New energy direct current collection topology circuit and power transmission system

Abstract

The application relates to a new energy direct current collection topology circuit and a power transmission system, wherein the circuit comprises a voltage regulation circuit, a commutation conversion circuit and a transformer, the commutation conversion circuit comprises two first bridge arms and second bridge arms which are connected in parallel with each other; the voltage regulation circuit is used for adjusting the waveform of the direct current voltage output by a new energy power generation system into a sine positive half wave, thereby obtaining a first adjusted voltage; the commutation conversion circuit is used for adjusting the waveform of the first adjusted voltage into a sine wave waveform through the lower bridge arm of the first bridge arm and the upper bridge arm of the second bridge arm, the upper bridge arm of the first bridge arm and the lower bridge arm of the second bridge arm, thereby obtaining a second adjusted voltage; and the transformer is used for adjusting the second adjusted voltage and then outputting the second adjusted voltage to the power grid corresponding to the new energy power generation system. In this way, stable and efficient power transmission between the new energy power generation system and the power grid can be realized in the mode of direct current collection and direct current transmission, and the stability of the power grid is improved.

Description

Technical Field

[0001] This application relates to the technical field of new energy power transmission, and in particular to a new energy DC collecting topology circuit and power transmission system. Background Technology

[0002] In desert, Gobi, and arid regions, new energy resources such as wind power and solar power are relatively abundant, which is conducive to large-scale, concentrated development. However, the harsh natural environment and grid infrastructure in these regions pose significant challenges to the large-scale development and efficient transmission of new energy power.

[0003] In related technologies, the alternating current converted from photovoltaic power by an inverter is typically collected through an AC power grid, then stepped up by a main transformer and sent into an AC transmission channel to be connected to the power grid.

[0004] However, in order to mitigate the voltage and frequency instability caused by fluctuations in new energy power, a large number of static var generators, synchronous condensers, and energy storage devices are required. The interaction between these power electronic devices and between them and the power grid can cause broadband oscillations, leading to a decrease in grid stability. Summary of the Invention

[0005] Therefore, it is necessary to provide a new energy DC collection topology circuit and power transmission system to address the aforementioned technical problems.

[0006] In a first aspect, this application provides a new energy DC collection topology circuit, which includes: a voltage regulating circuit, a commutation circuit and a transformer, wherein the commutation circuit includes two parallel first bridge arms and a second bridge arm.

[0007] The voltage regulating circuit is used to adjust the waveform of the DC voltage output by the new energy power generation system to a positive half-wave sine wave to obtain the first regulating voltage;

[0008] The commutation circuit is used to adjust the waveform of the first adjustment voltage to a sine wave waveform by alternately turning on the lower arm of the first bridge arm and the upper arm of the second bridge arm, and the upper arm of the first bridge arm and the lower arm of the second bridge arm, so as to obtain the second adjustment voltage.

[0009] The transformer is used to adjust the second regulating voltage and output it to the power grid corresponding to the new energy power generation system.

[0010] In one embodiment, the commutation circuit is configured to connect the upper arm of the first bridge arm and the lower arm of the second bridge arm to generate the positive half-wave of the sine wave of the second adjustment voltage; and to connect the lower arm of the first bridge arm and the upper arm of the second bridge arm to generate the negative half-wave of the sine wave of the second adjustment voltage.

[0011] In one embodiment, the new energy DC collection topology circuit further includes a control circuit, which is used to generate a first control signal and a second control signal according to the wavelength of the positive half-wave of the sine wave.

[0012] The commutation circuit is used to conduct the upper arm of the first bridge arm and the lower arm of the second bridge arm according to the first control signal to generate the positive half-wave of the sine wave of the second adjustment voltage, and to conduct the lower arm of the first bridge arm and the upper arm of the second bridge arm according to the second control signal to generate the negative half-wave of the sine wave of the second adjustment voltage.

[0013] In one embodiment, the commutation circuit is also used to charge the voltage regulating circuit with the DC voltage provided by the new energy power generation system during the process of establishing a power connection between the voltage regulating circuit and the new energy power generation system and the power grid, until the DC voltage output by the new energy power generation system reaches a preset voltage threshold, or to charge the voltage regulating circuit with the AC voltage provided by the power grid until the voltage regulating circuit receives the AC voltage provided by the power grid and reaches a preset voltage threshold.

[0014] In one embodiment, the upper arm of the first bridge arm, the lower arm of the first bridge arm, the upper arm of the second bridge arm, and the lower arm of the second bridge arm of the commutation circuit are each connected in series with a bridge arm reactor.

[0015] In one embodiment, the upper arm of the first bridge arm, the lower arm of the first bridge arm, the upper arm of the second bridge arm, and the lower arm of the second bridge arm are each connected in parallel with a first surge arrester.

[0016] In one embodiment, the upper arm of the first bridge arm, the lower arm of the first bridge arm, the upper arm of the second bridge arm, and the lower arm of the second bridge arm each include multiple reversing valves connected in series, and each reversing valve is connected in parallel with a second surge arrester.

[0017] In one embodiment, the voltage regulating circuit includes multiple voltage regulating sub-circuits connected in series, the number of which is determined based on the power grid transmission voltage and the rated output voltage of the voltage regulating sub-circuits.

[0018] In one embodiment, the new energy DC collection topology circuit also includes a protection circuit, which is connected to the first bridge arm, the second bridge arm and the transformer respectively.

[0019] Protection circuit, used to provide overcurrent protection for transformers.

[0020] Secondly, this application also provides a power transmission system, which includes a new energy DC aggregation topology circuit according to any of the first aspects provided above, a new energy power generation system, and a power grid corresponding to the new energy power generation system; the new energy DC aggregation topology circuit is electrically connected to the new energy power generation system and the power grid respectively.

[0021] The aforementioned new energy DC aggregation topology circuit and power transmission system include a voltage regulating circuit, a commutation and converter circuit, and a transformer. The commutation and converter circuit includes two parallel bridge arms, a first bridge arm and a second bridge arm. The voltage regulating circuit is used to adjust the waveform of the DC voltage output by the new energy power generation system to a sinusoidal positive half-wave to obtain a first regulated voltage. The commutation and converter circuit is used to adjust the waveform of the first regulated voltage to a sinusoidal waveform by alternately connecting the lower bridge arm of the first bridge arm and the upper bridge arm of the second bridge arm, and the upper bridge arm of the first bridge arm and the lower bridge arm of the second bridge arm, to obtain a second regulated voltage. The transformer is used to adjust the second regulated voltage and then output it to the power grid corresponding to the new energy power generation system. The new energy DC aggregation topology circuit of this application adjusts the waveform of the DC voltage output by the new energy power generation system to a sinusoidal half-wave after the voltage regulation circuit adjusts it. Then, by alternately conducting the lower arm of the first bridge arm and the upper arm of the second bridge arm, and the upper arm of the first bridge arm and the lower arm of the second bridge arm, the sinusoidal half-wave waveform of the first adjustment voltage is adjusted to a sinusoidal waveform, thus obtaining the second adjustment voltage, which is an AC voltage. The second adjustment voltage is then adjusted by a transformer according to the grid connection requirements of the power grid, realizing stable and efficient power transmission between the new energy power generation system and the power grid. Since stable and efficient power transmission between the new energy power generation system and the power grid is achieved through DC aggregation and DC transmission, there is no need to configure a large number of static var generators, synchronous condensers, and energy storage devices. This avoids the broadband oscillation problem caused by the interaction between these power electronic devices and between them and the power grid, thereby helping to improve the stability of the power grid. Attached Figure Description

[0022] Figure 1 This application provides schematic diagrams of the structure of a power transmission system according to some embodiments;

[0023] Figure 2 This application provides schematic diagrams of the structure of new energy DC collection topology circuits in some embodiments.

[0024] Figure 3 This is a schematic diagram of a commutation circuit provided in some embodiments of this application for adjusting the waveform of a sine wave to obtain a sine wave with a positive half-wave.

[0025] Figure 4 This is a schematic diagram of a commutation circuit provided in some embodiments of this application for adjusting the waveform of the positive half-wave of a sine wave to obtain the negative half-wave of a sine wave;

[0026] Figure 5 and Figure 6 This is a schematic diagram showing the alternating forward and reverse current supply when the power grid provides power to the voltage regulating circuit according to some embodiments of this application;

[0027] Figure 7Schematic diagrams of the structure of new energy DC collection topology circuits provided in other embodiments of this application;

[0028] Figure 8 This is a schematic diagram of the structure of a new energy DC collection topology circuit provided in some embodiments of this application.

[0029] Explanation of reference numerals in the attached figures:

[0030] 10. New energy power generation system; 20. New energy DC collection topology circuit; 210. Voltage regulation circuit; 212. Voltage regulation sub-circuit; 220. Commutation and converter circuit; 221. First bridge arm; 222. Second bridge arm; 230. Transformer; 240. Protection circuit; 30. Power grid. Detailed Implementation

[0031] To facilitate understanding of this application, a more complete description will be provided below with reference to the accompanying drawings, which illustrate embodiments of the present application. However, the present application can be implemented in many different forms and is not limited to the embodiments described herein. Rather, these embodiments are provided so that the disclosure of this application will be thorough and complete.

[0032] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application belongs. The terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the application.

[0033] It is understood that the terms "first," "second," etc., used herein may be used to describe various elements, but these elements are not limited by these terms. These terms are only used to distinguish one element from another. For example, without departing from the scope of this application, a first resistor may be referred to as a second resistor, and similarly, a second resistor may be referred to as a first resistor. Both the first resistor and the second resistor are resistors, but they are not the same resistor.

[0034] It is understood that the term "connection" in the following embodiments should be understood as "electrical connection," "communication connection," etc., if the connected circuits, modules, units, etc., have electrical signal or data transmission with each other.

[0035] It is understandable that "at least one" refers to one or more, and "multiple" refers to two or more. "At least a part of an element" refers to part or all of an element.

[0036] When used herein, the singular forms of “a,” “an,” and “the” may also include the plural forms unless the context clearly indicates otherwise. It should also be understood that the terms “comprising / including” or “having,” etc., specify the presence of the stated features, wholes, steps, operations, components, parts, or combinations thereof, but do not preclude the possibility of the presence or addition of one or more other features, wholes, steps, operations, components, parts, or combinations thereof. Meanwhile, the term “and / or” as used in this specification includes any and all combinations of the associated listed items.

[0037] In desert, Gobi, and arid regions, new energy resources such as wind power and solar power are relatively abundant, which is conducive to large-scale, concentrated development. However, the harsh natural environment and grid infrastructure in these regions pose significant challenges to the large-scale development and efficient transmission of new energy power.

[0038] In related technologies, AC collection and transmission are typically employed. The AC power converted from photovoltaic power by an inverter is collected through the AC power grid, stepped up by a main transformer, and then fed into the AC transmission channel, where it is connected to the power grid of nearby residential or industrial areas. However, to mitigate voltage and frequency fluctuations caused by renewable energy power generation and maintain grid stability, numerous static var generators, synchronous condensers, and energy storage devices are usually installed. However, these power electronic devices and their interaction with the grid can potentially trigger broadband oscillations, leading to grid instability, especially in desert, Gobi, and arid regions where grid instability is more prevalent.

[0039] To address the problems in the relevant technologies, firstly, referring to... Figure 1 and Figure 2 One embodiment of this application provides a new energy DC collection topology circuit 20, including a voltage regulating circuit 210, a commutation and converter circuit 220, and a transformer 230. The commutation and converter circuit 220 includes two parallel first bridge arms 221 and second bridge arms 222. The voltage regulating circuit 210 is used to adjust the waveform of the DC voltage output by the new energy power generation system 10 to a sinusoidal positive half-wave to obtain a first adjusted voltage. The commutation and converter circuit 220 is used to adjust the waveform of the first adjusted voltage to a sinusoidal waveform by alternately connecting the lower bridge arm of the first bridge arm 221 and the upper bridge arm of the second bridge arm 222, and the upper bridge arm of the first bridge arm 221 and the lower bridge arm of the second bridge arm 222, to obtain a second adjusted voltage. The transformer 230 is used to adjust the second adjusted voltage and output it to the power grid 30 corresponding to the new energy power generation system 10.

[0040] The new energy power generation system 10 can be a system composed of photovoltaic power generation equipment, a system composed of wind power generation equipment, or a system composed of multiple new energy power generation equipment. The new energy DC aggregation topology circuit 20 in this embodiment is... Figure 1 The number of fully controlled commutator converters can be determined according to the actual design requirements of the power system. The new energy DC aggregation topology circuit 20 is used to convert the DC voltage output by the new energy power generation system 10 into AC voltage and then connect it to the power grid 30 corresponding to the new energy power generation system 10.

[0041] The voltage regulating circuit 210 is connected to the output terminal of the new energy power generation system 10 via the DC bus. The new energy power generation system 10 includes a DC collecting device and a DC transformer 230. The DC collecting device is used to collect and integrate the DC power generated by multiple new energy power generation devices (such as photovoltaic panels, wind turbines, etc.) for subsequent unified processing and transmission. The DC transformer 230 is used to raise the DC voltage collected by the DC collecting device to medium voltage, high voltage, or even ultra-high voltage to meet the needs of long-distance, large-capacity power transmission. The commutation circuit 220 is also connected to the DC bus, and the transformer 230 is connected to the commutation circuit 220. A sine wave is a periodic waveform and the most basic form of AC signal. In power systems, sine waves are commonly used to describe the changes in AC voltage and current over time.

[0042] In this embodiment, since photovoltaic DC power generation does not have frequency and phase synchronization issues, the problem of AC power angle stability in the prior art can be fundamentally solved by adopting DC collection and commutation. In addition, compared with the prior art where random fluctuations in new energy output require a large number of auxiliary support equipment such as static var generators, synchronous condensers and energy storage, this embodiment reduces the amount of cables and power conversion links by using DC collection and commutation, reducing the dependence on auxiliary support equipment, thereby reducing access costs and losses, and also avoiding broadband oscillation problems caused by power electronic equipment and its interaction with the grid 30. Furthermore, the DC collection and commutation method in this embodiment does not require the inertial support of traditional synchronous power sources, thus solving the frequency and voltage stability problems of new energy units under weak grid 30 access conditions.

[0043] In some embodiments, refer to Figures 2 to 4 The commutation circuit 220 is used to connect the upper arm of the first bridge arm 221 and the lower arm of the second bridge arm 222 to generate the positive half-wave of the sine wave of the second adjustment voltage; and to connect the lower arm of the first bridge arm 221 and the upper arm of the second bridge arm 222 to generate the negative half-wave of the sine wave of the second adjustment voltage.

[0044] In a complete sine wave cycle, the segment of the waveform from the sine wave starting from 0 to its maximum value and then falling back to 0 is called the positive half-wave; correspondingly, the segment of the waveform from the sine wave starting from 0 to its minimum value and then rising back to 0 is called the negative half-wave.

[0045] Understandably, a sine wave is the most ideal voltage and current waveform in AC power grid 30, possessing excellent symmetry and periodicity. By precisely controlling the conduction sequence and timing of the commutation circuit 220, standard positive and negative half-waves of a sine wave are generated, ensuring that the output AC power has a stable frequency, phase, and amplitude, reducing harmonic content, improving power quality, and meeting the stringent power requirements of power grid 30.

[0046] Specifically, the control module in the commutation circuit 220 can control the upper arm of the first bridge arm 221 and the lower arm of the second bridge arm 222 to conduct, generating the positive half-wave of the sine wave of the second adjustment voltage; and control the lower arm of the first bridge arm 221 and the upper arm of the second bridge arm 222 to conduct, generating the negative half-wave of the sine wave of the second adjustment voltage; or the positive and negative half-waves of the sine wave of the second adjustment voltage can be generated by an external control module.

[0047] In this embodiment, the commutation circuit 220 conducts the upper arm of the first bridge arm 221 and the lower arm of the second bridge arm 222 to generate the positive half-wave of a sine wave, and conducts the lower arm of the first bridge arm 221 and the upper arm of the second bridge arm 222 to generate the negative half-wave of a sine wave, thereby converting the direct current into alternating current that meets the requirements of the power grid 30, thus realizing the effective connection and power transmission between the new energy power generation system 10 and the power grid 30.

[0048] In some embodiments, the new energy DC collection topology circuit 20 further includes a control circuit, which is used to generate a first control signal and a second control signal according to the wavelength of the positive half-wave of the sine wave.

[0049] The commutation circuit 220 is used to conduct the upper arm of the first bridge arm 221 and the lower arm of the second bridge arm 222 according to the first control signal to generate the positive half-wave of the sine wave of the second adjustment voltage, and to conduct the lower arm of the first bridge arm 221 and the upper arm of the second bridge arm 222 according to the second control signal to generate the negative half-wave of the sine wave of the second adjustment voltage.

[0050] Understandably, in a power system, standard alternating current (AC) is sinusoidal, exhibiting periodically changing positive and negative half-waves. By generating a control signal based on the wavelength of the positive half-wave, the on / off timing of the bridge arms in the commutation circuit 220 can be precisely controlled, ensuring that the positive and negative half-waves of the generated second regulating voltage conform to the characteristics of a standard sinusoidal wave in both time and amplitude. The control circuit can be an external control system to the new energy DC aggregation topology circuit 20, capable of real-time monitoring of the voltage, current, and other conditions of the new energy power generation system 10, the new energy DC aggregation topology circuit 20, and the power grid 30.

[0051] Both the first and second control signals can be pulse signals with specific amplitude, frequency, and duty cycle, used to control the on and off of electronic devices in the commutation circuit 220. Specifically, the first and second control signals are generated at the moment when the output voltage of the voltage regulation circuit 210 crosses zero, that is, at the lowest point of the positive half-wave of the sine wave. The first control signal is a pulse signal generated within the time period corresponding to the positive half-wave of the sine wave, and its function is to connect the lower bridge arm of the first bridge arm 221 and the upper bridge arm of the second bridge arm 222, allowing the current to flow along a specific path, thereby generating the positive half-wave of the sine wave. The second control signal is a pulse signal generated within the time period corresponding to the negative half-wave of the sine wave, controlling the upper bridge arm of the first bridge arm 221 and the lower bridge arm of the second bridge arm 222 to connect, realizing the generation of the negative half-wave of the sine wave.

[0052] In this embodiment, the control signal is generated based on the wavelength of the positive half-wave of the sine wave, which ensures that the commutation circuit 220 accurately turns on and off the corresponding bridge arms at the appropriate time, thereby generating high-quality sine wave AC power. This makes the output AC waveform closer to the standard sine wave, reduces the harmonic content, and improves the power quality.

[0053] In some embodiments, refer to Figure 2 The voltage regulating circuit 210 includes multiple voltage regulating sub-circuits 212 connected in series. The number of voltage regulating sub-circuits 212 is determined according to the transmission voltage of the power grid 30 and the rated output voltage of the voltage regulating sub-circuit 212.

[0054] Understandably, multiple series-connected voltage regulating sub-circuits 212 collectively bear the voltage that the entire voltage regulating circuit 210 needs to adjust, which is the transmission voltage of the power grid 30. Assuming that the rated output voltage of each voltage regulating sub-circuit 212 is relatively fixed, then in order to ensure that the output voltage of the voltage regulating circuit 210 meets the requirements of the power grid 30 transmission voltage, it is necessary to reasonably determine the number of series-connected voltage regulating sub-circuits 212.

[0055] Specifically, the number of voltage regulator circuits 212 can be obtained by dividing the transmission voltage of the power grid 30 by the rated output voltage of the voltage regulator circuit 212 and rounding up the quotient.

[0056] Among them, the voltage regulating sub-circuit 212 can be a voltage regulating sub-module (SM), also known as a half-bridge sub-module, for example... Figure 2 SM in A1 ~ SM AN All are voltage regulation sub-modules. The voltage regulation sub-circuit 212 internally includes a first fully controlled switch T1, a second fully controlled switch T2, a first anti-parallel diode D1, a second anti-parallel diode D2, a DC energy storage capacitor C, a voltage equalization resistor R, and a thyristor SCR. When the voltage regulation sub-circuit 212 needs to be activated, the first fully controlled switch T1 is turned on and the second fully controlled switch T2 is turned off, and the current flows through the first fully controlled switch T1 and the DC energy storage capacitor C. When the voltage regulation sub-circuit 212 does not need to be activated, the second fully controlled switch T2 is turned on and the first fully controlled switch T1 is turned off, and the current flows through the second fully controlled switch T2 and bypasses the DC energy storage capacitor C.

[0057] In some embodiments, refer to Figure 2 The upper arm of the first bridge arm 221, the lower arm of the first bridge arm 221, the upper arm of the second bridge arm 222, and the lower arm of the second bridge arm 222 all include multiple reversing valves connected in series.

[0058] The number of reversing valves is determined by the ratio of the total voltage that the power system needs to withstand to the rated voltage of a single reversing valve. However, in practical applications, considering the uneven voltage distribution, the number of reversing valves is usually increased appropriately on this basis.

[0059] Specifically, such as Figure 2 As shown, H A11 ~H A1M The upper arm that makes up the first arm 221, H A21 ~H A2M The lower bridge arm that forms the first bridge arm 221, H A31 ~H A3M The upper arm that forms the second arm 222, H A41 ~H A4M The lower arm that forms the second bridge arm 222.

[0060] In some embodiments, refer to Figure 2 The new energy DC collection topology circuit 20 also includes a protection circuit, which is connected to the first bridge arm 221, the second bridge arm 222 and the transformer 230 respectively; the protection circuit is used to provide overcurrent protection for the transformer 230.

[0061] The protection circuit includes a first reactor and a second reactor connected in series. One end of the first reactor is connected to the common connection point between the upper and lower bridge arms of the first bridge arm 221, and the other end of the first reactor is connected to the first input terminal of the transformer 230. One end of the second reactor is connected to the common connection point between the upper and lower bridge arms of the second bridge arm 222, and the other end of the second reactor is connected to the second input terminal of the transformer 230.

[0062] Specifically, such as Figure 2 As shown, the first reactor is Figure 2 L in A1 The second reactor is Figure 2 L in A2 .

[0063] Understandably, when a short circuit fault occurs in the circuit, the short circuit current will increase sharply, and the first and second reactors can limit the rapid change of current, thereby protecting the safety of each electrical component in the bridge arm.

[0064] In some embodiments, refer to Figure 5 and Figure 6 The commutation circuit 220 is also used to charge the voltage regulating circuit 210 with the DC voltage provided by the new energy power generation system 10 until the DC voltage output by the new energy power generation system 10 reaches a preset voltage threshold during the process of establishing a power connection between the voltage regulating circuit 210, the new energy power generation system 10 and the power grid 30. Alternatively, it can charge the voltage regulating circuit 210 with the AC voltage provided by the power grid 30 until the voltage regulating circuit 210 receives the AC voltage provided by the power grid 30 and it reaches a preset voltage threshold.

[0065] Specifically, at the initial moment, i.e., the startup moment, the new energy DC aggregation topology circuit 20 of this application needs to be charged first for successful startup. At the initial moment, if the new energy DC aggregation topology circuit 20 first establishes a power connection with the new energy power generation system 10, it will be charged by the DC voltage provided by the new energy power generation system 10; if the new energy DC aggregation topology circuit 20 first establishes a power connection with the power grid 30, it will be charged by the AC voltage provided by the power grid 30. The preset voltage threshold can be determined according to the voltage level of the power grid 30 and the grid connection requirements.

[0066] Reference Figure 5 When the AC voltage provided by the power grid 30 charges the new energy DC collection topology circuit 20, the current sequentially flows through the second reactor, the upper arm of the second bridge arm 222, the voltage regulating circuit 210, and the lower arm of the first bridge arm 221 before flowing into the transformer 230 through the first reactor. Furthermore, since the AC voltage provided by the power grid 30 is a sine wave, the current flows in the reverse direction during the latter half of one cycle of the sine wave. Figure 6 At this time, the current flows into the transformer 230 after passing through the first reactor, the upper arm of the first bridge arm 221, the voltage regulating circuit 210, and the lower arm of the second bridge arm 222 in sequence.

[0067] Reference Figure 7 In the second embodiment, unlike the first embodiment, the upper arm of the first bridge arm 221, the lower arm of the first bridge arm 221, the upper arm of the second bridge arm 222, and the lower arm of the second bridge arm 222 are each connected in parallel with a first surge arrester.

[0068] Understandably, the first surge arrester can protect the upper arm of the first bridge arm 221, the lower arm of the first bridge arm 221, the upper arm of the second bridge arm 222, and the lower arm of the second bridge arm 222 from overvoltage damage. For example... Figure 7 As shown, the first surge arrester connected in parallel to the upper arm of the first bridge arm 221 is MOV1, the first surge arrester connected in parallel to the lower arm of the first bridge arm 221 is MOV2, the first surge arrester connected in parallel to the upper arm of the second bridge arm 222 is MOV3, and the first surge arrester connected in parallel to the lower arm of the second bridge arm 222 is MOV4.

[0069] Specifically, when a power system is struck by lightning, the lightning carries enormous energy and acts directly on converter stations and other related facilities, instantly generating extremely high overvoltages. The first surge arrester can quickly conduct when lightning overvoltage occurs, diverting the lightning current to the ground, thereby limiting the voltage on the bridge arm to a safe range and protecting the safety of the bridge arm equipment.

[0070] In some embodiments, each reversing valve is connected in parallel with a second surge arrester.

[0071] Understandably, during switching operations, such as the opening and closing of switches and phase commutation, operational overvoltages can occur. These overvoltages may damage the switching valves. The second surge arrester can quickly conduct when an operational overvoltage occurs, limiting the overvoltage to a level that the switching valve can withstand, protecting its insulation and internal electronic components from damage. Furthermore, when lightning strikes transmission lines or equipment near the converter station, it generates lightning overvoltages in the system. The second surge arrester can promptly conduct these overvoltages to the ground, preventing them from impacting the switching valves, avoiding valve breakdown and damage, and ensuring the safe operation of the switching valves in lightning environments.

[0072] Specifically, such as Figure 7 As shown, the second surge arrester M in the upper arm of the first bridge arm 221 A11 ~ M A1MEach is connected in parallel with its corresponding reversing valve; similarly, the second surge arrester M in the lower arm of the first bridge arm 221 A21 ~ M A2M Each is connected in parallel with its corresponding reversing valve; the second surge arrester M in the upper arm of the second bridge arm 222 A31 ~ M A3M Each is connected in parallel with its corresponding directional control valve; the second surge arrester M in the lower arm of the second bridge arm 222 A41 ~ M A4M Each of them is connected in parallel with its corresponding reversing valve.

[0073] Reference Figure 8 In the third embodiment, unlike the second embodiment, the upper arm of the first bridge arm 221, the lower arm of the first bridge arm 221, the upper arm of the second bridge arm 222, and the lower arm of the second bridge arm 222 in the commutation circuit 20 of the new energy DC collection topology circuit 20 of this application are each connected in series with a bridge arm reactor.

[0074] Understandably, during the commutation process, the rapid switching on and off of the electronic switching devices in the upper and lower arms of the first bridge arm 221, the upper arm of the second bridge arm 222, and the lower arm of the second bridge arm 222 will cause a sharp change in current. The bridge arm reactor can limit the rate of change of current (di / dt), preventing excessive current changes from damaging the switching devices. Furthermore, when a short-circuit fault occurs in the commutation circuit 220, the bridge arm reactor can limit the magnitude of the short-circuit current, preventing excessive short-circuit current from causing serious damage to the converter equipment, transformer 230, busbars, etc., or even triggering a fault in the entire power system.

[0075] Specifically, such as Figure 8 As shown, the bridge arm reactor connected in series in the upper bridge arm of the first bridge arm 221 is L. A11 The bridge arm reactor connected in series with the lower bridge arm of the first bridge arm 221 is L. A21 The bridge arm reactor connected in series with the upper bridge arm of the second bridge arm 222 is L. A31 The bridge arm reactor connected in series in the lower bridge arm of the second bridge arm 222 is L. A41 .

[0076] Secondly, such as Figure 1 As shown, one embodiment of this application provides a power transmission system, including any of the new energy DC aggregation topology circuits 20 provided in the first aspect above, a new energy power generation system 10, and a power grid 30 corresponding to the new energy power generation system 10; the new energy DC aggregation topology circuit 20 is electrically connected to the new energy power generation system 10 and the power grid 30 respectively.

[0077] Specifically, based on the fact that the new energy DC collection topology circuit 20 can guarantee the stability of the power grid 30, the power system in this embodiment also has the beneficial effect of guaranteeing the stability of the power grid 30.

[0078] The technical features of the above embodiments can be combined in any way. For the sake of brevity, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0079] The embodiments described above are merely illustrative of several implementation methods of this application, and while the descriptions are specific and detailed, they should not be construed as limiting the scope of this patent application. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of this application, and these all fall within the protection scope of this application. Therefore, the protection scope of this application should be determined by the appended claims.

Claims

1. A new energy DC collecting topology circuit, characterized in that, include: The circuit includes a voltage regulating circuit, a commutation circuit, and a transformer, wherein the commutation circuit comprises two parallel first bridge arms and a second bridge arm. The voltage regulating circuit is used to adjust the waveform of the DC voltage output by the new energy power generation system to a positive half-wave sine wave to obtain the first regulating voltage; The commutation circuit is used to adjust the waveform of the first adjustment voltage to a sine wave waveform by alternately turning on the lower bridge arm of the first bridge arm and the upper bridge arm of the second bridge arm, and the upper bridge arm of the first bridge arm and the lower bridge arm of the second bridge arm, to obtain the second adjustment voltage. The transformer is used to adjust the second adjustment voltage and output it to the power grid corresponding to the new energy power generation system.

2. The new energy DC collection topology circuit according to claim 1, characterized in that, The commutation circuit is used to connect the upper arm of the first bridge arm and the lower arm of the second bridge arm to generate the positive half-wave of the sine wave of the second adjustment voltage; and to connect the lower arm of the first bridge arm and the upper arm of the second bridge arm to generate the negative half-wave of the sine wave of the second adjustment voltage.

3. The new energy DC collection topology circuit according to claim 2, characterized in that, The new energy DC collection topology circuit also includes a control circuit, which is used to generate a first control signal and a second control signal according to the wavelength of the positive half-wave of the sine wave. The commutation circuit is configured to, according to the first control signal, turn on the upper arm of the first bridge arm and the lower arm of the second bridge arm to generate the positive half-wave of the sine wave of the second adjustment voltage, and according to the second control signal, turn on the lower arm of the first bridge arm and the upper arm of the second bridge arm to generate the negative half-wave of the sine wave of the second adjustment voltage.

4. The new energy DC collection topology circuit according to any one of claims 1-3, characterized in that, The commutation circuit is also used to charge the voltage regulating circuit with the DC voltage provided by the new energy power generation system during the process of establishing a power connection between the voltage regulating circuit and the new energy power generation system and the power grid, until the DC voltage output by the new energy power generation system reaches a preset voltage threshold, or to charge the voltage regulating circuit with the AC voltage provided by the power grid until the voltage regulating circuit receives the AC voltage provided by the power grid and the preset voltage threshold.

5. The new energy DC collection topology circuit according to claim 1, characterized in that, The upper arm of the first bridge arm, the lower arm of the first bridge arm, the upper arm of the second bridge arm, and the lower arm of the second bridge arm of the commutation circuit are each connected in series with a bridge arm reactor.

6. The new energy DC collection topology circuit according to claim 1, characterized in that, Each of the upper arm of the first bridge arm, the lower arm of the first bridge arm, the upper arm of the second bridge arm, and the lower arm of the second bridge arm is connected in parallel with a first surge arrester.

7. The new energy DC collection topology circuit according to claim 6, characterized in that, Each of the upper arm of the first bridge arm, the lower arm of the first bridge arm, the upper arm of the second bridge arm, and the lower arm of the second bridge arm includes multiple reversing valves connected in series, and each reversing valve is connected in parallel with a second surge arrester.

8. The new energy DC collection topology circuit according to claim 1, characterized in that, The voltage regulating circuit includes multiple voltage regulating sub-circuits connected in series, the number of which is determined based on the transmission voltage of the power grid and the rated output voltage of the voltage regulating sub-circuit.

9. The new energy DC collection topology circuit according to claim 1, characterized in that, The new energy DC collection topology circuit also includes a protection circuit, which is connected to the first bridge arm, the second bridge arm and the transformer respectively. The protection circuit is used to provide overcurrent protection for the transformer.

10. A power transmission system, characterized in that, The power transmission system includes the new energy DC aggregation topology circuit, the new energy power generation system, and the power grid corresponding to the new energy power generation system as described in any one of claims 1-9; The new energy DC collection topology circuit is electrically connected to the new energy power generation system and the power grid, respectively.

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