JPH02155435A - Controller for system dc interlocking device - Google Patents

Abstract

PURPOSE:To drive a remaining converter without stopping even if one converter of interlocking operation is stopped due to its trouble, etc., and to easily invert a tide by controlling effective power constantly by voltage source type self-excited converters. CONSTITUTION:When the selector 93 of voltage source type self-excited converters 110, 210 of interlocking operation selects a maximum value, the converter 110 in which a DC voltage reference difference is added to a DC voltage reference Edp controls a DC voltage constantly under DC voltage constant control, and the other converter 210 in which the DC voltage reference difference is not added controls effective power constantly under effective power constant control. When the selector 93 of the converters 110, 210 of the interlocking operation selects a minimum value, the converter 210 in which the DC voltage reference difference is subtracted from the DC voltage reference Edp controls the DC voltage constantly under the DC voltage constant control, and the other converter 110 in which the DC voltage reference difference is not subtracted controls the effective power constantly under the effective power constant control.

Description

[Detailed Description of the Invention] [Purpose of the Invention (Industrial Application Field) The present invention is directed to the control of a system-DC interconnection device that transfers power between AC systems using a reduced pressure source type self-commutated power converter. Regarding equipment.

(Prior Art) FIG. 6 is a diagram illustrating a voltage source type self-excited power converter (hereinafter referred to as a converter). FIG. 7 shows a diagram illustrating one configuration example of an inverter main circuit constituting the converter. FIG. 8 shows a diagram explaining the operating principle of the inverter main circuit.

In FIGS. 6 and 7, 10 is an inverter, 20
3 is a DC capacitor, 30 is a grid interconnection reactor, and 40 is a grid interconnection transformer, which constitute the converter 1000. Further, 5Q indicates a DC power supply, and 100 indicates an AC system power supply (hereinafter referred to as a system).

In Figure 7, GU, GV, GW, GX, GY and G
Z indicates an ff-) turn-off thyristor (hereinafter referred to as GTO), which is a type of controllable rectifying element, and DU, D
V, DW, DX, DY and DZ indicate diodes. Further, PT and NT indicate DC terminals, and R, S and T indicate AC terminals, respectively.

How to adjust power by interconnecting the inverter main circuit consisting of the inverter 10 and DC capacitor 2Q shown in FIG. 6 with the grid 100 via the interconnecting reactor 30 and interconnecting transformer 4o. The operating principle is explained in Part 8.
This will be explained using figures.

The operating principle explained in Fig. 8 is similar to the description in pages 216 to 220 of Semiconductor Power Conversion Circuits J (first published on March 31, 1987), published by the Technical Committee on Semiconductor Power Conversion Systems of the Institute of Electrical Engineers of Japan. can be seen.

Now, in FIG. 8, the inverter main circuit is indicated by 1.

Furthermore, since the interconnection reactor 3o and the interconnection transformer 40 in FIG. 6 are both considered to be impedances, the interconnection reactor 3o and interconnection transformer 40 in FIG. 8 are combined as interconnection impedance 2.

To simplify the explanation, the transformation ratio of the interconnection transformer 4o is 1.
The ratio will be 1 to 1.

In FIG. 8(,), the inverter output voltage of the inverter main circuit 1 is v! The system voltage of N1 system 100 is vllY%
If the impedance of the grid connection impedance 2 is X1, the current flowing from the grid 100 to the inverter main circuit 1 via the grid connection impedance 2 is 1, and the phase difference angle of the inverter output voltage v1N with respect to the grid voltage vsY is φ, the operation vector diagram is shown in (b). t (e) It becomes like the figure. (b) is a vector diagram when the inverter main circuit 1 operates as a reactor. The amplitude of the inverter output voltage v4 is smaller than the amplitude of the grid voltage vsY, a voltage of (v8Y - vIN) is applied to the grid connection impedance 2, and the current flowing through the grid connection impedance 2 is in phase with the grid voltage v8Y. The current l has a component with a delay of 90' and a component with a delay of 90'.

This indicates that the inverter main circuit operates as a reactor and also obtains active power from the grid 100.

This relationship is expressed by the following formula.

In other words, the amplitude of the inverter output voltage vXN is the grid voltage v
If the phase of the inverter output voltage v4 is smaller than the amplitude of 8Y and the phase of the inverter output voltage v4 lags behind the phase of the grid voltage v1, the inverter main circuit l operates as a reactor and obtains active power from the grid 100. Above (1) # (2
), even if the amplitude of the inverter output voltage vIN is smaller than the amplitude of the grid voltage v8Y, if the phase of the inverter output voltage v4 is ahead of the phase of the grid voltage vsY, the inverter main circuit 1 will be delayed. It performs an operation of consuming reactive power and outputting active power to the grid 100.

In equation (1), when the phase of the inverter output voltage vxN is ahead of the grid voltage, the phase difference angle φ is treated as a positive value, and when it is delayed, it is treated as a negative value. A value indicates that active power is being supplied from the inverter main circuit 1 to the grid 100. Also(
In Equation 2), when Q is negative, inverter main circuit 1 operates as a capacitor, and when Q is positive, inverter main circuit 1 operates as a capacitor.
indicates that the reactor is operating.

Figure 8(c) shows the amplitude “IN” of the inverter output voltage v1N.
shows a motion vector when the following equation is satisfied with respect to the amplitude v8Y of the system voltage v8Y.

In this case, the current flowing through the interconnection impedance 2 becomes a current l having a component in phase with the grid voltage vsY and a component leading by 90°. This indicates that the inverter main circuit 1 operates as a capacitor and obtains active power from the grid 100.

Even when formula (3) is satisfied, as is clear from formula (1) e (2), when the phase difference angle φ is a positive value, the inverter main circuit 1 operates as a capacitor and supplies active power to the system 100. It shows.

The inverter output AC voltage Vo and the DC voltage Ed of the DC power supply 50 have the following relationship.

M in equation (4) is called the modulation degree, and has a value from 0 to 1.0. There is a method called waterfall control as a method for adjusting the modulation degree M. PWM control refers to the GTOGU and GV that make up the inverter main circuit in Figure 7.

The inverter output AC voltage is adjusted by adjusting the energization time width of GW, GX, GY, and CZ.

Substituting equation (4) into equations (1) and (2) gives the following (5)
Equations (6) and (6) are obtained.

It can be seen that power can be exchanged between the system 100 and the system 100.

Conventionally, a rectifier using a thyristor, a battery, or the like has often been used as the DC power supply 5Q. The DC power supply 50 is the same as the converter 1000 shown in FIG.
It is possible to obtain power from a system different from 00 and use it as a DC power source. Since a DC power supply cannot supply reactive power, it can be considered that it supplies active power. When formula (5) is modified, from formulas (5) and (6), the phase difference angle φ and the modulation degree M that adjusts the amplitude vIN of the inverter output voltage are used to calculate the
By adjusting the energization time widths of U, GV, GW, GX, GY, and GZ, a DC power supply of 5° can be obtained. DC power supply 50
When using the converter 1000 as a converter, in order to keep the polarity of the DC voltage Ed constant, the phase difference angle φ should be negative when the active power P is positive, that is, when the active power P is supplied from the grid to the converter. I understand. Conversely, it can be seen that when the active power P is negative, that is, when the active power P is supplied from the converter to the grid, the phase difference angle φ may be made positive. Also, in order to keep the DC voltage Ed constant even if the active power P changes, Md
It can be seen that nφ may be set to a predetermined value.

Incidentally, even when the converter 1000 is used as a DC power source, reactive power Q can be transferred to and from the grid.

The phase difference angle φ can be found from equations (5) and (6). That is, once the active power P and the reactive power Q are determined, the phase difference angle φ is determined, and the modulation degree M that makes the DC voltage Ed a predetermined value can be determined using equation (5). Therefore, when the converter 1000 is used as a DC power supply, reactive power can also be exchanged between the converter 1000 and the system.

From the above explanation, conventionally, the power transfer system shown in FIG. 9 has been used. FIG. 9 is a diagram illustrating the configuration of a conventional example of a grid interconnection device.

In FIG. 9, devices that perform the same functions as in FIG. 6 are numbered the same. 60 is a DC reactor, 7
1 is a current transformer, 72 is a DC voltage detector, 73 is an active power detector, 81 is a date controller inducer, and 82 is a reactive power standard setter.

9 is an error backing device, 94 is a subtracter, 96 is an active power reference setting device, and is an active power control device 910, which constitutes a DC voltage control device 920 (hereinafter referred to as AVR). 101 and 201 are strains, 110 and 2
10 indicates a conversion device.

In the conversion device 110, the active power P is detected by the active power detector 73 from the AC current signal from the current transformer 7 and the AC voltage signal of the system. The active power setter 96 outputs an active power reference Pdp. The subtractor amplifier 91 determines an active power command PAPR to be output to the dart control circuit 81 so as to make f-) the control device active power P equal to the active power reference Pdp in accordance with the error signal. For the error signal amplification t, a circuit that performs proportional-integral calculations is often used, but this is not the only option, and circuits that perform various calculations may also be used.

The reactive power standard setter 82 outputs the reactive power command Qref1 to the f-) control circuit 81. The dirt control circuit 81 is (
By setting P and Q in equations 5) and (6) as active power command PAPR and reactive power command Qref1, respectively, the modulation degree M and phase difference angle φ are determined, and each of the inverter main circuits 10 is determined based on these. A dart signal that determines the energization time width of the GTO element is output to the inverter 10. Due to the above operations, the converter 110 exchanges active power P and reactive power Q with the grid 101.

In the conversion device 210, a DC voltage detector 72 detects a DC voltage Ed. The DC voltage reference setter 97 outputs DC voltage references Ed, tl-. The subtracter 95 subtracts the DC voltage Ed from the DC voltage reference Edp and outputs an error signal to the error signal amplifier 92. The error signal amplifier 92 outputs an active power command PAV to the r-) control circuit 81 according to the error signal.
Output R. The AVR9'0 is determined by the action of the subtractor 95 and the temporary incubator 92 to determine the active power command PAVR to be output to the dart control circuit 81 so as to make the DC voltage Ed equal to the DC 1 voltage reference Ed. There is. Although a circuit that performs proportional-integral calculations is often used as the error signal amplification device 92, circuits that perform various calculations are not limited to this.

The reactive power reference setter 82 outputs a reactive power command Qref 2 to the f-) control circuit 81 . The dart control circuit 81 converts P and Q of equations (5) and (6) into active power command PAVR and reactive power command Q, respectively. By setting it to f2, the modulation degree M and the phase difference angle φ are determined, and a dart signal is output to the inverter 10, which determines the energization time width of each GTO element of the inverter main circuit 10.

As a result of the above operations, the converter 210 exchanges active power with the grid 201 so as to keep the DC voltage Ed constant, and also exchanges reactive power Q with the grid 201.

In the explanation of FIG. 9 so far, the converter 110 and the system 10
1 and the power transfer and conversion device 11210 and system 2
The operation has been explained as power exchange between the 01 and 01. However, the converter 110 and the converter 210 are connected via the DC reactor 60 in each converter, and the converter 2
10 operates as a DC constant voltage source, from the converter 210 to the converter 110 or vice versa.
10 to the conversion bag ffzro. When transmitting active power from the converter 210 to the converter 110, the active power is transferred from the system 201 to the system 101, and from the converter 110 to the converter 21.
When transmitting active power to grid 101, active power is transferred from grid 101 to grid 201.

The above relationship will be explained with reference to FIG. The vertical axis in FIG. 10 is the DC voltage Ed, and the horizontal axis shows the DC current d flowing from the converter 110 to the converter 210 in FIG. 9 as positive. The straight line ■ in Fig. 10 shows the operating characteristics of the conversion bag ff1210, and whether the DC current Id is flowing in the positive direction or the negative direction, the action of the AVR920 in the converter 2 no. The DC voltage Ed is set by the DC voltage standard Ed set by the DC voltage standard setting device 97,
This shows that it is working to make it equal to . In other words, as the DC current I goes from a negative value to a positive value,
From point f to Edp, point b and DC voltage E are moved to Edp. Curves ■ and ■ in FIG. 10 show the operation of the converting device 110. Curves ■ and curve ■ represent the active power P that the converting device 110 exchanges with the converting device 210 due to the action of the APR 910.
is the active power standard P set by the active power standard setter 96.
dp.

Curve 2 shows an operating curve where the active power reference Pd is a positive value, and curve 2 shows an operating curve where the active power reference Pdp is a negative value. The active power P is the DC voltage E, and the DC current l.
Using d, it is expressed as p = Edx Id (9). That is, the curves ■ and ■ are obtained by setting P in equation (9) to Pdp, and the DC voltage E and the DC current! The curve is inversely proportional to .

By the way, when the active power standard Pdp is zero, O in Figure 10
A straight line passes through the two points and Ed.

Now, transfer of active power between converter 110 and converter 210 when active power reference Pdp of converter 110 is positive will be described. In Figure 10, the conversion bag (4
The converter 110 operates to operate on a curve (2), and the converter 210 operates to operate on a straight line (2). Therefore, in the converter 110, the DC voltage E becomes Edp,
In the converter 210, power is exchanged at point b where the active power P becomes Pdp. This is the conversion device 110
This shows that active power is being sent from to the converter 210. Conversely, the active power reference P of the converter 110
When dp is negative, the converter 11θ and the converter 210 are operated at the point f, which is the intersection of the curve ■ and the straight line ■ in Figure 1O, and the converter 110 receives active power from the converter 210. It shows that there is. Also, the active power standard Pd
When p is zero, converter 110 and converter 210 operate at two points, and no active power is exchanged between the converters. However, even in this case, the converter 110 continues to operate to exchange reactive power with the system 101 and the converter 210 with the system 201, respectively.

(Problem to be solved by the invention) The conventional example shown in FIG. 9 has the following drawbacks.

In other words, the converter 12 that performs constant DC voltage control
10 stops operating due to a failure or the like, the conversion device 110 that performs active type constant power control has no choice but to stop operating even though it is capable of operating to exchange reactive power with the system 101. The problem is that you cannot get Of course, even if the converter 110 that performs effective type constant power control stops operating, the converter 210 that performs constant DC voltage control continues to operate at the two points in FIG. 10 where the DC current becomes zero. It is possible to transfer reactive power to and from the grid 201.

The purpose of the present invention is to solve the problems of the above-mentioned conventional examples, and to connect a plurality of converters in parallel through DC terminals or through a DC line, and exchange active power between each converter. Control of grid/DC interconnection equipment that allows stable operation of the remaining converters even if a converter suddenly stops operating, and allows for easy power flow reversal. The purpose is to provide equipment.

[Components of the invention (Means for solving problems) Means for achieving the above object of the invention are as follows.

In a system interconnection device that connects converters in parallel via DC terminals or DC lines and exchanges active power between each converter, a control device that controls the active power exchanged with the AC system of each converter is installed. , a constant effective room power control that controls the active power exchanged with the AC system to be equal to the active power reference value, a constant DC voltage control that controls the DC voltage to be equal to the DC voltage reference value, and a constant effective room power control that controls the A selector that selects the maximum value or minimum value of the output signal and the output signal of the constant DC voltage control, and a selector that subtracts or adds the DC voltage reference difference value between each voltage source type self-commutated converter from the DC voltage reference value. and a DC voltage reference difference switching signal output device that outputs a switching signal to switch between ON and OFF, and the selector of each converter in grid-connected operation is set to select the maximum value. , do not add the DC voltage reference difference from the DC voltage reference of one voltage source type self-commutated power converter, and add the DC voltage reference difference to the DC voltage reference of the other voltage source type self-commutated power converter. If a switching signal is output from the DC voltage reference difference switching signal output device to enable or disable the switching, and the selector of each converter performing grid-connected operation is set to select the minimum value. , the DC voltage reference difference is not subtracted from the DC voltage reference of one voltage source type self-commutated power converter, but the DC voltage reference difference is subtracted from the DC voltage reference of the other voltage source type self-commutated power converter. The switching signal is outputted from the DC voltage reference difference switching signal output device so that the switching signal does not change.

(Function) Explain how the means to solve the above problem works. If the selector of each converter operating in grid-connected operation selects the maximum value, the converter in which the DC voltage reference difference is added to the DC voltage reference will control the DC voltage to be constant using DC voltage constant control. However, in a converter to which other DC voltage reference differences are not added, the active power is controlled to be constant by constant effective room power control.

If the selector of each converter operating in grid-connected operation selects the minimum value, the converter whose DC voltage reference difference is subtracted from the DC voltage reference will keep the DC voltage constant using DC voltage constant control. In converters in which other DC voltage reference differences are not subtracted, the effective power is controlled to be constant by constant effective chamber power control.

How the means for solving the above problem works will be explained using an example.

(Example) Figure 1 is a diagram explaining the configuration of an example according to the present invention, and Figure 2 is a diagram explaining the configuration of an example according to the present invention.
3 and 3 respectively show diagrams for explaining the operation of the embodiment.

In FIG. 1, devices that perform the same functions as in FIG. 9 are given the same reference numerals. 90 indicates an active power control device; 93
indicate selectors, respectively.

A case will be described in which the selector 93 is set to select the minimum value. Conversion device 110 and conversion device 21
0 is the active power constant power control that performs the same function ♦) 10 is the active power P from the active power detector 73 as the active power reference P
dp, and if a DC voltage reference difference is input, the value ΔEdp is subtracted from the DC voltage reference value Edp, and if no DC voltage reference difference is input, the DC voltage is The active power command PAVR is outputted to the selector 93 to be controlled so as to match the voltage reference value itself. The selector 93 outputs a dart signal that determines the energization time width of the inverter 0 from the active power command PAPR and the reactive power command Q□ from the active power heavy setting device 82.

Active power reference Pd of converter 110 and converter 210
, the DC voltage reference difference ΔEd, the reactive power reference Qrsf, and the active power command Prelf are often different.

Therefore, from now on, Pd in the conversion device 110 is changed to Pdp1
*ΔEd to Δ”dpl + Qref to Qrefl
+ Called Pref or Praf I, Pd in the conversion device 210 is Pdp2 + ΔEdp is ΔEdp2 *
Assume that Qraf is set to Qraf2 + Pref to Praf2. Ed, has the same value.

Here, first, the converter 210 has a DC voltage reference difference Δ”dp.
The explanation will be given assuming that 2 is input. In this case, it is assumed that the active power standards pd1 and Pdp2 are set to the same positive value.

The operation of the embodiment will be explained using FIG. 2.

In Figure 2, as in Figure 10, the vertical axis represents the DC voltage Ed9,
On the horizontal axis, the DC current Id flowing from the converter 1tllO to the converter 210 is shown as positive, and the operations of the converter 110 and the converter 210 are shown as a solid line ■ and a dotted line ■, respectively.

First, the solid line ■ indicating the operation of the conversion device 110 will be explained. As the DC current value d changes from a negative value to a positive value, it moves on a straight line from point a to point b via point 21. At this time, the AVR 920 in the converter 110 has a DC voltage E,
The active power command value PAVR is outputted so as to make it equal to the DC voltage reference value Edp. APR in conversion device 110
In 910, the active power reference Pdp1 is a positive value, so the DC voltage Ed and DC current passing through point b, point X, and point C are
The active power command value PAPR is output so that the product of d becomes the active power reference Pdp1. However, the active power command value PA
In PR, since the active power P is less than the active power reference Pdp1 from point a to point 21 and immediately before reaching point b, the output of the subtractor 94 in the conversion device 110 is positive, and the arithmetic amplification Due to the action of the device 91, a value larger than the active power command value PλVR is output. As a result, the selector 93 that selects the minimum value in the conversion device 110 sets the active power command value PAVR as the active power command Prefjf-)
It is output to the control circuit 81. The operation from point b to point C via point The active power command PAVR, which is the output of APR9ZO, is larger than the active power command PAPR, which is the output of APR9ZO. Therefore, the DC voltage E
It is no longer possible to use d as the DC voltage reference Ed.

In other words, the active power command PAPR from APR910 is A
The active power command PAVR is smaller than the active power command PAVR from the VR920, and the selector 93 selects the active power command PAPR as the effective force command Pr6f1 and outputs it to the y-to control circuit 81. There is.

As described above, when the converter 110 increases the DC current Id from a negative value to a positive value, the converter 110 moves between point a and 2 in FIG.
It can be seen that the motion moves from point 1 to point b, and from point b to point C via point X.

Next, the dotted line ■ indicating the operation of the converter 210 will be explained. In FIG. 2, the direct current Id flowing from the converter 110 to the converter 210 is positive. This is converter H110
indicates that the state in which active power P is being sent from the grid 100 to the converter 110 is positive, and indicates the operation in which the converter is sending out AC power as DC power, that is, an operation called forward conversion. There is. Conversely, the operation in which the converter transmits DC power as AC power is called inverse conversion, and when converter R110 is performing inverse conversion, the DC current Id is negative. The conversion device 210 is performing an inverse conversion operation when the conversion device 110 is performing a forward conversion, and is performing a forward conversion operation when the conversion device 110 is performing an inverse conversion operation. That is, in the conversion device 110 and the conversion device 210, forward conversion and inverse conversion operations are performed in reverse.

Therefore, in FIG.
If we consider the positive direction of d to be the direction from the converting device 210 to the converting device 110, then the operation of the converting device 210 is represented on the same drawing (FIG. 2) as indicated by the dotted line ■. Since the DC voltage reference level in the converter 210 is Ed, -ΔEdp 2, if the DC current Id with respect to the converter 210 is increased from negative to positive, it will become 61 due to the action of the AVR 920 in the converter 210. From point to 22 points b
1 point, and if the DC current voltage d is further increased, the DC voltage E increases due to the action of the APR 910 in the converter 210.

The operating point is moved from point b1 toward point C1 on the curve where the product of and direct current Id is equal to the active power reference Pdp2.

Until now, the conversion device 110 and the conversion device M21 have been described using FIG.
Although the operations of the converter 110 and the converter 210 have been explained separately, the converter 110 and the converter 210 are interconnected and exchange active power. When the converting device 110 and the converting device 210 are performing the operations indicated by the solid line (■) and the dotted line (■) shown in FIG. 2, the operation will be performed at point X in FIG. 2. This is conversion device 11
0 tries to increase the DC voltage Ed to Edp, and the converter fl
1210 tries to lower the DC voltage Ed to Ed, -ΔHdp2, both the converter XZO and the converter 210 try to increase the DC current Id from the converter 110 to the converter 210. However, since the active power setting value Prof 1 of the converter 110 is positive, the converter 1
10 lowers the DC voltage Ed to Ed, -ΔHdp2
Move the operating point to the point. Accordingly, the conversion device 210
Also, due to the action of AVR910, operation will be performed at point X.

In this situation, active power is sent from the converter 110 to the converter 210 with the DC voltage Ed set to Ed and -ΔEdp2.

Even if the converter 110 stops operating while the converter 110 and the converter 210 are operating at point X in FIG.
When the DC current Id from the converter 110 becomes zero, the converter 210 can move its operating point to point 22 and continue operating. Further, even if the converting device 210 stops operating, the converting device 110 can continue operating by shifting the operating point to point 21 because the current to the converting device 210 becomes zero.

This shows the effect that even if one of the two interconnected converters stops operating, the remaining converter can operate to exchange reactive power with the grid. Figure 3 shows the converter 21 used to perform power flow reversal in the state shown in Figure 2.
The DC voltage reference difference ΔEdp 2 that was input to 0 is no longer input, and the DC voltage reference difference ΔEdp
It is a figure explaining the operation|movement of an Example when p1 is input. The selector 93 is set to select the minimum value as in the case of FIG.

The solid line in FIG. 3 indicates the operation of the converting device 110, and the dotted line indicates the operation of the converting device 210.

In FIG. 3, when the converter 110 and the converter 210 are both operating, the y point is the operating point, and when the converter 210 is stopped, the converter 110 can operate at point 21 and the converter 110 is stopped. When this occurs, the conversion device 210 indicates that operation can be performed at 22 points. It can be seen that even in this case, even if one of the two interconnected converters stops operating, the remaining converter can operate to exchange reactive power with the grid.

FIG. 4 is a diagram illustrating the operation of the embodiment when the selector 93 of FIG. 1 is set to select the maximum value.

In this case, a DC voltage reference difference Δ”dp2 is added to the DC voltage reference gd of the converter 210 (99 in FIG.
The following description will be made assuming that the DC voltage reference Ed of the conversion device 110 (which becomes an adder in this case) is set larger. Also, for convenience of explanation, the active power standard Pd of the converter 110 is
p1 is also a conversion device f! i2 Z O active power standard Pdp2
is also a negative value.

The solid line in FIG. 4 indicates the operation of the conversion device 110, and the dotted line indicates the operation of the conversion device 210.

In FIG. 4, when the converter @ 110 and the converter 210 are both operating, the operating point is 11 points, and when the converter 210 is stopped, the converter 110 can operate at 21 points, and the converter 110 is operating at 21 points. When the converter 210 stops, the converter 210 indicates that operation can be performed at 22 points.

It can be seen that even in this case, even if one of the two interconnected converters stops operating, the remaining one converter can operate to exchange reactive power with the grid.

Figure 5 shows a converter @
The DC voltage reference difference ΔEdp 2 that had been input to the converter 110 is no longer input, and the DC voltage reference difference Δ
FIG. 6 is a diagram illustrating the operation of the embodiment when Edp 1 is input. In Figure 5, 11 points are the operating points, and even in this case, even if one of the two connected converters stops operating, the remaining nine converters will remain connected to the grid. It is possible to operate to exchange reactive power between the two.

[Effects of invention As explained above, the present invention has the following effects.

In a system interconnection device that connects converters in parallel via DC terminals or DC lines and exchanges active power between each converter, a control device that controls the active power exchanged with the AC system of each converter is installed. , a constant active power control that controls the active power exchanged with the AC system to be equal to the active power reference value, a constant DC voltage control that controls the DC voltage to be equal to the DC voltage reference value, and an output signal of the constant active power control. and a selector for selecting the maximum value or minimum value of the output signal of the DC voltage constant control, and a selector for subtracting or adding the DC voltage reference difference value between each voltage source type self-commutated converter from the DC voltage reference value. If the selector of each converter in grid-connected operation is set to select the maximum value, , the DC voltage reference difference is not added to the DC voltage reference of one voltage source type self-commutated power converter, but the DC voltage reference difference is added to the DC voltage reference of the other voltage source type self-commutated power converter. Output a switching signal from the DC voltage reference difference switching signal output device so as to
If the selector of each converter in grid-connected operation is set to select the minimum value, subtract the DC voltage reference difference from the DC voltage reference of one voltage source self-commutated converter. A system in which a switching signal is output from a DC voltage reference difference switching signal output device so that the DC voltage reference difference is not subtracted from the DC voltage reference of the other voltage source type self-excited power converter. By configuring the control device of the DC interconnection device, even if one converter that is in grid-connected operation stops operating due to a failure etc., the remaining converters can continue operating without stopping. There is an effect.

Furthermore, when performing power flow reversal, it is only necessary to output a DC voltage reference difference switching signal that indicates whether or not to input the DC voltage reference difference, and even if there is a delay in the transmission of the switching signal, the DC voltage references are temporarily equalized. Since the operating point can be ensured by only one switch, and since it does not affect the operation of the converter, the power flow can be easily reversed without depending too much on the transmission of the switching signal.

[Brief explanation of the drawing]

FIG. 1 is a diagram illustrating a configuration example of a DC power transmission power flow reversal system according to an embodiment of the present invention, FIG. 2 is a diagram illustrating the operation of the embodiment of FIG. 1, and FIG. 3 is a diagram showing the state of FIG. 2. Figure 4 is a diagram explaining the operation when the current is reversed in the state shown in Figure 4, Figure 4 is a diagram explaining the operation different from Figure 2 of the embodiment in Figure 1, and Figure 5 is when the flow is reversed in the state shown in Figure 4. Figure 6 is a diagram explaining the voltage source type self-excited converter, and Figure 7 is an example of the configuration of the inverter main circuit that constitutes the voltage source type self-excited converter. Figure 8 is a diagram explaining the operating principle of the inverter main circuit in Figure 7, Figure 9 is a diagram explaining the configuration of a conventional grid interconnection device, and Figure 10 is the conventional example in Figure 9. It is a diagram explaining the operation of the grid interconnection device. 100, 200--AC system, 110, 210-
Voltage source type self-excited converter, 300... DC voltage reference difference output switching signal output device, 10... Inverter, 2°...
・DC capacitor, 30... Grid connection reactor, 4゜・
...Transformer, 60... DC reactor, 71... Converter, 72... DC voltage detector, 73... Active power detector, 81... Y-to control circuit, 82...・Reactive power standard setting device, 90...Active power control device, 910・
... Constant active power control device, 920 ... Constant DC voltage control device, 91.92 ... Error amplifier, 93 ... Selector, 94°95.99 ... Subtractor, 96 ... Effective Power standard setting device, 97...DC voltage standard setting device, 98
...DC voltage reference difference setting device. Applicant's Representative Patent Attorney Takehiko Suzue Ed Figure 10

Claims (2)

[Claims] (1) A voltage source type self-excited power converter that converts AC power to DC power, or conversely converts DC power to AC power, and transfers power between an AC system and a DC line. In a grid interconnection device that transfers power between each voltage source type self-commutated converter by connecting them in parallel through the DC terminals of the self-excited power converters or via a DC line, each voltage source type self-excited converter described above The control device for controlling the active power that the exciter converter transfers to and receives from the AC system is controlled so that the active power that is transferred to and from the AC system is equal to the active power reference value, and the DC voltage is controlled to be equal to the DC voltage reference value. Selecting the minimum value of the output signal of the constant DC voltage control and the constant active power control to be controlled, and the output signal of the constant DC voltage control to determine the predetermined active power that the voltage source type self-excited converter exchanges with the AC system. a selector that determines the DC voltage reference value; and a DC voltage reference difference switching signal output device that outputs a switching signal that switches whether or not to subtract the DC voltage reference difference value between each voltage source type self-commutated converter from the DC voltage reference value. The DC voltage reference difference is not subtracted from the DC voltage reference of one voltage source type self-commutated power converter, and the DC voltage reference difference is not subtracted from the DC voltage reference of the other voltage source type self-commutated power converter. 1. A control device for a system DC interconnection device, characterized in that a switching signal is output from a DC voltage reference difference switching signal output device so as to subtract . (2) A voltage source type self-excited power converter that converts AC power to DC power or conversely converts DC power to AC power and transfers power between an AC system and a DC line. In a grid interconnection device that transfers power between each voltage source type self-excited converter by connecting them in parallel through the DC terminals of the excited power converter or via the DC line, each voltage source type self-excited converter mentioned above Constant active power control that controls the active power that the converter exchanges with the AC system so that the active power that it exchanges with the AC system is equal to the active power reference value, and control that controls the DC voltage so that it is equal to the DC voltage reference value. A predetermined value of the active power that the voltage source type self-commutated converter transmits to and receives from the AC system by selecting the maximum value of the output signal of the constant DC voltage control and the constant effective force control and the output signal of the constant DC voltage control. and a DC voltage reference difference switching signal output device that outputs a switching signal for switching whether or not to add the DC voltage reference difference value between each voltage source type self-commutated converter from the DC voltage reference value. The DC voltage reference difference is not added to the DC voltage reference of one voltage source type self-commutated power converter, and the DC voltage reference difference is added to the DC voltage reference of the other voltage source type self-commutated power converter. 1. A control device for a system DC interconnection device, characterized in that a switching signal is output from a DC voltage reference difference switching signal output device so as to