JPH04217820A - Power flow control method, controller and control system - Google Patents

Abstract

PURPOSE:To provide a power flow control method and controller which can control both effective and reactive powers of power flow regardless of the relationship of voltages between different power systems. CONSTITUTION:Corresponding phases of different power systems are connected through primary windings of transformers while voltages are applied on the secondary windings thereof and then the magnitude and phase of control voltage are controlled with respect to the system voltage thus controlling power flow between the power systems. A voltage is induced in the primary winding according to the phase and the magnitude of the control voltage to be applied on the secondary winding of series transformer and thus induced voltage is employed in the control of current and power flowing between different power systems which pass through the series transformer. According to the invention, effective and reactive powers can be controlled independently by regulating the phase and the magnitude of the control voltage.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a power flow control method, a power flow control device, and a method of using the device, and particularly to a method suitable for controlling active power and reactive power passing through a power transmission line.

0002

2. Description of the Related Art As a method for controlling reactive power in a power transmission line, a method described in Japanese Patent Application Laid-Open No. 52-91141 is known. According to this, two power systems are connected by a series transformer, a phase modifier is connected to the secondary side of this transformer, the phase modifier is inserted in series between the two power systems, and this phase modifier is controlled. In this way, reactive power is transferred and received.

On the other hand, as a method capable of controlling the active power of a power transmission line, a method described in a literature (Hitachi Hyoron, October 1970 issue, P12-P17) is known. This method originally aims to suppress fault current, and according to this method, two power systems are connected by a series transformer that also serves as a current limiting reactor, and the voltage drop (phase change) caused by this transformer is reduced. To compensate, apply two other phase-to-phase voltages (voltages with an approximately 90° phase difference) to each phase of the secondary winding of that transformer to control the active power passing through the primary winding. That's what I do.

0004

[Problems to be Solved by the Invention] However, in the technique described in the above-mentioned conventional publication, the phase difference between the two systems is 30° to
It is limited to cases where the voltage phase of both systems is between 0° and 360°, although it is fine if the target is a loop power system.
When the voltage changes, that is, when the voltage at both ends is slipping, there is a problem that a predetermined control voltage cannot be obtained and power flow control cannot be performed.

[0005] In addition to the above-mentioned problem, the technique described in the latter document does not take into consideration the fact that the compensation voltage (power flow control voltage) is controlled in a vectorial manner (magnitude and phase angle). There is a problem that reactive power and reactive power cannot be controlled independently.

An object of the present invention is to solve the above-mentioned conventional problem. In other words, no matter what the relationship between the voltages of different power systems is, the active power and reactive power of the power flow of the line can be balanced. An object of the present invention is to provide a controllable power flow control method and a power flow control device.

[0007]

[Means for Solving the Problems] In order to achieve the above object, the present invention connects corresponding phases of different power systems through the primary winding of a transformer, and connects the secondary winding of the transformer. By applying a control voltage to the power grid and controlling the magnitude and phase of the control voltage with respect to the grid voltage, the power flow between the power grids is controlled.

The apparatus of the present invention for realizing the above method also includes a series transformer and a control voltage generator connected to a secondary winding of the series transformer and applying a control voltage to the secondary winding. Both ends of the primary winding of the series transformer are connected to different power systems for use.

[0009]

[Operations] With the above structure, according to the present invention, the above object is achieved by the following operations.

That is, depending on the phase and magnitude of the control voltage applied to the secondary winding of the series transformer, a voltage is induced in the primary winding, and this induced voltage causes a different voltage to pass through the series transformer. Can control current and power between power systems. By adjusting the phase and magnitude of the control voltage, it is possible to independently control the active power and reactive power that pass through. Furthermore, by adjusting the phase of the control voltage, control can be achieved even if the power system has a phase difference of 360°.

[0011] In order to generate a control voltage of arbitrary phase and magnitude, in the case of a three-phase system, three-phase control using the voltage at an arbitrary point of the primary windings of three series transformers as the power source is necessary. providing a tap in the secondary winding of the transformer, and connecting these secondary windings in series to the corresponding secondary winding of the series transformer,
The phase and magnitude of the control voltage can be adjusted by switching the taps of the control transformer.

[0012] Furthermore, each of the series transformers is provided with three secondary windings, and the secondary winding of the three-phase control transformer is powered by the voltage at any point of the primary windings of the three series transformers. Taps are provided in the windings and connected to the corresponding secondary windings of the series transformer so that the voltages of these secondary windings are added, and the taps of the control transformer are switched to adjust the phase of the control voltage and You can adjust the size.

[0013] Furthermore, an inverter is connected to the secondary winding of the series transformer via a three-phase transformer, and the inverter is controlled to adjust the phase of the excitation voltage applied to the secondary winding of the series transformer. You can adjust the size.

[0014]

[Embodiments] Hereinafter, embodiments of the present invention will be explained with reference to the drawings.

FIG. 1 shows a configuration diagram of a power flow control device according to an embodiment of the present invention. The device of this embodiment includes a series transformer 1 (1-1 to 1-3) for the a-phase to c-phase, and a control voltage generator 2 (2-1 to 2-3) for the a-phase to c-phase. It is composed of: The primary windings of each series transformer 1 are connected at both ends to corresponding phases of different power systems A and B, respectively. The control voltage generator 2 is formed phase-symmetrically, and for simplicity, only the a-phase control voltage generator 2-1 is shown in detail in the figure. The control voltage generator 2-1 includes a control transformer 3 whose primary winding is Y-connected.
(3-1 to 3-3). This control transformer 3
The neutral point of the primary winding of is grounded, and the other ends are connected to each phase of the power system A, respectively. Note that this connection point may be the power system B, or may be the midpoint of the primary winding of the series transformer 1 or any other point. On the other hand, control transformers 3-1 to 3
-3 each secondary winding is provided with a tap;
The secondary winding is connected to add the secondary voltages of each control transformer 3-1 to 3-3 in series, and this added voltage is used as the control voltage to connect the secondary winding of the A-phase series transformer 1-1. connected to excite.

The operation of the embodiment of FIG. 1 constructed as described above will be explained with reference to FIGS. 2 to 5. FIG. 2 is an equivalent circuit of a power system to which the embodiment of FIG. 1 is applied, and is represented by a positive-phase circuit in a three-phase balanced state. In Figure 2, VA and VB are the complex voltages of power systems A and B, respectively, x is the leakage reactance of series transformer 1, and VC is the primary-side converted value of the control voltage applied to the secondary side of series transformer 1. It is. Now, if we consider the case where VC = 0, the current passing through the device is as shown in FIG. 3, and is expressed by Equation 1.

[0017]

[Math 1]

[0018] At this time, the values of the passing active power P and reactive power Q at the end of the A system are expressed by Equation 2.

[0019]

[Math 2]

Here, (c) appended to I(c) indicates the conjugate complex number of I.

[0021] Also, at the B system end, it is expressed by Equation 3.

[0022]

[Math 3]

That is, in this case, the current and power are uniquely determined by the operating states VA and VB of the A and B systems and the circuit reactance x.

On the other hand, the operation when the control voltage VC is applied is as shown in FIG. 4, and the current is expressed by equation 4.

[0025]

[Math 4]

In this way, by applying VC, the passing current I can be freely controlled vectorwise, so that the active power P and reactive power Q of the passing power can be controlled independently.

In the case of the vector in FIG. 4, the passing current I and VA
are in phase, the power factor of the power flowing in from system A is 1.0, and the reactive power is zero. In this way, reactive power can also be freely controlled.

Incidentally, in the conventional method, since the phase of this control voltage cannot be controlled, the reactive power cannot be freely controlled. In addition, control could not be performed when the difference in phase angle between VA and VB changes over time and changes up to 360°, but according to the method shown in Figure 1, the control voltages are vector-synthesized, so Voltage can be generated in any vector, making the control described above possible.

Next, a method of generating the control voltage VC will be explained. The specified tidal current that should be controlled by the tidal current control device now is
It is specified by the power flowing in from the A system, and this value is defined as PA +jQA. The leakage reactance of the series transformer 1 is x, and the voltages across the series transformer 1 are VA and VB.
Then, the control voltage VC can be found from the following equation 5 using equations 2 and 4 as shown in equation 6.

[0030]

[Math 5]

[0031]

[Math 6]

VC given by this equation 6 is the control voltage to be induced in the primary winding of the series transformer 1, and the turns ratio (primary:secondary) of the series transformer 1 is 1:n. Then, the voltage to be applied to the secondary winding becomes nVC. Therefore, the control voltage for the a phase is set to nVCa, and the secondary voltage (100% tap voltage) of the parallel transformer 3 is set to Va, Vb, V for each phase.
c, these relationships are as shown in FIG. In the figure, θ is the phase difference between VC and VA as shown in Equation 6. Here, a method for synthesizing nVCa from Va, Vb, and Vc will be explained. The first method is to synthesize vector nVCa from two voltage vectors Va and Vb that sandwich it. As shown in FIG. 5, when nVCa is decomposed into Va and Vc vector components, Vaa and Vac are obtained, respectively. Then, as the tap value of the a-phase control transformer 3-1, |Vaa|/|Va|,
The tap value of the a-phase control transformer 3-2 is set to zero, and the tap value of the a-phase control transformer 3-3 is set to |Vac|/|Vc|. If the taps are selected in this manner, the output of the a-phase control voltage generator 2-1 becomes nVCa in FIG. 5, and a predetermined control voltage is obtained. Since the tap of the control transformer in the b-phase control voltage generator 2-2 is three-phase balanced, using the results for the a-phase, the tap ratio of the control transformer 3-1 is |Vac| /
|Vc|, and the tap ratio of the control transformer 3-2 is |Va
a|/|Va|, the tap of the control transformer 3-3 may be set to zero. Similarly, for the taps of the control transformer in the C-phase control voltage generator 2-3, the tap ratio of the control transformer 3-1 is zero, and the tap ratio of the control transformer 3-2 is set to |Vac|
/｜Vc｜, tap of control transformer 3-3｜Vac
|/|Va| may be used.

Next, in the second method, nVCa is converted to Va, V
This is a method in which the control transformers 3-1 to 3-3 of each phase are separated into three-phase components of b and Vc and taps are determined, and the taps may be determined in accordance with the above-mentioned method.

As described above, according to the embodiment of FIG. 1, nVCa is vectorially synthesized and determined by any synthesis method, so that nVCa of arbitrary phase and magnitude can be generated. Therefore, the voltage of A and B systems, VA
, VB have any phase relationship, the flow of passing power can be controlled to an arbitrary set value.

FIG. 6 shows a configuration diagram of a power flow control device according to another embodiment of the present invention. In this embodiment, as shown in the figure, the secondary windings of the series transformers 1-1 to 1-3 are configured with multiple windings, and each secondary winding is connected to a control transformer 3-1. ~
3 through a tap. That is, the above-mentioned control voltages are combined on the secondary winding side of the series transformers 1-1 to 1-3. Thereby, the control voltage is synthesized by the magnetic flux of the iron cores of the series transformers 1-1 to 1-3, and the same effect as the system shown in FIG. 1 can be expected.

FIG. 7 shows a configuration diagram of a power flow control device according to still another embodiment of the present invention. In this embodiment, the control voltage VC
In this method, the power flow is controlled not by synthesizing the power from the grid voltage, but by synthesizing it using a self-excited inverter. As shown in the figure, a power flow control device includes series transformers 1-1 to 1-3 and a self-commutated inverter. That is, series transformers 1-1 to 1-3 for a phase, b phase, and c phase,
It has a self-excited inverter 10 and a control transformer 11, and the power source of the self-excited inverter 10 uses energy charged in a capacitor 14 from the system voltage via a self-excited converter 13.

With this configuration, the output voltage of the control transformer 11 is VC, the leakage reactance of the series transformer 1 is x, the normal voltage of power system A is VA, and the voltage of power system B is VB. , if the passing current is I, then I can be expressed by the above-mentioned equation 4, and the operating characteristics of this embodiment are expressed by the above-mentioned equation 5. Also, the passing power PA+jQ
The necessary control voltage VC when A is given is given by Equation 6. In this embodiment, the control voltage VC is generated by a self-excited inverter 10. Therefore, according to the self-commutated inverter 10, the magnitude and phase of VC can be controlled to arbitrary values. can be controlled. Further, since the inverter 10 outputs or absorbs active power depending on the phase of the control voltage VC, the voltage of the power supply capacitor 14 fluctuates, but the converter 13 may be controlled to suppress this voltage fluctuation.

Further, in this embodiment, when a short circuit accident or the like occurs in the power transmission system, a large current is also induced in the secondary winding of the series transformer 1. A large current flows through the inverter 10 via the control transformer. At this time, when the inverter 10 is stopped, the inverter 1 of the control transformer 11
Since the circuit configuration is such that the 0 side is open, and the series transformer 1 changes from a leakage reactance value to an excitation reactance value, it can also be expected to be effective as a fault current limiting device.

Furthermore, in order to protect the semiconductor elements of the inverter 10 from system failures, the primary or secondary of the control transformer 11 is
It is also possible to open or short-circuit the next side. When opened, a current limiting effect can be expected as described above.

FIG. 8 shows the overall configuration of an embodiment of a power flow control system to which the power flow control device according to the present invention is applied, using a single wire connection. As shown in the figure, power systems A and B are connected by a series transformer 1. A control voltage generator 2 is connected to the secondary winding of the series transformer 1, and a control voltage having a variable controlled phase difference and magnitude is applied to the secondary winding. The phase difference and magnitude of this control voltage are determined by the control voltage calculation device 20 according to the command values of the active power PA and the reactive power QA sent from the power supply command center 30. This calculation uses the voltages VA and VB of both systems input from the voltage detectors 21 and 22, and calculates the control voltage VC based on Equation 6 described above.

Note that the control voltage calculation device 20 inputs the system frequency change amount Δf and performs the following correction calculation on the power command value P1 from the power dispatch center 30 to obtain the following correction calculation:
It is also possible to obtain the effect of frequency stabilization.

[0042]

[Math. 7]

Therefore, when the frequencies of the two systems are different, by using a voltage amplitude-modulated by the frequency difference as the control voltage, it is possible to link different frequencies, and there is also the effect that the passing power can be controlled.

Next, in the embodiment of FIG. 7 which uses a self-excited inverter, another embodiment of the present invention is shown in which the power source for the self-excited inverter is obtained from a power system different from the power system to which it is controlled. This will be explained using FIGS. 9, 10, and 11. According to these methods, no matter what state the power system whose power flow is being controlled is in, the control device draws in power from other systems that are not affected by this power system, so it can operate normally. There is an effect that can be done. In addition, if the power source is drawn from a system with a lower voltage class, it has the effect of keeping costs down economically.

The embodiment shown in FIG. 9 is the method shown in FIG. 7 in which the power flow is controlled by combining control voltages using a self-excited inverter, and the series transformers 1-1 to 1-1 for the a-phase, b-phase, and c-phase 1
-3, self-excited inverter 2, and control transformer 3. The characteristic feature here is that the power source for the self-excited inverter 2 is drawn from a large-scale power source 6, such as a power plant, and the energy charged in the capacitor 5 is used via the self-excited converter 4. . Because of this configuration, no matter what state the power system A and power system B are in, the self-excited inverter 2 is powered by the large-scale power supply 6, so the power system A or the power system B is The control device can operate without being affected by B.

In the embodiment of FIG. 10, the power source for the self-excited inverter 2 is supplied from the power system B to be controlled, and from the generator motor set 7.
It is drawn into the self-excited converter 4 via. With this configuration, it can be separated from the power system to be controlled by the generator motor set 7, and the self-excited inverter 2
The power supply can operate without being influenced by the power grid.

In the embodiment shown in FIG. 11, power for the self-excited inverter 2 is drawn into the self-excited converter 4 from the power system to be controlled via the DC power transmission 8.

In the embodiments described so far, when the active power or reactive power of one of two different power systems is controlled, the power flow of the other is uniquely determined, and it is difficult to independently control the power flow to the desired power flow. However, an embodiment of the present invention in which the power flow between two different power systems can be independently controlled on both sides will be described below with reference to the drawings.

FIG. 12 shows an overall configuration diagram of a power flow control system according to an embodiment of the present invention, and FIG. 13 shows a conceptual functional configuration. In this embodiment, in addition to the basic configuration of FIG. Since it is different in that it includes a reactive power compensator 6, the combination control with the static type reactive power compensator 6 will be mainly explained. This static type reactive power compensator 6 is connected to the power system B via a reactive power compensator transformer 7.

In this power flow control system, if the designated power flow to be controlled by the series transformer 1 is designated by the power flowing in from the power system A to which the static var compensator 6 is not connected, then The state is as shown in Equations 5 and 6 above, and by applying the control voltage VC shown in Equation 6 to the secondary winding of the series transformer 1, the active power and reactive power flowing from the power system A are controlled. can.

Next, it is assumed that the power flow to be controlled in power system B is specified by the reactive power flowing out to power system B, and this value is set as QB2. The reactive power flowing out from the series transformer 1 toward the power system B is QB1, and the reactive power supplied from the static var power compensator 6 is QS, and this pattern is shown in Fig. 14.
Shown below. At this time, reactive power QB2 flowing out to power system B
is QB2=QB1+QS.

Here, QS can be controlled by a thyristor control device by changing the value of current flowing through the static var compensator. Thereby, the reactive power QB2 flowing out to the power system B can be independently controlled regardless of the power flow state of the power system A.

In the embodiment shown in FIG. 12, the static reactive power compensator 6 is used in combination with the series transformer 1, but other embodiments include a shunt reactor whose capacity can be controlled or a power supply whose capacity can be controlled. It is also conceivable to use a capacitor in combination with the series transformer 1. A controllable shunt reactor is a thyristor-controlled reactor (TCR).
).

Furthermore, FIG. 15 shows an example in which the series transformer 1 and the synchronous phase modifier 9 are used in combination. The synchronous phase modifier 9 is
The supply of reactive power can be controlled by adjusting the field current, and when operated with the field over-excited, it acts as a kind of capacitor, and when operated with under-excitation, it acts as a kind of reactance. This allows fine-grained control.

In the embodiment of FIG. 8, the series transformer 1
We have explained how to automatically control power flow between power systems using signals from a power dispatch center. According to this method, it is possible to control the power flow so that it conforms to a predetermined command signal, but it is not suitable for the function of immediately suppressing fluctuations in the power system itself. Figure 1
8 shows an embodiment of the present invention that improves this point. In this device, the control voltage calculation device 20 calculates the voltages VA and VB across the series transformer 1 and command signals P1 and Q1 from the power dispatch center.
In addition, the control voltage command value is obtained by using the passing power P of the series transformer 1 as an input signal.

A control method for suppressing power fluctuation using the control voltage VC in the embodiment of FIG. 16 constructed as described above will be explained. Note that the following explanation also assumes that the above equations 1 to 7 hold true.

Power fluctuations appear as fluctuations in the active power flowing through the line. The relationship between the amount of change in the passing power and VC, that is, the power control characteristics of VC, is expressed by substituting the equation 4 into the equation 3 to obtain the equation 8, and if it is expanded as VC=V1C+jV2C, the equations 9 and 10 are obtained.

[0058]

[Math. 8]

[0059]

[Math. 9]

[0060]

[Math. 10]

Therefore, under the operating conditions shown in FIG. 16, the change ΔP in active power when VC is controlled to ΔVC = ΔV1C+jΔV2 is expressed by equation 11.

[0062]

[Math. 11]

Next, a ΔVC signal is calculated from the power passing through the series transformer 1 via a stabilizing signal converting circuit shown in FIG. The characteristics of the circuit shown in FIG. 17 are as follows.
1 to detect only the fluctuation inferiority ΔP, and furthermore, the gain and the phase of the fluctuation are changed by the first-order delay/lead circuit 32. Therefore, the characteristics of the circuit shown in FIG. 17 differ depending on the changing frequency, but if this is expressed as G(s), the passing power P
The relationship between ΔPs and the control amount ΔPs of the passing power by the phase adjuster is expressed by Equation 12.

[0064]

[Math. 12]

Next, when the dynamic characteristics of the power system are expressed using the above relational expression, the block diagram shown in FIG. 18 is obtained. Figure 1
8 represents the dynamic characteristics of a power system equivalently converted into one large synchronous generator, where M is the inertia constant of the equivalently converted generator, D is the braking coefficient, and K is the synchronization torque coefficient. It is. Also, △δ is the amount of change in phase angle of the rotor, △P
e and △Pd are the synchronization torque components during power fluctuation, respectively;
This is the braking torque component. ΔPa is the disturbance torque. F represents the control characteristic of the power passing through the series transformer based on the applied characteristic of the control voltage of the series transformer in FIG. 16, and is defined by Equation 11.

The above stabilization control ensures that the output torque △Ts has a damping characteristic, that is, △P
This can be achieved by appropriately setting the stabilizing circuit characteristic G(s) so that it becomes an in-phase component with d. This circuit constant needs to be determined appropriately depending on the period of power fluctuation, etc. As an example, the power fluctuation period is 1 second, T1=1 second, T2=0.
05 seconds, T3=1 second, △Pe to △Ps
The phase characteristic up to this point is approximately 55° phase lead. Therefore, △
The component of △Ps ×Sin55° of Ps is △Pd
It can be seen that the damping torque component is generated.

The above example describes one method of phase compensation, but the point is that 90° from △Pe to △Ps
The effect will be greatest if phase lead compensation can be obtained. In other examples, G=-1, T2=1.0, T3=0, etc. may be used.

Further, although the phase compensation circuit 32 shown in FIG. 17 has one stage, the same effect can be achieved even if it is a multi-stage compensation circuit so that appropriate phase compensation can be performed for various frequencies. Needless to say. This has made it possible to stabilize fluctuations between power systems, which was previously impossible.

Finally, control when a plurality of power systems are connected by a plurality of interconnection lines will be explained. Figure 19
shows an example in which power system A and power system B are interconnected by two interconnection lines, in which l1 and l2 are interconnection lines, Tr1 and Tr2 are series transformers, P1 and P2 are the active power of each interconnection line, Q1 and Q2
is interconnection line reactive power, S0, S1 to S4 are signal lines, Pc
, Qc indicate active power and reactive power. Interconnection line l1,l
2 active powers P1, P2 and reactive powers Q1, Q2 are taken in via transformers CT1, CT2 and signal lines S1, S2, and the active powers Pc and reactive powers Pc and Compare with Qc using equation 1
3. Perform according to number 14.

[0070]

[Math. 13]

[0071]

[Math. 14]

Here, ΔP and ΔQ are predetermined allowable control errors. If the conditions are met,
You can operate it in this state, and if you are not satisfied,
The control amount may be calculated by the following method, and the secondary voltage of the series transformer may be controlled via the signal lines S3 and S4 to satisfy the above conditions.

[0073] In other words, in Equation 6 above, this is the case where the system is interconnected by only one interconnection line, and it is interconnected by interconnection lines at n locations where series transformers with the same characteristics are installed. If so, consider the power command value in Equation 6 as 1/n. Alternatively, if the leakage reactances of the series transformers are different, each value may be used for X in Equation 6.

Next, when the active power Pc of the interconnection line, the reactive power Qc on the A system side, and the reactive power Qd on the B system side are specified, two series transformers are connected in series as shown in FIG. These control voltages VC1 and VC2 may be calculated and applied to the series transformer. In FIG. 20,
CT3 and CT4 are transformers, Tr1 to Tr4 are series transformers, S11 to S14 are signal lines, Q3 and Q4 are the reactive power of interconnection lines 1 and 2 on the grid B side, and Qd is the reactive power command value on the grid B side. The other functions are the same as those in FIG. 19. In the same figure, in the determination device C, the transformer CT
Based on the information and command values taken in from 1 to CT4,
In addition to the above numbers 13 and 14, number 15

[0075]

[Math. 15]

The determination device C determines whether the following conditions are satisfied. Here, ΔP and ΔQ are as described above. If the conditions are satisfied, it is sufficient to operate in this state; if the conditions are not satisfied, satisfy the control devices VC1 and VC2 using the following formula, and connect the signal lines S3, S4, S.
13, controlling the secondary voltage of the series transformer via S14;
The above conditions may be satisfied. in particular,
All you have to do is execute Equations 16 and 17.

[0077]

[Math. 16]

[0078]

[Math. 17]

Here, X1 and X2 are the leakage reactances of the two series transformers.

[0080] By doing this, each system can be operated under its own conditions without being aware of other systems, increasing the degree of freedom in operation, expanding the stability limit, and improving supply reliability. do.

[0081] The explanation so far has been based on an example in which power is applied equally to all interconnection lines, but when weighting each interconnection line, Pc, Qc,
The control voltage may be calculated by adding a weighting coefficient to Qd. Next, in the event of an interconnection line fault, it will be impossible to control the power, so
Based on the accident information, the faulty line may be disconnected, and control voltages may be calculated and controlled for the remaining interconnection lines excluding the faulty line. By doing this, the system can be operated without being affected by any accidents. For failures in the primary and secondary circuits of series transformers, the power flow in the interconnection line to which the failed device is connected becomes uncontrollable in any case of failure. The side and secondary side may be separated and the remaining interconnection lines excluding this interconnection line may be controlled.

As explained above, according to the present invention, by installing series transformers capable of vector-wise high-speed and continuous control of secondary voltages on multiple interconnection lines, the power of one interconnection line can be reduced. In response to a failure, the stability limit can be expanded without any problems, and the effect on stability is extremely large. Furthermore, since the secondary voltage of the series transformer can be controlled rapidly and continuously, disturbances in the system can be responded to immediately, which has an extremely large effect on stability. From the above points, the reliability of power supply will be significantly improved. Furthermore, since multiple interconnected systems are collectively controlled, the effectiveness will not be reduced due to a failure in one location.

[0083]

[Effects of the Invention] According to the present invention, there is provided a power flow control method and a power flow control device that can control the active power and reactive power of the power flow of a line regardless of the voltage relationship of different power systems. can do.

[Brief explanation of the drawing]

FIG. 1 is a basic configuration diagram of a power flow control device of the present invention.

FIG. 2 is a positive-phase equivalent circuit representing the circuit in FIG.

FIG. 3 is a voltage and current vector diagram for explaining the operation of the circuit in FIG.

FIG. 4 is a voltage and current vector diagram for explaining the operation of the circuit in FIG.

FIG. 5 is a diagram showing the relationship between control voltage and each phase voltage.

FIG. 6 is a diagram showing another embodiment of the power flow control device of the present invention.

FIG. 7 is a diagram showing another embodiment of the power flow control device of the present invention.

FIG. 8 is a configuration diagram of a power flow control system to which the power flow control device of the present invention is applied.

FIG. 9 is an embodiment diagram of the power flow control device of FIG. 7 which obtains power from another power system.

FIG. 10 is a diagram showing another embodiment of the power flow control device of FIG. 7 that obtains power from another power system.

FIG. 11 is a diagram showing another embodiment of the power flow control device of FIG. 7 that obtains power from another power system.

FIG. 12 is a configuration diagram of a power flow control system combined with a static reactive power control device.

FIG. 13 is a conceptual functional configuration diagram of the system in FIG. 12.

FIG. 14 is an explanatory diagram of the operation of the system in FIG. 12;

FIG. 15 is a diagram in which the system of FIG. 12 is combined with a synchronous phase modifier.

FIG. 16 is a system configuration diagram in which a power flow control device is combined with a power system stabilization device.

FIG. 17 is a diagram explaining the concept of phase adjustment control of the system in FIG. 16;

FIG. 18 is a block diagram for explaining the dynamic characteristics of the power system employing the system shown in FIG.

FIG. 19 is an example of application of the device of the present invention when power systems are connected by multiple interconnection lines.

FIG. 20 is an example of application of the device of the present invention when power systems are connected by multiple interconnection lines.

[Explanation of symbols]

A, B...power system, l...interconnection line, Tr...series transformer,
CT...transformer.

Claims (18)

[Claims] 1. Corresponding phases of different power systems are connected via a primary winding of a transformer, a control voltage is applied to a secondary winding of the transformer, and the phase of the control voltage with respect to the system voltage is determined. A power flow control method for controlling power flow between the power systems by controlling the power flow and the magnitude thereof. 2. A control voltage generator comprising a series transformer and a control voltage generator connected to a secondary winding of the series transformer and applying a control voltage having a variable phase and magnitude to the secondary winding. A power flow control device in which both ends of the primary winding of the series transformer are connected to different power systems. 3. Three series transformers each having both ends connected to a different three-phase power system, each connected to a secondary winding of each series transformer, and having a phase and a magnitude in the secondary winding. and three control voltage generators that apply variable control voltages, each of which is a three-phase transformer whose power source is the voltage at any point of the primary windings of the three series transformers. the secondary windings of the three-phase transformer are provided with taps, and these secondary windings are connected in series to connect two of the corresponding series transformers.
A power flow control device connected to the next winding. 4. Three series transformers each having both ends connected to a different three-phase power system, each connected to a secondary winding of each series transformer, and having a phase and a magnitude in the secondary winding. three control voltage generators that apply variable control voltages, each of the series transformers is provided with three secondary windings, and each of the control voltage generators It has a three-phase transformer whose power source is the voltage at any point on the primary winding of the transformer, and a tap is provided on the secondary winding of the three-phase transformer, so that the voltages of these secondary windings are added together. and a power flow control device connected to the secondary windings of the corresponding series transformers so as to be connected to the corresponding secondary windings of the series transformers. 5. Three series transformers each having both ends connected to a different three-phase power system, each connected to a secondary winding of each series transformer, and having a phase and a magnitude in the secondary winding. and three control voltage generators that apply variable control voltages, each of the control voltage generators having an inverter connected to the secondary winding of the series transformer via a three-phase transformer. A power flow control device that controls the inverter to adjust the phase and magnitude of a control voltage applied to the secondary winding of the series transformer. 6. Use of a power flow control device comprising a series transformer and a control voltage generator connected to a secondary winding of the series transformer and applying a control voltage to the secondary winding. In the method, different power systems are connected to both ends of the primary winding of the series transformer, and the magnitude and phase of the control voltage applied to the secondary winding are controlled by the control voltage generator to generate the different power. A method of using a power flow control device characterized by controlling power flow between systems. 7. Use of a power flow control device comprising a series transformer and a control voltage generator connected to a secondary winding of the series transformer and applying a control voltage to the secondary winding. In the method, different power systems are connected to both ends of the primary winding of the series transformer, and the magnitude and phase of the control voltage applied to the secondary winding are controlled by the control voltage generator to generate the different power. A method of using a power flow control device, which controls power flow between systems, and opens a secondary winding of the series transformer when a short circuit accident occurs in any of the power systems. 8. A control voltage generator comprising a series transformer and a control voltage generator connected to a secondary winding of the series transformer and applying a control voltage having a variable phase and magnitude to the secondary winding. and both ends of the primary winding of the series transformer are connected to different power systems,
A power flow control system configured to determine the phase and magnitude of the control voltage based on given command values of active power and reactive power, and control the control voltage generator based on this. 9. Three series transformers each having both ends connected to different three-phase power systems, each connected to a secondary winding of each series transformer, and having a phase and a magnitude in the secondary winding. and three control voltage generators that apply variable control voltages, each of the control voltage generators having an inverter connected to the secondary winding of the series transformer via a three-phase transformer. A power flow control device comprising: a power flow control device in which the power source for the inverter is drawn from a power source that is not affected by fluctuations in the power system whose power flow is to be controlled; 10. A control voltage generator comprising a series transformer and a control voltage generator connected to a secondary winding of the series transformer and applying a control voltage having a variable phase and magnitude to the secondary winding. A power flow control device is used by connecting both ends of the primary winding of the series transformer to different power systems, and a static var power compensator or a synchronous phase modulator is connected to one or both of the different power systems. , a power flow control method in which the power flows between the different power systems are controlled independently in both power systems by operating the power systems in combination. 11. A control voltage generator comprising a series transformer and a control voltage generator connected to a secondary winding of the series transformer and applying a control voltage having a variable phase and magnitude to the secondary winding. Both ends of the primary winding of the series transformer are connected to different power systems, and the power flow of one of the different power systems is adjusted to the phase of the control voltage based on the given command values of active power and reactive power. Based on this, the control voltage generator is controlled, and the other power flow of the different power system is controlled by the static reactive power compensator or the static reactive power compensator or A power flow control system configured to control a synchronous phase modifier. 12. For the purpose of independently controlling power flows between two different power systems in both systems, a series transformer and a phase transformer connected to a secondary winding of the series transformer, and a phase transformer connected to the secondary winding of the series transformer. and a control voltage generator for applying a control voltage of variable magnitude; A method of using the power flow control device, a static var compensator, and a synchronous phase modifier, which are used by connecting the static var compensator or synchronous phase modifier to one or both of two different power systems. 13. In a phase adjustment device interconnected with an electric power system, the amount of phase adjustment, or in the case of a series transformer system using secondary excitation, the control signal of the amount of secondary excitation voltage is used as the control signal of the phase adjustment device. Detect the passing power, extract its fluctuation,
A phase adjustment device characterized in that the signal is used as a control signal or that the signal is added with another signal to obtain a control signal. Claim 14: In a system where systems are interconnected at multiple points and each interconnection line is connected to a series transformer that can control the secondary voltage in a vectorial manner, each interconnection line A power system control device characterized in that it collects power flow, voltage, and fault information, and controls the secondary voltage and secondary circuit of the series transformer based on them and command values. 15. The power system control device according to claim 14, wherein two series transformers provided on the interconnection line are connected in series, and each transformer is controlled by a separate control signal. 16. The power system control device according to claim 14, wherein the method for controlling the secondary transformer of the series transformer uniformly controls all interconnection lines. 17. The power system control device according to claim 14, wherein the method for controlling the secondary voltage of the series transformer is performed according to a weight provided for each interconnection line. 18. The power system control device according to claim 14, wherein the command values are active power, reactive power, and voltage.