New energy power transmission system and control method

Abstract

The invention relates to the technical field of power transmission, in particular to a new energy power transmission system and a control method. The new energy power transmission system comprises a series compensation module which is connected in series with a power transmission line and is used for compensating line inductive reactance through capacitive reactance; the oscillation suppression module is connected with the series compensation module and used for suppressing line oscillation, the oscillation suppression module comprises a plurality of unit valve groups connected in series, and each unit valve group comprises a current conversion unit and a control unit; the control unit is used for collecting the energy storage voltage and the non-fundamental current and outputting a starting signal; and the commutation unit is used for injecting an oscillation suppression signal to the power transmission line according to the starting signal. Line inductive reactance is compensated through capacitive reactance of the series compensation module, and the short-circuit capacity of a grid-connected point is improved; the non-fundamental current of the line is detected through the oscillation suppression module, power oscillation is suppressed under the condition that the oscillation current exceeds a preset value, and the problems of insufficient short-circuit ratio and power oscillation of the new energy multi-field station of the long-distance transmission line in a remote area are effectively solved.

Description

Technical Field

[0001] The present application relates to the field of power transmission technology, and in particular to a new energy power transmission system and a control method. Background Art

[0002] With the large-scale integration of renewable energy sources into the grid, the proportion of renewable energy stations continues to increase, squeezing the market for traditional synchronous generators. The short-circuit ratio is a key indicator for measuring the strength of the AC grid in power systems, reflecting the grid's ability to support renewable energy sites. It is defined as the ratio of the AC system's short-circuit capacity to the rated capacity of the grid-connected equipment. Some renewable energy sites are located at a considerable electrical distance from the grid. When the renewable energy system output is high and the synchronous generator power supply is low, some renewable energy sites with weak connections to the grid face the problem of the short-circuit ratio of multiple renewable energy sites not meeting grid connection requirements.

[0003] Generally, new energy stations whose short-circuit ratios do not meet the requirements have similar characteristics, namely, the new energy stations are geographically relatively remote, and long-distance AC lines are usually connected to the grid, resulting in the short-circuit ratio not meeting the requirements. In addition, when the short-circuit ratio is less than 2.0, the system inertia is low and the damping is weak, and the output fluctuations of the new energy stations, such as wind speed changes and photovoltaic irradiation fluctuations, are prone to excite line power oscillations. Summary of the Invention

[0004] The embodiment of the present application aims to provide a new energy power transmission system and control method to solve the technical problems in the prior art of insufficient short-circuit ratio of the grid-connected side of multiple new energy stations and the susceptibility to power oscillation.

[0005] In order to solve the above technical problems, the embodiments of the present application disclose the following technical solutions: In a first aspect, an embodiment of the present application provides a new energy power transmission system, which is provided on a transmission line between a grid connection point of a new energy station and a power grid, comprising: A series compensation module, connected in series to the transmission line, for compensating the line inductive reactance through capacitive reactance; an oscillation suppression module connected to the series compensation module and configured to suppress line oscillations, the oscillation suppression module comprising a plurality of unit valve groups connected in series, one of the unit valve groups comprising a commutation unit and a control unit connected in parallel; The control unit is used to collect the energy storage voltage of the unit valve group and the non-fundamental current on the transmission line, and generate a start signal when the energy storage voltage reaches a set voltage and the non-fundamental current exceeds a preset value; The commutation unit is configured to receive the start signal and inject an oscillation suppression signal into the transmission line according to the start signal.

[0006] In one embodiment of the present application, the unit valve group also includes a bypass switch connected in parallel with the converter unit. In a shutdown situation, the control unit generates a shutdown signal to drive the bypass switch to close and withdraw the converter unit from the transmission line; the shutdown situation includes: the energy storage voltage does not reach the set voltage or is abnormal, the non-fundamental current does not exceed the preset value, and the control unit receives at least one of a shutdown instruction.

[0007] In one embodiment of the present application, the bypass switch includes a mechanical bypass switch and a thyristor bypass switch connected in parallel.

[0008] In one embodiment of the present application, an energy storage unit is further included, which is connected in series on the DC side of the unit valve group and is used to provide the energy storage voltage to the unit valve group. The energy storage unit includes a plurality of electrochemical energy storage batteries connected in series.

[0009] In one embodiment of the present application, the commutation unit is a fully controlled IGBT commutation circuit.

[0010] In one embodiment of the present application, the series compensation module includes a capacitor bank and a protection device. The capacitor bank is switchably connected in series with the power transmission line, and the protection device is connected in parallel with the capacitor bank for overvoltage protection.

[0011] In one embodiment of the present application, the capacitive reactance value of the capacitor bank is 30% to 60% of the total inductive reactance value of the transmission line.

[0012] In one embodiment of the present application, when the new energy station is fully powered, the short-circuit ratio of the grid connection point is lower than 2.0 or the short-circuit ratio of the boost-to-low voltage side is lower than 1.5.

[0013] In a second aspect, an embodiment of the present application provides a new energy power transmission control method, comprising: Compensate for the inductive reactance of the transmission line; collecting the non-fundamental current and the energy storage voltage of the transmission line, and generating a start signal when the energy storage voltage reaches a set voltage and the non-fundamental current exceeds a preset value; An oscillation suppression signal is injected into the power transmission line according to the start signal.

[0014] In one embodiment of the present application, in an outage situation, the bypass switch is driven to close and the converter unit is withdrawn from the transmission line; the outage situation includes: the energy storage voltage does not reach the set voltage or is abnormal, the non-fundamental current does not exceed the preset value, and at least one of a shutdown instruction is received.

[0015] In one embodiment of the present application, injecting an oscillation suppression signal into the transmission line according to the start signal includes: Extract the non-fundamental current, detect the frequency, amplitude and phase of the dominant oscillating current, calculate the reverse dominant oscillating current that needs to be injected, and calculate the adjustment instructions of each unit valve group, unlock the number of the unit valve groups that meet the start-up control conditions, and perform power control on each unit valve group.

[0016] The beneficial effects of the present application are as follows: the present application improves the short-circuit capacity of the grid connection point by compensating the line inductive reactance through the capacitive reactance of the series compensation module; detects the non-fundamental current of the line through the oscillation suppression module, and suppresses power oscillation when the oscillating current exceeds the preset value, effectively solving the problem of insufficient short-circuit ratio and power oscillation of multiple new energy stations in long-distance transmission lines in remote areas. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] In order to more clearly illustrate the technical solutions in the embodiments of the present application, the following briefly introduces the drawings required for use in the description of the embodiments. Obviously, the drawings described below are only some embodiments of the present application. For those skilled in the art, other drawings can be obtained based on these drawings without creative work.

[0018] Figure 1 This is a diagram of the architecture of a new energy power transmission system according to an embodiment of the present application; Figure 2 This is a structural diagram of a series compensation module according to an embodiment of the present application; Figure 3 This is a schematic diagram of the steps of the new energy power transmission control method according to an embodiment of the present application; Figure 4 This is a flowchart of the oscillation suppression startup of an embodiment of the present application; Figure 5 This is a flowchart of the oscillation suppression shutdown embodiment of the present application.

[0019] Description of reference numerals: 1. Series compensation module; 11. Capacitor bank; 12. Spark gap; 13. Damping circuit; 2. Unit valve group; 21. Control unit; 22. Commutation unit; 23. Bypass switch; 231. Mechanical bypass switch; 232. Thyristor bypass switch; 24. Energy storage unit; 101. New energy station; 102. Power grid; MOV1, first metal oxide surge arrester; MOV2, second metal oxide surge arrester; K1, first switch; K2, second switch; K3, third switch; K4, fourth switch; K5, fifth switch; MBS, main busbar switch. DETAILED DESCRIPTION

[0020] The technical solutions in the embodiments of the present application will be clearly and completely described below in conjunction with the drawings in the embodiments of the present application. Obviously, the described embodiments are only a part of the embodiments of the present application, rather than all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without making creative work are within the scope of protection of the present application. In addition, it should be understood that the specific implementation methods described herein are only used to illustrate and explain the present application, and are not used to limit the present application. In the present application, unless otherwise specified, the directional words used, such as "up", "down", "left", and "right", generally refer to the up, down, left, and right of the device in actual use or working state, specifically the drawing direction in the accompanying drawings.

[0021] In this application, unless otherwise specified or limited, terms such as "connected," "connected," and "stacked" should be understood broadly. For example, they may refer to fixed connections, detachable connections, or integration; they may refer to direct connections or indirect connections through an intermediate medium; they may refer to internal communication between two components or interaction between two components. Those skilled in the art will understand the specific meanings of these terms in this application based on the specific circumstances.

[0022] Those skilled in the art have noticed that the short-circuit ratio of the grid-connected side of multiple new energy stations is insufficient, and power oscillation is prone to occur. To solve this problem, it is usually required to increase the power supply of synchronous machines on the grid-connected side, such as adding new phase-shifting machines or grid-forming devices to increase the short-circuit capacity of the grid-connected point. However, the overall investment of adding phase-shifting machines or grid-forming devices is relatively large, and in some cases, the improvement in the short-circuit ratio of new energy stations is limited.

[0023] This application improves the short-circuit capacity of the grid connection point by compensating the line inductive reactance through the capacitive reactance of the series compensation module; detects the non-fundamental current of the line through the oscillation suppression module, and suppresses power oscillation when the oscillating current exceeds the preset value, effectively solving the problem of insufficient short-circuit ratio and power oscillation of multiple new energy stations in long-distance transmission lines in remote areas.

[0024] The specific implementation of this application is described below through examples: like Figure 1 As shown, an embodiment of the present application provides a new energy power transmission system, which is provided on a transmission line between a connection point of a new energy multi-station and a power grid 102, including: The series compensation module 1 is connected in series with the transmission line and is used to compensate the inductive reactance of the line through the capacitive reactance; An oscillation suppression module is connected to the series compensation module 1 and is used to suppress line oscillations. The oscillation suppression module includes N unit valve groups 2 connected in series. Each unit valve group 2 includes a commutation unit 22 and a control unit 21 connected in parallel. N is a positive integer. The number of N can be arbitrarily selected according to actual needs based on the output power of the unit valve group 2.

[0025] The control unit 21 is used to collect the energy storage voltage of the unit valve group 2 and the non-fundamental current on the transmission line, and generate a start signal when the energy storage voltage reaches a set voltage and the non-fundamental current exceeds a preset value; The commutation unit 22 is configured to receive a start signal and inject an oscillation suppression signal into the transmission line according to the start signal.

[0026] Specifically, the new energy transmission system of the present application is connected in series on the transmission line between the grid connection point of the new energy multi-station and the power grid 102. The new energy station 101 includes a photovoltaic station, a wind power station, etc. The voltage levels of the connected transmission lines mainly include 10kV, 35kV, 66Kv, 110kV, 220kV, and 500kV. The transmission line can be a single-circuit line or a double-circuit line.

[0027] In this application, when the output of the new energy station 101 is 70%, the short-circuit ratio of multiple stations at the grid connection point is lower than 2.0, and the short-circuit ratio of the power generation step-up and low-voltage side is lower than 1.5. According to national standards, the output needs to be restricted when the short-circuit ratio does not meet the standard, resulting in the maximum output of the station being limited to 70%, resulting in a serious power abandonment problem.

[0028] The new energy power transmission system of the present application includes a series compensation module 1 and an oscillation suppression module. The series compensation module 1 is used to compensate for the line inductive reactance through capacitive reactance. The series compensation module 1 includes a capacitor bank 11. The capacitive reactance value of the capacitor bank 11 is between 30% and 60% of the total inductive reactance value of the transmission line. By connecting the series compensation module 1, the connection impedance between the new energy station 101 and the power grid 102 is reduced, and the short-circuit capacity of the grid connection point of the new energy station 101 is increased.

[0029] By analyzing and calculating the above-mentioned new energy station 101 whose maximum output is limited to 70%, after connecting the series compensation module 1 with a series compensation degree of 40% to the transmission line, the short-circuit ratio requirement can be met when the new energy output is 100% in any operating mode, and unlimited power generation can be achieved throughout the year.

[0030] In an optional embodiment, as Figure 2 As shown, the series compensation module 1 of the present application includes a capacitor bank 11 and a protection device. The capacitor bank 11 is switchably connected in series with the transmission line, and the protection device is connected in parallel with the capacitor bank 11 for overvoltage protection.

[0031] Specifically, the series compensation module 1 of the present application is entirely provided on an insulating platform, and the series compensation module 1 includes: A capacitor bank 11, with both ends of the capacitor bank 11 connected in series to a power transmission line via a first switch K1 and a second switch K2, for compensating the inductive reactance of the line through capacitive reactance, thereby achieving a series compensation function for the power transmission line; A metal oxide lightning arrester is connected in parallel with the capacitor bank 11 for overvoltage protection; the metal oxide lightning arrester of the present application includes a first metal oxide lightning arrester MOV1 and a second metal oxide lightning arrester MOV2; Spark gap 12, connected in parallel with capacitor bank 11, serves as backup overvoltage protection for metal oxide surge arrester; The damping circuit 13 is connected in series with the spark gap 12 and is used to limit the afterflow in the circuit after the spark gap 12 breaks down.

[0032] The series compensation module 1 is also connected to: The third switch K3 is used to controllably bypass the capacitor bank 11 to stop the series compensation module 1 from working. It is usually operated under equipment maintenance conditions. The main bus switch MBS is connected in series with the transmission line to realize the connection and exit of the series compensation module 1 on the transmission line. When the main bus switch MBS is disconnected, the series compensation module 1 is connected to the transmission line; when the main bus switch MBS is closed, the series compensation module 1 is exited from the transmission line.

[0033] The fourth switch K4 and the fifth switch K5 are respectively connected to two sides of the line of the series compensation module 1 and are used to ground the two sides of the line of the series compensation module 1 .

[0034] Specifically, the oscillation suppression module is combined with the series compensation module 1 to inject an oscillation suppression signal through the multi-unit valve group 2 to suppress the high-frequency oscillation of the transmission line and suppress the line power fluctuation.

[0035] When the energy storage voltage of the unit valve group 2 reaches the set voltage and the non-fundamental current exceeds the preset value, the control unit 21 generates a start signal to drive the commutation unit 22 to inject an oscillation suppression signal. For example, the oscillation current of the transmission line is 25Hz, the amplitude is 500A, and the phase is 0°. The current injected by the commutation unit 22 is 25Hz, the amplitude is 500A, and the phase is 180°, thereby achieving reverse cancellation of the oscillation current.

[0036] In a preferred embodiment, the unit valve group 2 also includes a bypass switch 23, which is connected in parallel with the converter unit 22. In the event of a shutdown, the control unit 21 generates a shutdown signal to drive the bypass switch 23 to close, so that the converter unit 22 exits the transmission line. The shutdown conditions include: the energy storage voltage does not reach the set voltage or is abnormal, the non-fundamental current does not exceed the preset value, and the control unit 21 receives at least one of the shutdown instructions.

[0037] Specifically, the control unit 21 of the present application has a built-in sampling circuit for collecting the current on the transmission line and the equipment status in the unit valve group 2, such as the energy storage voltage of the energy storage unit 24. When it is monitored that the energy storage voltage is lower than the set voltage, it is determined that the energy storage voltage has not reached the set voltage, indicating that the energy storage unit 24 cannot provide the converter unit 22 with DC power that meets the power output requirements. In this state, the converter unit 22 cannot be put into operation.

[0038] The control unit 21 decomposes the current signal on the transmission line through fast Fourier transform and extracts the non-fundamental current component. When it is detected that the amplitude of the non-fundamental current is continuously below the preset value, it is determined that the non-fundamental current does not exceed the preset value. At this time, there is no significant oscillation in the line that needs to be suppressed, and the converter unit 22 does not need to operate. The oscillation suppression module of the present application is only started when the oscillating current is greater than the preset value, and is in standby mode during normal operation. Compared with other parallel phase-shifting schemes that improve the short-circuit ratio of multiple new energy stations, the overall system loss is extremely small.

[0039] The control unit 21 has a communication interface with the upper control system and can receive a shutdown command issued remotely. When a shutdown command is received, the shutdown process can be triggered immediately.

[0040] More specifically, the control unit 21 generates a shutdown signal to instruct the bypass switch 23 to perform a closing operation, and at the same time performs locking control on the commutation unit 22.

[0041] Before driving the bypass switch 23 to close, the control unit 21 first sends a locking signal to the commutation unit 22, cutting off the power devices in the commutation unit 22, so that the commutation unit 22 stops converting electric energy and outputting oscillation suppression signals; the control unit 21 controls the contacts of the bypass switch 23 to close. After the bypass switch 23 is closed, the commutation unit 22 is short-circuited, the current no longer passes through the commutation unit 22, and the commutation unit 22 stops suppressing oscillations.

[0042] This application combines the series compensation module 1 and the oscillation suppression module to reduce the electrical connection between the new energy station 101 and the power grid 102, which can greatly improve the short-circuit ratio level of the new energy station 101. Under reasonable configuration, it can achieve full power transmission of new energy and reduce the power restriction and power abandonment problems of new energy.

[0043] In an optional embodiment, the bypass switch 23 includes a mechanical bypass switch 231 and a thyristor bypass switch 232 connected in parallel.

[0044] Specifically, the thyristor has the characteristic of fast response speed and can be turned on in a very short time, thereby achieving a rapid short circuit of the commutation unit 22, thereby quickly isolating the commutation unit 22 from the transmission line, and avoiding damage to the commutation unit 22 due to continuous operation under abnormal working conditions.

[0045] The response speed of the mechanical bypass switch 231 is slower than that of the thyristor bypass switch 232. It will close and turn on only after a certain delay after the thyristor bypass switch 232 is turned on. However, after turning on, the contact resistance is small, the current-carrying capacity is strong, and the operating loss is low. It has the ability to bear the short-circuit commutation unit 22 for a long time.

[0046] In an optional embodiment, an energy storage unit 24 is further included, which is connected in series to the DC side of the unit valve group 2 and is used to provide energy storage voltage to the unit valve group 2. The energy storage unit 24 includes a plurality of electrochemical energy storage batteries connected in series.

[0047] Specifically, energy storage unit 24 is composed of multiple electrochemical energy storage cells connected in series to form a battery string structure. The electrochemical storage of energy storage unit 24 provides DC support for commutation unit 22. Commutation unit 22 converts the DC power of energy storage unit 24 into an AC signal with the same frequency and opposite direction as the line oscillating current.

[0048] The energy storage unit 24 is connected in series to the DC side of the unit valve group 2. Before the system starts, the energy storage unit 24 is pre-charged by the external charging power supply or the charging current of the transmission line until the series voltage reaches the set value. In the case of oscillation in the transmission line, the commutation unit 22 needs to inject a reverse oscillation current. At this time, the energy storage unit 24 discharges to maintain the DC side voltage stability. In the case of abnormal energy storage voltage, or a shutdown command is received, or the oscillation suppression is ended, the control unit 21 locks the commutation unit 22 and closes the bypass switch 23 to isolate the energy storage unit 24 from the transmission line.

[0049] In an optional embodiment, the commutation unit 22 is a fully controlled IGBT commutation circuit. By controlling the high-frequency on / off of insulated gate bipolar transistors (IGBTs), the commutation unit 22 inverts the DC power from the electrochemical energy storage unit 24 into an AC signal that is opposite to the oscillating current of the transmission line, thereby accurately offsetting the line power oscillation. This application uses 4 IGBT tubes to form an H-bridge structure to achieve bidirectional conversion of electrical energy between the DC side and the AC side.

[0050] Specifically, the control unit 21 performs fast Fourier decomposition on the current of the transmission line, extracts the non-fundamental current, detects the frequency, amplitude and phase of the dominant oscillating current, calculates the reverse dominant oscillating current that needs to be injected into the line, and calculates the adjustment instructions of each unit valve group 2, unlocks the number of unit valve groups 2 that meet the start-up control conditions, and performs power control on each unit valve group 2.

[0051] Specifically, under adverse operating conditions, when power oscillations occur in the transmission line, the oscillation suppression module can proactively detect the amplitude, phase, and frequency of the oscillating current. Reverse oscillating current is injected into the transmission line to suppress the oscillation, significantly reducing the oscillation risk at the new energy station 101, which has a weak connection to the power grid 102.

[0052] The present application also provides a new energy transmission control method, such as Figure 3 As shown, including: Step S1, compensating the inductive reactance value of the transmission line; Step S2, collecting the non-fundamental current of the transmission line and the energy storage voltage, and generating a start signal when the energy storage voltage reaches a set voltage and the non-fundamental current exceeds a preset value; Step S3: injecting an oscillation suppression signal into the transmission line according to the start signal.

[0053] In an optional embodiment, in the event of a shutdown, the bypass switch 23 is driven to close, and the converter unit 22 is withdrawn from the transmission line; the shutdown situation includes: the energy storage voltage does not reach the set voltage or is abnormal, the non-fundamental current does not exceed the preset value, and at least one of the shutdown instructions is received.

[0054] In an optional embodiment, injecting an oscillation suppression signal into the transmission line according to the start signal includes: Extract the non-fundamental current, detect the frequency, amplitude and phase of the dominant oscillating current, calculate the reverse dominant oscillating current that needs to be injected, and calculate the adjustment instructions of each unit valve group 2, unlock the number of unit valve groups 2 that meet the start-up control conditions, and perform power control on each unit valve group 2.

[0055] Two specific examples are given below: Figure 4 As shown, the steps of suppressing oscillation in this application are: Step A11, detecting whether the oscillating current in the transmission line current is greater than a preset value, and executing step A12 if the oscillating current is greater than the preset value; Step A12, detecting the status of each oscillation suppression module; Step A13: Detect the power level of the DC side energy storage unit 24 of the unit valve group 2 to determine whether direct startup is possible. After the energy storage unit 24 meets the DC voltage required for startup, the startup status is sent to the control unit 21. Step A14: The control unit 21 calculates the magnitude, phase, and frequency of the oscillation suppression current that needs to be injected into the transmission line, and converts the calculated current into an IGBT disconnection signal for each commutation unit 22. Step A15 : unlocking the number of unit valve groups 2 that meet the start-up control conditions, and performing power control on each unit valve group 2 .

[0056] like Figure 5 As shown, the decommissioning steps for this application are: Step A21: Determine whether one of the following three conditions is met: The oscillating current in the line current is less than the preset value; The control unit 21 receives a shutdown instruction; The voltage value of the electrochemical energy storage DC side of the unit valve group 2 is less than the preset voltage or abnormal; If one of the above three conditions is met, step A22 is executed; Step A22, locking the working commutation unit 22; Step A23: Close the thyristor bypass switch 232 and the mechanical bypass switch 231 in sequence.

[0057] The above is a detailed introduction to a new energy power transmission system and control method provided by the present application. Specific examples are used in this article to illustrate the principles and implementation methods of the present application. The description of the above embodiments is only used to help understand the method and core idea of the present application. At the same time, for those skilled in the art, according to the ideas of the present application, there will be changes in the specific implementation methods and application scope. In summary, the content of this specification should not be understood as limiting the present application.

Claims

1. A new energy power transmission system, characterized in that: The transmission line provided between the grid connection point of the new energy station (101) and the power grid (102) includes: A series compensation module (1) is connected in series to the power transmission line and is used to compensate for the inductive reactance of the line through the capacitive reactance; an oscillation suppression module connected to the series compensation module (1) and used to suppress line oscillations, the oscillation suppression module comprising a plurality of unit valve groups (2) connected in series, one of the unit valve groups (2) comprising a commutation unit (22) and a control unit (21) connected in parallel; The control unit (21) is used to collect the energy storage voltage of the unit valve group (2) and the non-fundamental current on the transmission line, and generate a start signal when the energy storage voltage reaches a set voltage and the non-fundamental current exceeds a preset value; The commutation unit (22) is used for receiving the start signal and injecting an oscillation suppression signal into the transmission line according to the start signal.

2. The new energy power transmission system according to claim 1, characterized in that: The unit valve group (2) further includes a bypass switch (23) connected in parallel with the commutation unit (22); in the event of a shutdown, the control unit (21) generates a shutdown signal for driving the bypass switch (23) to close, thereby withdrawing the commutation unit (22) from the transmission line; The shutdown condition includes at least one of: the energy storage voltage does not reach the set voltage or is abnormal, the non-fundamental current does not exceed the preset value, and the control unit (21) receives a shutdown instruction.

3. The new energy power transmission system according to claim 2, characterized in that: The bypass switch (23) comprises a mechanical bypass switch (231) and a thyristor bypass switch (232) connected in parallel.

4. The new energy power transmission system according to claim 1, characterized in that: It also includes an energy storage unit (24) connected in series to the DC side of the unit valve group (2) for providing the energy storage voltage to the unit valve group (2), and the energy storage unit (24) includes a plurality of electrochemical energy storage batteries connected in series.

5. The new energy power transmission system according to claim 1, characterized in that: The commutation unit (22) is a fully controlled IGBT commutation circuit.

6. The new energy power transmission system according to claim 1, characterized in that: The series compensation module (1) comprises a capacitor bank (11) and a protection device, wherein the capacitor bank (11) is switchably connected in series with the power transmission line, and the protection device is connected in parallel with the capacitor bank (11) for overvoltage protection.

7. The new energy power transmission system according to claim 6, characterized in that: The capacitive reactance value of the capacitor bank (11) is 30% to 60% of the total inductive reactance value of the transmission line.

8. The new energy power transmission system according to claim 1, characterized in that: When the new energy station (101) is fully powered, the short-circuit ratio of the grid connection point is lower than 2.0 or the short-circuit ratio of the step-up to low-voltage side is lower than 1.

5.

9. A new energy power transmission control method, characterized in that: include: Compensate for the inductive reactance of the transmission line; collecting the non-fundamental current and the energy storage voltage of the transmission line, and generating a start signal when the energy storage voltage reaches a set voltage and the non-fundamental current exceeds a preset value; An oscillation suppression signal is injected into the power transmission line according to the start signal.

10. The new energy power transmission control method according to claim 9, characterized in that: In a shutdown situation, the bypass switch (23) is driven to close, and the commutation unit (22) is withdrawn from the transmission line; the shutdown situation includes at least one of: the energy storage voltage does not reach the set voltage or is abnormal, the non-fundamental current does not exceed the preset value, and a shutdown instruction is received.

11. The new energy power transmission control method according to claim 9, characterized in that: Injecting an oscillation suppression signal into the transmission line according to the start signal includes: The non-fundamental current is extracted, the frequency, amplitude and phase of the dominant oscillating current are detected, the reverse dominant oscillating current to be injected is calculated, and the adjustment instructions of each unit valve group (2) are calculated, the number of the unit valve groups (2) with the start-up control conditions is unlocked, and the power control of each unit valve group (2) is performed.

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