CN106130021B - A T-shaped hybrid flexible tuning device - Google Patents

Abstract

The invention provides a T-type hybrid flexible tuning device. The tuning device includes a static synchronous compensator STATCOM and/or a static synchronous series compensator SSSC; the static synchronous compensator STATCOM is connected in parallel to the power transmission between two inductive compensation units. Line, the static synchronous series compensator SSSC is connected in series to the transmission line on one side of the inductive compensation unit. Compared with the existing technology, the invention provides a T-shaped hybrid flexible tuning device that can flexibly adjust the output to adapt to changes in the structure, parameters and operating modes of the transmission line, ensuring that the transmission line exhibits the characteristics of a half-wavelength transmission system. At the same time, it can also have functions such as power factor compensation, flexible grid connection control, transient overvoltage suppression and steady-state voltage control.

Description

A T-shaped hybrid flexible tuning device

Technical field

The invention relates to the technical field of half-wavelength AC power transmission, and in particular to a T-shaped hybrid flexible tuning device.

Background technique

Half Wavelength AC Transmission (HWACT) refers to ultra-long-distance three-phase AC transmission whose electrical distance is close to one power frequency half-wavelength, that is, 3000km (50Hz) or 2600km (60Hz). With the increasing demand for ultra-long-distance and high-power transmission, half-wavelength AC transmission technology, especially UHV half-wavelength AC transmission, has once again received much attention and research. A lossless half-wavelength AC line is like an ideal transformer with a transformation ratio of -1.0. The voltage at the head end and the voltage at the end are the same and opposite in phase. At the same time, half-wavelength AC transmission technology also has the following advantages: First, the power factor of half-wavelength AC transmission lines is relatively high, and when the transmission distance is equal to or slightly larger than half-wavelength, its structure is better than the existing ultra-long-distance transmission lines. Both AC and DC transmission systems are simpler; furthermore, for developing countries, the manufacturing of AC transmission equipment is simpler and more economical than the introduction, operation and maintenance of converter devices.

Half-wavelength AC transmission lines are limited by objective conditions, and the natural length of the actual line is difficult to be exactly half a wavelength. When the line length is less than half a wavelength, a tuning circuit or a compensation circuit needs to be used to artificially compensate the electrical length of the transmission line to achieve the purpose of artificial half-wavelength AC transmission lines. Currently, existing half-wavelength AC transmission compensation solutions are based on passive networks for transmission line tuning, such as the T-shaped tuning device shown in Figure 1 and the π-shaped tuning device shown in Figure 2. However, these two tuning solutions have limited the development and application of half-wavelength AC transmission technology to a certain extent. First, the passive tuning circuit has relatively poor adaptability to changes in system structure, operation mode or parameters, and is prone to losing half-wavelength. Second, when a short-circuit fault occurs inside the passive tuning circuit, it is easy to cause resonance and generate an overvoltage with a very high amplitude. This requires the lines and equipment to improve the corresponding insulation requirements, or requires the installation of corresponding overvoltage limiting measures to suppress it. Line overvoltage.

Contents of the invention

In view of the shortcomings of passive tuning circuits in the prior art, the present invention provides a T-shaped hybrid flexible tuning device.

The technical solution of the present invention is:

The tuning device is installed in an AC transmission system and includes a capacitive compensation unit and two inductive compensation units; one end of the capacitive compensation unit is connected between the two inductive compensation units connected in series, and the other end is grounded;

The tuning device includes a static synchronous compensator STATCOM and/or a static synchronous series compensator SSSC;

The static synchronous compensator STATCOM is connected in parallel to the transmission line between the two inductive compensation units, and the static synchronous series compensator SSSC is connected in series to the transmission line on one side of the inductive compensation unit.

The preferred technical solution further provided by the present invention is: the combined configuration of the static synchronous compensator STATCOM and the static synchronous series compensator SSSC in the tuning device includes:

The first combination configuration mode: the tuning device only includes a set of static synchronous series compensators SSSC;

The second combination configuration mode: the tuning device only includes a set of static synchronous compensators STATCOM;

The third combination configuration mode: the tuning device includes a set of static synchronous series compensators SSSC and a set of static synchronous compensators STATCOM;

The fourth combination configuration mode: the tuning device includes two sets of static synchronous series compensators SSSC;

Fifth combination configuration mode: the tuning device includes two sets of static synchronous series compensators SSSC and one set of static synchronous compensators STATCOM.

The preferred technical solution further provided by the present invention is: the parallel connection method in which the static synchronous compensator STATCOM is connected to the transmission line includes:

The static synchronous compensator STATCOM is directly connected in parallel to the transmission line; or,

The static synchronous compensator STATCOM is connected in parallel to the transmission line through a transformer, and increases the capacitive output of the static synchronous compensator STATCOM.

The preferred technical solution further provided by the present invention is: the series connection method in which the static synchronous series compensator SSSC is connected to the transmission line includes:

The static synchronous series compensator SSSC is directly connected in series to the transmission line; or,

The static synchronous series compensator SSSC is connected in series to the transmission line through a transformer, and reduces the inductive output of the static synchronous series compensator SSSC.

The preferred technical solution further provided by the present invention is: when the tuning device is installed in an AC power transmission system, its configuration includes:

Configured at the sending end of the AC line; or,

Configured at the receiving end of the AC line; or,

Configured at the sending and receiving ends of the AC line; or,

Configured in the middle of the AC line.

The preferred technical solution further provided by the present invention is:

When the tuning device is configured at the sending end of the AC line, it performs flexible tuning control, flexible grid connection control, power factor compensation, transient overvoltage suppression and steady-state voltage control on the AC transmission system;

When the tuning device is configured at the AC line receiving end, it performs flexible tuning control, flexible grid connection control, transient overvoltage suppression and steady-state voltage control on the AC transmission system;

When the tuning device is configured in the middle section of an AC line, it performs flexible tuning control, transient overvoltage suppression and steady-state voltage control on the AC transmission system.

The preferred technical solution further provided by the present invention is: the tuning device performs flexible tuning control on the AC power transmission system so that it meets the requirements of the half-wavelength AC power transmission system, including:

The output of the static synchronous series compensator SSSC is equivalent to a series inductance/series reactance of the AC transmission system; the output of the static synchronous compensator STATCOM is equivalent to a parallel capacitance of the AC transmission system;

The static synchronous series compensator SSSC and the inductive compensation unit are controlled to jointly output the inductance value required by the half-wavelength AC transmission system; the static synchronous compensator STATCOM and the capacitive compensation unit are controlled to jointly output the half-wavelength AC power transmission system. Wavelength AC transmission system required capacitance value.

The preferred technical solution further provided by the present invention is: when the line structure, parameters and/or operation mode of the AC transmission system change, by adjusting the equivalent inductance value output by the static synchronous series compensator SSSC and the static synchronous The equivalent capacitance value output by the compensator STATCOM makes the inductance value and capacitance value of the AC power transmission system meet the requirements of the half-wavelength AC power transmission system.

The preferred technical solution further provided by the present invention is: after the tuning device performs flexible tuning on the AC power transmission system to make it meet the requirements of the half-wavelength AC power transmission system, the AC power transmission system performs flexible grid connection control, power factor compensation, temporary state overvoltage suppression and steady-state voltage control.

The preferred technical solution further provided by the present invention is: the tuning device includes two sets of static synchronous series compensators SSSC and a set of static synchronous compensators STATCOM. The device's flexible grid-connected control of the AC power transmission system includes:

The output of the static synchronous series compensator SSSC far away from the grid is equivalent to a series inductance/series reactance, and the output of the static synchronous series compensator SSSC close to the grid is equivalent to a series voltage to control the static synchronous series The equivalent voltage value output by the compensator SSSC makes the voltage and phase of the two AC power supplies connected to the grid the same;

When the equivalent voltage value output by the static synchronous series compensator SSSC close to the grid connection reaches its maximum value, the output of the static synchronous series compensator SSSC far away from the grid is adjusted to be equivalent to a series voltage. The two static synchronous series compensators SSSC jointly control the connection of the AC power supply to the grid.

The preferred technical solution further provided by the present invention is: in the process of the tuning device performing flexible grid connection control on the AC power transmission system:

When the AC transmission system is connected to the grid and transitions from transient operation to steady-state operation, the output of the static synchronous series compensator SSSC is equivalent to a series inductance/series reactance, and the static synchronous series compensator is controlled. SSSC and the inductive compensation unit jointly output the inductance value required by the half-wavelength AC transmission system;

During the grid connection of the AC transmission system and the transition from transient operation to steady state operation, the equivalent capacitance value output by the static synchronous compensator STATCOM is adjusted to reduce the occurrence of disturbance at the grid connection.

The preferred technical solution further provided by the present invention is that the flexible grid connection method of the tuning device includes:

After the sending end AC power supply is connected to the AC power transmission system, the AC power transmission system is then connected to the grid with the receiving end AC power supply;

or,

After the AC power supply at the receiving end is connected to the AC power transmission system, the AC power transmission system is connected to the grid with the AC power supply at the sending end.

The preferred technical solution further provided by the present invention is: the tuning device is installed at the sending end of the AC line, and the power factor compensation for the AC transmission system includes:

The output of the static synchronous compensator STATCOM is equivalent to a parallel capacitor, and the equivalent capacitance value output by the static synchronous compensator STATCOM is controlled to compensate the reactive power of the AC transmission system.

The preferred technical solution further provided by the present invention is that the tuning device's transient overvoltage suppression of the AC power transmission system includes:

The output of the static synchronous compensator STATCOM is equivalent to a parallel reactance, and the static synchronous compensator STATCOM is controlled to absorb the reactive power of the AC transmission system to suppress the power frequency overvoltage of the line.

The preferred technical solution further provided by the present invention is: the tuning device's steady-state voltage control of the AC power transmission system includes:

When the line voltage of the AC transmission system is low, the output of the static synchronous compensator STATCOM is equivalent to a parallel capacitor, and the equivalent capacitance value output by the static synchronous compensator STATCOM is controlled to compensate the reactive power of the AC transmission system. , to support the line voltage;

When the line voltage of the AC transmission system is high, the output of the static synchronous compensator STATCOM is equivalent to a parallel capacitor with a small capacitance, or equivalent to a parallel inductance/reactance, and the static synchronous compensator is controlled. The equivalent capacitance value or equivalent inductance value output by STATCOM compensates the reactive power of the AC transmission system to support the line voltage.

The preferred technical solution further provided by the present invention is: the output of the static synchronous compensator STATCOM includes a basic output and an additional output;

The basic output is determined based on the requirements of the static synchronous compensator STATCOM for flexible tuning control of the AC power transmission system and the parallel connection mode of accessing the AC power transmission system;

The additional output is determined based on the requirements of the static synchronous compensator STATCOM for flexible grid connection control, power factor compensation, transient overvoltage suppression and steady-state voltage control of the AC transmission system.

The preferred technical solution further provided by the present invention is: the output of the static synchronous series compensator SSSC includes a basic output and an additional output;

The basic output is determined based on the requirements for flexible tuning control of the AC power transmission system by the static synchronous series compensator SSSC and the series connection mode of the AC power transmission system;

The additional output is controlled by flexible grid connection of the AC power transmission system according to the static synchronous series compensator SSSC.

The preferred technical solution further provided by the present invention is that when the tuning device includes two sets of static synchronous series compensators SSSC, the outputs of the two sets are the same or different.

Compared with the closest existing technology, the beneficial effects of the present invention are:

1. The present invention provides a T-type hybrid flexible tuning device. Its static synchronous compensator STATCOM and static synchronous series compensator SSSC can flexibly adjust their respective outputs to adapt to changes in the structure, parameters and operating modes of the transmission line, ensuring that The transmission line exhibits the characteristics of a half-wavelength transmission system, and can also have functions such as power factor compensation, flexible grid connection control, transient overvoltage suppression, and steady-state voltage control;

2. The T-type hybrid flexible tuning device provided by the present invention can flexibly adjust the voltage and phase of the half-wavelength transmission line through the static synchronous series compensator SSSC and the static synchronous compensator STATCOM compared to the ordinary power system grid connection method. , therefore, flexible grid connection only needs to pay attention to the voltage phase sequence and frequency, thereby reducing the increased workload of adjusting the voltages and phases of the two AC systems/AC power supplies to be connected to the grid, and reducing the technology required for grid connection. Require.

Description of the drawings

Figure 1: Schematic diagram of T-shaped tuning device;

Figure 2: Schematic diagram of π-type tuning device;

Figure 3: Schematic diagram of a T-shaped hybrid flexible tuning device in an embodiment of the present invention;

Figure 4: Schematic diagram of the T-shaped hybrid flexible tuning device configured at the sending end and receiving end of the AC line in the embodiment of the present invention;

Figure 5: Schematic diagram of a T-shaped hybrid flexible tuning device configured in the middle section of an AC line in an embodiment of the present invention.

Detailed ways

In order to make the purpose, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments These are some embodiments of the present invention, rather than all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts fall within the scope of protection of the present invention.

A T-shaped hybrid flexible tuning device provided by an embodiment of the present invention will be described below with reference to the accompanying drawings.

Figure 3 is a schematic diagram of a T-type hybrid flexible tuning device in an embodiment of the present invention. As shown in the figure, the tuning device in this embodiment includes a capacitive compensation unit, two inductive compensation units, a static synchronous compensator STATCOM and/or In the static synchronous series compensator SSSC, one end of the capacitive compensation unit is connected between two inductive compensation units in series, and the other end is grounded. in,

The capacitive compensation unit includes a parallel capacitor, and the inductive compensation unit includes a series inductor;

The static synchronous compensator STATCOM is connected in parallel to the transmission line between the two inductive compensation units;

The static synchronous series compensator SSSC is connected in series to the transmission line on one side of the inductive compensation unit.

In the tuning device of the present invention, the static synchronous compensator STATCOM and the static synchronous series compensator SSSC include five combination configuration modes, specifically:

The first combination configuration mode: the tuning device only includes a set of static synchronous series compensators SSSC;

The second combination configuration mode: the tuning device only includes a set of static synchronous compensators STATCOM;

The third combination configuration mode: the tuning device includes a set of static synchronous series compensators SSSC and a set of static synchronous compensators STATCOM;

The fourth combination configuration mode: the tuning device includes two sets of static synchronous series compensators SSSC;

The fifth combination configuration mode: the tuning device includes two sets of static synchronous series compensators SSSC and one set of static synchronous compensators STATCOM.

In the present invention, the parallel connection method of connecting the static synchronous compensator STATCOM to the transmission line includes:

(1) The static synchronous compensator STATCOM is directly connected in parallel to the transmission line.

(2) The static synchronous compensator STATCOM is connected in parallel to the transmission line through a transformer, and the capacitive output of the static synchronous compensator STATCOM is increased. In this embodiment, the voltage level of the half-wavelength transmission line is relatively high. The static synchronous compensator STATCOM is connected to the transmission line through the step-up transformer. At the same time, when the static synchronous compensator STATCOM is connected to the transmission line through the transformer, the short-circuit impedance of the transformer is equal to The value of the parallel capacitor is reduced, so the capacitive output of the static synchronous compensator STATCOM needs to be increased accordingly.

In the present invention, the series connection method of the static synchronous series compensator SSSC connected to the transmission line includes:

(1) The static synchronous series compensator SSSC is directly connected in series to the transmission line.

(2) The static synchronous series compensator SSSC is connected in series to the transmission line through a transformer, and the inductive output of the static synchronous series compensator SSSC is reduced. In this embodiment, the line current of the half-wavelength transmission line is relatively large. The static synchronous series compensator SSSC is connected to the transmission line through the transformer. At the same time, when the static synchronous series compensator SSSC is connected to the transmission line through the transformer, the leakage inductance of the transformer increases. The value of the series inductance, therefore, can correspondingly reduce the inductive output of the static synchronous series compensator SSSC.

When the tuning device in the present invention is installed in an AC transmission system, it includes five configuration modes, specifically:

(1) Configured at the sending end of the AC line.

In this embodiment, when the tuning device is configured at the transmitting end of the AC line, it performs flexible tuning control, flexible grid connection control, power factor compensation, transient overvoltage suppression and steady-state voltage control on the AC transmission system.

(2) Configured at the receiving end of the AC line.

Figure 4 is a schematic diagram of the T-type hybrid flexible tuning device configured at the sending end and receiving end of the AC line in an embodiment of the invention. As shown in the figure, in this embodiment, when the tuning device is configured at the receiving end of the AC line, the AC power transmission system is Flexible tuning control, flexible grid-connected control, transient overvoltage suppression and steady-state voltage control.

(3) Configured at the sending end and receiving end of the AC line.

(4) Disposed in the middle section of the AC line.

Figure 5 is a schematic diagram of the T-shaped hybrid flexible tuning device configured in the middle section of the AC line in an embodiment of the present invention. As shown in the figure, in this embodiment, when the tuning device is configured in the middle section of the AC line, flexible tuning control is performed on the AC power transmission system. Transient overvoltage suppression and steady-state voltage control.

In the present invention, the tuning device performs flexible tuning on the AC transmission system to make it meet the requirements of the half-wavelength AC transmission system, and then performs flexible grid connection control, power factor compensation, transient overvoltage suppression and steady-state voltage control on the AC transmission system. The following are detailed descriptions of flexible tuning control, flexible grid-connected control, power factor compensation, transient overvoltage suppression and steady-state voltage control.

1. Flexible tuning control

In this embodiment, the tuning device performs flexible tuning control on the AC power transmission system to make it meet the requirements of the half-wavelength AC power transmission system, specifically including:

Step S11: Perform inductive adjustment on the static synchronous series compensator SSSC, and make its output equivalent to a series inductance/series reactance of the AC transmission system; perform capacitive adjustment on the static synchronous series compensator STATCOM, and make its output equivalent to the AC transmission system. A parallel capacitor of the system;

Step S12: Control the static synchronous series compensator SSSC and the inductive compensation unit to jointly output the inductance value required by the half-wavelength AC transmission system; control the static synchronous compensator STATCOM and the capacitive compensation unit to jointly output the inductance value required by the half-wavelength AC transmission system. capacitance value.

It should be noted:

When the line structure, parameters and/or operation mode of the AC transmission system change, the equivalent inductance value output by the static synchronous series compensator SSSC and the equivalent capacitance value output by the static synchronous series compensator STATCOM are adjusted, so that the total capacitance value The inductance value satisfies the tuning of the half-wavelength AC transmission system, and finally the entire system exhibits the characteristics of the half-wavelength AC transmission system, that is, flexible tuning is achieved.

2. Flexible grid-connected control

The power system grid connection mainly includes four conditions, specifically:

(1) The frequency of the two AC systems/AC power supplies connected to the grid is the same.

(2) The voltages of the two grid-connected AC systems/AC power supplies are the same, and the maximum deviation should be within 5%.

(3) The phase sequence of the two AC systems/AC power supplies connected to the grid is the same.

(4) The voltage phases of the two AC systems/AC power supplies connected to the grid are the same.

The following describes the flexible grid-connected control using the tuning device shown in Figure 3. It is assumed that the AC transmission system in this embodiment meets the power system grid connection conditions (1) and (3), and the tuning device includes two sets of static synchronous series compensators SSSC and one set of static synchronous compensators STATCOM. The device performs flexible grid connection control on the AC transmission system, including:

The static synchronous series compensator SSSC far away from the grid is inductively adjusted, and its output is equivalent to a series inductance/series reactance. The output of the static synchronous series compensator SSSC close to the grid is equivalent to a series voltage. Control The equivalent voltage value output by the static synchronous series compensator SSSC makes the voltage and phase of the two AC power sources connected to the grid the same. In this embodiment, an AC system/AC power supply to be connected to the grid is added with the equivalent voltage output by the static synchronous series compensator SSSC, so that the voltage phases of the two AC systems/AC power supplies to be connected to the grid are consistent, thereby meeting the requirements of the parallelism of the power system. Four conditions of the net.

The flexible grid connection method of the tuning device in this embodiment includes:

After the sending-side AC power supply is connected to the AC transmission system, the AC transmission system is then connected to the grid with the receiving-side AC power supply; or, after the receiving-side AC power supply is connected to the AC transmission system, the AC transmission system is then connected to the grid with the sending-side AC power supply.

It should be noted:

(1) When the equivalent voltage value output by the static synchronous series compensator SSSC close to the grid connection reaches its maximum value, adjust the output of the static synchronous series compensator SSSC far away from the grid connection to be equivalent to one series voltage, two The static synchronous series compensator SSSC jointly controls the AC power grid connection.

(2) When the AC transmission system is connected to the grid and transitions from transient operation to steady state operation, the output of the static synchronous series compensator SSSC is equivalent to a series inductance/series reactance, and the static synchronous series compensator SSSC and inductance are controlled The compensation unit jointly outputs the inductance value required by the half-wavelength AC transmission system;

During the grid-connection of the AC transmission system and the transition from transient operation to steady-state operation, the equivalent capacitance value output by the static synchronous compensator STATCOM is adjusted to reduce the occurrence of disturbances at the grid connection.

Compared with the ordinary power system grid connection method, the flexible grid connection control in this embodiment can flexibly adjust the voltage and phase of the half-wavelength transmission line through the static synchronous series compensator SSSC and the static synchronous compensator STATCOM. Therefore, flexible grid connection only needs to pay attention to the voltage phase sequence and frequency, thereby reducing the increased workload of adjusting the voltage and phase consistency of the two AC systems/AC power supplies to be connected to the grid, and reducing the technical requirements for grid connection.

3. Power factor compensation

The following describes the flexible grid-connected control using the tuning device shown in Figure 3. It is assumed that the tuning device is installed at the sending end of the AC line. The device's power factor compensation for AC transmission systems includes:

The output of the static synchronous compensator STATCOM is equivalent to a parallel capacitor, and the equivalent capacitance value output by the static synchronous compensator STATCOM is controlled to compensate the reactive power of the AC transmission system.

It should be noted that when the power factor of the sending end AC power supply changes, the output of the static synchronous compensator STATCOM can be adjusted so that the parallel capacitor and the static synchronous compensator STATCOM can meet the requirements of flexible tuning and power factor compensation at the same time.

4. Transient overvoltage suppression

The following describes the flexible grid-connected control using the tuning device shown in Figure 3. The device's transient overvoltage suppression on the AC transmission system includes:

The output of the static synchronous compensator STATCOM is equivalent to a parallel reactance, and the static synchronous compensator STATCOM is controlled to absorb the reactive power of the AC transmission system to suppress the power frequency overvoltage of the line.

For example, when a single-phase ground fault occurs in an AC transmission system or a three-phase load shedding occurs at the terminal, causing power frequency overvoltage, the tuning device can be used to suppress transient overvoltage.

5. Steady-state voltage control

The following describes the flexible grid-connected control using the tuning device shown in Figure 3. The device's steady-state voltage control of the AC transmission system includes:

When the line voltage of the AC transmission system is low, the output of the static synchronous compensator STATCOM is equivalent to a parallel capacitor, and the equivalent capacitance value output by the static synchronous compensator STATCOM is controlled to compensate the reactive power of the AC transmission system to support the line. Voltage;

When the line voltage of the AC transmission system is high, the output of the static synchronous compensator STATCOM is equivalent to a parallel capacitor with a small capacitance, or equivalent to a parallel inductance/reactance, and the output of the static synchronous compensator STATCOM is controlled. The effective capacitance value or equivalent inductance value compensates the reactive power of the AC transmission system to support the line voltage.

The output of the static synchronous compensator STATCOM in the present invention includes basic output and additional output, where:

The basic output is determined based on the requirements of the static synchronous compensator STATCOM for flexible tuning control of the AC transmission system and its parallel connection to the AC transmission system.

The additional output is determined based on the requirements of the static synchronous compensator STATCOM for flexible grid connection control, power factor compensation, transient overvoltage suppression and steady-state voltage control of the AC transmission system. For example, the additional output can be determined based on the requirements of any one, two, three or four of flexible grid control, power factor compensation, transient overvoltage suppression and steady-state voltage control.

It should be noted that when the two sets of static synchronous series compensators SSSC of the tuning device shown in Figure 3 are used, the outputs of the two sets are the same or different.

The output of the static synchronous series compensator SSSC in the present invention includes the basic output and the additional output, where:

The basic output is determined based on the requirements of the static synchronous series compensator SSSC for flexible tuning control of the AC transmission system and the series connection mode of the AC transmission system.

Based on the static synchronous series compensator SSSC, the AC transmission system is flexibly connected to the grid to control the additional output.

The static synchronous compensator STATCOM and the static synchronous series compensator SSSC of a T-type hybrid flexible tuning device provided by the invention can flexibly adjust their respective outputs to adapt to changes in the structure, parameters and operating modes of the transmission line, ensuring that the transmission line appears It has the characteristics of half-wavelength transmission system and can also have passive tuning circuits such as power factor compensation, flexible grid connection control, transient overvoltage suppression and steady-state voltage control.

Obviously, those skilled in the art can make various changes and modifications to the present invention without departing from the spirit and scope of the invention. In this way, if these modifications and variations of the present invention fall within the scope of the claims of the present invention and equivalent technologies, the present invention is also intended to include these modifications and variations.

Claims (15)

1. A T-shaped hybrid flexible tuning device which is arranged in an alternating current transmission system; the tuning device comprises a capacitive compensation unit and two inductive compensation units; one end of the capacitive compensation unit is connected between the two inductive compensation units in series, and the other end of the capacitive compensation unit is grounded; it is characterized in that the method comprises the steps of,

the tuning device comprises a static synchronous compensator STATCOM and/or a static synchronous series compensator SSSC;

the static synchronous compensator STATCOM is connected in parallel to a power transmission line between the two inductive compensation units, and the static synchronous series compensator SSSC is connected in series to the power transmission line at one side of the inductive compensation units;

after the tuning device flexibly tunes the alternating current power transmission system to meet the requirement of the half-wavelength alternating current power transmission system, the alternating current power transmission system is subjected to flexible grid-connected control, power factor compensation, transient overvoltage suppression and steady-state voltage control;

the tuning device comprises two groups of static synchronous series compensators SSSC and a group of static synchronous compensators STATCOM, and the device for flexibly controlling grid connection of an alternating current transmission system comprises the following steps:

the output of the static synchronous series compensator SSSC far away from the grid connection is equivalent to a series inductance/series reactance, the output of the static synchronous series compensator SSSC close to the grid connection is equivalent to a series voltage, and the equivalent voltage value output by the static synchronous series compensator SSSC is controlled so that the voltages of two AC power supplies connected in the grid are identical and the phases are identical;

when the equivalent voltage value output by the static synchronous series compensator SSSC close to the grid connection position reaches the maximum value, the output of the static synchronous series compensator SSSC far away from the grid connection position is adjusted to be equivalent to one series voltage, and the two static synchronous series compensatorSSSCs jointly control the AC power supply to grid connection.

2. A T-hybrid flexible tuning device as claimed in claim 1, wherein the parallel connection of the static synchronous compensator STATCOM to the transmission line comprises:

the static synchronous compensator STATCOM is directly connected in parallel to the power transmission line; or,

the static synchronous compensator STATCOM is connected in parallel to the power transmission line through a transformer, and the capacity output quantity of the static synchronous compensator STATCOM is increased.

3. A T-hybrid flexible tuning device as defined in claim 1, wherein the serial connection of the static synchronous serial compensator SSSC to the transmission line comprises:

the SSSC is directly connected in series with the power transmission line; or,

the SSSC is connected in series with the power transmission line through a transformer, and the inductive output quantity of the SSSC is reduced.

4. A T-hybrid flexible tuning device as defined in claim 1, wherein said tuning device is configured for installation in an ac power transmission system in a manner comprising:

a transmitting end arranged on the alternating current circuit; or,

the receiving end is configured on the alternating current circuit; or,

the power supply device is arranged at a transmitting end and a receiving end of the alternating current circuit; or,

is arranged in the middle section of the alternating current circuit.

5. A T-hybrid flexible tuning device as defined in claim 4, wherein,

when the tuning device is configured at the transmitting end of the alternating current line, flexible tuning control, flexible grid-connected control, power factor compensation, transient overvoltage suppression and steady-state voltage control are carried out on the alternating current transmission system;

when the tuning device is configured at the receiving end of the alternating current line, flexible tuning control, flexible grid-connected control, transient overvoltage suppression and steady-state voltage control are carried out on the alternating current transmission system;

when the tuning device is configured in the middle section of the alternating current line, flexible tuning control, transient overvoltage suppression and steady-state voltage control are performed on the alternating current transmission system.

6. The T-hybrid flexible tuning device of claim 1, wherein the tuning device flexibly tunes the ac power transmission system to meet the requirements of the half-wavelength ac power transmission system, comprising:

equivalent the output of the static synchronous series compensator SSSC to a series inductance/series reactance of the ac transmission system; equivalent the output of the static synchronous compensator STATCOM as a parallel capacitor of the alternating current transmission system;

controlling the static synchronous series compensator SSSC and the inductive compensation unit to jointly output an inductance value required by the half-wavelength alternating current transmission system; and controlling the static synchronous compensator STATCOM and the capacitive compensation unit to jointly output a capacitance value required by the half-wavelength alternating current transmission system.

7. A T-hybrid flexible tuning device as claimed in claim 6, wherein when the line structure, parameters and/or operation mode of the ac power transmission system are changed, the inductance value and capacitance value of the ac power transmission system are made to meet the requirement of the half-wavelength ac power transmission system by adjusting the equivalent inductance value output by the SSSC and the equivalent capacitance value output by the STATCOM.

8. The T-type hybrid flexible tuning device of claim 1, wherein during flexible grid-tie control of the ac power transmission system by the tuning device:

when the grid connection of the alternating current transmission system is completed and the transient operation is transited to the steady operation, the output of the static synchronous series compensator SSSC is equivalent to a series inductance/series reactance, and the static synchronous series compensator SSSC and the inductive compensation unit are controlled to jointly output the inductance value required by the half-wavelength alternating current transmission system;

and in the process of grid connection of the alternating current transmission system and transition from transient operation to steady operation, adjusting an equivalent capacitance value output by the static synchronous compensator STATCOM so as to reduce disturbance at the grid connection.

9. The T-hybrid flexible tuning device of claim 1, wherein the flexible grid-tie of the tuning device comprises:

after the transmitting end alternating current power supply is connected with the alternating current power transmission system, the alternating current power transmission system is connected with the receiving end alternating current power supply in a grid mode; or after the receiving end alternating current power supply is connected into the alternating current power transmission system, the alternating current power transmission system is connected with the transmitting end alternating current power supply in a grid mode.

10. The T-hybrid flexible tuning device of claim 1, wherein the tuning device is mounted at a feed end of an ac line, and wherein power factor compensation of the ac power transmission system comprises:

and (3) equivalent output of the static synchronous compensator STATCOM is equivalent to a parallel capacitor, and the equivalent capacitance value of the output of the static synchronous compensator STATCOM is controlled to compensate reactive power of an alternating current transmission system.

11. A T-hybrid flexible tuning device as defined in claim 1, wherein said tuning device for transient overvoltage suppression of an ac power transmission system comprises:

and (3) equivalent the output of the static synchronous compensator STATCOM to be a parallel reactance, and controlling the static synchronous compensator STATCOM to absorb reactive power of an alternating current transmission system so as to inhibit power frequency overvoltage of a line.

12. A T-hybrid flexible tuning device as defined in claim 1, wherein said tuning device for steady state voltage control of an ac power transmission system comprises:

when the line voltage of the alternating current transmission system is lower, the output of the static synchronous compensator STATCOM is equivalent to a parallel capacitor, and the equivalent capacitance value output by the static synchronous compensator STATCOM is controlled to compensate reactive power of the alternating current transmission system so as to support the line voltage;

when the line voltage of the alternating current transmission system is higher, the output of the static synchronous compensator STATCOM is equivalent to a parallel capacitor with a smaller capacitance value or equivalent to a parallel inductor/reactance, and the equivalent capacitance value or equivalent inductance value output by the static synchronous compensator STATCOM is controlled to compensate the reactive power of the alternating current transmission system so as to support the line voltage.

13. A T-hybrid flexible tuning device as in claim 1, wherein the output of the static synchronous compensator STATCOM comprises a base output and an additional output;

determining the basic output quantity according to the requirement of the static synchronous compensator STATCOM on flexible tuning control of the alternating current transmission system and the parallel connection mode of the static synchronous compensator STATCOM to the alternating current transmission system;

and determining the additional output quantity according to the requirements of the static synchronous compensator STATCOM on flexible grid-connected control, power factor compensation, transient overvoltage suppression and steady-state voltage control of the alternating current transmission system.

14. A T-hybrid flexible tuning device as in claim 1, wherein the output of the static synchronous series compensator SSSC comprises a base output and an additional output;

determining the basic output quantity according to the requirement of the static synchronous series compensator SSSC on flexible tuning control of the alternating current transmission system and the series connection mode of the static synchronous series compensator SSSC connected to the alternating current transmission system;

and carrying out flexible grid-connected control on the alternating current transmission system according to the static synchronous series compensator SSSC to determine the additional output quantity.

15. A T-hybrid flexible tuning device as claimed in claim 1, wherein the tuning device comprises two sets of static synchronous series compensators SSSC, the outputs of which are the same or different.