JP3583647B2 - AC interconnection apparatus and control method thereof - Google Patents

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to interconnection of two AC systems, and more particularly, to an AC interconnection device that improves power flow control response and is inexpensive, and a control method thereof.
[0002]
[Prior art]
When interconnecting AC systems of the same frequency, there are interconnecting methods using a phase adjuster or an asynchronous interconnecting device via DC such as BTB (Back To Back). In the interconnection by the phase adjuster, there is no problem based on reactive power or active power control such as voltage stability or a generator twisting phenomenon, and there are few problems such as operation shutdown in the event of an AC system accident. Further, there is an advantage that the installation place can be relatively small and the cost is low. However, since the power flow control amount at the interconnection point differs depending on the state of the phase angle of the system, arbitrary power flow control is difficult. There is also a problem that a short-circuit current increases at the time of a system failure. On the other hand, the asynchronous interconnection device has the advantages that the power flow control is easy, the short-circuit current at the time of a system fault does not increase, and unnecessary loop power flow can be prevented. However, it is inferior to the phase adjuster in terms of cost and installation area.
[0003]
[Problems to be solved by the invention]
SUMMARY OF THE INVENTION An object of the present invention is to provide a low-cost AC interconnection device capable of arbitrarily and at high speed, controlling power flow, and being suitable for system stability at low cost, and a control method therefor, which overcomes the problems of the prior art.
[0004]
[Means for Solving the Problems]
The present invention relates to an AC interconnection device for interconnecting two AC systems, in which an asynchronous interconnection device (BTB or the like) capable of continuously controlling a power flow and a phase adjuster capable of performing a stepwise power flow control are connected in parallel. It is characterized by comprising.
[0005]
A phase adjuster having a tap adjuster (mechanical phase adjuster) is used as the phase adjuster. The asynchronous interconnection device is characterized in that the continuous power flow control capacity has an adjustment capacity of one tap or more of the phase adjuster.
[0006]
The present invention relates to a control method of an AC interconnection device according to claim 1, wherein the two AC systems are interconnected, and a phase angle obtained from a power flow with respect to a phase angle obtained by previously analyzing or measuring the power flow adjustment amount of the phase adjuster. It is characterized in that it is determined based on a tide chart.
[0007]
In addition, the asynchronous flow device controls a flow of a difference between a power flow control amount of a connection line and a flow flow adjusted by the phase adjuster by the asynchronous connection device.
[0008]
BEST MODE FOR CARRYING OUT THE INVENTION
FIG. 1 shows an embodiment to which the AC interconnection device of the present invention is applied. 1, 2, and 3 indicate three different AC systems. Reference numerals 11 and 12 denote AC / DC converters for converting AC to DC or DC to AC. The AC / DC converters 11 and 12 are paired to constitute an asynchronous interconnection device 10 such as a BTB. 20 is a mechanical phase adjuster having a tap adjuster, 31 and 32 are interconnection lines for interconnecting the two AC systems 1 and 2 by an asynchronous interconnection device such as BTB, and 41 and 42 are phase adjusters. Reference numeral 20 denotes a connection line for connecting the two AC systems 1 and 2, and 100 denotes a connection line power flow control device which receives a detection signal from a power flow detector 130 that detects the power flow of the two connection lines. Power flow command values are issued to the control devices 111 and 112 of the asynchronous interconnection device 10 and the control device 120 of the phase adjuster 20.
[0009]
Now, consider a case where the tidal current Pac of the interconnection line flows from the AC system 1 to the AC system 2. The interconnection line power flow control device 100 allocates the power flow Pac as the power flow command value Pdc to the asynchronous interconnection device 10 and the power flow command value Phs to the phase adjuster 20. Of course, the relationship of Equation 1 is established between the command values.
[0010]
(Equation 1)
Pac = Pdc + Phs
On the basis of a command from the interconnection line power flow control device 100, the asynchronous interconnection device 10 uses the two AC / DC converters 11 and 12 as a forward converter and an inverse converter, respectively, so that a direct current flows with the command value Pdc. Control the current.
[0011]
On the other hand, the phase adjuster 20 determines the phase angle θ corresponding to the power flow command value Phs according to the phase angle-power flow diagram calculated in advance, and adjusts the tap position corresponding to the phase angle θ so that the specified power flow Phs is determined. Let it flow.
[0012]
FIG. 2 shows a phase angle-power flow chart. The horizontal axis indicates the power flow command value and the phase angle of the phase adjuster, and the vertical axis indicates the power flow of the asynchronous interconnection device 10 and the power flow of the phase adjuster 20. The thick solid line indicates the power flow Pac with respect to the interconnection line power flow command value, the broken line indicates the power flow Pdc of the asynchronous interconnection device 10, and the thin solid line on the stairs indicates the power flow Phs with respect to the phase angle of the phase adjuster. A positive value of the tidal flow indicates a tidal flow from the AC system 1 to the AC system 2, and a negative value of the tidal flow indicates the reverse.
[0013]
As described above, assuming that the interconnected power flow command value is Pac, the interconnected power flow control device 100 transmits Pdc, phase to the control devices 111 and 112 of the asynchronous interconnected device 10 based on the phase angle-power flow diagram shown in FIG. The power command value of Phs is output to the control device 120 of the adjuster 20. In this case, the power flow of the phase adjuster 20 is a power flow corresponding to the phase angle θ1. At the stage when the tap position is switched to θ1, the phase adjuster 20 is set to flow the flow of Phs1, and the asynchronous interconnection device 10 is set to flow the remaining flow of flow Pdc1. The relationship of Equation 2 is normally obtained.
[0014]
(Equation 2)
Pac = Pdc1 + Phs1 = Pac1
Looking at the transitional movement, the asynchronous interconnecting device 10 responds quickly to the power flow control, and thus transmits power according to the relationship of Expression 3 until the tap of the phase adjuster 20 is switched and the power flow becomes Phs1.
[0015]
(Equation 3)
Pdc = Pac1
When the tap of the phase adjuster is switched to θ1, the asynchronous interconnection device 10 lowers the transmission power according to the relationship of Expression 4.
[0016]
(Equation 4)
Pdc = Pac1-Phs1
That is, the power flow Pac1 corresponding to the power flow command value Pac flows through the two interconnection devices.
[0017]
In this case, the tap position of the phase adjuster 20 is set to θ2 with respect to the interconnecting line power flow Pac, the power flow is inverted in the asynchronous interconnecting device 10, and the power flow control operation according to the relationship of Expression 5 is also possible.
[0018]
(Equation 5)
-Pdc2 = Phs2-Pac1
However, since the power flow is recirculated in the phase adjuster 20 and the asynchronous interconnection device 10, the efficiency is low, and such an operation is not commanded.
[0019]
The same applies to the case where the tidal flow is lowered or the tidal flow direction is changed. Until the tap position of the phase adjuster 20 is switched to the phase angle θ determined according to the phase angle-power flow diagram of FIG. 2, the asynchronous interconnection device 10 performs high-speed power flow control according to the command value. When the tap position of the phase adjuster is changed, the power flow command value of the asynchronous interconnection device 10 is changed, and an interconnecting line power flow that matches the power flow command value flows steadily.
[0020]
As described above, since the asynchronous interconnection device 10 operates to adjust the tidal flow rate to the command value at high speed, the tidal current control of the phase adjuster 20 does not need to be performed at high speed, and the phase adjuster having a mechanical tap adjuster is used. The configuration is sufficient. Therefore, it can be realized with a low-cost AC interconnection device.
[0021]
With such a configuration, a relatively slow power flow can be adjusted by the phase adjuster 20 and a rapidly changing power flow can be controlled by the asynchronous interconnection device 10, so that the phase adjuster 20 can be continuously operated. Even if the power flow cannot be controlled at a high speed, the power flow can be controlled continuously and at a high speed by the asynchronous interconnection device 10, so that a low-cost AC interconnection device can be realized.
[0022]
FIG. 3 is a block diagram of a power flow command value creation circuit of the asynchronous interconnection device included in the interconnection power flow control device. The adder 101 obtains a difference between the interconnected power flow command value Pac and the detected power flow Phsf of the interconnected line 41 from the interconnected line power flow detector 130. The arithmetic circuit 102 performs a proportional integral operation on the output of the adder 101. This calculation result becomes the power flow command value Pdc of the asynchronous interconnection device 10. The command value Pdc becomes a power flow command value of the control devices 111 and 112, and accordingly, the power flow of the interconnection line can be adjusted to the command value.
[0023]
FIG. 4 shows a configuration example of the phase adjuster. The phase adjuster 20 includes a parallel transformer Tr1 and a series transformer Tr2. The primary side of Tr1 is taken from an intermediate point between the series windings Sa, Sb, Sc of Tr2 of the series transformer. The secondary side is provided with a tap winding TPW, and the tap position is determined by a phase angle command value from the phase adjuster control device 120. The secondary side of Tr1 is connected to the excitation windings EXa, EXb, EXc of Tr2, and causes the series windings Sa, Sb, Sc to generate a voltage of a component perpendicular to the transmission line voltage, respectively.
[0024]
FIG. 5 is a block diagram for obtaining a tap position from a power flow command value provided in the phase adjuster control device. The tide flow Phs with respect to the phase angle θ calculated or measured in advance from the system diagram and adjusted by the phase adjuster 20 is obtained, for example, as shown in FIG. The tap command value creation circuit 121 having this characteristic determines the tap position Tap from the tide flow Phs. When the tap position Tap is determined, the tap position of the parallel transformer Tr1 is adjusted by a tap driving device (not shown).
[0025]
If the continuous power flow control capacity of the asynchronous interconnection device 10 is at least equal to or greater than the adjustment capacity corresponding to one tap of the mechanical phase adjuster 20, the following delay of the phase adjuster 20 is reduced by the asynchronous interconnection device 10 Tide control.
[0026]
【The invention's effect】
ADVANTAGE OF THE INVENTION According to this invention, there exists an effect which can implement | achieve power flow control continuously and at high speed with the low cost AC interconnection device.
[Brief description of the drawings]
FIG. 1 is a configuration diagram of an AC interconnection device according to an embodiment of the present invention.
FIG. 2 is a phase angle-power flow chart.
FIG. 3 is a block diagram of a power flow command value creation circuit according to one embodiment.
FIG. 4 is a configuration diagram of a mechanical phase adjuster according to one embodiment.
FIG. 5 is a control block diagram of a phase adjuster according to one embodiment.
[Explanation of symbols]
1, 2, 3 ... AC system, 10 ... Asynchronous interconnection device, 11, 12 ... AC / DC converter, 20 ... Phase adjuster, 31, 32, 41, 42 ... Interconnection line, 100 ... Interconnection line power flow control device 101, an adder, 102, an arithmetic circuit, 111, 112, a control device of an asynchronous interconnection device, 120, a control device of a phase adjuster, 121, a tap command value creation circuit, 130, an interconnection line power flow detector, Pac ... Linked power flow command value, Pdc: Power flow command value of asynchronous interconnection device, Phs: Power flow command value of phase adjuster, Phsf: Power flow detection value, Tr1: Parallel transformer, TPW: Tap winding, Tr2: Series transformer , EXa, EXb, EXc ... exciting winding, Sa, Sb, Sc ... series winding.

Claims (4)

In an AC interconnection device that interconnects two AC systems,
Asynchronous interconnection device that can continuously control power flow and phase adjuster with tap adjuster that can control power flow stepwise are connected in parallel ,
An AC interconnection device, wherein a power flow control is performed by the asynchronous interconnection device for a follow-up delay caused by the phase adjuster . The AC interconnection device according to claim 1 ,
The AC interconnection device, wherein the asynchronous interconnection device has, as its continuous power flow control capacitance, an adjustment capacitance of one tap or more of the phase adjuster. The control method for an AC interconnection device according to claim 1, wherein the two AC systems are interconnected.
A method for controlling an AC interconnection device, characterized in that a power flow adjustment amount of the phase adjuster is determined based on a phase angle-power flow diagram obtained from a power flow with respect to a phase angle previously analyzed or measured. The control method for an AC interconnection device according to claim 1, wherein the two AC systems are interconnected.
A method of controlling an AC interconnection device, wherein a power flow of a difference between a power flow control amount of an interconnection line and a tide flow adjusted by the phase adjuster is controlled by the asynchronous interconnection device.

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