JP2000175361A - Alternating current direct current hybrid power transmission system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To utilize existing transmission lines effectively, and to enhance the power transmitting ability by providing a DC power transmitting apparatus which connects a plurality of AC power systems mutually, and a compensating voltage generating series compensating gear for adjusting equivalent reactances of the AC power systems. SOLUTION: Substations SS1, SS2 are connected to 50 Hz and 60 Hz systems respectively. A DC power transmission equipment HVDC connects both, 50 Hz and 60 Hz systems, converts three-phase 50 Hz AC power into DC power by an AC to DC power converter CNV, and transmits it through a transmission line Ld. In addition, it is converted into three-phase 60 Hz AC power by a DC to AC power converter INV, and is supplied to the substation SS2. A series compensating gear SCG set on a transmission line for an AC power system generates a compensating voltage having a phase shifted approximately by ninety degrees as against the current of a corresponding transmission line, cancels a great portion of the inductance component of the transmission line, and system interconnection of DC power transmission where an AC transmission line reactance is approximately zero. If a grounding fault occurs in the transmission line, and an excessive current flows, a by-pass circuit switch SW is closed, and the compensating gear SCG is protected by a by-pass current.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an AC / DC hybrid power transmission system combining AC power transmission and DC power transmission.

[0002]

2. Description of the Related Art Most of transmission lines and distribution lines in Japan are of an AC power transmission system with a frequency of 50 Hz or 60 Hz.
In some cases, DC transmission is used for coordination between systems and long-distance transmission.

FIG. 27 is a system configuration diagram showing the concept of DC power transmission and AC power transmission. In the figure, G is a power plant, SS
Is a substation, TR1 and TR2 are transformers, CNV is AC /
DC power converter, INV is DC / AC power converter, Ld
Represents a DC reactor, and X represents a reactance of an AC transmission line.

FIG. 27A shows a DC power transmission system, in which AC power generated at a power plant G is converted to DC by an AC / DC power converter CNV. The DC power is
It is sent to the substation on the receiving side via a DC transmission line. Therefore, the DC / AC power converter INV converts the DC power into AC power again and supplies the AC power to another substation or a demand load.

[0005] This DC power transmission system has an advantage that power is transmitted over a long distance without any voltage drop due to reactance of the transmission line because power is once converted to DC. Also,
Even if two AC systems have different frequencies, they can be connected. However, a power converter with the same capacity as the transmission capacity is required on each of the power transmission side and the power reception side,
New DC transmission lines must be constructed, resulting in a costly system.

Further, when power is to be supplied to a load during power transmission, it is necessary to temporarily convert DC into AC power, and therefore a power converter is required, which results in an uneconomical system. I will.

On the other hand, FIG. 27 (b) shows an AC power transmission system, which has the advantage that the voltage can be freely changed by the transformers TR1 and TR2, and the power can be transmitted as it is. In addition, most of the current transmission lines are AC transmission lines, and economical power supply using these lines effectively is possible.

However, there is a disadvantage that transmission lines of different frequencies cannot be directly connected, and if there is a reactance X in the transmission line, the voltage drop becomes a problem, and the active power that can be transmitted is limited. .

In FIG. 28, (a) shows a simplified equivalent circuit of an AC transmission line, and (b) shows the relationship between the transmission power and the phase angle θ. In the figure, when the voltage Vs at the transmitting end, the voltage Vr at the receiving end, the phase difference is θ, and the reactance of the transmission line is X, the active power P that can be transmitted is represented by the following equation.

[0010]

P = (Vs.Vr / X) .sin .theta. Accordingly, when the transmission line becomes long, the reactance X increases, and the active power that can be transmitted is limited.

In normal power transmission, the system is operated with a phase difference θ of 30 ° or less. However, when power fluctuations occur in the system and the phase difference θ exceeds 90 °, a so-called step-out phenomenon of the generator may occur. Power transmission. In a system where the reactance X of the transmission line is large, there is a disadvantage that the maximum value of the transmission power is small and the phase difference θ fluctuates greatly even with a small power fluctuation, and the system tends to be unstable.

[0012]

In the case of AC power transmission, it is economical if the voltage can be freely changed by a transformer and long-distance AC power can be transmitted using an existing power transmission line. In addition, there is a great merit for those who use electricity. However, the active power that can be transmitted is limited by the influence of the reactance of the transmission line.

On the other hand, DC power transmission is said to be suitable for long-distance power transmission because it is not affected by reactance of the transmission line. However, the existing transmission line cannot be used, and a large-capacity power converter for the transmission capacity is required, which increases the system cost. Also, during power transmission,
When power is to be supplied to a load, it is necessary to temporarily convert DC to AC power, and a power converter for that purpose is required.

For this reason, DC power transmission is installed in a minimum necessary section, and an AC / DC hybrid power transmission system mainly using an AC power transmission section has been adopted. In this hybrid power transmission system, the DC transmission section can transmit a large amount of power without being affected by the reactance of the transmission line, but the AC transmission section, which occupies the majority, can transmit power due to the reactance of the transmission line. There was a problem of limiting power.

The present invention effectively utilizes an existing AC transmission line, eliminates the influence of reactance of the AC transmission line, enhances the transmission capacity of the transmission line, and has to rely on submarine cables and underground cables. To provide an economical AC / DC hybrid power transmission system that utilizes the advantages of AC power transmission and DC power transmission in the power transmission section, using DC power transmission to eliminate the effects of stray capacitance of power cables and effectively connecting AC systems. With the goal.

[0016]

To achieve the above object, an AC / DC hybrid power transmission system according to claim 1 of the present invention comprises a plurality of AC power systems, a DC power transmission device connecting the AC power systems, An AC / DC hybrid power transmission system comprising: a series compensator for generating a compensation voltage for adjusting an equivalent reactance of the AC power system.

The DC power transmission device connects between AC power systems, and converts three-phase AC into DC with an AC / DC power converter, sends power through a DC transmission line, and converts DC with a DC / AC power converter. It is converted again into three-phase AC, and power is exchanged between AC systems.

When a current type converter is used as a power converter of a DC power transmission device, the direction of DC current is constant, and the direction of power flow can be changed by changing the polarity of DC voltage. In this case, a DC reactor is inserted to suppress the pulsation of the DC current.

When a voltage type converter is used as the power converter of the DC power transmission device, the polarity of the DC voltage does not change.
By changing the direction of the DC current, the direction in which the power flows can be changed. In this case, a DC smoothing capacitor is inserted to suppress the pulsation of the DC voltage.

In the DC power transmission section, there is only a voltage drop due to the resistance, and is not affected by the reactance of the transmission line.
The series compensator installed on the transmission line of the AC power system generates a compensation voltage having a phase shifted by approximately 90 ° with respect to the current flowing through the transmission line, and adjusts the reactance of the transmission line.

Basically, since an AC transmission line has a large inductance component, a compensation voltage of a capacitance component is generated so as to cancel the inductance component. By changing the value of the compensation voltage, it is possible to freely adjust the equivalent reactance of the transmission line.

As a result, the limit of the power transmission capacity in the AC power transmission section is improved, and efficient operation of the AC / DC hybrid power transmission system becomes possible. In addition, DC power transmission is an economical power transmission system mainly for the AC transmission section by installing it in the minimum necessary power transmission section, such as when connecting AC systems with different frequencies or when transmitting power using submarine cables. Can be realized. Furthermore, existing transmission lines can be used, and long-distance power transmission is possible while supplying power to the load.

According to a second aspect of the present invention, there is provided an AC / DC hybrid power transmission system which adjusts a plurality of AC power systems, a DC power transmission device connecting the AC power systems, and an equivalent reactance of the AC power system. An AC / DC hybrid power transmission system comprising: a series compensator for generating a compensation voltage for suppressing power fluctuation.

The DC power transmission device connects between AC power systems. The AC / DC power converter converts three-phase AC to DC, sends power through a DC transmission line, and converts DC through a DC / AC power converter. It is converted again into three-phase AC, and power is exchanged between AC systems.

When a current type converter is used as a power converter of a DC power transmission device, the direction of DC current is constant, and the direction of power flow can be changed by changing the polarity of DC voltage. In this case, a DC reactor is inserted to suppress the pulsation of the DC current.

When a voltage type converter is used as the power converter of the DC power transmission device, the polarity of the DC voltage does not change.
By changing the direction of the DC current, the direction in which the power flows can be changed. In this case, a DC smoothing capacitor is inserted to suppress the pulsation of the DC voltage.

In the DC power transmission section, there is only a voltage drop due to the resistance, and is not affected by the reactance of the transmission line.
The series compensator installed on the transmission line of the AC power system generates a compensation voltage having a phase shifted by approximately 90 ° with respect to the current flowing through the transmission line, and adjusts the reactance of the transmission line.

Basically, since an AC transmission line has a large inductance component, a compensation voltage of a capacitance component is generated so as to cancel the inductance component. By changing the value of the compensation voltage, it is possible to freely adjust the equivalent reactance of the transmission line.

Further, even if an electric vibration phenomenon (power fluctuation) occurs in the transmission line for some reason, the vibration phenomenon can be suppressed by outputting the compensation voltage from the series compensator. That is, power fluctuations can be quickly suppressed by detecting the power fluctuation of the transmission line and controlling the compensation voltage of the series compensator so as to suppress the power fluctuation.

As a result, the limit of the power transmission capacity in the AC power transmission section is improved, and the efficient operation of the AC / DC hybrid power transmission system becomes possible. In addition, DC power transmission is an economical power transmission system mainly for the AC transmission section by installing it in the minimum necessary power transmission section, such as when connecting AC systems with different frequencies or when transmitting power using submarine cables. Can be realized. Furthermore, existing transmission lines can be used, and long-distance power transmission is possible while supplying power to the load.

According to a third aspect of the present invention, there is provided an AC / DC hybrid power transmission system having a plurality of AC power systems, a DC power transmission device connecting the AC power systems, and an equivalent reactance of a transmission line of the AC power system. An AC / DC hybrid power transmission system including a series compensator for generating a compensation voltage so as to be substantially zero.

The DC power transmission device connects between AC power systems. The AC / DC power converter converts three-phase AC into DC, sends power through a DC transmission line, and converts DC into DC / AC power converter. It is converted again into three-phase AC, and power is exchanged between AC systems. In the DC transmission section, there is only a voltage drop due to the resistance, and there is no effect of the reactance of the transmission line.

The series compensator installed on the transmission line of the AC power system generates a compensation voltage whose phase is shifted by approximately 90 ° with respect to the current flowing through the transmission line, and the compensation voltage is increased by the inductance of the transmission line. A compensation voltage is generated so as to cancel out the portion. As a result, the reactance of the AC transmission line becomes substantially zero, and it becomes possible to eliminate the influence of the reactance.

In this manner, it is possible to interconnect an AC transmission line with zero equivalent reactance and a DC transmission which is not affected by reactance, and a long-distance AC / DC hybrid power transmission system via a power system of different frequency can be provided. Can be provided.

According to a fourth aspect of the present invention, there is provided the AC / DC hybrid power transmission system according to any one of the first to third aspects, wherein the series compensator is provided when an overcurrent occurs due to a ground fault or the like of the transmission line. And an AC / DC hybrid power transmission system including a circuit for bypassing the overcurrent.

When a large current flows through a transmission line due to a ground fault or the like, a bypass circuit is turned on to protect the series compensator, and an overcurrent flows through the bypass circuit. As a bypass circuit, a bidirectional switch in which thyristors are connected in anti-parallel is used, an overcurrent is detected, and a firing signal is given to the thyristor to turn it on. The ground fault current is eventually released by the circuit breaker, and the overcurrent subsides.

At that time, when the supply of the firing signal to the thyristor is stopped, the thyristor turns off naturally by the power supply voltage. Thereafter, the series compensator is operated again to suppress power fluctuation at the time of re-input. Thereby, even if an accident occurs, operation can be performed without breaking the device, and a highly reliable system can be provided.

According to a fifth aspect of the present invention, in the AC / DC hybrid power transmission system according to any one of the first to fourth aspects, the series compensator is connected to a series transformer and a secondary side of the transformer. AC-DC hybrid power transmission system composed of a voltage-type self-excited inverter.

The primary winding of the series transformer is connected in series to the transmission line. A voltage-type self-excited inverter is connected to the secondary winding to generate a compensation voltage. In a large capacity AC transmission line, high-voltage transmission of several hundred kV is required. The transformer is
It insulates the self-excited inverter from the high-voltage transmission line and plays the role of raising or lowering the compensation voltage generated from the self-excited inverter to an optimum value.

According to a sixth aspect of the present invention, in the AC-DC hybrid power transmission system according to any one of the first to fourth aspects, the series compensator includes a series capacitor and a compensation voltage connected in series to the series capacitor. An AC / DC hybrid power transmission system including a generator.

The series capacitor of the series compensator acts to cancel most of the inductance of the AC transmission line, and adjusts the equivalent reactance of the entire transmission line by the compensation voltage generator. Thus, the capacity of the compensation voltage generator can be reduced, and an economical system can be provided. Further, the compensation voltage generating device has an action of suppressing power fluctuation of the AC transmission line, and also has a role of suppressing a resonance phenomenon generated by the inductance of the transmission line and the series capacitor.

According to a seventh aspect of the present invention, in the AC / DC hybrid power transmission system according to the sixth aspect, the series capacitor is divided into a plurality of portions on the AC transmission line and arranged.

The inductance of the AC transmission line is represented by a distribution constant. To compensate for the inductance,
The series capacitor is divided and divided into several parts. As a result, changes in the voltage phase and amplitude depending on the position of the AC transmission line are reduced, and stable power transmission capability can be improved.

According to an eighth aspect of the present invention, in the AC-DC hybrid power transmission system according to any one of the first to fourth aspects, the series compensator includes a series capacitor and a compensation connected in parallel to the series capacitor. This is an AC / DC hybrid power transmission system including a current generator.

The series capacitor acts to cancel most of the inductance of the AC transmission line, and supplies a compensation current to the series capacitor by a compensation current generator.
Reduce power fluctuations in AC transmission lines. The capacity of the compensation current generator can be small. Further, when a ground fault or the like occurs in the system, most of the overcurrent at the time of the fault flows to the series capacitor, so that the compensation current generator does not have a large adverse effect.

According to a ninth aspect of the present invention, in the AC / DC hybrid power transmission system according to any one of the first to fourth aspects, the series compensator includes a first series capacitor and the first series capacitor. An AC / DC hybrid power transmission system including a second series capacitor connected in series and a compensation current generator connected in parallel to the second series capacitor.

The first series capacitor acts to cancel most of the inductance of the AC transmission line, and the second series capacitor
The reactance of the entire transmission line is adjusted by the series capacitor and the compensation current generator. The compensation current generator supplies a compensation current to the second series capacitor to suppress power fluctuation of the AC transmission line. The capacity of the compensation current generator can be further reduced. Further, when a ground fault or the like occurs in the system, most of the overcurrent at the time of the fault flows to the first and second series capacitors, so that the compensation current generator does not have a large adverse effect.

According to a tenth aspect of the present invention, in the AC / DC hybrid power transmission system according to the eighth or ninth aspect, the compensation current generator is an AC / DC hybrid power transmission system including a current source self-excited converter. .

The compensation current generator connected in parallel to the series capacitor is constituted by a current source self-excited converter. The current source self-excited converter is a DC / AC power converter composed of a self-extinguishing element such as a GTO, has a current source on the DC side, and converts the DC current into a required AC current. The magnitude and phase of the DC current can be freely adjusted, and a necessary compensation current can be supplied to the series capacitor.

[0050] An AC / DC hybrid power transmission system according to claim 11 of the present invention is the AC / DC hybrid power transmission system according to claim 8 or 9, wherein the compensation current generating device is a current type separately excited converter. .

The current-type separately-excited converter connected in parallel to the series capacitor performs commutation by using the voltage applied to the series capacitor, and is necessary by adjusting the magnitude of the DC current of the converter. And supply a compensation current to the series capacitor. Since the sum of the current flowing through the transmission line and the compensation current flows through the series capacitor, the applied voltage of the series capacitor, that is, the compensation voltage can be adjusted by changing the magnitude of the compensation current. The separately-excited converter can be constituted by a thyristor, and an AC / DC hybrid power transmission system with a low device cost can be provided.

According to a twelfth aspect of the present invention, in the AC / DC hybrid power transmission system according to the eighth or ninth aspect, the compensation current generating device comprises a current source converter.
An AC / DC hybrid power transmission system using a superconducting coil as a current source of the converter.

A superconducting coil is used as a DC power supply for the current-type self-excited converter, and has a function of storing energy. This makes it possible to supply or absorb short-time active power from the current-type self-excited converter, and to provide an effect of rapidly suppressing power fluctuation.

According to a thirteenth aspect of the present invention, in the AC / DC hybrid power transmission system according to the eighth or ninth aspect, the compensation current generator is an AC / DC hybrid power transmission system comprising a current control type self-excited converter. is there.

The current control type self-excited converter is a voltage type self-excited converter having a reactor on the AC output side, and has a voltage source on the DC side. A current flowing through the reactor on the AC side is detected and compared with a command value to perform closed loop control. The current flowing through this reactor is the compensation current flowing through the series capacitor.

According to a fourteenth aspect of the present invention, in the AC / DC hybrid power transmission system according to the eighth or ninth aspect, the compensation current generating device is constituted by a current control type self-excited converter, and the voltage of the converter is controlled. This is an AC / DC hybrid power transmission system using a storage battery as a power source.

A storage battery (battery) is prepared as a voltage source on the DC side of the current control type self-excited converter. The storage battery is
Energy can be stored, and short-time active power can be supplied or absorbed from the current control type self-excited converter. This makes it possible to compensate for the active power of the AC transmission line, and to stabilize the transient power fluctuation.

[0058] An AC / DC hybrid power transmission system according to claim 15 of the present invention is the AC / DC hybrid power transmission system according to claim 9, wherein the first series capacitor is divided and arranged at a plurality of locations on the transmission line. .

The inductance of the AC transmission line is represented by a distributed constant. To compensate for the inductance,
The first series capacitor is divided and divided into several parts. As a result, changes in the voltage phase and amplitude depending on the position of the AC transmission line are reduced, and stable power transmission capability can be improved.

[0060] In the AC-DC hybrid power transmission system according to claim 16 of the present invention, in any one of claims 1 to 15, the DC power transmission device includes a self-excited AC / DC power converter, a DC transmission line, and a self-excited AC / DC power converter. This is an AC / DC hybrid power transmission system that includes an excited DC / AC power converter and has a function of adjusting reactive power on the AC side.

The power converter of the DC power transmission device is constituted by a self-excited converter. The self-excited converter can control the magnitude of the AC side current and the phase with respect to the power supply voltage to arbitrary values,
Active power and reactive power can be adjusted simultaneously. Thus, when another load or the like connected to the AC transmission line generates reactive power, reactive power for compensating the reactive power is generated from the self-excited converter to stabilize the system voltage.

When a stray capacitance is present in an AC transmission line, a current flows through the capacitance, and this current can be compensated for by a DC power transmission device.

According to a seventeenth aspect of the present invention, there is provided the AC / DC hybrid power transmission system according to any one of the first to sixteenth aspects, wherein the DC power transmission device comprises an AC / DC hybrid power transmission system whose DC transmission line is constituted by a power cable. System.

In the case of long-distance power transmission, if land is available, it is economical to draw an overhead transmission line on the land and to transmit power by AC. However, when transmitting power from land to land over the sea, it is economical to install a transmission line by crawling the seabed with a power cable.

In an urban area, an overhead power transmission line using a steel tower is economically transmitted through an underground cable because the installation position of the steel tower is limited and the land price is high. In such a case, when attempting to transmit power by alternating current, the floating capacitance of the power cable becomes a problem, and there is a concern that a large amount of reactive current flows and the required active power cannot be transmitted.

Therefore, in a section where power is transmitted by a submarine cable or underground cable, the power is once converted to DC by DC power transmission. With DC transmission, the effect of stray capacitance on the power cable is eliminated.

An AC / DC hybrid power transmission system according to claim 18 of the present invention compensates for a plurality of AC power systems, a DC power transmission device connecting the AC power systems, and an inductance of a transmission line of the AC power system. Therefore, the present invention provides an AC / DC hybrid power transmission system including a series capacitor divided into a plurality of units, and switching means for changing the number of stages of the series capacitor.

The series capacitor normally acts to cancel most of the inductance of the AC transmission line. However, when a ground fault or the like occurs in the system and power fluctuations occur, the number of stages of the series capacitors is switched, and the power fluctuations are suppressed by changing the equivalent reactance of the transmission line.

According to a nineteenth aspect of the present invention, there is provided an AC / DC hybrid power transmission system comprising: a plurality of AC power systems; a DC power transmission device connecting the AC power systems; and an inductance component of at least one transmission line of the AC power system. And a thyristor control reactor device connected in parallel with the capacitor.

The thyristor control reactor device can control the magnitude of the current flowing through the reactor by adjusting the firing phase of the thyristor. By adjusting the current of the thyristor control reactor device connected in parallel to the series capacitor, the voltage applied to the series capacitor changes, and the equivalent reactance of the AC transmission line also changes.

When the power fluctuation occurs, the fluctuation can be suppressed promptly by adjusting the equivalent reactance of the transmission line. In the AC / DC hybrid power transmission system according to claim 20 of the present invention, in claim 18 or 19, the DC power transmission device includes a self-excited AC / DC power converter, a DC transmission line, and a self-excited DC / AC power conversion. And an AC / DC hybrid power transmission system having a function of adjusting the reactive power on the AC side.

The power converter of the DC power transmission device is constituted by a self-excited converter. The self-excited converter can control the magnitude of the AC side current and the phase with respect to the power supply voltage to arbitrary values,
Active power and reactive power can be adjusted simultaneously. Thus, when another load or the like connected to the AC transmission line generates reactive power, reactive power for compensating the reactive power is generated from the self-excited converter to stabilize the system voltage.

When the AC transmission line has a stray capacitance, a current flows through the capacitance, and the current can be compensated for by the DC power transmission device.

The AC-DC hybrid power transmission system according to claim 21 of the present invention is the AC-DC hybrid power transmission system according to any one of claims 18 to 20, wherein the series capacitor is divided into a plurality of portions on the transmission line. It is a power transmission system.

The inductance of the AC transmission line is represented by a distributed constant. To compensate for the inductance,
The series capacitor is divided and divided into several parts. As a result, changes in the voltage phase and amplitude depending on the position of the AC transmission line are reduced, and stable power transmission capability can be improved.

In the AC / DC hybrid power transmission system according to claim 22 of the present invention, in any one of claims 18 to 21, the series capacitor short-circuits an overvoltage or overcurrent generated in the AC transmission line. This is an AC / DC hybrid power transmission system provided with a circuit for performing the following.

When a ground fault or the like occurs in the AC transmission line,
Depending on the location of the accident, the installation of a series capacitor may cause overcurrent or overvoltage. To prevent this, a bypass circuit that short-circuits the series capacitor is provided. When the series capacitor is eliminated, the transmission line becomes an inductance component, which can prevent the accident from spreading.

[0078]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 relates to claims 1 to 4 and is a configuration diagram showing an AC / DC hybrid power transmission system according to a first embodiment of the present invention.

In the figure, G is a power plant, SS1 and SS2 are substations, L is inductance of an AC transmission line, SCG is a series compensator, SW is a bypass circuit switch, HVDC is a DC power transmission device, and CNV is AC / DC power. A converter, INV indicates a DC / AC power converter, and Ld indicates an inductance of a DC transmission line.

The substation SS1 is connected to a 50 Hz system, and the substation SS2 is connected to a 60 Hz system. The DC power transmission device HVDC connects the 50 Hz system and the 60 Hz system, and has a three-phase AC / DC power converter CNV.
Hz AC power is converted into DC power, transmitted through the transmission line Ld, and further converted by the DC / AC power converter INV.
The power is converted into AC power of 60 Hz and supplied to the substation SS2.

The series compensator SCG generates a compensation voltage Vo of a component orthogonal to the current I flowing in the transmission line, compensates for the inductance L of the AC transmission line, and causes power fluctuation in the transmission line. If they do, they serve to suppress them. As a result, the limit of the power transmission capacity in the AC power transmission section is improved, and efficient operation of the AC / DC hybrid power transmission system becomes possible.

Further, the DC power transmission is installed in the minimum necessary power transmission section, such as when connecting AC systems of different frequencies or when power transmission using a submarine cable is performed. Power transmission system can be realized. Furthermore, existing transmission lines can be used, and long-distance power transmission is possible while supplying power to the load.

The series compensator SCG installed on the transmission line of the AC power system,
A compensation voltage having a phase shifted by about 90 ° can be generated, and the compensation voltage can be generated so as to cancel most of the inductance of the transmission line. As a result, the reactance of the AC transmission line becomes substantially zero, and it becomes possible to eliminate the influence of the reactance.

That is, it is possible to interconnect an AC transmission line with zero equivalent reactance and a DC transmission that is not affected by reactance, and to provide a long-distance AC / DC hybrid power transmission system via a power system of a different frequency. Can be.

In the case where a ground fault or the like occurs in the power transmission line and an excessive current flows, the bypass circuit switch SW is closed to protect the series compensator SCG so as to bypass the current. Thereby, even if an accident occurs, operation can be performed without breaking the device, and a highly reliable system can be provided.

FIG. 2 relates to claim 5 in which the first
FIG. 3 is a configuration diagram illustrating a series compensation device according to the embodiment. In the figure, UVW is a three-phase AC transmission line, L is an inductance of the transmission line, Tr is a series transformer, VSI is a voltage source P
WM control inverter, Ed is DC voltage source, CT is current detector, PT is voltage detector, DPD is power detector, DPC
NT is a power fluctuation suppression control circuit, AVR is a voltage control circuit,
PWMC indicates a pulse width modulation (PWM) control circuit.

The primary side of the series transformer Tr is connected in series to the transmission line for each phase, and the secondary side is connected to a pulse width modulation control (PWM).
Control) voltage source inverter VSI is connected. In a large capacity AC transmission line, high-voltage transmission of several hundred kV is required.
The transformer Tr insulates the self-excited inverter from the high-voltage transmission line, and serves to step up / down the compensation voltage generated from the self-excited inverter to an optimum value.

The voltage source inverter VSI is connected in a three-phase bridge, and generates an AC voltage Vo proportional to the voltage command value Vor by PWM control. S1 to S6 are self-extinguishing elements such as GTO, and diodes are connected to each element in anti-parallel. Normally, the compensation voltage Vo generates a component orthogonal to the current I flowing through the transmission line, and adjusts the equivalent reactance of the transmission line. Vob is the command value, and by adjusting this value, the reactance X of the transmission line can be adjusted to be substantially zero.

On the other hand, when power fluctuation occurs in the transmission line,
The suppression control is performed as follows. That is, the current detector CT
And the voltage detector PT detect the three-phase AC voltage and current of the power transmission line, and use the detected power and the reactive power Q by the power detection circuit DPD. When power fluctuations occur, P and Q change. The fluctuations ΔP and ΔQ are extracted and given to the next power fluctuation suppression control circuit DPCNT.

When power fluctuation occurs, the fluctuations ΔP and ΔQ
The compensation voltage Voa changes according to the compensation voltage command value Vo.
2r = Voa + Vob is supplied to the PWM control circuit PWMC to suppress power fluctuation. Here, Vob is a compensation voltage command value provided for adjusting the equivalent reactance of the AC transmission line.

As the DC voltage source Ed, a separate power supply may be prepared, but here, the DC voltage source is made by itself. That is, a DC smoothing capacitor is prepared as a DC voltage source, and the voltage Ed is controlled to be constant. First, the DC command value Edr is compared with the DC voltage detection value Ed,
The deviation is amplified by the DC voltage control circuit AVR. AVR
The output signal Vo1r controls the DC voltage Ed by giving a compensation voltage command of an in-phase component (or an anti-phase component) to the current I flowing in the transmission line.

Hereinafter, each operation will be described with reference to a voltage / current vector diagram on the AC side. FIG. 3 shows an equivalent circuit of a transmission line for explaining a steady operation of the system according to the first embodiment, and a vector diagram of voltage and current.
(A) is an equivalent circuit without a series compensator, (b) is (a)
(C) shows a voltage-current vector diagram of the equivalent circuit when a series compensator is inserted, and (d) shows a voltage-current vector diagram of the equivalent circuit of (c).

In the figure, Vs is the voltage on the power transmission side, Vr is the voltage on the power reception side, L is the inductance of the transmission line, I is the current, and Vo
Is a compensation voltage, and ω is a power supply angular frequency. The resistance of the transmission line is ignored because it is sufficiently small.

FIG. 3B is a vector diagram without the series compensator. When the current I flows, a voltage drop of jωL · I occurs, and the phase difference θ between the transmission voltages Vs and Vr increases. As the current I increases, the phase difference θ increases, and when it exceeds 90 °, the active power P cannot be transmitted any more. In the case of a generator, the synchronizing speed cannot be maintained, causing a step-out.

On the other hand, FIG. 3 (d) shows a vector diagram when the series compensator of the present invention is inserted, and generates a compensation voltage Vo of a component substantially orthogonal to the flowing current I. Thus, the voltage drop jωL · I due to the inductance L of the transmission line can be canceled, and the equivalent reactance of the transmission line can be reduced. As a result, the phase difference θ between the transmission voltage Vs and the reception voltage Vr is reduced, and the power transmission capability can be improved.

In particular, if Vo = −jωL · I, power transmission with an equivalent reactance X = 0 becomes possible. In this case, V
r and Vs can be matched. In the zero-reactance power transmission, even if the current I increases, the phase difference θ between Vs and Vr does not move, and the system becomes strong against power fluctuation. However, in the series compensator of FIG. 2, it is necessary to increase the compensation voltage Vo in proportion to the current I of the transmission line.

FIG. 4 is an equivalent circuit of a transmission line for explaining the power fluctuation suppressing operation of the system according to the first embodiment.
FIG. 4 shows a voltage-current vector diagram. In the figure, the same elements as those in FIG. 3 are denoted by the same reference numerals.

FIG. 4B shows a voltage-current vector diagram in a steady state, in which a compensation voltage of Vo = −jωL · I is generated, and the equivalent reactance X of the transmission line is almost zero. . That is, the voltages Vs and Vr are in a state in which the magnitude and the phase match.

FIG. 4C shows an operation vector diagram in the case where, for example, the supply current to the DC power transmission device of FIG. 1 fluctuates for some reason and power fluctuation occurs. That is, the current variation is {I, which is in-phase component with the transmission current I (active power variation) {Ip, quadrature component (reactive power variation)}.
Divide into Iq.

The series compensator SCG generates a compensation voltage ΔVo for suppressing power fluctuation in addition to the steady compensation voltage Vo. This compensation voltage △ Vo has a component △ V
p and a quadrature component ｑVq, and the in-phase component △ Vp is in the opposite direction to the active power fluctuation current △ Ip,
Vq is generated in a direction opposite to the reactive power fluctuation current △ Iq.

That is, for the fluctuating current ΔI, the compensation voltage ΔV becomes a voltage equivalent to the voltage drop ΔI × R due to the resistance, and functions to attenuate the power fluctuation quickly. In this way, it is possible to provide a stable AC / DC hybrid power transmission system by quickly attenuating the power fluctuation including the DC power transmission device.

FIG. 5 shows an equivalent circuit of a transmission line and a voltage / current vector diagram for explaining the control operation of the series compensator of FIG. In the figure, the same elements as those in FIG. 3 are denoted by the same reference numerals.

FIG. 5B shows a voltage-current vector diagram in a certain steady state. In the series compensator of FIG. 2, when the DC voltage Ed becomes smaller than the command value Edr, the deviation ε becomes a positive value, and Vo1r is increased.

FIG. 5C shows a vector diagram at that time, in which a compensation voltage Vop having a component in phase with the current I is generated by the command value Vo1r. As a result, active power proportional to I × Vop is supplied to the voltage-source inverter VSI, and the DC voltage Ed is increased.

On the other hand, when the DC voltage Ed becomes larger than the command value Edr, the direction of Vop is reversed, active power is released from the inverter VSI to the transmission line, and the DC voltage Ed decreases. In this way, the DC voltage source of the voltage source inverter VSI can be secured by itself. of course,
The voltage source inverter may be configured by bringing another power source.

FIG. 6 relates to claim 6 and is a configuration diagram showing an AC / DC hybrid power transmission system according to a second embodiment of the present invention. In the figure, G is a power plant, SS1,
SS2 is a substation, L is inductance of AC transmission line, C
AP is a series capacitor, CVG is a compensation voltage generator, S
W1 and SW2 are bypass circuit switches, HVDC is a DC power transmission device, CNV is an AC / DC power converter, INV is a DC / AC power converter, and Ld is the inductance of the DC transmission line.

The substation SS1 is connected to a 50 Hz system, and the substation SS2 is connected to a 60 Hz system. The DC power transmission device HVDC connects the 50 Hz system and the 60 Hz system, and has a three-phase AC / DC power converter CNV.
Hz AC power is converted into DC power, transmitted through the transmission line Ld, and further converted by the DC / AC power converter INV.
The power is converted into AC power of 60 Hz and supplied to the substation SS2.

The series capacitor CAP is connected in series with the inductance L of the transmission line to reduce the equivalent reactance X of the transmission line. Also, the compensation voltage generator CVG
Generates a compensation voltage Vo of a component orthogonal to the current I flowing in the transmission line, adjusts the equivalent reactance of the AC transmission line, and suppresses the power fluctuation in the transmission line when it occurs. Play a role.

As described above, in the present embodiment, the series capacitor CAP and the compensation voltage generator CVG constitute the series compensator SCG of the present invention. Further, when a ground fault or the like occurs in the transmission line and an excessive current flows, the bypass circuit switches SW1 and SW2 are closed to bypass the current. In particular, the series circuit CAP is short-circuited at the time of an accident by the bypass circuit switch SW1, and the equivalent reactance X of the transmission line is increased, thereby serving to prevent an increase in the fault current of the transmission line.

FIG. 7 is a block diagram showing a series compensator in the system according to the second embodiment. In the figure, UVW is a three-phase AC transmission line, L is the inductance of the transmission line, CA
P is a series capacitor, Tr is a series transformer, VSI is a voltage type PWM control inverter, Ed is a DC voltage source, SW
u, SWv, and SWw denote bypass circuits, and OCT denotes an overcurrent detector.

The series capacitor CAP acts to cancel the inductance L of the transmission line. The compensation voltage generator CVG includes a series transformer Tr and a voltage-type self-excited inverter VSI, adjusts the reactance of the transmission line, and suppresses and controls the power fluctuation of the transmission line. The voltage-source inverter VSI requires a smaller capacity as compared with the method shown in FIG. Therefore, more economical long-distance AC power transmission can be achieved.

The bypass circuits SWu, SWv, SWw are:
When an overcurrent flows in the transmission line, the state is controlled to a conduction state, and the overcurrent flows. Thus, the compensation voltage generator C
Protects VG from overcurrent.

FIG. 8 shows an equivalent circuit of a transmission line and a voltage / current vector diagram for explaining the operation of the system according to the second embodiment. In the figure, Vs is the voltage on the power transmission side, Vr is the voltage on the power reception side, L is the inductance of the transmission line, CAP is the series capacitor, I is the current, Vo is the compensation voltage, and ω is the power supply angular frequency. The resistance of the transmission line is ignored because it is sufficiently small.

In FIG. 8, (a) and (b) show an equivalent circuit of a transmission line without a series compensator and a voltage-current vector diagram, and (c) and (d) show a series compensator. 5 shows an equivalent circuit of a transmission line and a voltage-current vector diagram in the case.

In the vector diagram of FIG. 8B, when the current I flows through the transmission line, a voltage drop of jωL · I occurs, and the phase difference θ between the transmission-side voltage Vs and the reception-side voltage Vr is reduced. Get out. When the current I is behind the voltage Vr, the voltage Vr becomes smaller than the voltage Vs.

In the vector diagram of FIG.
Flows, the inductance L of the transmission line is j
A voltage drop of ωL · I occurs, and a voltage drop of I / (jωC) occurs in the series capacitor CAP. Both act in a canceling direction, and the equivalent reactance of the transmission line decreases.
Further, by generating the compensation voltage Vo from the compensation voltage generator, the difference between the power transmission side voltage Vs and the power reception side voltage Vr is
As shown in the figure, the phase difference θ also decreases.
Further, the magnitudes of the voltage Vr and the voltage Vs are also substantially the same.

When power fluctuation occurs in the transmission line, a compensation voltage Vo is generated from the compensation voltage generator CVG to suppress the fluctuation. In this system, the compensation voltage generator CV
The voltage generated from G may be small, and the capacity of a power converter (such as a voltage-type self-excited inverter) used therein can be reduced.

FIG. 9 relates to claim 7 and is a configuration diagram showing an AC / DC hybrid power transmission system according to a third embodiment of the present invention. In the figure, G is a power plant, SS1,
SS2 is a substation, Ll and L2 are inductances of AC transmission lines, CAP11 and CAP12 are series capacitors, CV
G is a compensation voltage generator, HVDC is a DC power transmitter, CN
V indicates an AC / DC power converter, INV indicates a DC / AC power converter, and Ld indicates an inductance of a DC transmission line.

The substation SS1 is connected to a 50 Hz system, and the substation SS2 is connected to a 60 Hz system. The DC power transmission device HVDC connects the 50 Hz system and the 60 Hz system, and has a three-phase AC / DC power converter CNV.
Hz AC power is converted into DC power, transmitted through the transmission line Ld, and further converted by the DC / AC power converter INV.
The power is converted into AC power of 60 Hz and supplied to the substation SS2.

The series capacitors CAP11 and CAP12 are divided into transmission lines and arranged, and the inductance L of the transmission lines is reduced.
1 and L2 to reduce the equivalent reactance X of the transmission line. In addition, the compensation voltage generator CVG is a compensation voltage Vo of a component orthogonal to the current I flowing in the transmission line.
And adjusts the equivalent reactance of the AC transmission line, and suppresses power fluctuations in the transmission line when they occur.

As described above, in the present embodiment, the series capacitors CAP11 and CAP12 and the compensation voltage generator CVG
This constitutes the series compensator SCG of the present invention. The series capacitor CAP11 compensates for the transmission line inductance L1, and the CAP12 compensates for the inductance L2. The inductance of the AC transmission line is represented by a distributed constant. In order to compensate for the inductance, the series capacitor is divided and arranged in several parts.

As a result, changes in voltage phase and amplitude depending on the position of the AC transmission line are reduced, and stable power transmission capability can be improved. FIG. 10 relates to claim 8 and is a configuration diagram showing an AC / DC hybrid power transmission system according to a fourth embodiment of the present invention.

In FIG. 10, G is a power station, SS1, S
S2 is the substation, L is the inductance of the AC transmission line, CA
P is a series capacitor, CIG is a compensation current generator, SW
Is a bypass circuit switch, HVDC is a DC power transmission device, C
NV indicates an AC / DC power converter, INV indicates a DC / AC power converter, and Ld indicates an inductance of a DC transmission line.

The substation SS1 is connected to a 50 Hz system, and the substation SS2 is connected to a 60 Hz system. The DC power transmission device HVDC connects the 50 Hz system and the 60 Hz system, and has a three-phase five-phase system using an AC / DC power converter CNV.
The AC power of 0 Hz is converted to DC power, transmitted via the transmission line Ld, and further converted to 3-phase 60 Hz AC power by the DC / AC power converter INV to supply power to the system of the substation SS2. .

The series capacitor CAP and the compensating current generator CIG connected in parallel with it constitute a series compensating device of the present invention, which reduces the equivalent reactance X of the AC transmission line and the power system including the DC power transmitting device. It plays the role of suppressing power fluctuations.

The series capacitor CAP acts to cancel most of the inductance L of the AC transmission line, supplies a compensation current Ic to the series capacitor CAP by the compensation current generator CIG, and suppresses power fluctuation of the AC transmission line. . As a result, the capacity of the compensation current generator CIG can be smaller than that of the method shown in FIG.

Further, when a ground fault or the like occurs in the system, most of the overcurrent at the time of the fault flows to the series capacitor CAP, so that the compensation current generator is not largely affected. When a ground fault or the like occurs in the system, the bypass circuit switch SW short-circuits the series capacitor CAP to restore the equivalent reactance X of the AC transmission line so that the current does not become excessive. Overcurrent to protect the compensation current generator.

FIG. 11 relates to claims 10 and 12 and is a block diagram showing a series compensator in the system of the fourth embodiment. In the figure, UVW is a three-phase AC transmission line, L is an inductance of the transmission line, CAP is a series capacitor, Tr is a series transformer, CSI is a current-type PWM control inverter, DCL is a DC current source, Cf is a filter capacitor, and CT is a capacitor. A current detector, PT is a voltage detector, DPD is a power detection circuit, DPCNT is a power fluctuation suppression circuit, ACR is a current control circuit, and PWMC is a PWM control circuit.

The series capacitor CAP acts to cancel the inductance L of the transmission line. Further, the compensation current generator is composed of a series transformer Tr and a current source self-excited inverter CSI, adjusts the reactance of the transmission line, and controls the power fluctuation of the transmission line.

The primary side of the series transformer Tr is connected in parallel to the series capacitor CAP for each phase, and the current side inverter CSI of pulse width modulation control (PWM control) is connected to the secondary side.

The current source inverter CSI is a reverse blocking GTO.
And the like, and are connected in a three-phase bridge. The current source inverter CSI is PW
AC current Ic proportional to current command value Icr by M control
To the series capacitor CAP. The filter capacitor Cf absorbs a harmonic current generated with the PWM control.

The applied voltage Vo of the series capacitor CAP is
It is determined by the sum current of the current I flowing through the transmission line and the compensation current Ic, and becomes a compensation voltage as a series compensator.
Normally, the compensation voltage Vo generates a component orthogonal to the current I flowing through the transmission line, and adjusts the equivalent reactance of the transmission line.

Icb is a command value of the steady compensation current of the compensation current generator. By adjusting this value, the reactance X of the transmission line can be adjusted to be almost zero.

On the other hand, when power fluctuation occurs in the transmission line,
The suppression control is performed as follows. That is, the current detector CT
And the voltage detector PT detect the three-phase AC voltage and current of the power transmission line, and use the detected power and the reactive power Q by the power detection circuit DPD. If there is power fluctuation, P and Q change. Therefore, the fluctuations △ P and 取 り 出 し Q are taken out and given to the next power fluctuation suppression control circuit DPCNT, and the effective power △
The compensation current command Ica is adjusted according to P and the invalid component △ Q,
Reduce power fluctuations.

As the DC current source Id, a separate power supply may be prepared, but here, the DC current source is made by itself. That is, a DC reactor DCL is prepared as a DC current source, and the current Id is controlled to be constant. First, the DC command value Idr is compared with the DC current detection value Id,
The deviation is amplified by the DC current control circuit ACR. ACR
Is given by giving a compensation current command of a component orthogonal to the current I flowing in the transmission line (in-phase component or anti-phase component with respect to the voltage Vo applied to the series capacitor CAP: effective component). The DC current Id is controlled.

The current-source PWM control inverter CSI has G
A DC / AC power converter composed of a self-extinguishing element such as TO, which has a current source on the DC side and converts the DC current to a required AC current. The magnitude and phase of the compensation current Ic can be freely adjusted, and the necessary compensation current Ic can be supplied to the series capacitor CAP.

Here, a description has been given of a normal DC reactor DCL as the DC current source, but by using a superconducting coil as the DC current source, energy can be stored. That is, energy can be taken in and stored from the AC power system when necessary, and the energy can be released on the contrary. For this reason, even when there is a power fluctuation in the system for a relatively long period, active power can be stored via the current source self-excited inverter CSI, or conversely, active power can be released to the system. As a result,
More stable operation of the system is possible.

FIG. 12 shows an equivalent circuit of a transmission line and a voltage-current vector diagram for explaining the operation of the system according to the fourth embodiment. In the figure, Vs is the voltage on the power transmission side, Vr is the voltage on the power reception side, L is the inductance of the transmission line, CAP is the series capacitor, I is the transmission current, and Vo is the series capacitor CA.
P is the applied voltage (compensation voltage), Ic is the compensation current, and ω is the power supply angular frequency. The resistance of the transmission line is ignored because it is sufficiently small.

In the vector diagram of FIG. 12B, when the current I flows, a voltage drop of jωL · I occurs in the inductance L of the transmission line. Further, by supplying a compensation current Ic having the same phase component as the transmission current I from the compensation current generator to the series capacitor CAP, a voltage of Vo = (I + Ic) / (jωC) is applied to the series capacitor CAP.

[0140] Both act in a canceling direction, and the equivalent reactance of the transmission line decreases. If the compensation current Ic is adjusted so that Vo = −jωL · I, the equivalent reactance X of the transmission line can be made substantially zero, and as shown in the vector diagram of FIG. And the power receiving side voltage Vr.

When power fluctuation occurs in the transmission line, a compensation current Ic is generated from the compensation current generator to suppress the fluctuation. In this system, the transmission current I flows through the series capacitor CAP, and if the series capacitor CAP cancels most of the inductance L of the transmission line, the steady compensation current Ic generated from the compensation current generator becomes The capacity of the power converter (current-type self-excited inverter or the like) used therein can be reduced.

Even when an overcurrent flows in the transmission line due to a ground fault or the like, most of the overcurrent flows in the series capacitor CAP.
, The influence on the compensation current generator CIG is small.

FIG. 13 relates to claim 11.
FIG. 14 is another configuration diagram of the series compensator of the system according to the fourth embodiment. In the figure, UVW is a three-phase AC transmission line, L is the inductance of the transmission line, CAP is a series capacitor, Tr is a series transformer, LCI is a separately excited inverter, DCL is a DC current source, CT is a current detector, and PT is a voltage. Detector, DP
D is a power detection circuit, DPCNT is a power fluctuation suppression circuit, K
Denotes a proportional element, ACR denotes a current control circuit, and PHC denotes a phase control circuit.

The series capacitor CAP acts to cancel the inductance L of the transmission line. The compensation current generator CIG includes a series transformer Tr and a separately-excited inverter LCI, adjusts reactance of the transmission line, and suppresses power fluctuation of the transmission line.

A primary side of the series transformer Tr is connected in parallel to a series capacitor CAP for each phase, and a separately-excited inverter LCI is connected to a secondary side. Separately-excited inverter LC
I is composed of six thyristors S1 to S6 and is connected in a three-phase bridge. The separately-excited inverter LCI is:
The current is naturally commutated using the voltage applied to the series capacitor CAP, and a necessary compensation current Ic is supplied to the series capacitor CAP by adjusting the magnitude of the DC current Id.

In FIG. 13, since the direction of the compensation current Ic is reversed, the applied voltage V
o is determined by a difference current between the current I flowing through the transmission line and the compensation current Ic, and becomes a compensation voltage as a series compensator. Normally, the compensation voltage Vo generates a component orthogonal to the current I flowing through the transmission line, and adjusts the equivalent reactance of the transmission line.

Icb is a command value of a steady compensation current of the compensation current generator, and by adjusting this value, the reactance X of the transmission line can be adjusted to be substantially zero.

As the DC current source Id, a separate power supply may be prepared, but here, the DC current source is made by itself. That is, a DC reactor DCL is prepared as a DC current source, and the current Id is controlled to be constant. First, the DC command value Idr is compared with the DC voltage detection value Id,
The deviation is amplified by the DC current control circuit ACR. ACR
Is the phase control input signal of the separately-excited inverter LCI, and controls the firing control angle α of the thyristor.
The phase angle α is a delay angle of the compensation current Ic with respect to the voltage Vo applied to the series capacitor CAP.

Specifically, when v * = 0, α = 90 °
And the DC voltage Vd of LCI becomes zero. Idr>
In the case of Id, v *> 0, the phase angle α <90 °, the DC voltage Vd of the LCI becomes positive, and the current Id flowing through the DC reactor DCL increases. Also, Idr <
In the case of Id, v * <0, α> 90 °, and L
DC voltage Vd of CI becomes negative, and DC reactor DCL
The current Id flowing through is reduced.

In this way, the current Id flowing through the DC reactor DCL can be controlled, and if the DC current Id is increased, the magnitude of the compensation current Ic can be changed in proportion thereto.

Normally, v * = 0, and the compensation current I
c is a current delayed by approximately 90 ° with respect to the applied voltage Vo of the series capacitor CAP. Therefore, Ic has a phase opposite to that of the transmission current I, and the voltage applied to the series capacitor CAP is Vo
= (I−Ic) / (jωC), and Vo increases as Ic increases.

On the other hand, when power fluctuation occurs in the transmission line,
The suppression control is performed as follows. That is, the current detector CT
And the voltage detector PT detect the three-phase AC voltage and current of the power transmission line, and use the detected power and the reactive power Q by the power detection circuit DPD. When power fluctuations occur, P and Q change. The fluctuations ΔP and ΔQ are extracted and given to the next power fluctuation suppression control circuit DPCNT. The DC current command Idr is adjusted according to the effective component ΔP, and the phase control input signal v * is adjusted according to the invalid component ΔQ. When the power fluctuation occurs, the magnitude of the compensation current Ic and the phase angle α are changed according to ΔP and ΔQ, and the power fluctuation can be suppressed. Note that FIG. 13 shows a case where only the DC current command Idr is adjusted according to the active power fluctuation ΔP.

FIG. 14 shows a transmission line equivalent circuit and a voltage / current vector diagram for explaining the operation of the series compensator of FIG. When the current I flows through the transmission line, a voltage drop jωL · I occurs due to the inductance L, and a voltage of I / (jωC) is also applied to the series capacitor CAP. This voltage acts in a direction to cancel the voltage drop of the inductance L, and reduces the equivalent reactance of the transmission line.

The separately-excited inverter LCI always takes a current Ic delayed with respect to the voltage Vo applied to the series capacitor CAP, and Ic is normally 90 ° delayed from Vo. Therefore, when the direction of the compensation current Ic is determined in the direction shown in FIG. 13, Ic and the transmission current I have the same phase. Therefore, by flowing the compensation current Ic, the current I-Ic flowing through the series capacitor CAP increases, and the applied voltage (compensation voltage) Vo also increases.

FIG. 15 relates to claim 13.
FIG. 14 is a diagram illustrating still another configuration of the series compensator in the system according to the fourth embodiment. In the figure, UVW is a three-phase AC transmission line, L is an inductance of the transmission line, CAP is a series capacitor, Tr is a series transformer, Lf is a filter reactor, VSI is a current control type inverter, Ed is a DC voltage source, and CT and CTc. Is a current detector, PT is a voltage detector, D
PD is a power detector, DPCNT is a power fluctuation suppression control circuit, AVR is a voltage control circuit, ACR is a current control circuit, P
WMC indicates a pulse width modulation (PWM) control circuit.

The primary side of the series transformer Tr is connected in series to the transmission line for each phase, and the secondary side is connected to a current control type inverter VSI of pulse width modulation control (PWM control) via a filter reactor Lf. ing.

The current control type inverter VSI is composed of self-turn-off devices S1 to S6 such as GTO and diodes connected in anti-parallel to the respective devices, and is connected in a three-phase bridge. The current control type inverter VSI has a current command value I
cr and the detected value of the current Ic flowing through the filter reactor Lf are compared, and feedback control is performed. The output current Ic of the inverter is supplied to the series capacitor CAP, and controls the voltage Vo applied to the series capacitor CAP.

The applied voltage Vo of the series capacitor CAP is
It is determined by the sum current of the current I flowing through the transmission line and the compensation current Ic, and becomes a compensation voltage as a series compensator.
Normally, the compensation voltage Vo generates a component orthogonal to the current I flowing through the transmission line, and adjusts the equivalent reactance of the AC transmission line.

Icb is a command value of a steady compensation current of the compensation current generator. By adjusting this value, the reactance X of the transmission line can be adjusted to be almost zero.

On the other hand, when power fluctuation occurs in the transmission line,
The suppression control is performed as follows. That is, the current detector CT
And the voltage detector PT detect the three-phase AC voltage and current of the power transmission line, and use the detected power and the reactive power Q by the power detection circuit DPD. When power fluctuations occur, P and Q change. The fluctuations ΔP and ΔQ are extracted and given to the next power fluctuation suppression control circuit DPCNT. When the power fluctuation occurs, the compensation voltage Ica changes according to ΔP and ΔQ, and the power fluctuation is suppressed.

As the DC voltage source Ed, a separate power supply may be prepared, but here, the DC voltage source is made by itself. That is, a DC smoothing capacitor is prepared as a DC voltage source, and the applied voltage Ed is controlled to be constant.

First, the DC voltage command value Edr is compared with the DC voltage detection value Ed, and the difference is compared with the DC voltage control circuit AVR.
Amplify with The output signal Ic1r of the AVR is a component orthogonal to the current I flowing in the transmission line (series capacitor CA
By giving a compensation current command of the same phase or the opposite phase component to the voltage Vo applied to P, the DC voltage Ed
Is controlling.

FIG. 16 relates to claim 14.
FIG. 14 is a diagram illustrating still another configuration of the series compensator in the system according to the fourth embodiment. In the figure, UVW indicates a three-phase AC transmission line, L indicates an inductance of the transmission line, CAP indicates a series capacitor, Tr indicates a series transformer, Lf indicates a filter reactor, VSI indicates a current control type inverter, and Bat indicates a storage battery (battery). .

In the present embodiment, a battery is used as the DC voltage source of the current control type inverter. For this reason,
Even if there is a power fluctuation of a relatively long cycle in the system, active power can be accumulated via the compensation current generator CIG,
Conversely, active power can be released to the grid. As a result, more stable system operation is possible.

FIG. 17 relates to claim 9 and is a configuration diagram showing an AC / DC hybrid power transmission system according to a fifth embodiment of the present invention. In the figure, G is a power plant, SS
1, SS2 is a substation, L is the inductance of the AC transmission line, CAP1 is the first series capacitor, CAP2 is the second
Series capacitor, CIG is a compensation current generator, SW
1, SW2 is a bypass circuit switch, HVDC is a DC power transmission device, CNV is an AC / DC power converter, INV is a DC / AC power converter, and Ld is the inductance of the DC transmission line.

The substation SS1 is connected to a 50 Hz system, and the substation SS2 is connected to a 60 Hz system. The DC power transmission device HVDC connects the 50 Hz system and the 60 Hz system, and has a three-phase five-phase system using an AC / DC power converter CNV.
The AC power of 0 Hz is converted to DC power, transmitted via the transmission line Ld, and further converted to 3-phase 60 Hz AC power by the DC / AC power converter INV to supply power to the system of the substation SS2. .

The first series capacitor CAP1, the second series capacitor CAP2 and the capacitor CAP2
The compensating current generator CIG connected in parallel to the power supply constitutes the series compensator of the present invention, and has a function of reducing the equivalent reactance X of the AC transmission line and suppressing power fluctuations of the power system including the DC transmission device. Fulfill.

The first series capacitor CAP1 acts so as to cancel out most of the inductance L of the AC transmission line, supplies the compensation current Ic to the second series capacitor CAP2 by the compensation current generator CIG, and applies it to the CAP2. By suppressing the power fluctuation of the AC transmission line by adjusting the applied voltage (compensation voltage) Vo, the capacity of the compensation current generator CIG can be further reduced.

When a ground fault or the like occurs in the system, most of the overcurrent at the time of the fault is caused by the second series capacitor C
It does not flow to AP2 and does not adversely affect the compensation current generator CIG.

Bypass circuit switches SW1 and SW2
When an earth fault or the like occurs in the system, the first series capacitor CAP1 and the second series capacitor CAP2 are short-circuited to restore the equivalent reactance X of the AC transmission line so that the current does not become excessive. At the same time, an overcurrent flows through the bypass circuit to
Protect IG.

FIG. 18 is a block diagram showing a series compensator in the system according to the fifth embodiment. In the figure, UVW
Is a three-phase AC transmission line, L is the inductance of the transmission line, C
AP1 is a first series capacitor, CAP2 is a second series capacitor, Tr is a series transformer, Lf is a filter reactor, VSI is a current control type inverter, Ed is a DC voltage source, CT and CTc are current detectors, and PT is a voltage. Detector,
DPD is a power detector, DPCNT is a power fluctuation suppression control circuit, AVR is a voltage control circuit, ACR is a current control circuit, P
WMC indicates a pulse width modulation (PWM) control circuit.

The primary side of the series transformer Tr is connected to the second
Is connected in parallel to the series capacitor CAP2, and a current control type inverter VSI of pulse width modulation control (PWM control) is connected to the secondary side via a filter reactor Lf.

The current control type inverter VSI is composed of self-turn-off devices S1 to S6 such as GTO, and diodes connected in anti-parallel to the respective devices, and is connected in a three-phase bridge. The current control type inverter VSI has a current command value I
cr and the detected value of the current Ic flowing through the filter reactor Lf are compared, and feedback control is performed. The output current Ic of the inverter is supplied to a second series capacitor CAP2, and a voltage V applied to the second series capacitor CAP2.
control o.

The voltage Vo applied to the second series capacitor CAP2 is determined by the sum of the current I flowing through the transmission line and the compensation current Ic, and becomes a compensation voltage as a series compensation device. Normally, the compensation voltage Vo generates a component orthogonal to the current I flowing through the transmission line, and adjusts the equivalent reactance of the transmission line.

On the other hand, when the transmission current I flows through the first series capacitor CAP1, a voltage is generated that cancels the voltage drop of the inductance L of the transmission line, and the first series capacitor CAP1 has a function of reducing the equivalent reactance X of the transmission line. I do.

Icb is a command value of a steady compensation current of the compensation current generator, and by adjusting this value, together with the first series capacitor CAP1, makes the equivalent reactance X of the transmission line almost zero. It can also be adjusted to be

On the other hand, when power fluctuation occurs in the transmission line,
The suppression control is performed as follows. That is, the current detector CT
And the voltage detector PT detect the three-phase AC voltage and current of the power transmission line, and use the detected power and the reactive power Q by the power detection circuit DPD. When power fluctuations occur, P and Q change. The fluctuations ΔP and ΔQ are extracted and given to the next power fluctuation suppression control circuit DPCNT. When the power fluctuation occurs, the compensation voltage Ica changes according to ΔP and ΔQ, and the power fluctuation is suppressed.

As the DC voltage source Ed, a separate power supply may be prepared, but here, the DC voltage source is made by itself. That is, a DC smoothing capacitor is prepared as a DC voltage source, and the applied voltage Ed is controlled to be constant.

First, the DC voltage command value Edr is compared with the DC voltage detection value Ed, and the deviation is compared with the DC voltage control circuit AVR.
Amplify with The output signal Ic1r of the AVR is obtained by giving a compensation current command of a component orthogonal to the current I flowing through the transmission line (in-phase or anti-phase component with respect to the voltage Vo applied to the second series capacitor CAP2). , DC voltage Ed.

FIG. 19 shows an equivalent circuit of a transmission line and a voltage / current vector diagram for explaining the operation of the system according to the fifth embodiment. In the figure, Vs is the voltage on the power transmission side, Vr is the voltage on the power reception side, L is the inductance of the transmission line, CAP1 is the first series capacitor, CAP2 is the second series capacitor, I is the transmission current, and Vo is the second current. Series capacitor CAP
2, an applied voltage (compensation voltage), Ic is a compensation current, and ω is a power supply angular frequency. The resistance of the transmission line is ignored because it is sufficiently small.

In the vector diagram of FIG. 19B, when the current I flows, a voltage drop of jωL · I occurs in the inductance L of the transmission line. The first series capacitor CAP1 is supplied with I / (jωC
The voltage of 1) is generated. Both act in a canceling direction, and the equivalent reactance of the transmission line decreases.

Further, the transmission current I
And the compensation current Ic having the same phase component as the second series capacitor CA
By supplying the voltage to P2, a voltage of Vo = (I + Ic) / (jωC2) is applied to the second series capacitor CAP2.

If the compensation current Ic is adjusted so that Vo = −j (ωL−1 / ωC) · I, the equivalent reactance X of the transmission line can be made almost zero, and the vector diagram of FIG. As described above, the power transmission side voltage Vs and the power reception side voltage Vr can be matched.

When power fluctuation occurs in the transmission line, a compensation current Ic is generated from the compensation current generator to suppress the fluctuation. In this system, the transmission current I flows through the first series capacitor CAP1, and is generated from the compensation current generator CIG if the first series capacitor CAP1 cancels out most of the inductance L of the transmission line. The stationary current Ic can be small, and the capacity of the power converter (current-type self-excited inverter or the like) used therein can be very small.

Even when an overcurrent flows through the transmission line due to a ground fault or the like, most of the overcurrent flows through the second series capacitor CAP2.
There is little effect on

FIG. 20 is a configuration diagram showing an AC / DC hybrid power transmission system according to the sixth embodiment of the present invention.
In the figure, G is a power station, SS1 and SS2 are substations, L is inductance of an AC transmission line, CAP11 and CAP12 are first series capacitors, CAP2 is a second series capacitor, CIG is a compensation current generator, SWl, SW2, SW
3 is a bypass circuit switch, HVDC is a DC power transmission device,
CNV indicates an AC / DC power converter, INV indicates a DC / AC power converter, and Ld indicates an inductance of a DC transmission line.

The substation SS1 is connected to a 50 Hz system, and the substation SS2 is connected to a 60 Hz system. The DC power transmission device HVDC connects the 50 Hz system and the 60 Hz system, and has a three-phase five-phase system using an AC / DC power converter CNV.
The AC power of 0 Hz is converted to DC power, transmitted via the transmission line Ld, and further converted to 3-phase 60 Hz AC power by the DC / AC power converter INV to supply power to the system of the substation SS2. .

First series capacitors CAP11, CAP
12, the second series capacitor CAP2 and the second
The compensation current generator CIG connected in parallel to the series capacitor CAP2 constitutes the series compensator of the present invention, reduces the equivalent reactance X of the AC transmission line, and suppresses the power fluctuation of the power system including the DC transmission device. Plays the role of suppressing.

First Series Capacitors CAP11, CAP
Reference numeral 12 acts to cancel most of the inductance L of the AC transmission line, and the second is provided by the compensation current generator CIG.
Supply the compensation current Ic to the series capacitor CAP2 of
By adjusting the voltage (compensation voltage) Vo applied to AP2, power fluctuation of the AC transmission line is suppressed. The capacity of the compensation current generator CIG can be further reduced.

If a ground fault or the like occurs in the system, most of the overcurrent at the time of the fault is caused by the second series capacitor C
It does not flow to AP2 and does not adversely affect the compensation current generator CIG.

When a ground fault or the like occurs in the system, the bypass circuit switches SW1, SW2, and SW3 short-circuit the first series capacitors CAP11, CAP12 and the second series capacitor CAP2 to short-circuit the equivalent reactance X of the AC transmission line. To prevent the current from becoming excessive, and protect the compensation current generator CIG by flowing an overcurrent through the bypass circuit.

Here, the first series capacitor is CAP
11 and CAP12, and they were separately arranged at two locations on the transmission line. That is, the inductance of the AC transmission line is a distributed constant, and the size and phase of the voltage of the AC transmission line are made uniform by arranging a series capacitor for compensating the inductance at a plurality of locations.

That is, the series capacitor CAP11 compensates for the inductance L1 of the transmission line, and
AP12 compensates for inductance L2. As a result, changes in the voltage phase and amplitude depending on the position of the AC transmission line are reduced, and stable power transmission capability can be improved.

FIG. 21 relates to claim 16 and claim 17, and is a configuration diagram showing a DC power transmission device constituting the AC / DC hybrid power transmission system of the present invention. In the figure, CNV is a self-excited AC / DC power converter, INV is a self-excited DC / AC power converter, PWRC is a power cable,
CF1 and CF2 are capacitors for harmonic filter, PWM
C1 and PWMC2 are pulse width modulation control (PWM control) circuits, IsC1 and IsC2 are AC current control circuits, and PQC
1 and PQC2 denote an active / reactive power control circuit, and IdC denotes a DC current control circuit.

CNV and INV are current type self-excited converters, and control respective input currents Is1 and Is2 by PWM control. The magnitudes and phases of the input currents Is1 and Is2 can be freely controlled. That is, in addition to controlling the active power P transmitted and received by DC power transmission, it is possible to separately control the reactive power on the AC side of each converter.

Thus, for example, the substation SS1 side (50 Hz system side) is adjusted while adjusting the active power P for DC transmission.
And the power factor can be improved. In other words, the phase of the voltage Vr and the phase of the current I can be matched in the voltage-current vector diagram of FIG.
Furthermore, the voltage Vs of the power plant is determined by the series compensator SCG.
In both cases, the phases can be matched.

Thus, the capacity of the power transmission equipment of the AC power system and the capacity of the generator itself can be greatly reduced, and an economical AC / DC hybrid power transmission system can be provided.

Although FIG. 21 shows a current-type self-excited converter, it is needless to say that the same effect can be obtained even if a DC power transmission device is constituted by a voltage-type self-excited converter.
If the transmission section has to run underground or under the sea, it is economical to connect with a power cable. In FIG. 21, power transmission is performed using a power cable PWRC as a DC transmission line. The power cable has a large floating capacitance between the ground and the ground, and a leading reactive current flows in the AC power transmission.
Therefore, the effect of the series compensator of the present invention is greatly exhibited by using the power cable in the DC power transmission section and connecting the AC power transmission section with an overhead line.

FIG. 22 relates to claims 18 and 20 and is a configuration diagram showing an AC / DC hybrid power transmission system according to a seventh embodiment of the present invention. In the figure,
G is a power station, SS1 and SS2 are substations, L is inductance of AC transmission lines, CAP1, CAP2, and CAP3 are series capacitors, SW1, SW2, and SW3 are bypass circuit switches, HVDC is a DC power transmission device, and CNV is AC / DC. A power converter, INV indicates a DC / AC power converter, and Ld indicates an inductance of a DC transmission line.

The substation SS1 is connected to a 50 Hz system, and the substation SS2 is connected to a 60 Hz system. The DC power transmission device HVDC connects the 50 Hz system and the 60 Hz system, and has a three-phase five-phase system using an AC / DC power converter CNV.
The AC power of 0 Hz is converted to DC power, transmitted via the transmission line Ld, and further converted to 3-phase 60 Hz AC power by the DC / AC power converter INV to supply power to the system of the substation SS2. .

Bypass circuit switches SW1, SW2, S
W3 is the series capacitors CAP1, CAP2, CAP3
Also serves as a switch to switch the number of input stages. That is, the series capacitors CAP1, CAP2, CAP3 are:
Usually, it acts to cancel most of the inductance L of the AC transmission line. However, if a ground fault or the like occurs in the system and power fluctuation occurs, the series capacitor CAP
The number of input stages of 1 to CAP3 is switched, and the equivalent reactance of the transmission line is changed to suppress the power fluctuation.

If a ground fault or the like occurs in the system and an overcurrent flows through the AC transmission line, the bypass circuit switches SW1
SW3 is turned on to suppress the overcurrent by restoring the equivalent reactance of the transmission line.

In FIG. 22, a self-excited converter is used as the power converter of the DC power transmitting device HVDC,
The reactive power on the AC side of each converter can be freely controlled. As a result, for example, the substation SS1 can be operated with a power factor of 1, and furthermore, if the equivalent reactance of the transmission line is almost zero-compensated by the series capacitors CAP1 to CAP3, the installed capacity of the AC transmission system can be improved. Can be reduced, and the capacity of the generator can be reduced.

Further, when power fluctuation occurs, if the reactive power control by the DC power transmitting device HVDC is performed simultaneously with switching of the number of stages of the series capacitors CAP1 to CAP3, the fluctuation can be suppressed more quickly.

FIG. 23 relates to claim 19,
FIG. 16 is a configuration diagram illustrating an AC / DC hybrid power transmission system according to an eighth embodiment of the present invention. In the figure, G is a power plant, SS
1, SS2 is a substation, L is the inductance of an AC transmission line, CAP1 and CAP2 are series capacitors, PCR is a phase control reactor, Th is a bidirectional thyristor, Lt is an AC reactor, HVDC is a DC power transmission device, and CNV is AC / DC. Power converter, INV is DC / AC power converter, L
d indicates the inductance of the DC transmission line.

The substation SS1 is connected to a 50 Hz system, and the substation SS2 is connected to a 60 Hz system. The DC power transmission device HVDC connects the 50 Hz system and the 60 Hz system, and has a three-phase five-phase system using an AC / DC power converter CNV.
The AC power of 0 Hz is converted to DC power, transmitted via the transmission line Ld, and further converted to 3-phase 60 Hz AC power by the DC / AC power converter INV to supply power to the system of the substation SS2. .

The phase control reactor PCR is composed of a bidirectional thyristor Th and an AC reactor Lt, and the equivalent capacitance can be continuously changed together with the second series capacitor CAP2 connected in parallel.

That is, by adjusting the firing phase angle of the thyristor, the current flowing through the reactor Lt can be controlled. When the current of Lt is small, the impedance becomes a capacitive impedance, and when the current of Lt is increased, And inductive impedance. Thereby, the equivalent reactance of the AC transmission line can be adjusted, and power fluctuation can be suppressed.

FIG. 24 relates to claim 21.
It is a lineblock diagram showing an AC / DC hybrid power transmission system of a ninth embodiment of the present invention. In the figure, G is a power plant, SS
1, SS2 is a substation, L1, L2 are inductances of AC transmission lines, CAP11, CAP12, CAP2 are series capacitors, PCR is a phase control reactor, Th is a bidirectional thyristor, Lt is an AC reactor, HVDC is a DC power transmission device, and CNV. Indicates an AC / DC power converter, INV indicates a DC / AC power converter, and Ld indicates an inductance of a DC transmission line.

The substation SS1 is connected to a 50 Hz system, and the substation SS2 is connected to a 60 Hz system. The DC power transmission device HVDC connects the 50 Hz system and the 60 Hz system, and has a three-phase five-phase system using an AC / DC power converter CNV.
The AC power of 0 Hz is converted to DC power, transmitted via the transmission line Ld, and further converted to 3-phase 60 Hz AC power by the DC / AC power converter INV to supply power to the system of the substation SS2. .

The first capacitors CAP1 and CAP2 are divided and disposed on the transmission line, and compensate for the transmission line inductances L1 and L2, respectively. Phase control reactor P
CR is a bidirectional thyristor Th and an AC reactor Lt
And a second series capacitor CA connected in parallel.
Together with P2, the equivalent capacitance can be changed continuously.

That is, by adjusting the firing phase angle of the thyristor, the current flowing through the reactor Lt can be controlled. When the current of Lt is small, the parallel circuit of the capacitor CAP2 and the phase control reactor PCR becomes capacitive. , And if the current of Lt is increased, the impedance becomes inductive. Thereby, the equivalent reactance of the AC transmission line can be adjusted, and power fluctuation can be suppressed.

The inductance of the AC transmission line is represented by a distribution constant. To compensate for the inductance,
The first series capacitor is divided and divided into several parts. Here, CAP11 and CAP12 are divided and arranged. As a result, changes in the voltage phase and amplitude depending on the position of the AC transmission line are reduced, and stable power transmission capability can be improved.

FIG. 25 is a configuration diagram showing an AC / DC hybrid power transmission system according to the tenth embodiment of the present invention. In the figure, G is a power plant, SS1 and SS2 are substations, L is the inductance of an AC transmission line, CAP1 and CAP2 are series capacitors, PCR1 and PCR2 are phase control reactors, Th1 and Th2 are bidirectional thyristors, Lt1 and Lt.
2 denotes an AC reactor, SW1 and SW2 denote bypass circuit switches, HVDC denotes a DC power transmission device, CNV denotes an AC / DC power converter, INV denotes a DC / AC power converter, and Ld denotes the inductance of the DC transmission line.

The substation SS1 is connected to a 50 Hz system, and the substation SS2 is connected to a 60 Hz system. The DC power transmission device HVDC connects the 50 Hz system and the 60 Hz system, and has a three-phase five-phase system using an AC / DC power converter CNV.
The AC power of 0 Hz is converted to DC power, transmitted via the transmission line Ld, and further converted to 3-phase 60 Hz AC power by the DC / AC power converter INV to supply power to the system of the substation SS2. .

The phase control reactor PCR1 comprises a bidirectional thyristor Th1 and an AC reactor Lt1.
Together with the first series capacitor CAP1 connected in parallel, the equivalent capacitance can be continuously changed. That is, by adjusting the firing phase angle of the thyristor Th1, the current flowing through the reactor Lt1 can be controlled. When the current of Lt1 is small, the impedance becomes a capacitive impedance. Impedance.

Similarly, the phase control reactor PCR2 is
A second series capacitor CAP2 configured by a bidirectional thyristor Th2 and an AC reactor Lt2 and connected in parallel
In addition, the equivalent capacitance can be continuously changed. Thereby, the equivalent reactance of the AC transmission line can be adjusted, and power fluctuation can be suppressed.

FIG. 26 is a configuration diagram showing an AC / DC hybrid power transmission system according to an eleventh embodiment of the present invention. In the figure, G is a power station, SS1 and SS2 are substations, L
1, L2 is the inductance of the AC transmission line, CAP1, C
AP2 is a series capacitor, PCR1 and PCR2 are phase control reactors, Th1 and Th2 are bidirectional thyristors, L
t1 and Lt2 are AC reactors, SW1 and SW2 are bypass circuit switches, HVDC is a DC power transmission device, CNV is an AC / DC power converter, INV is a DC / AC power converter, and Ld is the inductance of the DC transmission line.

[0219] The substation SS1 is connected to a 50 Hz system, and the substation SS2 is connected to a 60 Hz system. The DC power transmission device HVDC connects the 50 Hz system and the 60 Hz system, and has a three-phase five-phase system using an AC / DC power converter CNV.
The AC power of 0 Hz is converted to DC power, transmitted via the transmission line Ld, and further converted to 3-phase 60 Hz AC power by the DC / AC power converter INV to supply power to the system of the substation SS2. .

The phase control reactor PCR1 is composed of a bidirectional thyristor Th1 and an AC reactor Lt1,
Together with the first series capacitor CAP1 connected in parallel, the equivalent capacitance can be continuously changed.

That is, by adjusting the firing phase angle of thyristor Th1, the current flowing through reactor Lt1 can be controlled. When the current of Lt1 is small,
The impedance becomes capacitive, and if the current of Lt1 is increased, the impedance becomes inductive.

Similarly, the phase control reactor PCR2 is
A second series capacitor CAP2 configured by a bidirectional thyristor Th2 and an AC reactor Lt2 and connected in parallel
In addition, the equivalent capacitance can be continuously changed. Thereby, the equivalent reactance of the AC transmission line can be adjusted, and power fluctuation can be suppressed.

The inductance of an AC transmission line is represented by a distribution constant. To compensate for the inductance,
The series capacitor and the phase control reactor are divided and arranged in several parts. Here, it is divided into two parts. As a result, changes in the voltage phase and amplitude depending on the position of the AC transmission line are reduced, and stable power transmission capability can be improved.

[0224]

As described in detail above, in the AC / DC hybrid power transmission system of the present invention, the limit of the power transmission capacity in the AC power transmission section is improved, and the efficient operation of the AC / DC hybrid power transmission system becomes possible. In addition, DC power transmission is an economical power transmission system mainly for the AC transmission section by installing it in the minimum necessary power transmission section, such as when connecting AC systems with different frequencies or when transmitting power using submarine cables. Can be realized. Further, the existing transmission line can be used, and power can be transmitted over a long distance while supplying power to a load on the way. In addition, power fluctuations can be quickly suppressed, and an economical and highly reliable AC / DC hybrid power transmission system can be provided.

[Brief description of the drawings]

FIG. 1 is a configuration diagram showing an AC / DC hybrid power transmission system according to a first embodiment of the present invention.

FIG. 2 is a configuration diagram showing a series compensator in the system according to the first embodiment;

FIG. 3 is a voltage-current vector diagram for explaining the operation of the system according to the first embodiment.

FIG. 4 is a voltage-current vector diagram for explaining a power fluctuation suppressing operation of the system according to the first embodiment.

FIG. 5 is a voltage-current vector diagram for explaining a control operation of the series compensator of FIG. 2;

FIG. 6 is a configuration diagram showing an AC / DC hybrid power transmission system according to a second embodiment of the present invention.

FIG. 7 is a configuration diagram showing a series compensator in the system according to the second embodiment.

FIG. 8 is a voltage / current vector diagram for explaining the operation of the system according to the second embodiment.

FIG. 9 is a configuration diagram illustrating an AC / DC hybrid power transmission system according to a third embodiment of the present invention.

FIG. 10 is a configuration diagram showing an AC / DC hybrid power transmission system according to a fourth embodiment of the present invention.

FIG. 11 is a configuration diagram showing a series compensator in a system according to a fourth embodiment.

FIG. 12 is a voltage / current vector diagram for explaining the operation of the system according to the fourth embodiment.

FIG. 13 is another configuration diagram of the series compensator in the system according to the fourth embodiment.

FIG. 14 is a voltage-current vector diagram for explaining the operation of the series compensator of FIG. 13;

FIG. 15 is still another configuration diagram of the series compensator in the system according to the fourth embodiment.

FIG. 16 is still another configuration diagram of the series compensator in the system according to the fourth embodiment.

FIG. 17 is a configuration diagram illustrating an AC / DC hybrid power transmission system according to a fifth embodiment of the present invention.

FIG. 18 is a configuration diagram showing a series compensator in the system according to the fifth embodiment.

FIG. 19 is a voltage and current vector diagram for explaining the operation of the system according to the fifth embodiment.

FIG. 20 is a configuration diagram illustrating an AC / DC hybrid power transmission system according to a sixth embodiment of the present invention.

FIG. 21 is a configuration diagram showing a DC power transmission device included in the AC / DC hybrid power transmission system of the present invention.

FIG. 22 is a configuration diagram showing an AC / DC hybrid power transmission system according to a seventh embodiment of the present invention.

FIG. 23 is a configuration diagram showing an AC / DC hybrid power transmission system according to an eighth embodiment of the present invention.

FIG. 24 is a configuration diagram showing an AC / DC hybrid power transmission system according to a ninth embodiment of the present invention.

FIG. 25 is a configuration diagram showing an AC / DC hybrid power transmission system according to a tenth embodiment of the present invention.

FIG. 26 is a configuration diagram showing an AC / DC hybrid power transmission system according to an eleventh embodiment of the present invention.

FIG. 27 is a system configuration diagram showing the concept of conventional DC power transmission and AC power transmission.

FIG. 28 is a simplified equivalent circuit diagram for explaining the power transmission capability of a conventional AC transmission line, and a characteristic diagram showing the relationship between the transmitted power and the phase angle.

[Explanation of symbols]

G: Power station SS, SS1, SS2: Substation L, L1, L2: Inductance of AC transmission line SCG: Series compensation device HVDC: DC transmission device CNV: AC / DC power converter INV: DC / AC power converter Ld : DC transmission line inductance Tr: Series transformer VSI: Voltage source inverter Ed: DC voltage source DPD: Power detection circuit DPCNT: Power fluctuation suppression control circuit PWMC: Pulse width modulation control circuit AVR: DC voltage control circuit ACR: Compensation current Control circuits CAP, CAP1, CAP2, CAP3, CAP11,
CAP12: Series capacitor CVG: Compensation voltage generator SW, SW1, SW2, SW3, SWu, SWv, SW
w: bypass circuit switch CIG: compensation current generator CSI: current source self-excited inverter DCL: DC reactor (DC current source, superconducting coil) LCI: separately-excited inverter PHC: phase control circuit K: proportional constant Lf: AC reactor Bat: Storage battery (battery) PWRC: Power cable CF1, CF2: Harmonic filter capacitor PWM1, PWM2: Pulse width modulation control circuit IsC1, IsC2: AC current control circuit PQC1, PQC2: Active / reactive power control circuit IdC: DC current control circuit VdC : DC voltage control circuit PCR, PCR1, PCR2: Phase control reactor Th, Th1, Th2: Thyristor Lt, Lt1, Lt2: AC reactor TR1, TR2: Transformer X: Reactance of AC transmission line

 ──────────────────────────────────────────────────続 き Continued on the front page F-term (reference)

Claims (22)

[Claims] 1. A power transmission system comprising: a plurality of AC power systems; a DC power transmission device connecting the AC power systems; and a series compensator for generating a compensation voltage for adjusting an equivalent reactance of the AC power system. An AC-DC hybrid power transmission system characterized by the above-mentioned. 2. A plurality of AC power systems, a DC power transmission device connecting the AC power systems, and a series for adjusting an equivalent reactance of the AC power system and generating a compensation voltage for suppressing power fluctuation. An AC / DC hybrid power transmission system, comprising: a compensation device. 3. A plurality of AC power systems, a DC power transmission device connecting the AC power systems, and series compensation for generating a compensation voltage such that an equivalent reactance of a transmission line of the AC power system becomes substantially zero. An AC / DC hybrid power transmission system, comprising: 4. The series compensator according to claim 1, further comprising a circuit for bypassing the overcurrent when an overcurrent occurs due to a ground fault or the like of the transmission line. The AC / DC hybrid power transmission system according to any one of the above. 5. The series compensator according to claim 1, wherein the series compensator comprises a series transformer and a voltage source self-excited inverter connected to a secondary side of the transformer. 2. An AC / DC hybrid power transmission system according to (1). 6. The system according to claim 1, wherein the series compensator comprises a series capacitor and a compensation voltage generator connected in series to the series capacitor.
The AC / DC hybrid power transmission system according to any one of the above. 7. The AC / DC hybrid power transmission system according to claim 6, wherein the series capacitor is divided and arranged at a plurality of locations on the AC transmission line. 8. The alternating current according to claim 1, wherein the series compensator comprises a series capacitor and a compensation current generator connected in parallel to the series capacitor. DC hybrid power transmission system. 9. The series compensator includes a first series capacitor, a second series capacitor connected in series to the first series capacitor, and a compensation current connected in parallel to the second series capacitor. The AC / DC hybrid power transmission system according to any one of claims 1 to 4, comprising a generator. 10. The AC / DC hybrid power transmission system according to claim 8, wherein the compensation current generator is constituted by a current source self-excited converter. 11. The AC / DC hybrid power transmission system according to claim 8, wherein the compensation current generator is constituted by a current type separately excited converter. 12. The compensation current generator according to claim 8, wherein the compensation current generator comprises a current source self-excited converter, and a superconducting coil is used as a current source of the converter.
2. The AC / DC hybrid power transmission system according to 1. 13. The AC / DC hybrid power transmission system according to claim 8, wherein the compensation current generator is constituted by a current control type self-excited converter. 14. The alternating current according to claim 8, wherein the compensation current generating device comprises a current control type self-excited converter, and a storage battery is used as a voltage source of the converter. DC hybrid power transmission system. 15. The AC / DC hybrid power transmission system according to claim 9, wherein the first series capacitor is divided and arranged at a plurality of locations on the transmission line. 16. The DC power transmission device includes a self-excited AC / DC power converter, a DC transmission line, and a self-excited DC / AC power converter, and has a function of adjusting reactive power on the AC side. The AC / DC hybrid power transmission system according to any one of claims 1 to 15, wherein: 17. The AC / DC hybrid power transmission system according to claim 1, wherein the DC power transmission device has a DC transmission line formed of a power cable. 18. A plurality of AC power systems, a DC power transmission device connecting the AC power systems, a series capacitor divided into a plurality of components to compensate for an inductance of a transmission line of the AC power system, and An AC / DC hybrid power transmission system, comprising: switching means for changing the number of stages of input of a capacitor. 19. A plurality of AC power systems, a DC power transmission device connecting the AC power systems, a series capacitor for canceling most of an inductance of at least one transmission line of the AC power system, and a parallel connection to the capacitor. And a thyristor control reactor connected to the power transmission system. 20. The DC power transmission device includes a self-excited AC / DC power converter, a DC transmission line, and a self-excited DC / AC power converter, and has a function of adjusting reactive power on the AC side. 20. The method according to claim 18, wherein
2. The AC / DC hybrid power transmission system according to 1. 21. The transmission line according to claim 1, wherein the series capacitor is divided into a plurality of portions on the transmission line.
The AC / DC hybrid power transmission system according to any one of claims 8 to 20. 22. The AC / DC converter according to claim 18, wherein the series capacitor includes a circuit for short-circuiting an overvoltage or an overcurrent in the AC transmission line when the overvoltage or the overcurrent occurs. Hybrid power transmission system.