A system, method, apparatus and related devices for hybrid compensation of commutation margin

Abstract

The application discloses a commutation margin hybrid compensation system, method and device and related equipment, and the system comprises at least one 12-pulse converter bridge, at least two converter transformers, a smoothing reactor, a network-side AC bus, at least two commutation margin hybrid compensation devices, the commutation margin hybrid compensation device comprising a valve-side AC bus, a shunt capacitor bank and at least one current source converter; the shunt capacitor bank and the current source converter are both connected in parallel on the valve-side AC bus; the shunt capacitor bank is configured to provide reactive compensation to the 12-pulse converter bridge and filter out high-order harmonics; the current source converter is configured to increase the actual extinction angle of the 12-pulse converter bridge by outputting a preset harmonic current. The scheme effectively increases the commutation margin, reduces the risk of commutation failure, accurately compensates for reactive power and harmonics nearby, saves the traditional AC filter, reduces the occupied area, and reduces the loss and cost.

Description

Technical Field

[0001] This application relates to the field of DC power transmission technology, and in particular to a commutation margin hybrid compensation system, method, apparatus and related equipment. Background Technology

[0002] High-voltage direct current (HVDC) transmission technology has been widely used in global power grids due to its unique advantages in large-capacity, long-distance power transmission. Among these technologies, grid-commutated converters based on semi-controlled thyristor devices are mature, have large capacity, and relatively low cost, making them the mainstream solution for current engineering applications. However, this technology has several inherent drawbacks:

[0003] Conventional high-voltage direct current (HVDC) transmission systems, employing semi-controlled thyristor devices and line-commutated converters (LCCs), are prone to commutation failures when the DC inverter station is connected to a weak AC system. Furthermore, the system generates significant harmonics and consumes approximately 40%-60% of the DC power as reactive power, requiring reactive power compensation and filtering devices at the AC bus. This necessitates a large footprint, increases the capacity requirements of the converter transformer, and deteriorates its electromagnetic operating environment. When AC system voltage fluctuates or DC system operating conditions change, frequent switching of converter transformer tap positions and activation / deactivation of reactive power compensation devices are necessary to meet the DC system's voltage and reactive power demands. HVDC transmission systems using capacitor-commutated converters (CCCs) can effectively reduce commutation failure rates and reactive power consumption by increasing the actual turn-off angle and decreasing the apparent turn-off angle. However, CCCs are susceptible to fault overvoltages and degraded recovery performance during asymmetrical AC system faults, limiting their practical application. In HVDC transmission systems employing absorption and shunt capacitor commutated converters (ASCCs), the parallel capacitors can replace conventional grid-side filters and reactive power compensation devices, improving commutation and reducing the capacity of the converter transformer. However, ASCCCs suffer from difficulties in grouping, inflexible reactive power adjustment, slow response speed, and reactive power compensation capability easily affected by AC voltage. Furthermore, due to commutation voltage distortion, the actual extinction angle is smaller than the apparent extinction angle, making it difficult to set the constant extinction angle control in the DC system. High-voltage direct current (HVDC) transmission systems employing self-adaptive commutated converters (SLCCs) connect a static var generator and filter (SVF) converter chain in parallel on the valve side of the converter transformer. This allows for simultaneous full compensation of reactive power and harmonics, and provides voltage support during AC system faults, thus improving the DC system's ability to withstand commutation failures. However, SLCCs require large-capacity active devices with capacities approaching those of the eliminated grid-side AC filters and reactive power compensation devices. Furthermore, they need to operate at higher switching frequencies to compensate for higher harmonics, which not only increases the number of converter chain sub-modules and active power losses but also increases control complexity. Moreover, the higher harmonics generated near the switching frequency cannot be eliminated.

[0004] In summary, existing technical solutions all have their own significant limitations, such as suppressing commutation failure, reactive power compensation and harmonic suppression, or difficulty in balancing cost and control complexity. They have not yet provided a comprehensive solution that can simultaneously and effectively improve commutation reliability, achieve flexible and accurate reactive power and harmonic compensation, and simplify the configuration of equipment in the station without significantly increasing system complexity and cost. Summary of the Invention

[0005] Based on the above problems, this application provides a commutation margin hybrid compensation system, method, device and related equipment. This solution implements a fixed actual arc extinction angle and reactive power-voltage control in a hybrid active and passive compensation architecture, which significantly improves the system's ability to resist commutation failure, while achieving local accurate compensation of reactive power and harmonics with lower cost and complexity. This simplifies the equipment configuration of the converter station and reduces the footprint and operating losses.

[0006] In a first aspect, embodiments of this application provide a commutation margin hybrid compensation system, the system comprising:

[0007] At least one 12-pulse commutator bridge, each 12-pulse commutator bridge including a high-voltage pole 6-pulse commutator bridge and a low-voltage pole 6-pulse commutator bridge connected in series;

[0008] At least two converter transformers, with their grid-side windings connected to the grid-side AC bus;

[0009] The smoothing reactor is connected at one end to the DC side of the 12-pulse converter bridge and at the other end to the DC transmission line.

[0010] The grid-side AC busbar is located between the AC power grid and the converter transformer, and is connected to the AC power grid and the grid-side winding of the converter transformer, respectively.

[0011] At least two commutation margin hybrid compensation devices are connected to the converter transformer and the 12-pulse converter bridge. Each commutation margin hybrid compensation device includes a valve-side AC bus, a parallel capacitor bank, and at least one current-source converter. Both the parallel capacitor bank and the current-source converter are connected in parallel to the valve-side AC bus. The parallel capacitor bank is configured to provide reactive power compensation and filter out high-order harmonics to the 12-pulse converter bridge. The current-source converter is configured to increase the actual arc-extinguishing angle of the 12-pulse converter bridge by outputting a preset harmonic current.

[0012] In one possible implementation, the converter transformer includes:

[0013] Y / y type converter transformer, the grid-side winding of the Y / y type converter transformer is connected to the grid-side AC bus, and the valve-side winding of the Y / y type converter transformer is connected to the high-voltage pole 6-pulse converter bridge.

[0014] Y / Δ type converter transformer, the grid-side winding of the Y / Δ type converter transformer is connected to the grid-side AC bus, and the valve-side winding of the Y / Δ type converter transformer is connected to the low-voltage pole 6-pulse converter bridge.

[0015] The commutation margin hybrid compensation device includes:

[0016] High-voltage pole commutation margin hybrid compensation device, the high-voltage pole commutation margin hybrid compensation device is connected between the high-voltage pole 6-pulse converter bridge and the Y / y type converter transformer;

[0017] The low-voltage pole commutation margin hybrid compensation device is connected between the low-voltage pole 6-pulse converter bridge and the Y / Δ converter transformer.

[0018] In one possible implementation, the current source converter adopts a three-phase half-bridge structure, including three-phase bridge arms and an energy storage inductor. The AC side of the current source converter is connected to the valve-side AC bus. The positive terminal of the DC side of the current source converter is connected to one end of the energy storage inductor, and the negative terminal of the DC side of the current source converter is connected to the other end of the energy storage inductor.

[0019] Secondly, embodiments of this application provide a commutation margin hybrid compensation method, which is achieved by coordinating the control of a 12-pulse commutator bridge and a current source converter. This method includes:

[0020] Based on the feedback of AC bus voltage and DC current on the grid side, the firing angle of the 12-pulse converter bridge is generated by coordinating the fixed-view arc extinction angle control and the constant current control to control the DC power transmission.

[0021] Based on the AC bus voltage on the grid side and the reactive power exchanged between the converter station and the AC system, the fundamental modulation signal of the current source converter is generated through reactive power-voltage dual-loop control to provide dynamic reactive power support and voltage regulation.

[0022] Based on the detected actual arc extinction angle of the 12-pulse converter bridge and its 5th harmonic current at the outlet, the 5th harmonic modulation signal of the current source converter is generated by controlling the actual arc extinction angle and the 5th harmonic current feedforward control, which is used to increase the commutation margin.

[0023] The fundamental modulation signal and the harmonic modulation signal are combined to generate the final modulation wave, and the switching signal for driving the current source converter is generated based on the modulation wave.

[0024] In one possible implementation, the fundamental modulation signal of the current source converter is generated through reactive power-voltage dual-loop control, including:

[0025] Through reactive power outer loop control, a voltage compensation signal is generated based on the deviation between the reactive power exchanged between the converter station and the AC system and the given power value.

[0026] Through voltage inner loop control, a voltage deviation signal is generated based on the grid-side AC bus voltage, the given voltage value, the voltage compensation signal, and an operating point deviation voltage generated based on the effective value of the output current of the current source converter. The voltage deviation signal is then adjusted to generate the q-axis command current of the current source converter.

[0027] In one possible implementation, the fifth harmonic modulation signal of the current source converter is generated by controlling the actual arc extinction angle and the fifth harmonic current feedforward control, including:

[0028] The minimum actual arc extinction angle of the 12-pulse converter bridge is detected, and the minimum actual arc extinction angle is compared with the given value of the actual arc extinction angle. The basic amplitude of a 5th harmonic modulation signal is generated by proportional-integral adjustment.

[0029] The amplitude of the fifth harmonic component of the output current of the 6-pulse converter bridge is detected, and the amplitude of the fifth harmonic component is superimposed on the base amplitude as a feedforward to obtain the final amplitude of the fifth harmonic modulation signal.

[0030] In one possible implementation, generating the final modulated wave and generating the switching signal for driving the current source converter based on the modulated wave includes:

[0031] The fundamental frequency modulation signal is added to the fifth harmonic modulation signal to obtain the synthesized modulation signal;

[0032] The synthesized modulated signal is compared with the triangular carrier signal to generate a binary logic switching function;

[0033] The binary logic switching function is input into the ternary logic generator, and combined with the zero-state value discrimination logic, the switching signals of each bridge arm of the current source converter are generated.

[0034] Thirdly, embodiments of this application provide a commutation margin hybrid compensation device, the device comprising:

[0035] The first generation module is used to generate the firing angle of the 12-pulse converter bridge based on the feedback of the grid-side AC bus voltage and DC current, and through the coordination of constant arc extinction angle control and constant current control, so as to control the DC power transmission.

[0036] The second generation module is used to generate the fundamental modulation signal of the current source converter based on the grid-side AC bus voltage and the reactive power exchanged between the converter station and the AC system through reactive-voltage dual-loop control, so as to provide dynamic reactive power support and voltage regulation.

[0037] The third generation module is used to generate the 5th harmonic modulation signal of the current source converter based on the detected actual arc extinction angle of the 12-pulse converter bridge and its 5th harmonic current at the outlet, through fixed actual arc extinction angle control and 5th harmonic current feedforward control, in order to increase the commutation margin.

[0038] The fourth generation module is used to synthesize the fundamental modulation signal and the harmonic modulation signal to generate the final modulation wave, and generate the switching signal to drive the current source converter based on the modulation wave.

[0039] Fourthly, embodiments of this application provide a computer storage medium storing multiple instructions adapted for loading by a processor and executing the steps of the above-described method.

[0040] Fifthly, embodiments of this application provide an electronic device, including a memory, a processor, and a computer program stored in the memory and executable on the processor, the computer program being adapted to be loaded by the processor and to execute the steps of the method described above.

[0041] The beneficial effects of the technical solutions provided in some embodiments of this application include at least the following: By using a hybrid compensation device composed of a passive parallel capacitor bank and an active current source converter (CSC), coordinated compensation is performed on the valve side of the converter transformer, effectively increasing the commutation margin of the thyristor valve and significantly reducing the probability of commutation failure at the inverter station. This hybrid compensation architecture allows the parallel capacitors to undertake the majority of steady-state reactive power compensation and high-order harmonic filtering tasks, thereby significantly reducing the steady-state operating capacity and overall cost of the active device (CSC), overcoming the disadvantages of high cost, high loss, and complex control in traditional STATCOM full compensation schemes. Simultaneously, by employing fixed actual arc extinction angle control and valve-side 5th harmonic current feedforward control, the commutation process can be precisely controlled, overcoming the commutation voltage distortion problem. Furthermore, this control is decoupled from the original DC control and protection system, avoiding power fluctuations. Furthermore, the adopted reactive power-voltage dual-loop control strategy ensures rapid transient voltage support while achieving flexible and precise steady-state reactive power adjustment. This enables the converter station to operate at unity power factor and meet harmonic standards without installing traditional AC filters and reactive power compensation capacitor banks. Ultimately, this achieves a comprehensive effect of simplifying converter station equipment configuration, reducing footprint, lowering converter transformer capacity, improving electromagnetic operating environment, and reducing equipment operating frequency. Attached Figure Description

[0042] To more clearly illustrate the technical solutions in the embodiments of this application, the accompanying drawings used in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0043] Figure 1 This is a schematic diagram of a commutation margin hybrid compensation system provided in an embodiment of this application;

[0044] Figure 2 This is an exemplary schematic diagram of a current source converter provided in an embodiment of this application;

[0045] Figure 3 A commutation margin hybrid compensation circuit diagram provided for an embodiment of this application;

[0046] Figure 4 A flowchart illustrating a hybrid compensation method for commutation margin provided in an embodiment of this application;

[0047] Figure 5 An exemplary schematic diagram of the apparent extinction angle and actual extinction angle of a DC system provided in this application embodiment;

[0048] Figure 6 A schematic diagram of a CSC reactive-voltage dual-loop control provided in this application embodiment;

[0049] Figure 7 A schematic diagram of CSC fixed actual arc extinction angle control and 5th harmonic current feedforward control provided for embodiments of this application;

[0050] Figure 8 A structural block diagram of a commutation margin hybrid compensation device provided in this application embodiment;

[0051] Figure 9 This is a schematic diagram of the structure of an electronic device provided in an embodiment of this application. Detailed Implementation

[0052] To make the features and advantages of this application more apparent and understandable, the technical solutions in the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this application, and not all embodiments. Based on the embodiments of this application, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this application.

[0053] In the following description, when referring to the accompanying drawings, the same numbers in different drawings denote the same or similar elements unless otherwise indicated. The embodiments described in the following exemplary embodiments do not represent all embodiments consistent with this application. Rather, they are merely examples of apparatuses and methods consistent with some aspects of this application as detailed in the appended claims.

[0054] In the description of this application, it should be understood that the terms "first," "second," etc., are used for descriptive purposes only and should not be construed as indicating or implying relative importance. Those skilled in the art can understand the specific meaning of the above terms in this application based on the specific circumstances. Furthermore, in the description of this application, unless otherwise stated, "multiple" refers to two or more. "And / or" describes the relationship between related objects, indicating that three relationships can exist. For example, A and / or B can represent: A existing alone, A and B existing simultaneously, or B existing alone. The character " / " generally indicates that the preceding and following related objects are in an "or" relationship.

[0055] As mentioned earlier, high-voltage direct current (HVDC) transmission technology plays an indispensable role in modern power grids as a key means of achieving long-distance, high-capacity power transmission. Among them, grid-commutated converters (LCCs) based on semi-controlled thyristor devices have constituted the absolute mainstream of HVDC projects for decades due to their mature technology, high capacity, and relatively controllable cost. However, with the development of power systems, especially when the DC endpoint is located in a structurally weak receiving-end AC grid (i.e., a "weak AC system"), a series of inherent defects of conventional LCC-HVDC technology have become increasingly prominent, severely restricting its operational performance and reliability.

[0056] The main problems with conventional LCC-HVDC systems can be summarized as follows:

[0057] 1. High risk of commutation failure: The thyristor valve commutation of the LCC inverter station relies on the reverse voltage provided by the connected AC system. When connected to a weak AC system, the system voltage amplitude is unstable and prone to distortion. Furthermore, the voltage support capability is insufficient when subjected to AC-side disturbances (such as short-circuit faults), which can easily lead to the inability to complete the commutation process, i.e., "commutation failure". This is one of the most significant faults threatening the safe operation of the DC system, potentially causing DC power transmission interruption and impacting the power grids on both sides.

[0058] 2. Severe Reactive Power Consumption and Harmonic Pollution: LCC converters themselves do not generate reactive power during operation; instead, they consume a significant amount of reactive power, typically reaching 40% to 60% of the transmitted DC power. Simultaneously, their switching operations generate abundant characteristic subharmonics (such as the 5th, 7th, 11th, and 13th harmonics). To compensate for reactive power and filter harmonics, large AC filter banks and reactive power compensation capacitors must be centrally installed on the AC bus side of the converter station. This auxiliary facility not only occupies a huge area (often referred to as a "filter field"), significantly increasing land costs and the complexity of equipment within the station, but also forces the converter transformer's design capacity to cover this reactive power exchange, increasing transformer size and cost, and worsening the electromagnetic environment during operation, leading to increased vibration and noise.

[0059] 3. Frequent and cumbersome operation and adjustment: When AC system voltage fluctuates or DC transmission power changes, the system's reactive power demand also changes. To maintain voltage stability and reactive power balance, the traditional solution is to frequently switch reactive power compensation capacitor banks (mechanical switching operation) and adjust the converter transformer taps (mechanical tap switching). These operations have slow response speeds, are prone to wear and tear on mechanical parts, increase the maintenance burden and failure risk, and cannot achieve smooth, continuous, and precise adjustment.

[0060] To overcome the aforementioned shortcomings, existing technologies have explored various improved converter topologies, but each introduces new problems: Series Capacitor Commutated Converter (CCC): This type of converter increases the commutation voltage by connecting capacitors in series on the valve side of the converter transformer, thereby increasing the actual turn-off angle and reducing the probability of commutation failure and reactive power consumption. However, in the event of an asymmetrical fault in the AC system, a dangerous overvoltage can occur on the series capacitor in a CCC, and the system recovery characteristics after fault clearance are poor, limiting its engineering application. Assimilated and Parallel Capacitor Commutated Converter (ASCCC): This type of converter uses parallel capacitors on the valve side to replace part of the grid-side filtering and compensation devices, which helps improve commutation and reduce transformer capacity requirements. However, its reactive power compensation capacity is basically fixed and cannot be flexibly and precisely adjusted according to system needs; the response speed is slow, and the compensation effect is greatly affected by the AC voltage amplitude. More importantly, the distortion of the commutation voltage causes the actual arc-extinguishing angle to be smaller than the measured apparent arc-extinguishing angle, making the tuning of DC control systems that rely on the apparent arc-extinguishing angle difficult and posing potential operational risks. Multi-Source Adaptive Commutation Converter (SLCC): This is a more aggressive approach, attempting to achieve "full compensation" for reactive power and harmonics by connecting a static var generator (SVF) converter chain composed of large-capacity, fully controlled devices in parallel on the valve side of the converter transformer. While it effectively supports voltage and improves immunity to commutation failure, it comes at a very high cost: the capacity of the SVF converter chain needs to be close to that of the eliminated AC filter field, leading to a sharp increase in the cost of active devices, system active power losses, and control complexity. To effectively compensate for higher harmonics, its switching frequency needs to be set relatively high, which increases the number of sub-modules and generates harmonics near the switching frequency that are difficult to eliminate.

[0061] In view of this, this application provides a hybrid commutation margin compensation system, method, apparatus, and related equipment. The aim is to achieve coordinated compensation at the converter transformer valve side using a hybrid compensation device composed of a passive parallel capacitor bank and an active current source converter (CSC), effectively increasing the commutation margin of the thyristor valve and significantly reducing the probability of commutation failure at the inverter station. This hybrid compensation architecture allows the parallel capacitors to undertake the majority of steady-state reactive power compensation and high-order harmonic filtering tasks, thereby significantly reducing the steady-state operating capacity and overall cost of the active device (CSC), overcoming the disadvantages of high cost, high losses, and complex control in traditional STATCOM full compensation schemes. Simultaneously, by employing fixed actual arc extinction angle control and valve-side 5th harmonic current feedforward control, the commutation process can be precisely controlled, overcoming commutation voltage distortion problems. Furthermore, this control is decoupled from the original DC control and protection system, avoiding power fluctuations. Furthermore, the reactive power-voltage dual-loop control strategy adopted ensures rapid support of transient voltage while achieving flexible and precise adjustment of steady-state reactive power. This enables the converter station to achieve unity power factor operation and meet harmonic standards without installing traditional AC filters and reactive power compensation capacitor banks.

[0062] Please see Figure 1 , Figure 1 This is a schematic diagram of a commutation margin hybrid compensation system provided in an embodiment of this application. Figure 1 As shown, the commutation margin hybrid compensation system 100 includes: at least one 12-pulse converter bridge 110, which includes a high-voltage pole 6-pulse converter bridge and a low-voltage pole 6-pulse converter bridge connected in series; at least two converter transformers 120, namely converter transformer 1201 and converter transformer 1202. The grid-side winding of the converter transformer 120 is connected to the grid-side AC bus 140; a smoothing reactor 130, one end of which is connected to the DC side of the 12-pulse converter bridge 110, and the other end is connected to the DC transmission line; the grid-side AC bus 140 is located between the AC grid and the converter transformer 120, and is connected to the AC grid and the grid-side winding of the converter transformer respectively; at least two commutation margin hybrid compensation devices 160, namely commutation margin hybrid compensation device 1601 and commutation margin hybrid compensation device 1602. The commutation margin hybrid compensation device 160 is connected to the converter transformer 120 and the 12-pulse converter bridge 110. The commutation margin hybrid compensation device 160 includes a valve-side AC bus, a parallel capacitor bank, and at least one current source converter. The parallel capacitor bank and the current source converter are both connected in parallel to the valve-side AC bus. The parallel capacitor bank is configured to provide reactive power compensation to the 12-pulse converter bridge 110 and filter out high-order harmonics. The current source converter is configured to increase the actual arc extinction angle of the 12-pulse converter bridge by outputting a preset harmonic current.

[0063] Please see Figure 2 , Figure 2 This is an exemplary schematic diagram of a current source converter provided in an embodiment of this application, such as... Figure 2 As shown, the current source converter (CSC) uses a large inductor as an energy storage element on the DC side. This inductor is key to its designation as a "current source," maintaining the stability and smoothness of the DC-side current, allowing the AC-side output current to be directly controlled by the switching state. In this embodiment, the current source converter adopts a three-phase half-bridge structure, including three-phase bridge arms and an energy storage inductor. The AC side of the current source converter is connected to the valve-side AC bus. The positive terminal of the DC side of the current source converter is connected to one end of the energy storage inductor, and the negative terminal of the DC side is connected to the other end of the energy storage inductor. Each phase's upper and lower bridge arms of the current source converter consist of multiple multi-chip packaged IGBT modules and a diode connected in series. Each module uses a multi-chip packaged IGBT device with a rated voltage greater than or equal to 4500V and a rated current greater than or equal to 500A. In one possible implementation, the converter transformer includes: a Y / y type converter transformer, the grid-side winding of which is connected to the grid-side AC bus, and the valve-side winding of which is connected to the high-voltage pole 6-pulse converter bridge; and a Y / Δ type converter transformer, the grid-side winding of which is connected to the grid-side AC bus, and the valve-side winding of which is connected to the low-voltage pole 6-pulse converter bridge; the commutation margin hybrid compensation device includes: a high-voltage pole commutation margin hybrid compensation device connected between the high-voltage pole 6-pulse converter bridge and the Y / y type converter transformer; and a low-voltage pole commutation margin hybrid compensation device connected between the low-voltage pole 6-pulse converter bridge and the Y / Δ type converter transformer.

[0064] Please see Figure 3 , Figure 3 A commutation margin hybrid compensation circuit diagram is provided for an embodiment of this application, such as... Figure 3 As shown, the overall structure is a bipolar 12-pulse high-voltage direct current (HVDC) transmission system, comprising two converter units: a high-voltage unit and a low-voltage unit. The DC system consists of a high-voltage unit and a low-voltage unit, with a DC current i. d Flow through smoothing reactor L d The converter bridge structure includes a high-voltage 6-pulse converter bridge and a low-voltage 6-pulse converter bridge. The AC side of the converter bridge is connected to the valve-side winding of the converter transformer via the valve-side AC bus. The DC sides of the converter bridges are connected in series and connected to the smoothing reactor L. dIt is connected to DC transmission lines. The hybrid compensation device structure, at the high-voltage pole, connects the high-voltage pole converter bridge to the valve side of its corresponding converter transformer, including: parallel capacitor bank C (passive part) and current source converter CSC (active part). At the low-voltage pole, the hybrid compensation device connects the low-voltage pole converter bridge to the valve side of its corresponding converter transformer, including: parallel capacitor bank C (passive part) and current source converter CSC (active part). The parallel capacitor bank and current source converter (CSC) of each pole are connected in parallel to the valve side AC bus of that pole. Regarding the AC system, the grid-side winding of the converter transformer is connected to the grid-side AC bus (marked as B in the diagram). P The grid-side AC bus passes through the system's equivalent impedance Z. s Connected to the AC system. The parallel capacitors in the commutation margin hybrid compensation device filter out characteristic harmonics above the 11th order generated by the 6-pulse converter bridge, filter out switching harmonics generated by the current source converter, compensate for the reactive power consumed by the 6-pulse converter bridge, reduce the commutation angle, accelerate the commutation speed, and increase the commutation margin. The current source converter in the commutation margin hybrid compensation device controls the 5th harmonic current flowing into the converter transformer, increases the actual arc-extinguishing angle of the 6-pulse converter bridge, and increases the commutation margin. When an AC system fault occurs, the current source converter dynamically supports the AC bus voltage of the converter station.

[0065] This application provides a hybrid commutation margin compensation system. By implementing coordinated control in a hybrid compensation architecture consisting of an active current source converter (CSC) and a passive parallel capacitor, the system commutation margin can be significantly increased, the risk of commutation failure can be effectively reduced, and the reactive power and characteristic harmonics (especially the 5th harmonic) generated by the converter station can be accurately compensated locally. This eliminates the need for traditional bulky AC filters and reactive power compensation devices. Ultimately, while improving system reliability and flexibility, the system significantly reduces the converter station's footprint, lowers equipment capacity requirements and operating losses, achieving a balance between economy and reliability.

[0066] Please see Figure 4 , Figure 4 This is a flowchart illustrating a commutation margin hybrid compensation method provided in an embodiment of this application. The execution entity in this embodiment can be an electronic device performing commutation margin hybrid compensation, a processor within the electronic device performing the commutation margin hybrid compensation method, or a commutation margin hybrid compensation service within the electronic device performing the commutation margin hybrid compensation method. For ease of description, the following uses a processor within an electronic device as an example to illustrate the specific execution process of the commutation margin hybrid compensation method.

[0067] like Figure 4 As shown, the commutation margin hybrid compensation method may include at least:

[0068] S401. Based on the feedback of the grid-side AC bus voltage and DC current, the firing angle of the 12-pulse converter bridge is generated through the coordination of fixed-view arc extinction angle control and constant current control to control DC power transmission.

[0069] Specifically, to ensure the 12-pulse converter bridge maintains stable DC power transmission while guaranteeing its safe operation and preventing commutation failure, the system first calculates the current apparent arc extinction angle by real-time monitoring of the grid-side AC bus voltage waveform. and compare it with a given security reference value. A comparison is made; simultaneously, the system continuously monitors the actual current I of the DC line. d and compare it with the command value I of the DC current. dref The two deviation signals are compared. They are then processed by independent PI controllers: the apparent arc-extinguishing angle deviation is processed by the PI controller to generate a trigger lead angle β used to maintain commutation margin. γ The DC current deviation is processed by a PI converter to generate a trigger lead angle β for stabilizing power transmission. i To ensure the system always operates under safer conditions, the control system will calculate β in real time. γ With β i The parameters are compared, and the larger value is automatically selected as the final trigger lead angle command. A larger trigger lead angle means earlier thyristor triggering, thus allowing more time for the commutation process. Finally, this selected trigger lead angle command is inverted by 180°, converted into the final trigger angle α, and sent to the thyristor gate drive circuit, thereby achieving precise control of DC power and active protection during the commutation process. Please refer to [link to relevant documentation]. Figure 5 , Figure 5 An exemplary schematic diagram of the apparent extinction angle and actual extinction angle of a DC system provided in this application embodiment is shown below. Figure 5 As shown, the voltage waveform u Pcb The curve u represents the grid-side AC bus voltage. Ccb0 The diagram illustrates the commutation voltage waveform when only the parallel capacitor bank is engaged, a condition similar to the ASCCC scheme. Under this condition, the engagement of the parallel capacitor provides reactive power and raises the valve-side voltage, significantly accelerating the commutation speed and reducing the commutation angle μ. Therefore, at the same firing angle α, its apparent extinction angle γ is [not specified]. app Compared to conventional LCC systems, it is larger, thus reducing the risk of commutation failure. However, the key improvement of this invention lies in the active control of the 5th harmonic current through a current source converter (CSC), thereby further optimizing the commutation process. (Curve u) Ccb1This diagram illustrates the commutation voltage waveform after CSC fully compensates for the 5th harmonic current generated by the 6-pulse converter bridge, with the addition of a parallel capacitor. At this point, the 5th harmonic current flowing into the converter transformer is effectively suppressed, and the commutation voltage waveform u... Ccb1 The distortion is corrected so that the actual extinguishing angle is reduced from γ. real0 Increase to γ real1 The commutation margin is substantially improved. More importantly, the control strategy of this invention has greater flexibility and proactivity. In fact, within the acceptable operating range of the system, the current source converter can be controlled to output a fifth harmonic current exceeding the full compensation required, even if the fifth harmonic current flowing through the converter transformer reverses. This control strategy can correct the commutation voltage u to a greater extent. Ccb The waveform actively creates a waveform greater than γ. real1 A larger actual arc-extinguishing angle provides the system with active commutation margin adjustment capability.

[0070] S402. Based on the grid-side AC bus voltage and the reactive power exchanged between the converter station and the AC system, a fundamental modulation signal for the current source converter is generated through reactive power-voltage dual-loop control to provide dynamic reactive power support and voltage regulation.

[0071] Specifically, to achieve precise support for AC bus voltage and flexible adjustment of system reactive power, this embodiment utilizes the division of labor and cooperation between inner and outer loops to enable the current source converter (CSC) to quickly respond to transient voltage fluctuations and accurately maintain steady-state reactive power balance. It should be noted that the converter station is connected to the AC grid via the point of common coupling (PCC) of the grid-side AC bus and forms a complete DC transmission system with the counterpart converter station via DC transmission lines. Those skilled in the art will understand that "converter station" here refers broadly to power facilities that realize AC / DC power conversion, typically including but not limited to converter transformers, converter valves, control and protection systems, and reactive power compensation and filtering devices; the embodiments in this application do not impose specific limitations. In specific implementation, the system first sets a long-term voltage control target through reactive power outer loop control: continuously detecting the actual reactive power Q exchanged between the converter station and the AC system. m It is then compared to a given power value, typically set to the value Q required to maintain unity power factor operation. ref The obtained reactive power deviation signal is sent to a converter with a proportional coefficient K. Q With a larger integral time constant T Q The integral stage is used for processing, and a voltage compensation signal u is generated through this slow adjustment process. Q This control structure can achieve zero steady-state error tracking of reactive power and avoid u-error caused by sudden changes in reactive power commands. QThis generates a step change. This signal is primarily used to respond to slow changes in system load and to set the reference point for the voltage inner loop. Subsequently, the system achieves a rapid dynamic response through voltage inner loop control: it samples the grid-side AC bus voltage u in real time. m and compare it with the given voltage value u ref and voltage compensation signal u Q The sums are compared, and to improve the adaptability and stability of the control, a value based on the effective value I of the CSC output current is also introduced. G The generated nonlinear operating point deviation voltage Δu, the voltage inner loop generates the voltage deviation signal u using the following formula. error :

[0072]

[0073] In the formula, u ref Given a voltage, Δu is the effective value of the current I according to the current source converter. G The generated operating point deviation voltage, I, is generated when the current source converter compensates for inductive reactive power. G When the current source converter compensates for capacitive reactive power, I is positive. G If negative, by I G The relational expression for generating Δu is:

[0074]

[0075] In the formula, k max λ is the maximum voltage deviation coefficient, tanh is the hyperbolic tangent function, and λ is the voltage-current sensitivity coefficient. error After passing through a PI circuit and being limited, the q-axis command current i of the current source converter is generated. q_ref The d-axis command current i of the current source converter d_ref By detecting the actual current i of the energy storage inductor dc With the energy storage inductor command current i dc_ref The deviation between them is then generated through the PI stage. d_ref and i q_ref The signal is then subtracted from the d-axis and q-axis components of the actual current of the current source converter, and then passed through a PI converter, inverse Parker transform, and lag-shifted by 30° to generate the fundamental modulation signal i of the current source converter. abc1m .

[0076] Please see Figure 6 , Figure 6 This document provides a schematic diagram of a CSC reactive power-voltage dual-loop control system as an embodiment of this application. Figure 6 As shown, in the voltage inner loop control, the system monitors the grid-side AC bus voltage u in real time. mThis serves as the primary feedback signal. The detected signal is processed through an inertial loop to achieve necessary filtering and phase compensation. Simultaneously, the voltage compensation signal u from the reactive power outer loop output... Q It is introduced as part of the voltage inner loop reference value. A key design feature is the introduction of a value related to the RMS output current I of the current source converter (CSC). G The relevant nonlinear function f(u) generates the aforementioned operating point deviation voltage Δu, which dynamically adjusts the controller's sensitivity. Specifically, the actual voltage u... m With a given voltage reference and outer loop compensation u Q The voltage deviation signal, which is a composite reference voltage composed of the nonlinear deviation voltage Δu, is compared with the voltage deviation signal. After precise calculation and amplitude limiting by the PI regulator, the final voltage deviation signal is used to generate the q-axis command current i for controlling the reactive power output of the CSC. q_ref This enables rapid closed-loop regulation of the voltage inner loop, achieving dynamic support for the AC bus voltage.

[0077] S403. Based on the detected actual arc extinction angle of the 12-pulse converter bridge and its 5th harmonic current at the outlet, the 5th harmonic modulation signal of the current source converter is generated through the control of the actual arc extinction angle and the feedforward control of the 5th harmonic current to increase the commutation margin.

[0078] Specifically, in order to actively improve the commutation voltage waveform by precisely controlling the 5th harmonic current output by the current source converter (CSC), thereby effectively increasing the system's actual extinction angle and commutation margin, the system first calculates the minimum actual extinction angle γ of the 12-pulse converter bridge in real time by detecting the zero-crossing point of the valve-side voltage of the converter transformer. real This angle reflects the true safety margin of the commutation process after taking into account the effects of voltage distortion, and will detect γ real Compared with the set actual arc extinction angle safety reference value γ real_ref The difference is compared and fed into a PI controller for calculation, generating a fundamental amplitude I of the 5th harmonic modulation signal used to compensate for the actual arc extinction angle deficiency. 5m To significantly improve the dynamic response speed of the control and provide immediate compensation for major disturbances, the system synchronously detects the 5th harmonic component contained in the output current of the 6-pulse converter bridge and extracts its amplitude I5. This amplitude I5 is then used as a feedforward quantity and directly superimposed on the base amplitude I of the aforementioned PI regulator output. 5m The above factors together constitute the final 5th harmonic modulation signal command amplitude. This feedforward-feedback composite control strategy ensures that when the PI regulator output is zero, the system can fully compensate for the 5th harmonic current generated by the converter bridge, thereby actively eliminating the main harmonic sources that cause voltage distortion and a reduction in the actual arc extinction angle. The final 5th harmonic modulation signal i of the high-voltage current source converter...abc5m The expression is:

[0079]

[0080] In the formula, ω is the fundamental angular frequency, and j2 is the fundamental phase of the output current of the high-voltage electrode 6-pulse converter bridge.

[0081] Please see Figure 7 , Figure 7 A schematic diagram of CSC fixed actual arc extinction angle control and 5th harmonic current feedforward control provided for embodiments of this application is shown below. Figure 7 As shown, the control system first detects the voltage (u) on the valve side of the converter transformer. C,abc By accurately calculating the zero-crossing point of the 12-pulse converter bridge, the minimum actual arc-extinguishing angle γ can be determined. real Compare this measured value with the set safety reference value γ. real_ref The deviation is compared, and after being processed by a PI controller, the fundamental amplitude I of a 5th harmonic modulation signal is output. 5m To achieve rapid compensation for major disturbances, the system simultaneously tracks the output current (i) of the 6-pulse converter bridge via a phase-locked loop (PLL). abc The phase ωt+j2 of the current is calculated, and the amplitude of the 5th harmonic current I5 is extracted through a low-pass filter (LPF). This amplitude I5 is used as a feedforward quantity and is compared with the base amplitude I of the PI controller output. 5m The values ​​are directly added together to form the final 5th harmonic current command amplitude. In the signal generation stage, the system uses the acquired fundamental phase information ωt+j2 to generate unit amplitude sine waves of the three-phase 5th harmonic modulation signals via a sine function generator. These are then multiplied by the command amplitude to finally synthesize the three-phase 5th harmonic modulation signal i. abcm5 The modulated signal is then fed into the SPWM modulation module, compared with the triangular carrier wave, and then converted into the actual drive signal for the power switching device by a ternary logic generator. This controls the CSC to output a compensation current that is opposite in phase and related in amplitude to the inherent 5th harmonic current of the converter bridge, thereby canceling the 5th harmonic flowing into the transformer, correcting the commutation voltage waveform, and ultimately increasing the actual arc extinction angle. In addition, this control loop introduces a blocking control signal ctrl. When the system detects a severe AC fault, the ctrl signal is set to 0, forcibly clearing the amplitude of the 5th harmonic modulation signal output from the aforementioned PI regulator and feedforward path to zero, causing the actual arc extinction angle control to temporarily exit, and the 5th harmonic modulation signal i abcm5 No further output. At this point, the current source converter will be entirely controlled by the fundamental modulation signal i generated by the reactive-voltage dual-loop control. abcm1The drive concentrates all capacity to provide dynamic reactive power to support the rapidly dropping AC bus voltage; this is the highest priority control objective. Under normal conditions where no serious system faults occur, the Ctrl signal is 1, and the actual arc extinction angle control and reactive power-voltage dual-loop control work in coordination.

[0082] S404. The fundamental modulation signal and the harmonic modulation signal are combined to generate the final modulation wave, and the switching signal for driving the current source converter is generated based on the modulation wave.

[0083] Specifically, the system will generate the fundamental modulation signal i from the aforementioned reactive power-voltage dual-loop control. abc1m The 5th harmonic modulation signal i generated by the actual arc extinction angle control abc5m Algebraic addition is performed at the signal level to synthesize a final modulated wave containing both the fundamental frequency and the 5th harmonic. This composite modulated wave is fed into an SPWM modulation module based on triangular carrier comparison. By comparing the modulated wave with a high-frequency triangular carrier in real time, a series of binary logic pulse signals are generated. These pulse signals are then fed into a ternary logic generator, which, according to specific switching combination logic, converts the binary signals into ternary switching functions that define the correct on and off states of each IGBT in the current source converter (CSC). The matrix form of the ternary logic generator is as follows:

[0084]

[0085] In the formula, the binary logic switch function p is 1 when the modulating wave is greater than the carrier wave, and -1 otherwise. The zero-state value discrimination unit includes a modulation signal region judgment module, a ternary logic switch combination judgment module, and a zero-state value judgment module. To ensure the continuity of the DC-side current path at any time and avoid the danger of open circuit, the system also includes a zero-state value discrimination unit. This unit intelligently selects the appropriate zero-state switching mode based on the current modulation region and switch combination state, and finally outputs all bridge arm switch signals to ensure the safe and reliable operation of the CSC, thereby driving the converter to accurately output the required compensation current.

[0086] This embodiment provides a hybrid compensation method for commutation margin. A hybrid compensation device, consisting of a passive parallel capacitor bank and an active current source converter (CSC), performs coordinated compensation at the valve side of the converter transformer, effectively increasing the commutation margin of the thyristor valve and significantly reducing the probability of commutation failure at the inverter station. This hybrid compensation architecture allows the parallel capacitors to undertake the majority of steady-state reactive power compensation and high-order harmonic filtering tasks, thereby significantly reducing the steady-state operating capacity and overall cost of the active device (CSC), overcoming the disadvantages of high cost, high losses, and complex control in traditional STATCOM full compensation schemes. Simultaneously, by employing fixed actual arc extinction angle control and valve-side 5th harmonic current feedforward control, the commutation process can be precisely controlled, overcoming commutation voltage distortion problems. Furthermore, this control is decoupled from the original DC control and protection system, avoiding power fluctuations. Furthermore, the reactive power-voltage dual-loop control strategy adopted ensures rapid support of transient voltage while achieving flexible and precise adjustment of steady-state reactive power. This enables the converter station to achieve unity power factor operation and meet harmonic standards without installing traditional AC filters and reactive power compensation capacitor banks.

[0087] Please see Figure 8 , Figure 8 This is a structural block diagram of a commutation margin hybrid compensation device provided in an embodiment of this application. Figure 8 As shown: The commutation margin hybrid compensation device includes: a first generation module 810, a second generation module 820, a third generation module 830, and a fourth generation module 840. Wherein:

[0088] The first generation module 810 is used to generate the firing angle of the 12-pulse converter bridge based on the feedback of the grid-side AC bus voltage and DC current, through the coordination of fixed-view arc extinction angle control and constant current control, so as to control the DC power transmission.

[0089] The second generation module 820 is used to generate the fundamental modulation signal of the current source converter based on the grid-side AC bus voltage and the reactive power exchanged between the converter station and the AC system through reactive-voltage dual-loop control, so as to provide dynamic reactive power support and voltage regulation.

[0090] The third generation module 830 is used to generate the fifth harmonic modulation signal of the current source converter based on the detected actual arc extinction angle of the 12-pulse converter bridge and its output fifth harmonic current, through fixed actual arc extinction angle control and fifth harmonic current feedforward control, in order to increase the commutation margin.

[0091] The fourth generation module 840 is used to synthesize the fundamental modulation signal and the harmonic modulation signal to generate the final modulation wave, and generate the switching signal to drive the current source converter based on the modulation wave.

[0092] In some possible embodiments, the second generation module 820 includes:

[0093] The first generation unit is used to generate a voltage compensation signal based on the deviation between the reactive power exchanged between the converter station and the AC system and its given value through reactive power outer loop control.

[0094] The second generation unit is used to generate a voltage deviation signal by means of voltage inner loop control, based on the grid-side AC bus voltage, the given voltage, the voltage compensation signal, and an operating point deviation voltage generated based on the effective value of the output current of the current source converter, and to adjust the voltage deviation signal to generate the q-axis command current of the current source converter.

[0095] In some possible embodiments, the third generation module 830 includes:

[0096] The third generation unit is used to detect the minimum actual arc extinction angle of the 12-pulse converter bridge and compare it with the given value of the actual arc extinction angle. It generates the basic amplitude of a 5th harmonic modulation signal through proportional-integral adjustment.

[0097] The detection unit is used to detect the amplitude of the fifth harmonic component of the output current of the 6-pulse converter bridge and superimpose it onto the base amplitude as a feedforward to obtain the final amplitude of the fifth harmonic modulation signal.

[0098] In some possible embodiments, the fourth generation module 840 includes:

[0099] The unit is used to add the fundamental modulation signal and the 5th harmonic modulation signal to obtain the synthesized modulation signal;

[0100] The fourth generation unit is used to compare the synthesized modulated signal with the triangular carrier signal to generate a binary logic switching function;

[0101] The fifth generation unit is used to input the binary logic switching function into the ternary logic generator and, in conjunction with the zero-state value discrimination logic, generate the switching signals of each bridge arm of the current source converter.

[0102] It should be noted that the commutation margin hybrid compensation device provided in the above embodiments is only illustrated by the division of the above functional modules when executing the commutation margin hybrid compensation method. In practical applications, the above functions can be assigned to different functional modules as needed, that is, the internal structure of the device can be divided into different functional modules to complete all or part of the functions described above. In addition, the commutation margin hybrid compensation device and the commutation margin hybrid compensation method embodiments provided in the above embodiments belong to the same concept, and the implementation process is detailed in the method embodiments, which will not be repeated here.

[0103] The sequence numbers of the embodiments in this application are for descriptive purposes only and do not represent the superiority or inferiority of the embodiments.

[0104] Please see Figure 9 , Figure 9 This is a schematic diagram of the structure of an electronic device provided in an embodiment of this application. Figure 9 As shown, the electronic device 900 may include: at least one processor 901, at least one network interface 904, a user interface 903, a memory 905, and at least one communication bus 902.

[0105] The communication bus 902 is used to enable communication between these components.

[0106] The user interface 903 may include a display screen, and the optional user interface 903 may include a standard wired interface or a wireless interface.

[0107] The network interface 904 may optionally include a standard wired interface or a wireless interface (such as a Wi-Fi interface).

[0108] The processor 901 may include one or more processing cores. The processor 901 connects to various parts within the electronic device 900 using various interfaces and lines, and performs various functions and processes data by running or executing instructions, programs, code sets, or instruction sets stored in the memory 905, and by calling data stored in the memory 905. Optionally, the processor 901 may be implemented using at least one hardware form of Digital Signal Processing (DSP), Field-Programmable Gate Array (FPGA), or Programmable Logic Array (PLA). The processor 901 may integrate one or a combination of several of the following: Central Processing Unit (CPU), Graphics Processing Unit (GPU), and modem. The CPU primarily handles the operating system, user interface, and applications; the GPU is responsible for rendering and drawing the content required for display; and the modem handles wireless communication. It is understood that the modem may also not be integrated into the processor 901 and may be implemented as a separate chip.

[0109] The memory 905 may include random access memory (RAM) or read-only memory. Optionally, the memory 905 may include a non-transitory computer-readable storage medium. The memory 905 can be used to store instructions, programs, code, code sets, or instruction sets. The memory 905 may include a program storage area and a data storage area, wherein the program storage area may store instructions for implementing an operating system, instructions for at least one function (such as touch function, sound playback function, image playback function, etc.), instructions for implementing the above-described method embodiments, etc.; the data storage area may store data involved in the above-described method embodiments, etc. Optionally, the memory 905 may also be at least one storage device located remotely from the aforementioned processor 901. Figure 9 As shown, the memory 905, which serves as a computer storage medium, may include an operating system, a network communication module, a user interface module, and a commutation margin hybrid compensation application program.

[0110] exist Figure 9 In the illustrated electronic device 900, the user interface 903 is mainly used to provide an input interface for the user and to acquire user input data; while the processor 901 can be used to call the commutation margin hybrid compensation application stored in the memory 905 and specifically perform the following operations:

[0111] Based on feedback from the grid-side AC bus voltage and DC current, the firing angle of the 12-pulse converter bridge is generated through the coordination of fixed-actuation angle control and constant current control to control DC power transmission. According to the grid-side AC bus voltage and the reactive power exchanged between the converter station and the AC system, a fundamental modulation signal for the current source converter is generated through reactive power-voltage dual-loop control to provide dynamic reactive power support and voltage regulation. Based on the detected actual arc-extinguishing angle of the 12-pulse converter bridge and its output 5th harmonic current, a 5th harmonic modulation signal for the current source converter is generated through fixed-actuation angle control and 5th harmonic current feedforward control to increase commutation margin. The fundamental modulation signal and the harmonic modulation signal are synthesized to generate the final modulation wave, and a switching signal to drive the current source converter is generated based on the modulation wave.

[0112] In some possible embodiments, the processor 901 executes reactive-voltage dual-loop control to generate the fundamental modulation signal of the current source converter, specifically for performing:

[0113] Through reactive power outer loop control, a voltage compensation signal is generated based on the deviation between the reactive power exchanged between the converter station and the AC system and its given value. Through voltage inner loop control, a voltage deviation signal is generated based on the grid-side AC bus voltage, the given voltage, the voltage compensation signal, and an operating point deviation voltage generated based on the effective value of the output current of the current source converter. The voltage deviation signal is then adjusted to generate the q-axis command current of the current source converter.

[0114] In some possible embodiments, the processor 901 executes a 5th harmonic modulation signal for the current source converter by controlling the actual arc extinction angle and the 5th harmonic current feedforward, specifically for performing:

[0115] The minimum actual arc extinction angle of the 12-pulse converter bridge is detected and compared with the given value of the actual arc extinction angle. The basic amplitude of a 5th harmonic modulation signal is generated by proportional-integral adjustment. The amplitude of the 5th harmonic component of the outlet current of the 6-pulse converter bridge is detected and superimposed on the basic amplitude as a feedforward quantity to obtain the final amplitude of the 5th harmonic modulation signal.

[0116] In some possible embodiments, the processor 901 generates the final modulated wave and, based on the modulated wave, generates a switching signal to drive the current source converter, specifically for performing:

[0117] The fundamental modulation signal is added to the 5th harmonic modulation signal to obtain the synthesized modulation signal; the synthesized modulation signal is compared with the triangular carrier signal to generate a binary logic switching function; the binary logic switching function is input into a ternary logic generator and combined with the zero-state value discrimination logic to generate the switching signals of each bridge arm of the current source converter.

[0118] This application also provides a computer-readable storage medium storing instructions that, when executed on a computer or processor, cause the computer or processor to perform the above-described instructions. Figure 4 One or more steps in the illustrated embodiment. If the constituent modules of the above-described commutation margin hybrid compensation device are implemented as software functional units and sold or used as independent products, they can be stored in the computer-readable storage medium.

[0119] In the above embodiments, implementation can be achieved, in whole or in part, through software, hardware, firmware, or any combination thereof. When implemented in software, it can be implemented, in whole or in part, as a computer program product. The computer program product includes one or more computer instructions. When the computer program instructions are loaded and executed on a computer, all or part of the processes or functions described in the embodiments of this application are generated. The computer can be a general-purpose computer, a special-purpose computer, a computer network, or other programmable device. The computer instructions can be stored in a computer-readable storage medium or transmitted through the computer-readable storage medium. The computer instructions can be transmitted from one website, computer, server, or data center to another website, computer, server, or data center via wired (e.g., coaxial cable, fiber optic, Digital Subscriber Line (DSL)) or wireless (e.g., infrared, wireless, microwave, etc.) means. The computer-readable storage medium can be any available medium accessible to a computer or a data storage device such as a server or data center that integrates one or more available media. The available media may be magnetic media (e.g., floppy disks, hard disks, magnetic tapes), optical media (e.g., digital versatile discs (DVDs)), or semiconductor media (e.g., solid state disks (SSDs)).

[0120] Those skilled in the art will understand that all or part of the processes in the above embodiments can be implemented by a computer program instructing related hardware. This program can be stored in a computer-readable storage medium, and when executed, it can include the processes of the embodiments of the above methods. The aforementioned storage medium includes various media capable of storing program code, such as Read Only Memory (ROM), Random Access Memory (RAM), magnetic disks, or optical disks. Unless otherwise specified, the technical features of this embodiment and its implementation schemes can be combined arbitrarily.

[0121] The above description of the disclosed embodiments enables those skilled in the art to make or use this application. It will be apparent to those skilled in the art that various modifications can be made to these embodiments, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of this application. Therefore, this application is not to be limited to the embodiments shown herein, but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A commutation margin hybrid compensation system, characterized in that, The system includes: At least one 12-pulse commutator bridge, each of the 12-pulse commutator bridges comprising a high-voltage 6-pulse commutator bridge and a low-voltage 6-pulse commutator bridge connected in series; At least two converter transformers, the grid-side windings of which are connected to the grid-side AC bus; The converter transformer includes: Y / y type converter transformer, wherein the grid-side winding of the Y / y type converter transformer is connected to the grid-side AC bus, and the valve-side winding of the Y / y type converter transformer is connected to the high-voltage pole 6-pulse converter bridge. The Y / Δ type converter transformer has its grid-side winding connected to the grid-side AC bus, and its valve-side winding connected to the low-voltage pole 6-pulse converter bridge. The commutation margin hybrid compensation device includes: A high-voltage pole commutation margin hybrid compensation device is connected between the high-voltage pole 6-pulse converter bridge and the Y / y type converter transformer. A low-voltage pole commutation margin hybrid compensation device is connected between the low-voltage pole 6-pulse converter bridge and the Y / Δ converter transformer. A smoothing reactor, one end of which is connected to the DC side of the 12-pulse converter bridge, and the other end of which is connected to the DC transmission line. The grid-side AC busbar is located between the AC power grid and the converter transformer, and is connected to the AC power grid and the grid-side winding of the converter transformer, respectively. At least two commutation margin hybrid compensation devices are provided, which are connected to the converter transformer and the 12-pulse converter bridge. Each commutation margin hybrid compensation device includes a valve-side AC bus, a parallel capacitor bank, and at least one current-source converter. The parallel capacitor bank and the current-source converter are both connected in parallel to the valve-side AC bus. The parallel capacitor bank is configured to provide reactive power compensation and filter out high-order harmonics to the 12-pulse converter bridge. The current-source converter is configured to increase the actual arc-extinguishing angle of the 12-pulse converter bridge by outputting a preset harmonic current.

2. The system as described in claim 1, characterized in that, The current source converter adopts a three-phase half-bridge structure, including three-phase bridge arms and an energy storage inductor. The AC side of the current source converter is connected to the valve-side AC bus. The positive terminal of the DC side of the current source converter is connected to one end of the energy storage inductor, and the negative terminal of the DC side of the current source converter is connected to the other end of the energy storage inductor.

3. A commutation margin hybrid compensation method, applied to the system according to any one of claims 1 to 2, characterized in that, The method includes: Based on the feedback of the AC bus voltage and DC current on the grid side, the firing angle of the 12-pulse converter bridge is generated by coordinating the fixed-view arc extinction angle control and the constant current control to control the DC power transmission. Based on the grid-side AC bus voltage and the reactive power exchanged between the converter station and the AC system, the fundamental modulation signal of the current source converter is generated through reactive power-voltage dual-loop control to provide dynamic reactive power support and voltage regulation. Based on the detected actual arc extinction angle of the 12-pulse converter bridge and its 5th harmonic current at the outlet, the 5th harmonic modulation signal of the current source converter is generated by controlling the actual arc extinction angle and the 5th harmonic current feedforward control, in order to increase the commutation margin. The fundamental modulation signal and the harmonic modulation signal are combined to generate the final modulation wave, and a switching signal to drive the current source converter is generated based on the modulation wave.

4. The method as described in claim 3, characterized in that, The generation of the fundamental modulation signal of the current source converter through reactive power-voltage dual-loop control includes: Through reactive power outer loop control, a voltage compensation signal is generated based on the deviation between the reactive power exchanged between the converter station and the AC system and the given power value. Through voltage inner loop control, a voltage deviation signal is generated based on the grid-side AC bus voltage, the given voltage value, the voltage compensation signal, and an operating point deviation voltage generated based on the effective value of the output current of the current source converter. The voltage deviation signal is then adjusted to generate the q-axis command current of the current source converter.

5. The method as described in claim 3, characterized in that, The generation of the 5th harmonic modulation signal of the current source converter through fixed actual arc extinction angle control and 5th harmonic current feedforward control includes: The minimum actual arc extinction angle of the 12-pulse converter bridge is detected, and the minimum actual arc extinction angle is compared with the given value of the actual arc extinction angle. A base amplitude of a 5th harmonic modulation signal is generated by proportional-integral adjustment. The amplitude of the fifth harmonic component of the output current of the 6-pulse converter bridge is detected, and the amplitude of the fifth harmonic component is superimposed on the base amplitude as a feedforward to obtain the final amplitude of the fifth harmonic modulation signal.

6. The method as described in claim 3, characterized in that, The process of generating the final modulated wave and generating a switching signal to drive the current source converter based on the modulated wave includes: The fundamental frequency modulation signal is added to the fifth harmonic modulation signal to obtain the synthesized modulation signal; The synthesized modulated signal is compared with the triangular carrier signal to generate a binary logic switching function; The binary logic switching function is input into the ternary logic generator, and combined with the zero-state value discrimination logic, the switching signals of each bridge arm of the current source converter are generated.

7. A commutation margin hybrid compensation device, characterized in that, The apparatus is used to implement the method according to any one of claims 3 to 6, the apparatus comprising: The first generation module is used to generate the firing angle of the 12-pulse converter bridge based on the feedback of the grid-side AC bus voltage and DC current, and through the coordination of constant arc extinction angle control and constant current control, so as to control the DC power transmission. The second generation module is used to generate the fundamental modulation signal of the current source converter based on the grid-side AC bus voltage and the reactive power exchanged between the converter station and the AC system through reactive power-voltage dual-loop control, so as to provide dynamic reactive power support and voltage regulation. The third generation module is used to generate the 5th harmonic modulation signal of the current source converter based on the detected actual arc extinction angle of the 12-pulse converter bridge and its outlet 5th harmonic current, through fixed actual arc extinction angle control and 5th harmonic current feedforward control, in order to increase the commutation margin. The fourth generation module is used to synthesize the fundamental modulation signal and the harmonic modulation signal to generate the final modulation wave, and generate a switching signal to drive the current source converter based on the modulation wave.

8. A computer storage medium, characterized in that, The computer storage medium stores a plurality of instructions adapted for loading by a processor and executing the steps of the method as described in any one of claims 3 to 6.

9. An electronic device, characterized in that, It includes a memory, a processor, and a computer program stored in the memory and executable on the processor, wherein the processor executes the program to implement the steps of the method as described in any one of claims 3 to 6.

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