of the hybrid DC transmission system.

[0003]

SUMMARY OF THE INVENTION An object of the present invention is to combine a self-excited converter and a separately-excited converter capable of transmitting DC power without stopping even when an AC system accident occurs on the separately-excited converter side. Another object of the present invention is to provide a control device for hybrid type DC power transmission equipment.

[0004]

In order to solve the above-mentioned problems, in a control device for hybrid type DC power transmission equipment,
The control device of the self-excited converter detects the first comparing means for detecting that the current of the DC transmission line is smaller than a specified value, and the input AC voltage of the separately excited converter is below a specified value. And a AND means for outputting a logical product of the output of the first comparing means and the output of the second comparing means, and the voltage set value of the self-excited converter based on the current of the DC transmission line. And a signal selecting means for selecting either the output value of the setting value creating means or the rated DC voltage setting value as the input DC voltage setting value based on the output of the AND means. When the current flowing through the transmission line falls below the specified value and at the same time the input AC voltage of the separately excited converter falls below the specified value, set the input DC voltage set value of the self-excited converter to a voltage lower than the rated DC voltage set value. To do. Further, in the control device for the hybrid type DC power transmission equipment, the control device for the self-excited converter includes a first comparison means for detecting that the current of the DC transmission line is smaller than a specified value, and an input for the separately excited converter. The second that detects that the AC voltage has dropped below a specified value
And the AND means for outputting the logical product of the output of the first comparing means and the output of the second comparing means, and the rated DC voltage set value or the rated DC voltage set value based on the output of the AND means. With a signal selecting means for selecting any one of the lower constant values as the input DC voltage set value, the current flowing in the DC transmission line becomes a specified value or less, and at the same time, the AC voltage of the separately excited converter is set to a specified value or less. Then, the input DC voltage set value of the self-excited converter is set to a constant value lower than the rated DC voltage set value.

[0005]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 shows an embodiment of a hybrid DC power transmission facility including a separately-excited converter and a self-excited converter provided with a control device to which the present invention is applied. Describing according to the numbers in the figure, 1 is a forward converter composed of a separately excited converter, 2 is an inverse converter composed of a self-excited converter, 11, 21 are AC systems, 12 and 22 are converters. Connected AC busbars, 13 and 23 are circuit breakers, 14 and 24 are conversion transformers, 15 is a DC reactor for smoothing DC current, 25 is a DC capacitor, 30a is a DC transmission line main line, and 30b is a return route. . In the case of frequency conversion or asynchronous interconnection, there may be no transmission line. Reference numeral 16 is a control device for the separately excited converter 1, and 17 is an AC voltage transformer for detecting the voltage of the separately excited converter 1 on the AC system side, and the detected output is indicated by V1. Reference numeral 18 denotes a first DC current transformer that detects a DC current on the forward converter side, and the detected output is indicated by Id. Reference numeral 26 is a second DC current transformer for detecting the current on the DC transmission line side of the inverse converter, and the detected output is indicated by Ii. A DC voltage transformer 27 detects the voltage of the DC transmission line of the inverse converter, and the detected output is indicated by Vc. 28
Is an AC voltage transformer that detects the voltage on the AC side of the inverse converter, and the detected output is indicated by V2. Reference numeral 29 is an AC current transformer, and the detected output is indicated by I2. 207 is P
The Q detector is an output calculated from the AC voltage detection value V2 and the AC current detection value I2 as active power P2 and reactive power Q2.
Indicate. Reference numeral 30 denotes a control device of the self-excited converter 2 which is an inverse converter.

Next, the control device will be described. 101 receives the current setting value Idp and the DC current detection value Id as inputs,
Is a constant current control circuit for controlling the DC output voltage of the separately excited converter 1 so as to be equal to Idp. Generally, a value obtained by dividing the transmission power command value Pp by the DC voltage Vd is given as the current setting value. That is,

## EQU1 ## Idp = Pp / Vd 102 is a phase control circuit that outputs a gate pulse whose phase is controlled according to the output of the constant current control circuit 101, and the gate pulse is guided to the separately excited converter 1. Reference numeral 200 denotes a set value creation circuit that creates a DC voltage set value Vp by using the DC current Ii as an input, and the details will be described later. 201 receives the DC voltage set value Vp and the DC voltage detection value Vc as input, and
Is a DC voltage control circuit for controlling the DC voltage of the self-exciting converter 2 so that V becomes equal to Vp, 202 is a transmission power command value P
203. p, and the active power control circuit for controlling the DC voltage of the self-excited converter 2 so that P2 becomes equal to Pp by inputting the active power P2 calculated from the AC voltage detection value V2 and the AC current detection value I2. Is the reactive power command value Qp and the reactive power Q2 calculated from the AC voltage detection value V2 and the AC current detection value I2, and controls the DC voltage of the self-excited converter 2 so that Q2 becomes equal to Qp. This is a power control circuit, and this output becomes the command value of the reactive current. 204
Is a signal selection circuit that selects an appropriate output from the DC voltage control circuit 201 and the active power control circuit, and this output becomes the command value of the active component current. Reference numeral 205 denotes a non-interference current control circuit which receives the detected alternating current I2 as an input and divides it into an active component and a reactive component, and controls each to be equal to the active component current command value and the reactive component current command value. 2 includes a 2-axis / 3-axis conversion of the output of the non-interference current control circuit 205 and an inverse conversion circuit into a 3-phase signal. Reference numeral 206 denotes a PWM pulse creation circuit that creates a PWM on / off gate pulse from the output of the non-interference current control circuit 205, and the created pulse is guided to the self-excited converter 2.

FIG. 2 shows an example of input / output characteristics of the set value generating circuit 200. This input / output characteristic has a direct current Ii on the inverse converter side as an input,

[Formula 2] Ii <Ii2: Vp = Vp2 (AVR2) Ii2 <Ii <Ii1: Vp = F (Ii) Ii1 <Ii: Vp = Vp1 (AVR1) Ii3 <Ii: Constant power control (APR) characteristic Has become. Here, a function having F (Ii): Ii as a variable is shown.

Continuing with the description of the block of the control device for the self-excited converter 2 in FIG. 1, reference numeral 210 is a second part for detecting the DC current on the DC transmission line side of the DC capacitor 25 of the self-excited converter 2.
The first comparison circuit which inputs "Ii" which is the detection output of the DC current transformer 26, outputs "1" when the magnitude of Ii is less than or equal to a specified value, and outputs "0" otherwise.
Reference numeral 211 denotes an AC voltage transformer 1 of the AC system of the separately excited converter 1.
When V1 which is the detection output of 7 is input, it becomes "1" when the magnitude of V1 becomes less than the specified value, and "0" otherwise.
Is an AND circuit, which outputs "1" only when both outputs of the first comparison circuit and the second comparison circuit are "1", and other times Outputs "0". A switch circuit 213 uses the output of the AND circuit 212 as an input condition for switching,
When the output is "0", the rated DC voltage set value Vp1 is selected, and when the output is "1", the set value creation circuit 200 is selected to become the set value Vp of the DC voltage control circuit 201.

Now, if an accident occurs in the AC system of the separately excited converter 1 and the voltage becomes lower than the DC voltage of the self-excited converter 2, the output of the second comparison circuit 211 becomes "1", and Since no direct current flows, the output of the first comparison circuit becomes "1" and the output of the AND circuit becomes "1".
Therefore, the switch circuit 213 uses the set value generation circuit 200.
Output the output of. In the setting value generation circuit 200, the input I
The voltage setting Vp according to the characteristic shown in FIG. 2 is output according to the magnitude of i, and this value becomes the setting value of the DC voltage control circuit 201, and feedback is performed so that the DC capacitor voltage Vc becomes equal to the setting value Vp. Controlled. When the voltage set value of the self-excited converter 2 is lowered and a direct current flows, the output of the first comparison circuit 210 becomes "0" and the output of the AND circuit 212 becomes "0". Therefore, the switch circuit 213
Will be switched. Therefore, the first comparison circuit 2
The resetting of 10 from "1" to "0" is preferably performed with a set time when the second comparison circuit 211 representing the recovery of the AC voltage is reset. When the accident is removed and the AC voltage is restored, the output of the second comparison circuit 211 becomes "
Since the output of the AND circuit becomes "0" after the set time, the output of the switch circuit 213 switches to the rated voltage set value Vp1 and returns to the normal rated operation.
Although Vp1 in FIG. 2 is set to the same value as the rated DC voltage setting value, even if different values are set, the switch circuit 213 switches to a fixed Vp1 depending on the values of Ii and V1, so that no adverse effect occurs. In addition, the APR characteristics are shown in FIG.
This characteristic is a DC voltage-current characteristic determined by the active power control circuit 202, and is not a characteristic that the set value generation circuit 200 should have.

FIG. 3 shows the DC voltage Vd characteristics with respect to the DC current Id of the two converters including the forward converter and the inverse converter at this time. During normal operation, the inverse converter (self-excited converter 2: INV) is under the control of the constant voltage control AVR1, and the forward converter (separately excited converter 1: REC) is under the constant current control,
Shown by the solid line. The operation of each transducer is at the intersection o of the two curves. When an accident occurs in the AC system on the forward converter side and the AC voltage drops, the control of REC becomes the minimum control angle operation as shown by the thin line, and the inverse converter switches to the characteristic of FIG. 2 as shown by the broken line. The operating point of each converter at this time is o '. That is, even if the DC voltage on the side of the separately excited converter becomes smaller than the voltage on the side of the inverse converter, the DC voltage of the self-excited converter 2 is lowered according to the DC current Ii. It is possible to continue the operation without stopping the power transmission when it runs out.

FIG. 4 shows another embodiment of the present invention. The same numbers as in FIG. 1 indicate the same functions. In FIG. 1, the set value Vp of the DC voltage control circuit 201 of the control circuit 30 of the self-excited converter 2 is created by the DC current Ii. However, in the present embodiment, Vpx1 and Vpx2 which are constant values do not depend on Ii.
I am trying. Only the switching of this set value is performed by Ii and the magnitude of the AC voltage V1 on the separately excited converter side. Now, take Vpx1 equal to the rated DC voltage setting value, select Vpx2 as the minimum DC voltage setting value that the self-exciting converter 2 can output, and Vpx1 when the output of the AND circuit 212 is "0", and V when it is "1".
It is assumed that the switch circuit 213 is set so as to select px2. The operation of each converter at this time is shown in FIG. The solid line shows the operation during normal rated operation, and the intersection of the two curves represents the operating point o. The forward converter (REC) is operated under constant current control and the inverse converter (INV) is operated under constant voltage control. It When an accident occurs in the AC system of the forward converter of the separately excited converter 1 and the voltage drops, the forward converter enters the minimum control angle operation, and the inverse converter V1 drops and Ii stops flowing, so the switch circuit 213 switches to Vpx2.
The operation of the forward converter is as shown by the broken line, and the operating point is o '
Becomes That is, even if the DC voltage on the side of the separately excited converter becomes smaller than the voltage on the side of the inverse converter, the DC voltage of the self-excited converter 2 is lowered according to the DC current Ii. There is no loss of power transmission,
The operation can be continued. When the accident is removed, the AC voltage V1 is recovered, so the output of the second comparison circuit becomes "0", and the switch circuit switches to Vpx1 to return to normal rated operation. In this case, it is practical that the switch circuit 213 switches to Vpx1 after a set time from when the output of the second comparison circuit becomes "0".

FIG. 6 shows another embodiment of the present invention. In the present embodiment, the voltage setting value Vp of the self-exciting converter 2 is created by the DC current value Ii. Since those having the same numbers as those in FIG. 1 represent the same function, only different elements will be described. Reference numeral 220 denotes a second setting value generating circuit, which is the DC current − of the setting value generating circuit 200 shown in FIG. The voltage characteristic is similar to that of the voltage characteristic, but the voltage setting value Vp is returned by the reset signal of V1. That is, when Vp is lowered to Vp2 based on the decrease in the direct current Ii, Ii2 flows, but when Vp changes to a high value according to the characteristic of FIG. 2 in response to this Ii,
DC current stops flowing again. For this reason, the return from Vp2 is made after waiting for the recovery of the AC voltage V1. Therefore, the operation is similar to that of FIG. According to the present embodiment, as described above, even if the DC voltage on the side of the separately excited converter becomes smaller than the voltage on the side of the inverse converter, the DC voltage of the self-excited converter 2 is lowered according to the DC current Ii. Thus, the DC current does not stop flowing and the power transmission is not stopped, and the operation can be continued.

In the embodiments shown in FIGS. 1, 4, and 6, the DC current Ii of the self-excited converter 2 and the AC voltage V1 of the separately excited converter 1 are set to their respective prescribed values only for a moment due to some disturbance. The following may occur. In such a case, if the DC voltage set value Vp of the self-excited converter 2 is changed, the hybrid DC power transmission equipment may malfunction. In order to avoid this malfunction, in each of the embodiments, the change of the DC voltage setting value Vp of the self-excited converter 2 is performed by changing the DC current Ii of the self-excited converter 2 and the AC voltage V1 of the separately excited converter 1.
May be performed when the value has continued for a preset time or longer and a prescribed value or lower.

[0014]

As described above, according to the present invention,
By installing a simple control circuit in the control device for the self-excited converter, a self-excited converter and a separately excited converter that can continue operation of DC transmission without stopping even if an AC system accident occurs on the forward converter side are combined. It is possible to realize a hybrid type DC power transmission facility configured together. Further, when the DC current of the self-excited converter and the AC voltage of the separately excited converter continue to be equal to or less than a specified value for a preset time or more, by changing the DC voltage set value of the self-excited converter, It is possible to prevent a malfunction as a hybrid type DC power transmission facility and perform a stable operation.

[Brief description of drawings]

FIG. 1 is an embodiment of a hybrid DC power transmission facility including a separately-excited converter and a self-excited converter including a control device to which the present invention is applied.

FIG. 2 is a diagram showing a DC voltage characteristic of a self-excited converter of the present invention with respect to a DC current.

FIG. 3 is a diagram showing operating points on the voltage-current characteristics of each converter of a hybrid DC transmission facility including a separately excited converter and a self-excited converter, which are the objects of the present invention.

FIG. 4 is another embodiment of the present invention.

FIG. 5 is a diagram showing operating points on the voltage-current characteristics of each converter of the hybrid type DC power transmission equipment constituted by the separately excited converter and the self-excited converter, which are the objects of the present invention.

FIG. 6 is another embodiment of the present invention.

[Explanation of symbols]

1: Separately-excited converter, 2: Self-excited converter, 11, 21: AC system, 12, 22: AC bus, 30a: DC transmission line main line, 30b: Return line, 16: Control device of separately-excited converter,
17: AC voltage transformer, 18: first DC current transformer,
26: second DC current transformer detector, 27: DC voltage transformer, 28: AC voltage transformer, 29: AC current transformer,
30: Self-excited converter control device, 101: Constant current control circuit, 102: Phase control circuit, 200: First set value creation circuit, 201: DC voltage control circuit, 202: Active power control circuit, 203: Invalid Power control circuit, 204: signal selection circuit, 205: non-interference current control circuit, 206: PWM pulse generation circuit, 210: first comparison circuit, 211: second
Comparing circuit, 212: AND circuit, 213: Switch circuit, 220: Second setting value creating circuit

─────────────────────────────────────────────────── ─── Continuation of the front page (72) Kiyoshi Takenaka 2-1-11-1 Iwatokita, Komae-shi, Tokyo Inside Central Research Institute of Electric Power Industry (72) Masahiro Takasaki 2--11-11 Iwatokita, Komae-shi, Tokyo No. 1 Central Research Institute of Electric Power Industry (72) Inventor Naoki Yibo 2-11-11 Iwatokita, Komae-shi, Tokyo Inside Central Research Institute of Electric Power Industry (56) Reference JP-A-7-284224 (JP, A) ) JP-A-5-212779 (JP, A) JP-A 1-311825 (JP, A) JP-A 11-27865 (JP, A) JP-A-58-51737 (JP, A) JP-A 11- 299107 (JP, A) (58) Fields surveyed (Int.Cl. ⁷ , DB name) H02J 5/00 H02J 1/00 301 H02J 3/36 H02M 7/48

Claims (5)

(57) [Claims] 1. A separately excited converter for converting alternating current into direct current,
In a control device for a hybrid type DC power transmission facility in which a self-exciting converter for converting DC to AC is connected via a DC transmission line, the control device controls the control device for the separately excited converter and the self-excited converter. The control device for the self-excited converter includes a first comparison unit that detects that the current of the DC transmission line is smaller than a specified value, and an input AC voltage of the separately excited converter is specified. Second comparing means for detecting that the value is less than or equal to a value, AND means for outputting a logical product of the output of the first comparing means and the output of the second comparing means, and the current of the DC transmission line Based on the set value creating means for creating the voltage set value of the self-excited converter, and based on the output of the AND means, either the output value of the set value creating means or the rated DC voltage set value is input DC voltage. Signal to select for set value When the current flowing through the DC transmission line is below a specified value and the input AC voltage of the separately excited converter is below a specified value at the same time, the input DC voltage setting of the self-excited converter is included. A control device for a hybrid type DC power transmission facility, wherein a value is set to a voltage lower than the rated DC voltage set value. 2. The control of a hybrid DC power transmission facility according to claim 1, wherein the input DC voltage set value of the self-excited converter is continuously lowered based on the magnitude of the current of the DC power transmission line. apparatus. 3. A separately excited converter for converting alternating current to direct current,
In a control device for a hybrid type DC power transmission facility in which a self-exciting converter for converting DC to AC is connected via a DC transmission line, the control device controls the control device for the separately excited converter and the self-excited converter. The control device for the self-excited converter includes a first comparison unit that detects that the current of the DC transmission line is smaller than a specified value, and an input AC voltage of the separately excited converter is specified. A second comparing means for detecting that the value is less than or equal to a value; an AND means for outputting a logical product of an output of the first comparing means and an output of the second comparing means; and an output of the AND means. Based on the rated DC voltage set value or a constant value lower than the rated DC voltage set value based on the signal selection means for selecting the input DC voltage set value, the current flowing through the DC transmission line is below a specified value. And at the same time When the AC voltage of the converter is equal to or less than a specified value, the input DC voltage set value of the self-excited converter is set to a constant value lower than the rated DC voltage set value of the hybrid DC transmission facility. Control device. 4. The input of the self-excited converter according to any one of claims 1 to 3, after a preset time elapses after the input AC voltage of the separately excited converter returns to a specified value. A control device for a hybrid DC power transmission facility, wherein a DC voltage setting value is returned to the rated DC voltage setting value. 5. The input DC voltage set value of the self-exciting converter according to claim 1, wherein the current flowing through the DC power transmission line is continuously maintained for a preset time or more and is equal to or less than a specified value. And / or if the input AC side voltage of the separately excited converter continues to fall below a specified value for a preset time or longer, a voltage lower than the rated DC voltage set value is set. Control device for hybrid type DC power transmission equipment.