JPS59103520A - Power tide control system for substation parallel system dc multiterminal 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 The present invention relates to a power flow control system for a DC multi-terminal system using a converter station parallel system, and is aimed at increasing the reliability of converter station control.

For example, in a DC multi-terminal system that uses a converter station parallel system, as shown in the system diagram shown in Figure 1, a DC line 1. Forward conversion station DEI1. connected in parallel via L2. DS2 and DC line6.
Inverter stations Is, , Is2 connected in parallel via IJ4
In a DC four-terminal system formed by connecting the two in parallel via a DC line, a method of controlling the power flow through operation as shown in the conventional method is used.

That is, by controlling each converter station, constant current control is performed at each rated current value (111 d21 d! 11 d4, Figure 2 (cL) (1)) (C
) (d) (The voltage drop due to the increase in current in Figure 2 is based on the voltage drop at the converter station, and is not intentionally created.) As shown by the intersection of the broken line shown inside and the DC voltage-current characteristic curve diagram of each converter station, the forward converter station DB1.
The sum of the current setting values of DB2 (engine □, earthwork (12) and the sum of the current settings of the inverse conversion station engineering S1.
), as shown in equation (1), is required to ensure the charging current of the grid, suppress current fluctuations in the event of an accident, etc. The voltage and current setting values of each converter station are controlled so as to always give a so-called current margin Δz, and the required (Id++Iaz
) (Id3+Id4)=ΔId ・・・・・・(
1) Operation is based on power distribution. In this way, due to some reason, the forward conversion station □
By performing responsive control of each converter station accurately and quickly so as to obtain the following conditions, it is possible to shift to a new operating point and continue stable operation under the new power flow.

By the way, in order to ensure a current margin that is extremely small compared to the total current value due to the difference in current setting values as mentioned above, in response to changes in operating conditions, information signals such as voltage and current from each converter station must be Based on this, there is a need for a centralized control that can accurately control each converter station in conjunction. However, generally forward conversion station DS,.

Between DS2, inverse conversion station Is, and Ej2, and further forward,
There is usually a distance between inverse transform stations. For this reason, even if a central control device CC is provided in a specific converter station among each converter station, for example in the forward converter station DS2 shown in FIG. 1, and the converter station controller LC2 can be directly connected, other converters ．． , I
When connecting between the control devices LO, LO, and LO4 of S, S2 and the central control device 00, transmission of information signals,
We have no choice but to rely on the systems SL, , SL, , SL4. Therefore, these conventional systems have the disadvantage that a highly reliable transmission system is required, which is free from any predisposing factors that would impede accurate transmission of control information.

In power flow control, the present invention automatically obtains the required current margin by controlling the set DC voltage at each converter station (() without centrally controlling each converter station in relation to each other using a transmission system. , it is possible to change the power flow to a new operating point.

Next, the details will be explained using the drawings.

The features of the present invention are as follows. For example, the first
Forward conversion station Ds1 of the four-terminal system shown in the figure. Ds2, 5th
The DC voltage and current characteristics shown in the figure (αb), that is, the rated value I,
4. Until the constant current side leg is performed at Id2, the DC voltage decreases as the DC current increases (cL, ) (α
2). In addition, as shown in Figure 5 (cHd) in the inverse converter S+ and ■s2, the DC voltage and current increase as the DC current increases until constant current control is performed at the rated value IC151 and d4. Characteristic (b,)
(b2), the forward conversion station DS4. The overall characteristic (A) of DS2, J:, inverse conversion process, and that of IS2 (B) are made to have DC voltage-current characteristics with an opposite voltage slope.

The voltage difference between the two at the initial stage of current flow allows current to flow for charging the DC line.

In addition, by changing the set value of the DC voltage at one point in the converter station, for example, DS, by operating at the intersection of characteristics A and B, that is, a stable operating point where the current of the forward and reverse converter station is in positive and negative balance. For example, as shown by the dotted line (dotted line) in Figure 5 (α), you can leave the slope as it is and move it up and down, or
Alternatively, by changing the inclination, the stable operating point is moved as shown by PI/ in the figure, thereby controlling the tidal current.

In this way, for example, even if the AC side voltage changes and power flow control based on this is required, the DC side voltage can be used as control information and the voltage setting value of the relevant converter station can be changed to move to a new stable operating point. By doing so, we will be able to operate stably with new trends. Therefore, for example, even if centralized control that depends on the transmission system is required to set the DC voltage and current characteristics of each converter station, voltage control can be controlled independently of the transmission system in response to changes in system conditions such as those mentioned above. The more information you can respond to, the more dependence you have on the transmission system, and the more reliable your control can be.

Next, a control system and a starting method for a forward/reverse converter station for embodying the present invention will be described. Regarding restarting after a stoppage due to a track accident, the explanation will be omitted since the restarting operation can be performed after waiting for the reverse converter station where the accident occurred to become a bypass bear.

The off-line diagram is a block system diagram showing the control system of a forward conversion station, and is a conventional control system that includes a slope coefficient setting circuit (1) and a slope control circuit (2) that determine the distribution amount of power flow. be. Then, the output of the comparison circuit (3) between the standard voltage value EE3 and the detected DC voltage value CH, and the slope coefficient setting circuit (
The comparison circuit (5) compares the output of the standard current specified phase ' obtained through the comparison circuit (4) with the standard current specified phase ' obtained through the comparison circuit (4) through the DC current detection value ieL
), and in addition to the slope control circuit (2),
The phase control angle φd of the converter is controlled to have the voltage-current characteristics shown in FIG. Note that (6) is a comparison circuit between the output for setting the maximum DC current limit value ■ and the DC voltage detection value □, (7) is the maximum DC current limit circuit, and (8) is the current limit value setting at voltage drop. Circuit (9) is a maximum current value selection circuit;
(10) is a limiter, which increases the maximum DC current limit value by controlling the maximum DC current limit setting output unit, and increases the maximum DC current limit value at the rated current value as shown in FIG.
) Constant current control is performed like CI in ). In addition, the output of the current limiting circuit (8) during low voltage installation causes the
b) As shown in step (2), the current is limited when the voltage is lower than necessary.

FIG. 8 is a block system diagram showing the control system of the inverse converter, and the conventional control system includes a slope coefficient setting circuit (1),
A slope control circuit (2) is provided to control the phase control angle θ of the inverse converter, and the difference from the forward converter is that a constant margin angle control circuit (1) and a minimum value selection circuit (2) are provided. The only difference is in the features provided.Next, the activation of the system of the present invention will be explained.

The inverse converter station S + + unit S2 is put into a bypass pair state, and the forward converter stations DS, DS2 are put into a deblock state, and a voltage is applied to the DC line. And Figure 9 (α
) (As shown in the characteristic diagram shown in clause (C) (d), forward conversion station D
s1. Gradually increase the current maximum control value of Ds2. Then, when it is confirmed that the DC current -5 has flowed through the inverter Is,..., TS2, the inverter s4... ■Tee lock s2. Then, each DC line L, L4. L
2. 'L3. L4 etc. are the forward conversion station Ds1. Ds2 and inverse conversion work s1. ■Due to the current difference with s2, it is charged and operated at point y shown in the comprehensive characteristic diagram in Figure 1o.After that, by increasing the maximum current limit value to 1In21"m5, the operating point moves from p to p. Then, a stable operating point P is reached, and a steady operating state is established under the load distribution amount corresponding to the voltage gradient of each converter station.

As is clear from the above description, the present invention is applicable to forward and inverse converters, in which the DC voltage decreases as the DC current increases in the forward converter station, and the DC voltage increases as the DC current increases in the inverse converter. The DC voltage current characteristic has a reverse DC voltage slope, and the line is charged by the current difference between the forward and reverse converters at the start of operation, and then the line is charged at the point where the DC currents of the forward and reverse converters are balanced. I try to do that. Therefore, power flow control corresponding to fluctuations in AC voltage can be performed using voltage as control information.

Therefore, compared to the case where each converter station is centrally controlled to obtain current merging as in the conventional system, there is less dependence on the control information transmission system, and control can be made that much more reliable.

[Brief explanation of the drawing]

Figure 1 is a system diagram of a DC multi-end system that uses a converter station parallel system, Figures 2, 3, and 4 are control characteristic diagrams of a converter station using the conventional system, and Figures 5 and 6 are based on the present invention. The control characteristic diagram of each converter station, its general characteristic diagram, OFF diagram, and FIG. )(d) and FIG. 1o are control characteristic diagrams and comprehensive characteristic diagrams of each converter station at the time of startup of the system of the present invention. DS,,DS2...Forward conversion station, Engineering S,, Engineering s2...
- Inverse converter, L, L4. L2. L3. L4--DC line, cc... Centralized control device, LO4, LO
2, LC3, LO4, ... Conversion station control device, SL,
, SL2. SL3. ．． 5L4--Information transmission system, (1
) -...Slope coefficient setting circuit, (2)...Slope control circuit, (3) (4) (5) (6)... Comparison circuit, (7
)...DC current maximum value limiting circuit, (8)...Current limit value setting circuit at voltage drop, (9)...Maximum value selection circuit, (1o)...Limiter, (11)...・Constant margin angle control circuit, (12)...minimum value selection circuit, Es
...Standard voltage value, Ed...DC voltage detection value, ■o
...Standard current specified value, ...DC current detection value. Patent applicant Otsuka, patent attorney representing the Central Research Institute of Electric Power Industry (1 person from outside the university)

Claims (1)

[Claims] (i) The forward conversion station is operated with a DC voltage-current characteristic in which the DC voltage decreases as the DC current increases, and the reverse conversion station is operated with a DC voltage-current characteristic in which the DC voltage increases as the DC current increases. , a converter station parallel type DC multi-terminal power flow control system, characterized in that power flow control is performed by moving the DC current equilibrium point of a forward/reverse converter station according to changes in the DC voltage of the converter station.