JPS60241716A - Operation control system of multiterminal transmission system - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Application of the Invention] The present invention relates to an operation control method for a DC multi-terminal power transmission system, and particularly to an operation control method for a DC multi-terminal power transmission system suitable for stable operation in the event of an accident.

[Prior art]

In order to stably operate a parallel DC multi-terminal power transmission system in which three or more converters are connected in parallel to a DC transmission line (the length of the transmission line may be O), one converter station of the multi-terminal power transmission system ( vessel)
It is better to have the DC system voltage determined at 1, and the current determined at the remaining locations. A specific method for this purpose is an operation control method that provides a current margin between the sum of the current settings of the forward converter and the sum of the current settings of the inverse converter, based on the same idea as in the case of two-terminal power transmission. However, the drawback is that a high-speed communication device is required to always satisfy this relationship. As a countermeasure to this problem, an operation control method is being considered in which the converter is provided with a margin in advance and the margin is used up in the event of an abnormality to ensure stable operation at all times. However, even with this operation control method, stable operation cannot be achieved unless the voltage setting value of the DC multi-terminal power transmission system is carefully selected and the voltage of the system is determined.

For example, there are two forward converters (EC
I, RFe5) The inverter is 2) (InVl, Cv
2) Considering a 4-terminal power transmission system configured with a DC reactor DCLf connected in parallel to the line DL, let's assume that the actual current value 11 of each converter is 'i = 'i of ReC1.
10'O(A), fz of Re C2 = 50 (A
), Ig of Invl = 50 (A), Inv2 = 14
100 (A).

The operation during steady operation at this time corresponds to 100 points on the voltage (Vd)-'WL flow (Ia) characteristic of each converter shown in FIG. 2(a).

In the figure, Is Is Is I4 is the current setting value of each converter, and there is a relationship of (11+Iz) (Is+l4)=ΔId. However, ΔId: current margin. Moreover, the current flowing through each converter is i1+1. ==i, -1-i4 1+ :jz :j3:j4=100:50:50:1
There are 00 relationships. Also, the voltage setting value of each converter has El.
There is a relationship of =B4>R2>R3.

In addition, in Figure 1, T is a transformer, AC is an alternating current system, and C
0N0 is a central control device, C0N1 to C0N4 are terminal control devices, and C0N0 and C0NI to C0N4 are connected by communication devices C0M0 to C0M4. When InVl suddenly stops due to a failure in such a state, if the communication system COM is normal, the current setting value is adjusted so that stable operation can be achieved by reducing the current of FL6C1 or ReC2 by stopping Invl. However, when there is an abnormality in the communication system (for example, fading when using microwaves), the current setting value cannot be adjusted, so no current flows through R6C2, and
Since the 11t current and the current setting value of Inv2 are equal, the above-mentioned current margin is lost, and stable operation cannot be performed. This is shown in FIG. 2(b).

[Purpose of the invention]

SUMMARY OF THE INVENTION In order to eliminate the above-mentioned disadvantages, it is an object of the present invention to provide a control system that allows stable operation even in abnormal situations by appropriately selecting voltage determination for a multi-terminal power transmission system.

[Summary of the invention]

It has become clear that the above-mentioned inconvenience occurs because the voltage setting value of each converter in a multi-terminal system is not properly given. Therefore, in the present invention, the forward converter with the largest power transmission power or the power receiving power We decided to determine the voltage of the multi-terminal system using the smallest inverter.

[Embodiments of the invention]

First, the operating state when the voltage of the multi-terminal system is determined at each terminal will be explained.

FIG. 3 shows the Becl voltage setting value E1 as Re1C2O setting value E! Healthy state when set lower (Figure 3 (a)
)) and when InVl suddenly stops ((b) in the same figure), and in both cases, the stable operating point @o1 ml
Or you can get 10#.

Similarly, Fig. 4 shows the operating point "0#" of each converter in a steady state when ReC2 is used to determine the voltage. As shown in Figure 4(B), a stable operating point cannot be obtained and operation cannot be performed.However, as shown in Figure 4(C),
B, if you let l(, ecl determine the voltage without ec2 determining the voltage), even if 1nVl stops, the stable operating point will be changed to 60'', allowing operation.Furthermore, Fig. 5 (ω indicates the operating state when InV2 is made to determine the voltage, but if InV2 makes an emergency stop from this state, stable operation cannot be performed as shown in Fig. 5 (b), and in this case, Fig. 3 A countermeasure is to set the operating state as explained in (a) or Fig. 4 (C).In other words, in the case of an emergency stop of the reverse converter, the voltage setting value of the converter with a large power transmission power of the forward converter is lowered. The important thing to keep in mind is that in the event of an emergency stop of the inverter, the next voltage-determining converter in the multi-terminal system will be selected in order from the one with the lowest voltage setting value, so ensure that the aforementioned current margin is sufficiently large. Also, one of the inverters
Similarly, in order to ensure a current margin in the event of an emergency stop of the inverter, it is a good idea to have one with a small receiving power determine the voltage. For this reason,
The current of the converter is constantly monitored, and the forward converter with the highest power transmission power is given priority over the reverse converter with the lowest power reception power to determine the voltage of the system. In addition, the voltage setting value of the converter should be set lower for converters with large power transmission power than those with small power, and on the other hand, set lower than those with low power reception power so that the voltage setting value of the converter is more likely to be automatically selected by the converter station to determine the voltage in the event of an abnormality. I made it so.

An embodiment of the present invention is shown in FIGS. 6 to 8. FIG. 6 shows processing software for selecting a converter for determining the voltage of a multi-terminal system, which is one of the processing contents of the central control unit C0N0 shown in FIG. First, the system voltage is determined by forward converter 1.
(Determine YES if the EC is to be used, and NO if the inverse converter is to be used. This is given arbitrarily by the operator. Next, the current setting value of the forward converter or inverse converter is determined. Among these, a converter with a large current setting value is selected if it is a forward converter, and a converter with a small current setting value is selected if it is an inverse converter, and then a voltage margin application command is issued to the selected converter via the communication device. This process completes the process of commanding the voltage determining converters of the system.

In addition, the central control device issues commands to each terminal, such as conversion power commands, forward/reverse conversion operation commands, and system start/stop commands, and sends commands to each terminal control device via the communication device. Therefore, the current setting value of each converter station described above is known in the central control unit, and the above-mentioned processing can be performed without any problem. t#1, in the above, the converted power setting value may be used instead of the current setting value to select the converter with the maximum value or the minimum value. In this case, the current setting value is the value obtained by dividing the converted power value by the DC voltage, and since the DC voltage is equal at each terminal if the loss of the transmission line is ignored, the current setting value can be considered as the converted power setting value. .

Figure 7 shows converter voltage ffd) - current (Ia) 4? Il is the current setting value (given by the central controller), E+' is the voltage setting value, which is a preset value, Δknee is the current margin, and ΔE1 is the voltage margin, which are all set in advance. Whether or not to add the current or voltage setting value to the current or voltage setting value is commanded from the central controller, and if the voltage margin ΔT application command is enabled, the voltage setting value of the applied converter station is added to the multi-terminal system converter. This is the lowest voltage setting value among them and determines the voltage of the grid.

FIG. 8 shows a block diagram of a specific control circuit of each terminal control device C0NI. C0M1 is the terminal communication device, SW
I, SW2 are switches that are turned on and off according to commands from the central control device, SUMl, 80M2 are adders that add with the polarity shown in the figure, II is the current setting value, ΔIa is the current margin, li is the current flowing through the converter, E,' are the voltage setting values, eI is the DC line voltage of the converter, and ΔE1 is the voltage margin, and the relationship between each setting value is shown in FIG. Also, I
I is the command value sent from the central controller, ΔL, Δ
E l rEI' is a known quantity set in advance.

M1　AMP2 is an amplifier that amplifies the current deviation and voltage deviation, respectively; LV is a voltage selection circuit that selects a smaller output value from among the outputs of the amplifier AMP1 or AMP2;
GA is a gate amplifier circuit; By combining the control circuit and the converter (consisting of a three-phase thyristor bridge), a converter having the voltage-current characteristics shown in FIG. 7 can be obtained.

The voltage-current characteristic of the converter when no voltage margin or current margin is added is as shown by the solid line in Figure 7.The operating point during steady operation is 01 point when the converter is operating in a forward direction, and the operating point is 01 when the converter is operating in a reverse direction. 02 points when . When the converter determines the voltage, a voltage margin is added to this voltage setting value, and the characteristics are as shown by the dashed line. At this time, when the forward converter is operating, the current setting value is set to II+Δ■-, and when the reverse converter is operating, the current setting value is set to L-Δcm, 4. The operating point is the Os, 02 point, which is the same as in the case where voltage determination is not performed.

From the embodiments shown in FIGS. 6 to 8, it is clear that the voltage determination described above can be performed by the converter with the largest power transmission power or the converter with the smallest power reception power. , as shown in FIGS. 3 and 4, stable operation can be achieved in the event of an abnormality.

In the above-mentioned embodiment, the method of giving the voltage setting value of the voltage determining converter station of the grid is explained, and in the ninth example, the voltage setting value of the converter that specifies the current other than the voltage determining terminal is also changed according to the converted power. Even if the voltage determining converter erroneously makes an emergency stop, the next converter with a larger converted power will be selected as the voltage determining terminal, which is preferable. At this time, it is best to give priority to the forward converter over the inverse converter in order to secure a voltage margin in the event of an abnormality.The processing software that determines the voltage determination order of the central control unit for this purpose is shown in Figure 9. show. First, the converters are ranked in descending order of the converted power among the forward converters, and then the converters are ranked in the descending order of the converted power among the inverse converters. In this case, it is preferable that the voltage setting values for each terminal be given from the central controller. This is because if the voltage setting value is set in advance at each terminal, and the voltage margin value is sent to each terminal via the communication device, if the same analog amount is sent, sending the voltage setting value will cause fewer troubles. This is because each terminal control device can be easily configured. A block diagram of the control circuit for each terminal at this time is shown in Fig. 1O, and as mentioned above, the voltage setting values B and / are sent from the central controller as well as the current setting values I+. In this case, consideration of voltage margins as described in the previous embodiments is unnecessary. The other blocks are as shown in Fig. 8 and 1-j, and the illustrations are omitted.

With this operation control method, the voltage determining terminal is selected according to the converted power, and the voltage setting values of other converters are determined accordingly, so even if the voltage determining terminal stops in an emergency, The next voltage determining terminal is automatically selected, allowing stable operation.

[Brief explanation of the drawing]

Fig. 1 is a multi-terminal power transmission system diagram that is the subject of the present invention, Figs. 2 to 5 are voltage-current characteristic diagrams of the converter in Fig. 1, and Fig. 6 is a voltage-current characteristic diagram of the converter of the present invention. Process 70- for selecting a determined terminal, FIG. 7 is a voltage/voltage R characteristic diagram of a converter, FIG. 8 is a block diagram of a 7W control circuit of each terminal control device, and FIG. 9 is a diagram according to another embodiment of the present invention. There are 10 problems in the control circuit of the voltage determining terminal and each terminal 2pf control device performed by the central control device. ACI~AC4...Current transformation system, Tr...Transformer, F
LeC1~几eC2・lil conversion station (vessel), Inv1~
InV2...Inverter (device), DCL...DC reactor, DL...DC transmission line, C0N0...Central control device, C0NI to C0N4...Each terminal control device, C
0N0~C0M4... Communication device, SUw1~8UW2
...Adder, AMPI~AMP2...Amplifier, Lv
...Bottom pressure selection circuit, AP...Automatic pulse phase shifter, G
A...Gate amplifier, 8W1~SW2...Switch. Agent Patent Attorney Akio Takahashi C0N0 r, otIU Katsu 2 Zu <b) Goe 3 Swords ((1) (b) High School 4 Zu (C) Katsu 50 (b) Me 7 (2)

Claims (1)

[Claims] 1. In a DC multi-terminal power transmission system in which three or more converters are connected in parallel to a DC transmission line, either the forward converter with the largest transmitting power or the inverse converter with the smallest receiving power An operation control method for a DC multi-terminal power transmission system characterized by determining the voltage of the terminal system. 2. In the DC multi-terminal power transmission system according to claim 1, among the plurality of forward converters, the setting value of the DC voltage of one having a large power transmission power is set to be different from that of the other forward converters. This is an operation control method for multi-terminal power transmission systems that is characterized by lowering the power consumption. 3. In the DC multi-terminal power transmission system as set forth in claim 1, the setting value of the DC voltage of the one with the smallest receiving power among the plurality of inverters is set higher than that of the other inverters. An operation control method for multi-terminal power transmission systems that is characterized by lowering the power consumption.